ORIGIN OF THE SOLAR SYSTEM
1. Origin of rings of giant planets
We will begin this chapter with the issue of origin of the smallest bodies of the Solar System, and complete it with the question of origin of the largest body – the Sun itself.
In the course of increase of masses of planets and other celestial bodies, the period of their evolution comes when they become able to hold not only heavy gases, but also light ones: hydrogen and helium in their atmospheres. Concerning the presence and chemical composition of atmospheres of celestial bodies, the latter pass through three stages in their development. The small bodies of the Solar System – small ice planets, comets, asteroids, small and little satellites and meteoric bodies – apparently, do not have any atmosphere. Or, rather, they acquire it during a regular galactic winter, but then they lose it, since the gravitational attraction at their surfaces is small, and so atoms and molecules of gases dissipate into interplanetary space.
However, the masses of celestial bodies gradually increase at the expense of silicate and ice components and the time comes when they become able to hold the atmosphere consisting of heavy gases – nitrogen, carbon dioxide, oxygen, etc. near them. But, at this stage of development, they cannot hold the light gases – hydrogen and helium, being the most widespread chemical elements in the Universe.
When the giant planets were smaller by size and mass and did not represent the giants yet, they did not have powerful hydrogen-helium atmospheres either. At that time, they did not differ from such celestial bodies as modern Pluto, Titan or Callisto. But their masses gradually rose, and so, one fine day, these formerly ice planets began to hold light gases in their atmospheres. Their masses then reached about 10 Earth masses. After that, they began to grow rapidly, mainly at the expense of light gases; their masses and sizes began to increase, while the densities, taking atmospheres into account – to decrease. Light atmosphere consisting mainly of hydrogen and helium reaches huge dimensions, being dozens thousand kilometres high.
In such a hydrogen-helium atmosphere, the clouds consisting of droplets and tiny crystals of carbon dioxide, water, methane, ammonia, etc. are permanently available. The atmosphere, together with clouds, rotates simultaneously with planets around their axes. At that, the cloud layers reach great heights: on Jupiter – 70 thousand km, on Saturn – 60 thousand km, on Uranus and Neptune – about 25 thousand km above the planet centres.
Since the clouds reach so big heights and the giant planets rotate very quickly around their axes, the clouds being located in the upper layers of atmospheres of giant planets have large linear velocities with respect to planet centre. At Saturn, upper layers of clouds circulate the centre of the planet at the speed of about 10 km/sec, at Jupiter – about 12 km/sec. For comparison: earthly clouds circulate around the axis of the planet at the speed of only about 0.5 km/sec.
However, the atmosphere of giant planets does not end where the cloud cover ends. Suffice it to say that the earthly atmosphere stretches up to 2 000 km above the surface, while clouds – only to 15 km. The same takes place for the giant planets. One might suppose that the upper layers of hydrogen-helium atmosphere stretch much higher than the cloud layer; apparently, they reach the nearest small satellites representing the innermost ring of a giant planet. At that, the linear velocity of atoms and molecules of gases of upper atmospheric layers almost reaches the orbital speed of tiny satellites of the nearest ring.
At present, under conditions of galactic summer, the picture is such. But, at the beginning of galactic winter, the situation changes sharply. We have already said that, during galactic winters, all the celestial bodies are subject to deceleration in gaseous environment; at that, they begin to approach the central body. Tiny satellites of giant planets, being constituents of their rings, are in the nearest position to the planets and, consequently, have the biggest orbital speeds. They have the smallest masses, dimensions and densities of all the satellites. Therefore, they have enormous relative decelerations that are multiply larger than those of other satellites. As a result, they become the first victims of approaching galactic winter. When the Solar System sinks into the gas-dust environment of a nebula or galactic plane, small satellites of the rings of giant planets quickly slow down their motion, approach the planets, enter into the upper layers of atmosphere (at that time, winter atmosphere of the planets has, apparently, not formed yet), slow down even more and fall onto the surfaces of the planets. However, in some cases they do not reach the surface, having been heated, evaporated and joined, at least in part, the cloud layer.
Then, during galactic winter, the mass and dimensions of the planet (especially of its atmosphere) grow; rotational velocity and linear speed of upper layers of atmosphere increase as well. When the planet and its atmosphere reach a sufficiently large dimension and rotational speed, the upper layers of atmosphere begin to circulate around the planet axis at first cosmic speed. But the planet continues to grow; its rotational speed increases as well, causing further increase of linear speed of upper layers of atmosphere. Finally, this speed reaches such a level that gaseous rings begin to be formed, as we have already said. The number of these rings will increase more and more; in the end, the giant planets will have gaseous discs of huge diameters.
However, the growth of extension of atmosphere and of rotational velocity of the planet lead to the fact that the clouds, consisting of droplets and crystals of water, carbon dioxide, ammonia, methane and other substances of ice component, will continue to rise above the surface of the planet. At that, their linear velocity will rise and reach the first cosmic speed. As a result, ice component (on the heels of gaseous component) will begin to shift to gaseous disc under the influence of centrifugal force. This transfer will embrace the part of ice component, being located in the upper layers of atmosphere in the form of cloud cover, as well as some amount of dust. This process will last up to the end of galactic winter.
Then the galactic winter ends and the onflow of substance onto the surface of the planet and into its atmosphere stops. Meanwhile, the transfer of atmospheric substance from the equatorial zone of the planet to the gaseous disc goes on. This leads to the decrease of extension of atmosphere and, consequently, the reduction of linear velocity of upper layers of atmosphere, including the speed of movement of upper clouds around the planet. This stops the process of dissipation of cloud layer, although the dissipation of light gases from the upper over-cloud layer continues for a long time.
Simultaneously, the gradual dissipation of hydrogen, helium, nitrogen, oxygen and, probably, other gases from the gaseous disc takes place, leading to the decrease of its capacity, thickness and diameter. But the ice component of gaseous disc mainly remains in its place. It is not subject to rapid dissipation into interplanetary space, since its linear velocity is lower than parabolic speed; at the same time, it does not fall down, towards the planet surface, because its linear velocity is more than the first cosmic speed.
Having isolated itself from the atmosphere, the gaseous disc begins its independent existence, cooling down more and more, so that droplets of liquid become hard. But the consolidation of substance of gaseous disc took place previously as well; now this process simply speeds up. Soon the whole disc changes its form: it turns from a cloud of liquid droplets, tiny crystals and still remaining vapours to billions of tiny satellites. The satellites, that appeared previously, scoop out the liquid part of ice component, thereby increasing their dimensions and masses. Finally, the substance, being torn off the atmosphere and remaining at the orbit around planet, turns to hard small satellites of various sizes: from millimetres to dozens of meters. At that, all of them circle the planet in its equatorial plane, without a slightest deviation from the latter, so that their inclination should be equal to zero. However, we cannot say the same about their eccentricities.
If we compare the rings of different giant planets, we could also see distinctions between them. If the chemical composition of clouds of giant planets is different, then the difference in chemical composition of rings is possible. It should be noted that the chemistry of ring satellites includes not only ice component of clouds, but also dust from cosmic precipitations. It should also be pointed out that, on completion of galactic winter, the small ring satellites replenish their substance at the expense of ice component of satellites of the planets that lose it owing to heating by means of tidal friction. If it was not for this replenishment of tiny ring satellites by the ice component of nearest big satellites and even by the dust from the surfaces of small satellites, then the rings would, probably, have disappeared at all or, at least, they would be of lower density. Maybe, the unique rings will be discovered around Neptune, that, probably, circle the planet in reverse direction being supposedly created by Triton. Or, maybe, only some outer rarefied rings circle the planet in reverse direction, while the inner ones, also rarefied, circulate in forward direction, since they could be formed from atmosphere. However, since Neptune rotates slowly, it may have no rings with forward circulation. The density of rings is directly proportional to the mass of planet atmosphere and its rotational speed. The low density of Jovian rings can be explained by proximity of the Sun that promote the dry evaporation (sublimation) of substance of tiny ring satellites and its dissipation into interplanetary space together with the stream of dissipating hydrogen and helium. After all, the rings of giant planets, first of all – the rings of Jupiter being the nearest to the Sun, on completion of galactic winter, do not have any protection from sun rays, in contrast to the surfaces of planets being screened by cloud cover.
Owing to proximity of Jupiter to the Sun, smaller number of ring satellites of smaller dimensions and masses could be formed. Besides, they, probably, reduce in size and mass during all the galactic summer under the influence of Sun radiation. Low density of rings of Uranus could be explained by the fact that this planet, unlike other giant planets, periodically turns to the Sun in such a way that its rings face the Sun not edgewise and not on the small angle, but by all the surface, so that the sun rays fall onto the rings of Uranus almost obliquely. As a result, the unit of area of rings of Uranus gets somewhat greater amount of sun ray energy than that of the rings of Saturn. Therefore, the ice component of rings of Uranus and Jupiter, being subject to stronger heating by sun rays than that of Saturn, gradually dissipates into interplanetary space by means of sublimation. So the rings of Uranus and Jupiter have almost not retained ice component, but there is still silicate component that, as some scientists think, is being replenished at the expense of small satellites, for example, Amaltea of Jupiter, as well as the satellites being located between the rings of disc.
The disc of Saturn, probably, replenishes not only silicate, but also ice component (water ice, frozen carbon dioxide, methane, ammonia, etc.) at the expense of substance of satellites.
2. The origin of giant planets
In the previous chapters, we have found out the following: first, during galactic winters, all the celestial bodies of the Solar System increase their dimension and masses, i.e. they expand. Second, during galactic winters, the celestial bodies approach the central body, so that, with every galactic winter they are closer to the Sun than before; besides, satellites approach their planets.
At that, the growth of celestial bodies takes place with different paces. The fastest is the growth of giant planets and the Sun; the slowest is the expansion of terrestrial planets and other silicate bodies. The approach of celestial bodies to their central bodies takes place under the influence of, first, deceleration of celestial bodies in the gas-dust environment of diffuse matter, and, second, owing to strengthening the gravitational attraction of celestial bodies to the central body, since their masses increase, while the distances between them reduce.
Consequently, the celestial bodies of common origin should submit to some common rules. For example, the mass of giant planets should increase with approaching the Sun. As a whole, they obey this regularity, though there is an exception – the mass of Neptune is somewhat bigger than that of Uranus. But among the rest of giant planets, this regularity is distinct enough: the mass of Jupiter is 3.35 times bigger than that of Saturn, while the latter is 6.5 times bigger than mass of Uranus. If this rule is not by chance, then there should be big planets beyond the orbits of Neptune and Pluto, their masses being several Earth masses, then one Earth mass, etc. One should bear in mind, however, that the growth of masses of celestial bodies is not so unilateral and straightforward. It is accompanied by periodical decrease of masses of some or other planets. It could be explained by different reasons: rapid axial rotation under the influence of centrifugal force; small masses of many celestial bodies, being not able to hold atmosphere, especially hydrogen and helium; heating by solar energy; warming by the tidal friction.
We have already mentioned that Jupiter has, probably, decreased by mass and goes on decreasing at present by means of a powerful vortex in the zone of big Red Spot owing to proximity of Jupiter to the Sun and its relatively rapid axial rotation. We have also said that, probably, Triton was previously the fifth big planet, but then, having become dangerously close to Neptune, it had lost almost all its substance under the action of tidal friction and orbited Neptune.
One could also suppose that previously Pluto and Charon were independent big planets with masses of several Earth masses. Then, destroying each other, they had lost the major part of their masses; only several per cent of it remained. If it is true, then previously there were seven big planets: the fifth one was Triton, the sixth – Pluto and the seventh – Charon.
One more regularity lies in the fact that the distances between the planets of common origin should be interdependent. For example, if the relative deceleration of all the giant planets is the same, they would be situated at approximately the same distances from one another. But their relative decelerations are different and so are the distances between them. If we, using only the dependence of interplanetary distances of giant planets upon their relative decelerations, and neglecting their relative accelerations, draw up the table, in which we put the distances between the giant planets in the past, calculated by means of simple formulas: à1=à+50W; à2=à+100W è a3=a+150W, then it would turn out that the giant planets “shift” in such a way that the distances between them would become level.
But if we continue this table, then interplanetary distances would deviate from one another again, at that – more and more. It could be explained by the fact that, in distant past, the values of relative decelerations were different from modern ones.
Indeed, if we “reduce” Jupiter down to the dimension and mass of Saturn and shift it to the orbit of the latter, then the relative deceleration of Jupiter would be equal to that of Saturn. And if we “reduce” Saturn down to Neptune, then its relative deceleration would decrease as well. It means that the modern values of relative decelerations of giant planets could be used only for a limited period of their evolution, but not for this evolution as a whole (here, we don’t consider the relative accelerations of planets, thereby distorting the real picture).
From the first table we can see that Jupiter has shifted from the orbit located in 5.2 AU from the Sun to the distance of 16.1 AU from the Sun. Does it mean that, in distant past, there was no one other giant planet between the Sun and Jupiter? If we suppose that the planets gradually approach the Sun and that there should be commensurable distances between the planets of common origin, then we must inevitably agree with the fact that, in distant past, there were other giant planets closer to the Sun than Jupiter. One may ask: where are those planets? One of possible answers may be such: these giant planets approached the Sun one by one and disappeared in its depths. Another answer is possible. We know from the table of relative decelerations, that the relative deceleration of Saturn is approximately by 25 % more than that of Jupiter. Therefore, during galactic winters, Saturn approaches the Sun quicker than Jupiter does. Besides, we know that the relative acceleration of Jupiter is 6 to 7 times more than that of Saturn. Consequently, during galactic summer, including present time, Jupiter moves away from the Sun faster than Saturn does. However, the distance between Jupiter and Saturn (4.3 AU) is less than that between Jupiter and the Sun (5.2 AU). But we already know that the distances between two “neighbouring” planets should decrease in the course of approaching the Sun. If the distance between Jupiter and Saturn is equal to 4.3 AU, then the distance between Jupiter and the closer giant planet should be smaller still. So where is it? Where should it be located?
If we neglect the relative accelerations of the planets and only take their relative decelerations into account, then it’s easy to calculate that when Saturn finds itself at the modern orbit of Jupiter, having approached by 4.3 AU to the Sun, Jupiter will approach the Sun by 3.44 AU and will circle the Sun at the distance of 1.76 AU from the latter, i.e. it will be almost at the modern Martian orbit. Consequently, it is here that this hypothetic before-Jupiter giant planet should be located (if it existed at all, of course). So where is it? A possible answer: probably, Mars (and maybe Earth) is this planet; previously, it was a giant planet, like Jupiter, but then, having approached too close to the Sun, it had lost first its hydrogen-helium atmosphere, that constituted, maybe, 99% of its mass, and then – almost all the ice component, so that modern Mars retained only silicate core, and even, maybe, not all the core, since the dust being formed at the surface of silicate Martian core could be captured by powerful eddy flows in atmosphere and rush into interplanetary space.
On the other hand, if previously giant planets were smaller by dimensions and mass and farther from the Sun than they are today, one should admit that new giant planets should always appear instead of the ones disappearing in the depths of the Sun and near it. And these new planets do not appear from the outside, but are being constantly generated in the Solar System. Or, rather, they are not generated but grown from the ice planets located at the periphery of the Solar System. One of them is a small planet Pluto, beyond which, without a doubt, there are a number of larger ice planets with masses comparable to that of Earth and Mars, and – still farther – a series of smaller planets with masses commensurable to that of Pluto and its satellite Charon.
It is from ice planets that the giant planets originate.
3. Origin of Pluto and other ice planets
Thus, beyond the zone of giant planets, there is a zone of ice planets; one of them is Pluto – the only one known so far. Undoubtedly, Pluto is not the biggest ice planet. The most massive ice planets are, apparently, bigger than Venus and Earth by mass and, especially, by dimensions, while the least massive ones are not larger than even Charon. At that, the more massive ice planets should be located closer to the Sun, while the least massive – at the periphery of the zone of ice planets.
Beyond the zone of ice planets, there is a zone of smaller bodies of the Solar System – comets that differ from the ice planets not only quantitatively: by dimensions, masses and densities, but also qualitatively. This qualitative distinction lies in the fact that comets are non-differentiated celestial bodies, while in the depths of planets the process of differentiation of depth substance takes place or, at least, begins. It is from the zone of comets – the most distant zone of the Solar System – that the ice planets arise.
Comets, gradually increasing by dimension and mass and the same way gradually approaching the Sun, turn, in the course of time, into small ice planets, in the depths of which, the process of depth differentiation of substance begins. However, by no means all the comets turn into ice planets: only negligibly small part of them, maybe, one in a million, just as far from all the ice planets become giant planets. For example, Pluto is not destined to be a giant planet. Its mass and density are too small; therefore, it has excessively large relative deceleration. And so, Pluto, before having become a giant planet, would approach Neptune too much and could fall onto its surface, increasing Neptune’s mass, or (though it is less probable) enter its orbit, turning to its new satellite. One might suppose that Triton had suffered the same fate: previously, it was a planet; then it had orbited Neptune. It is more likely that Pluto would take the lead over Neptune, or even Uranus as well, in its way to the Sun.
The same way, not all the comets are destined to become ice planets. Many of them will perish in the struggle for place under the Sun, not having turned into planets, if they, owing to their big relative deceleration, come too close to a planet, being closer to the Sun, or to a larger comet, and, either fall onto their surfaces increasing their masses, or orbit them turning into their satellites. However, transformation of a comet (or an ice planet) to a satellite could only delay its death, since satellites, though not all of them, also approach their planets owing to deceleration in gaseous environment and fall onto their surfaces in the course of time.
Such a fate waits for the majority of small bodies of the Solar System. Just a little number of them will become large celestial bodies, and only a handful of them will turn into planets.
We have already mentioned above that comets have big eccentricities: about 0.3 to 0.4 and more. Ice planets have somewhat smaller eccentricities: about 0.1 to 0.3. Still smaller are those of giant and terrestrial planets: as a rule, they are not more than 0.1. The biggest are the eccentricities of the smallest and, at the same time, the farthest comets; and just because they perish most of all, since the probability of collision of a celestial body with other ones is directly proportional to its eccentricity and inversely proportional to the inclination of its orbit. In the plane of the Solar System, in which the major part of its celestial bodies moves, small bodies have little chances to survive.
The fact that large comets and ice planets have big eccentricities leaves a mark on distances between giant planets. Ice planets and large comets, apparently, cannot be located closer to each other, than a certain distance between their orbits – about 10 AU, for a very long time, since, in the case of smaller distance, their orbits would cross each other, as its is the case for Pluto and Neptune; planets or big comets having intersecting orbits will collide sooner or later. Pluto, having the eccentricity of 0.25, has not collided with Neptune so far only because of large inclination of its orbit – about 17°. However, in the nearest galactic winter, the distance between the planets and the inclination of Pluto’s orbit will reduce; therefore, such a collision will be quite probable.
4. Origin of asteroids
Asteroids, like ice planets, originate from comets, but the way of their origin is greatly different from that of ice planets. If ice planets descend from comets at the periphery of the Solar System – beyond the farthest giant planet Neptune, then asteroids originate from comets near the Sun – closer than the nearest giant planet Jupiter.
As we have already mentioned, between the orbits of each pair of neighbouring giant planets, there are comet belts resembling the asteroid belt located between the orbits of Mars and Jupiter. At that, the number and aggregate mass of the second comet belt between the orbits of Saturn and Uranus is, probably, several times more than the number and aggregate mass of the first comet belt between the orbits of Jupiter and Saturn. The same way, the third comet belt between the orbits of Uranus and Neptune is, perhaps, several times larger than the second comet belt.
The origin of comet belts between the orbits of giant planets is connected with the fact that the eccentricities of planets decrease more and more in process of their evolution; as a result, free spaces or gaps between them appear, so that the closest of two planets reaches the point of aphelion that it used to reach previously no more; the same concerns the farther planet in perihelion.
If comets, with their big eccentricities, move along their orbits in such a way that the latter cross each other, and if ice planets with their somewhat smaller eccentricities move along their orbits so that the aphelion of a closer planet and the perihelion of a farther neighbouring one touch or almost touch each other, then the giant planets with their small eccentricities circle the Sun in such a way that there are large free gaps between their orbits. But the Nature “cannot stand emptiness”, and so this free gap is being taken by thousands of comets.
As a matter of fact, comets in the Solar System are everywhere: not only in free spaces between the giant planets, but also near them. However, the latter comets disappear quickly, being captured by the planets, into the sphere of attraction of which they find themselves. Therefore, long-term existence of the majority of comets near the planet orbits is impossible. Their trajectories will cross sooner or later, that stops the existence of comets. However, in the zones between the giant planets with their small eccentricities, there are big gaps, in which comets can exist for a longer time – during the whole galactic summer. At that, many of them expand, having captured smaller comets and increasing their masses and dimensions at the expense of the latter.
During every galactic winter, comets, having small masses and densities, and, consequently, big relative decelerations, begin to approach the Sun. Their distances from the Sun reduce more and more; they become closer and closer to the orbit of the nearest giant planet, the latter approaching to the Sun multiply slower.
One might suppose that every comet, having approached the orbit of a planet, should fall onto its surface, change its circumsolar orbit for a circumplanet one, or, finally, change its orbit sharply and move away from the Solar System along a hyperbolic trajectory. However, as a matter of fact, the things are somewhat different. The availability of asteroid belt between the orbits of Mars and Jupiter, as well as the fact that small asteroids in it are located not only farther from the Sun than large ones, but also closer than they, testifies to the fact that small bodies of the Solar System can, under favourable conditions, overtake the larger celestial bodies, so that smaller bodies, being farther from the Sun before the galactic winter, can find themselves closer to it during a regular galactic winter.
Of course, not all the small bodies can overtake larger ones. Many of them will be captured by large bodies in the course of overtaking, but some of them can pass this dangerous zone safely.
Some of characteristics of celestial bodies can be either more or less favourable for survival of celestial bodies during overtaking the larger bodies. These characteristics include: relative deceleration, eccentricity and inclination of the orbit of celestial body to the plane of Solar System.
The bigger is the relative deceleration of a celestial body, the quicker is its approach to the Sun and the quicker is its passage through the dangerous zone, i.e. the orbit of a planet. Under equal densities and distances from the central body, the relative deceleration is inversely proportional to the body’s mass; therefore, the smaller bodies, under equal other conditions, have a better chance to overtake a planet safely. Consequently, comets can overtake giant planets, while ice planets, apparently, can not. Smaller comets have better chance, than larger ones. Meteoric bodies are still easier to pass through the dangerous zone.
Of two similar comets with different eccentricities, it is, obviously, easier for the one with smaller eccentricity to pass through the orbit of a giant planet, since it takes smaller place in the plane and volume of the Solar System. And of two comets with different orbit inclinations, the one with bigger inclination of orbit to the orbital plane of planet being overtaken has, under equal other conditions, better chance to pass through dangerous zone.
During the planets overtake by comets, a kind of selection of celestial bodies with maximum number of favourable characteristics takes place (figuratively speaking, “Darwin’s natural selection” for celestial bodies). And this is the explanation of the fact that there are no large bodies comparable to Earth, Triton or Pluto between the orbits of giant planets. They, apparently, cannot pass safely through the dangerous zone, while comets, especially those having small dimensions and masses and, consequently, big relative decelerations, small eccentricities and large orbit inclinations, do this easily.
One might suppose that approximately half of all the comets of a comet belt can transfer to another such belt. The rest of them falls onto the surfaces of giant planet and its satellites or enters the orbits around the giant planet becoming its satellites. Having passed safely through the orbit of giant planet, a half of comets gets the orbits located uniformly between the orbits of giant planets. As a result, during galactic summer, about a quarter of them is being captured by a planet, near which their orbits are located, while another quarter is being gradually captured by the other planet. And only about one half of those comets having successfully crossed the dangerous zone will survive to the next galactic winter and begin a new transfer. Thus, the number of comets, in the course of their transfer from a comet belt to another one, may be reduced approximately four times. And this means that the number of comets in each comet belt is approximately four times larger than that in the neighbouring belt being closer to the Sun.
So how can comets succeed in passing by giant planets, escaping their powerful gravitational attraction? The question is that a planet itself takes only a negligibly small part of the length of its orbit, the latter being equal to billions and dozens of billion kilometers. And while the planet is on one side of the Sun, the comets crossing its orbit can be located on the other side of the Sun or simply far apart from the planet. At that, comets cannot collide with the planet, since their periods of circulation at that time are equal and they move in the same direction. And when the comets are closer to the Sun and their periods of circulations become shorter than that of the planet, they, undoubtedly, will sooner or later find themselves on the same side of the Sun as the planet will be; however, by that time, they will be at the safe distance from the planet orbit, especially those having large inclinations of the orbits to the planet orbit, big relative decelerations and small eccentricities.
In the light of the aforesaid, it’s easy to understand the origin of asteroids, located in the asteroid belt between the orbits of Mars and Jupiter. In every galactic winter, comets of the second comet belt migrate to the first comet belt, while the comets of the latter simultaneously move through the orbit of Jupiter. At that, about one half of them perishes, falling onto the surfaces of Jupiter or its satellites, or enters Jovian orbits as its satellites. It is possible that some large satellites of Jupiter and other giant planets have also acquired their own tiny satellites in such a way.
The comets, having moved from the first comet belt, spread more or less uniformly along the distance between the Sun and Jupiter. Then, during a regular galactic summer, about one half of them are gradually captured by Jupiter and terrestrial planets, in the attraction sphere of which these comets find themselves by the end of a regular galactic winter. Another half of comets avoids such a fate, being located in the safe zone between the orbits of Mars and Jupiter.
Thus, the number of comets of the first comet zone, having crossed the orbit of Jupiter, decreases approximately four times. At that, their aggregate mass reduces even more sharply, since the comets, having settled in the asteroid belt, lose, under the influence of solar radiation, all or almost all the ice component representing the major part of their masses (perhaps, 90 to 99%), thereby turning from ice or, rather, snow comets to silicate asteroids.
5. Origin of satellites
The small celestial bodies – comets and asteroids – approach the Sun quicker than the larger ones do. At that, they overtake planets, come close to planet orbits and cross them continuing to approach the Sun.
However, not all the small bodies manage to cross the planet orbits safely. Many of them, during crossing the planet orbit, pass too close to the planet, and the latter capture them by its gravitational attraction. At that, the majority of small bodies fall onto the planet surface, but some part of them enters the circumplanet orbits and become its satellites. Later on, the satellites, in the course of deceleration in gaseous environment during galactic winters, approach their planets and, in the end, many of them enter the planet atmosphere and fall onto its surface, increasing its mass and dimensions. However, the satellites with different masses approach the planet at different speeds, owing to their different relative decelerations. Small satellites approach the central body quicker than larger ones. They overtake the latter and begin to cross their orbits. Some of them do it successfully, and they find themselves ahead of larger satellites; another group of them fall onto the surface of these larger satellites, making the latter still larger; some of them, possibly, enter the orbits around big satellites. Small satellites, having overtaken a larger one, continue to move towards its planet. At that, they overtake other, medium satellites and are being partially captured by them. All these processes create a great diversity in the distribution of planet satellites by their masses, dimensions, distances to the planets and between them, etc.
However, in the satellite system, like in planet one, some regularity can be traced, though being somewhat less distinct. For example, masses of nearby satellites of Jupiter multiply exceed those of distant satellites. And the smaller masses of Io and Europa in comparison with those of Ganymede and Callisto can be explained by the fact that previously the masses of Io and Europa were larger than those of Ganymede and Callisto, but then they had lost all their ice component owing to heating their depths under the influence of tidal friction, their density doubled and they became smaller than Ganymede and Callisto. As for Amaltea, it has either entered its modern orbit from the orbit around Io under the disturbance of powerful gravitational attraction of Jupiter, to which Io and its former satellite came too close; transferred to Jovian orbit from a circumsolar orbit; or formed from the asteroids, that managed to cross the orbits of Galilean satellites on their path from the periphery of the planet-satellite system of Jupiter.
If we suppose that Ariel and Umbriel – the neighbouring satellites of Uranus – were previously of larger dimensions and masses, than Titania and Oberon, but then, under the influence of tidal friction, that had simultaneously decelerated their axial rotation, they had lost the major part of their ice component; and if we assume that the same took place with the neighbouring satellites of Saturn, then the violation of regularity of reducing the masses of celestial bodies with the distance from the central body would become less acute, though it would partly remain, especially for the satellites of Saturn. If satellites do not lose some part of their substance in the course of approaching the planet, starting with some critical distance, under the influence of heating stipulated by tidal friction in the bodies of satellites, caused by gravitational attraction of planets and nearby satellites owing to the rotation of satellites, that lose their substance because of either their eccentricities, being not equal to zero, or proximity of a nearby, especially more massive satellite, then the masses of satellites would, as a rule, be inversely proportional to their distances to the planets, with the exception of small satellites having excessively big relative decelerations. But since the satellites, under the influence of tidal friction heating, lose their ice components; quite another rule in their masses appears: the most massive are the satellites located approximately in the middle of the rank of satellites, while masses of other satellites gradually reduce on both sides of the largest one. Ganymede, Titan and Titania are the largest satellites of their planets with forward circulation, which are located approximately in the middle of their satellite systems.
One might suppose that Hyperion has lost the major part of its mass under the influence of tidal friction caused by Titan; and it is the latter, that has acquired the ice component of the former. Maybe, previously Hyperion was twice as large as Japetus, while Titan was considerably smaller. In the future, Hyperion will come still closer to Titan and will, probably, enter an orbit around it, as it was the case for Triton. Like Triton, Hyperion should have the excessive density, since it has lost a considerable part of its ice component. Triton had not only lost almost all its substance, but also entered the orbit around Neptune; Hyperion has also lost a lot of its substance, but it has not entered the sphere of attraction of Titan yet. One can say that Hyperion is now at an earlier stage of development, in comparison with Triton.
Larger mass of Tethys, comparing to that of Dione, can, apparently, be explained by the fact that the former had been formed out of two large bodies, like Neptune and Titan, with the only difference: Neptune and Titan, though having captured the major part of substance of Triton and Hyperion, haven’t stopped the independent existence of the latter; they will do this in the future. Tethys, in its turn, has captured its neighbouring satellite completely, and this joined pair has overtaken Neptune and Triton by one phase of its evolution, while Titan and Hyperion – by two phases. It is also possible that Dione has lost an abnormally large amount of its substance.
If all the satellites are released from their ice component or, on the contrary, the ice component of all the satellites are returned to them completely, then the largest satellites would find themselves close to their planets, while smaller ones – far from them. The largest satellite of Jupiter would be Io, while that of Uranus – Ariel.
The fact that some small satellites are located closer to their planets, than larger ones are, can be explained by their later origin during the transition from circumsolar to circumplanet orbits. It seems that Miranda, having bigger orbit inclination to the equatorial plane of Uranus, than other, larger satellites, confirms this rule. After all, the inclination of the orbit of planet or satellite to the equatorial plane of central body decreases in the course of time. Therefore, one might suppose that Miranda entered the orbit around Uranus from a circumsolar orbit later than other satellites did.
If it is so, then the satellites entering circumplanet orbits can perform such a transition both in such a way that they find themselves at the periphery of the planet-satellite system; in such a way that they can find themselves ahead of other, including larger, satellites; and in such a way that they begin to circle near the planet.
Celestial bodies, in process of transition from circumsolar to circumplanet orbit, should, apparently, change the direction of their circulation from forward to reverse. If such a change of circulation direction is an indispensable condition of transition from circumsolar to circumplanet orbits, then all the satellites, having come to the circumplanet orbits recently, should have the reverse direction of circulation. They include Triton, Phoebe and four small satellites of Jupiter. If such a change of direction of circulation is a rule, then many of small satellites at the periphery of planet-satellite systems, that will be discovered in the future, should have either reverse direction of circulation, or large orbit inclinations.
Triton, with its reverse direction of circulation, force us to draw a conclusion that both the smallest bodies of the Solar System, and larger ones – meteoric bodies and comets, asteroids and little planets – can transfer from circumsolar to circumplanet orbit. Transition of a large celestial body from hyperbolic to elliptical orbit is, apparently, impossible, since this body, approaching another body with by far greater mass, acquires such a high speed that it cannot slow down by means of deceleration in diffuse environment. But the transfer of a large celestial body from circumsolar to circumplanet orbit, under concourse of favourable circumstances, in particular, in dense gas-dust environment, is, obviously, possible. It doesn’t mean that the satellites have transferred from circumsolar to circumplanet orbits, having the same masses and dimensions as they have today. Most probably that they entered the circumplanet orbits, being of much smaller dimensions and masses, and then they expanded during galactic winters both at the expense of diffuse matter, and owing to falling other, smaller satellites and comets onto their surfaces.
If the transition of relatively large bodies from circumsolar to circumplanet orbit is possible in principle, then some large satellites (including Triton) could become such in this very way; among them – the Moon that, probably, circled the Sun along the orbit located between the orbits of Earth and Mars. But the relative deceleration of the Moon was several times larger than that of Earth; as a result, the Moon, that (like Ceres) was formed previously in the asteroid belt, had come too close to Earth and entered the orbit around it. At that, the Moon, apparently, changed its direction of circulation from forward to reverse, but then, during a number of galactic winters, its orbit gradually turned around once more. Let us suppose that the Moon was previously an independent planet, being located not far from Earth and having an orbital speed of 29 km/s, i.e. by 1 km/s less than that of Earth having the speed of 30 km/s. Satellite Moon has an orbital speed of 31 km/s relative to the Sun, when the direction of its motion around Earth coincides with the direction of its circulation around the Sun, and 29 km/s with respect to the Sun, when the direction of its movement relative to Earth is opposite to the direction of its motion relative to the Sun.
If the planet Moon, during its approach to Earth, either owing to big relative deceleration of the Moon, or because of large relative acceleration of Earth, but most likely by both these reasons, passed near the sphere of Earth attraction (on the outside), when Earth was overtaking the Moon, then the latter would decrease its speed under the influence of Earth attraction (perturbation) until they find themselves on a line with the Sun (in lower junction). Then, during Earth’s overtake of the Moon; the latter would increase its speed up to its former value under the influence of Earth attraction. During deceleration, the Moon would approach the Sun, while during acceleration it would return to its previous place.
During a regular overtaking of the Moon by Earth, the former could enter the sphere of attraction of the latter, and, having decreased its velocity down to, say, 28 km/s, enter the near-earth orbit, having then again increased the speed up to 29 km/s, since this very speed is necessary for the satellite Moon with reverse circulation around Earth. Besides, in that time, the Moon was subject to deceleration in gas-dust environment that promoted its transition to near-earth orbit.
Not so long ago, the question was discussed in scientific press, whether Mercury was a satellite of Venus in the past, but then, under the influence of powerful gravitational attraction of the Sun, entered the orbit around the latter. If Mercury really was a satellite of Venus, then it should, still earlier, enter the orbit around Venus from a circumsolar orbit, located between the orbits of Venus and Earth. Having larger relative deceleration than Venus, Mercury could come close to the latter and enter the orbit around it, at that having reversed its forward circulation; Mercury could not only stop the slow forward axial rotation of Venus under the influence of tidal friction, but could also make Venus rotate slowly in reverse direction. Thereby, Mercury had automatically changed the direction of its circulation around Venus from reverse to forward, while Venus had approached the Sun. As a result of its “recapture” by the Sun, Mercury returned to circumsolar orbit, having overtaken Venus in its motion to the Sun. However, some questions arise here that are to be solved. The first question: why have Mercury forced Venus to rotate in opposite direction, while Charon couldn’t make Pluto do the same? After all, the ratios of their masses are almost the same – 15 : 1. This question could be answered somehow, if we suppose, for example, that Venus once had one more big satellite, like the Moon, that, having approached to the planet under the influence of tidal friction (like modern Phobos and Triton do), fell onto its surface and, having imparted its momentum to Venus, made the latter rotate in opposite direction, since this hypothetical satellite previously circled Venus in reverse direction.
However, the second, much more serious question arises: if Mercury was a satellite of Venus, then it should not move away from Venus (like the Moon from Earth), but approach it, since, first, Venus rotates slowly and its rotation period would be less than the circulation period of Mercury, and, second, Venus rotates in reverse direction. However, this question can also be answered, if we suppose, for example, that the second satellite, having fallen onto Venus surface, made the latter rotate quickly in reverse direction, so that the rotation period of Venus became shorter than the circulation period of Mercury; as a result, the latter began to quickly move away from Venus and, having overstepped the limits of its sphere of attraction, transferred to a circumsolar orbit.
However, we have no evidence of this; one can assert equally well that Mercury has never been a satellite of Venus. Its big relative acceleration explains us why, in spite of its large relative deceleration, it has not entered the solar atmosphere and disappeared in the depths of the Sun so far. During galactic winters (at least – severe ones, when the Solar System crosses branches of the Galaxy), Mercury approaches the Sun, while during galactic summers it returns to its pervious place.
6. The origin of terrestrial planets
If the giant planets descend from ice planets located farther from the Sun, and if the ice planets descend from large comets located still farther from the Sun, then it is obvious that the terrestrial planets should descend from the neighbouring celestial bodies situated somewhat farther from the Sun. It’s easy to see that three groups of celestial bodies of the Solar System can be regarded as parent bodies for the terrestrial planets: first, giant planets or, rather, their silicate cores; second, large satellites of giant planets, such as Io, Europa, Ganymede and Callisto; and, third, large asteroids, such as Ceres, Pallada, Vesta, Gigea, etc.
If modern Jupiter loses its atmosphere in the zone of the powerful whirlwind (the big red spot), then we can suppose that all the hydrogen, and later – helium and other gaseous substances will leave Jupiter in the end and it will, having decreased its mass multiply, turn to the fifth terrestrial planet. After that, it will come closer to the Sun, since its relative deceleration will increase sharply (15 to 20 times), its rotation speed will reduce both at the expense of deceleration by the Sun, and owing to the dissipation of substance into cosmic space; so that it will have not only the mass of a typical terrestrial planet, but also the rotation period nearly equal to that of Earth or Mars. After that, Jupiter will regain atmosphere, first, similar to the modern Martian one, then, in the course of approaching the Sun and heating – like that of Earth, and later – of Venus.
The same will happen later to Saturn that will turn to the sixth terrestrial planet in distant future, then – to Uranus and Neptune that are destined to become the seventh and eighth silicate planets.
This will happen, if the terrestrial planets have really descended from the giant planets. To prove this, it is necessary to determine the dimensions and masses of silicate cores of giant planets, especially of Jupiter, that should be comparable to dimensions and masses of terrestrial planets. Some scientists think that the diameter of silicate core of Jupiter is approximately equal to 8 to 9 thousand km. If it proves to be true, it would be an argument in favour of the hypothesis of origin of the terrestrial planets from the cores of giant planets. But this is not complete proof. It is also necessary to prove the fact that Jupiter really loses the substance of its atmosphere and its mass decreases, at that, apparently, quicker and quicker. Or the fact that Jupiter decreased in the past, or will decrease in future with approaching the Sun and heating and, at the same time, in the course of increase of its rotation speed.
One may ask: what would happen to the Galilean satellites of Jupiter, if the latter, in distant future, reduce down to the dimension and mass of a terrestrial planet? It is obvious that, in such a case, the satellites would move away from Jupiter and, in the end, leave the sphere of its attraction and enter circumsolar orbits. Isn’t the fate of “Greeks” and “Trojans” the same? Why are the large satellites of Jupiter, in contrast to those of Saturn, located close to the planet? Maybe, previously, it had distant large satellites as well, but then they left their master in the course of decrease of its mass and entered the circumsolar orbits? And the Galilean satellites had not time to so, because a severe galactic winter began, i.e. the Solar System plunged into a galactic branch, and the Galilean satellites had approached to Jupiter again under the influence of deceleration in diffuse matter of the branch.
If this is the case, one might suppose that the large asteroids were the satellites of Jupiter as well. Then, with the decrease if Jupiter’s mass, they entered circumsolar orbits, and still later approached the Sun owing to deceleration in gas-dust environment. We may suppose that the Moon is of the same origin, with the only difference: the Moon, in distant past, was a satellite of not Jupiter, but of a giant planet Mars. With the reduction of mass of Mars, the Moon left the latter and changed its orbit for a circumsolar one; later it had overtaken Earth and entered the orbit around it.
If it is so, then the former giant planets Earth and Venus should also have large satellites in the distant past. So where are they now? It’s easy to see that Mercury could be a large satellite of giant planet Venus; then, with the reduction of mass of the latter (and not under the influence of tidal friction), it left its orbit, turned to an independent planet (like the Moon) and remains such so far (in contrast to the Moon). It is interesting that the mass ratio of Mars and the Moon, being equal to 9:1, is similar to the same ratio for Venus and Mercury, that is equal to 15:1 now, but in the past, when Mercury was more massive, it, apparently, was equal to 12:1 or even 10:1. Pluto and Charon have approximately the same mass ratio.
One might suppose that the giant planet Earth also had a large satellite and their mass ratio was similar to the above figures. It means that this former Earth satellite had the mass in the range between those of Mercury and Mars. And this satellite (having left its near-earth orbit, when Earth, loosing its substance, was turning from a giant to a terrestrial planet) became an independent planet, and then entered an orbit around Venus, having come close to it, and still later fell onto its surface, making Venus rotate in reverse direction.
Such is the picture of origin of terrestrial planets; it should be noted that it is simplified. The point is that the terrestrial planets continued to expand even after their formation from giant planets. It means that during their origin they were somewhat smaller than they are today. Mars was the last terrestrial planet to be formed. Perhaps, its modern dimensions are similar to those of new-born terrestrial planets – Venus and Earth. But the satellites of giant planets, during the formation of the last terrestrial planets, were also smaller. Mercury, being a satellite of giant planet Venus, was as large as modern Moon, Io or Europa; later, it became larger (together with expansion of Venus and Earth), mainly at the expense of asteroids. The same concerns the former satellite of giant planet Earth. It was as large as the Moon, Io or Europa; then it became larger.
If it is so, then the modern silicate core of Jupiter is in the same ratio with its satellites, i.e. it is some 10 times as massive as they are; its mass is approximately equal to that of Mars. And the core of Saturn is 3 to 4 times smaller being comparable with Mercury, while the cores of Uranus and Neptune are comparable to the Moon. In the future, all of them will expand.
One can also imagine other version of origin of terrestrial planets. For example, we can think that not only Venus, Earth and Mars, but also Mercury descended from a giant planet. Or that not only Mercury and the Moon were formed from former satellites of giant planets, but also Mars is of the same origin. However, in such a case, we have to regard the Moon and Mars as former satellites of Jupiter.
Let’s consider this version of origin of the Moon and Mars by the example of the Galilean satellites. At present, as we have said above, the Galilean satellites move away from Jupiter under the influence of tidal mechanism and, probably, decrease of Jupiter’s mass. At that, Io is the quickest to move away, while Callisto is the slowest. As a result, Io could overtake Europa and they could join into a unite satellite with the mass of 1.8 Moon masses. In its turn, this satellite could overtake Ganymede and join with it into a still larger satellite with the mass of 3.8 Moon masses. If then Callisto and this giant satellite leave the Jovian orbits and enter the circumsolar ones, Callisto, during a regular severe galactic winter, would overtake the other satellite, having 4 times larger relative deceleration in gas-dust environment of galactic branch, and would find itself closer to the Sun that this large satellite. At that, they would lose their ice components, but, at the same time, acquire a lot of silicate component at the expense of both dust and asteroids and comets. In some moment of time, the mass of Callisto would be equal to that of the Moon, while the mass of the second former giant satellite, formed from substance of Io, Europa and Ganymede, would become approximately equal to that of Mars. Maybe, the Moon and Mars had been formed in this very way? And, perhaps, Mercury, Venus and Earth as well?
If it is found that the silicate core of Jupiter is not of Mars dimension, but huge (15 to 20 Earth masses), and if it turns out that Jupiter does not lose the substance of its atmosphere and will not lose it in the future, even if it approaches the Sun to the distance of modern Martian orbit, one can advance one more assumption about origin of terrestrial planets, namely that the latter had descended not from silicate cores of the giant planets and not from their big satellites, but from large asteroids. Let’s consider this hypothesis.
If it were not the fact that the comets of the first comet belt, coming inside the orbit of Jupiter, lose their ice component, turning to asteroids, that form the only asteroid belt in the Solar System, then they would, having created one more comet belt (the nearest one to the Sun), continue to approach the Sun during galactic winters and disappear in its depths one by one, increasing its mass. However, the circumstance that comets lose their ice component under the influence of solar radiation and become asteroids has far reaching consequences.
The point is that the density of asteroids is multiply larger than that of comets; as a result, the relative deceleration of asteroids, during their formation from comets decreases several times, in spite of simultaneous reduction of their average mass. And the small relative deceleration of asteroids, comparing to that of comets, leads to the fact that they approach the Sun multiply slower than comets do. If comets, during a certain period of time, move from one comet belt to another for the distance of 5 to 10 AU, then asteroids, during the same period, move, perhaps, for only 1 to 1.5 AU. At that, asteroids continue to consolidate themselves.
The larger comets (though, maybe, not all of them) are being captured by the planets, the orbits of which they cross. Asteroids are also being captured by terrestrial planets during intersection of their orbits, but the speed of approaching the asteroids to the Sun is insignificant in comparison with that of terrestrial planets. This difference cannot be compared with the difference between the speeds of approaching of giant planets and comets to the Sun. After all, comets approach the Sun quicker than asteroids, while giant planets; on the contrary, do this some 20 times slower than terrestrial planets. Therefore, asteroids, unlike comets, have time to expand at the expense of other, smaller asteroids, comets, meteoric bodies and dust up to relatively large dimensions, sometimes to the size of a small planet.
At present, the process of consolidation of asteroids in the asteroid belt owing to their collisions with each other take place; at the same time, some asteroids split up. The appearance of the largest asteroids: Ceres, Pallada, Vesta, etc. was the result of this consolidation. During the next galactic winter, this process will gain strength and it will continue after completion of winter. As a result, a considerable part of asteroid belt will join the largest of asteroids (apparently, Ceres), and the fifth terrestrial planet with the mass and dimension between the Moon and Mars will appear.
During the next severe galactic winter, the terrestrial planets will slightly approach the Sun, giving the place for the new planet that will shift sunward down to the modern orbit of Mars. Mars will approach Earth owing to its larger relative deceleration. And Mercury could come very close to the Sun and even disappear in its depths. After that, there will be four terrestrial planets again, but the nearest of them will be not Mercury but Venus, while the farthest one – not Mars but Ceres.
As we have already said, the comets of the first comet belt, coming inside the orbit of Jupiter during galactic winters, settle themselves along the whole distance between the Sun and Jupiter, including the proximity of the terrestrial planets and the gaps between them. But these gaps are small, and, during galactic summer, all the comets, having settled there and turned to small asteroids, fall a prey to the planets under the influence of gravitational attraction of the latter. Some of them could enter the circumplanet orbits and exist as satellites for some time (Phobos, Deymos).
During the origin of terrestrial planets in the zone of asteroid belt, being constantly fed by comets from the first comet belt in the course of galactic winters, their relative deceleration will decrease, since the growth of mass, under equal other conditions, causes the reduction of relative deceleration. If, for example, all the four terrestrial planets are located at the same orbit, then the relative deceleration of Earth and Venus would be 2 to 2.5 times smaller than that of Mercury and Mars. But the mass of the smallest planets, like the Moon or Mercury, is multiply larger than that of the biggest asteroids; and so, their relative decelerations are many times smaller. As a result, asteroids overtake the planets during galactic winters and some part of them fall onto their surfaces, making small and large craters in them; all the planets and their satellites are covered with such craters.
The masses of terrestrial planets, like those of all the other celestial bodies, will increase with every galactic winter. But the paces of this increase will be much different. The planets, situated close to the asteroid belt, will grow quicker than the others, while the growth of those located close to the Sun will be the slowest. Consequently, the former will include asteroids (among them – Ceres) and the planet Mars, the latter – Mercury and Venus. As a result, Mars could, in the future, become as large as modern Venus and Earth by dimension and mass, while Ceres will, probably, overtake the Moon, then Mercury, and later – modern Mars. After all, with the increase of distance between Mars and Jupiter in the course of approaching Mars and other terrestrial planets to the Sun, the width of asteroid belt will grow. At the same time, the number and dimensions of asteroids will increase. At first, the agglomeration of asteroids will proceed slowly, then this process will accelerate, and when the largest asteroids reach some critical size, it would, probably, become very rapid, so that all (or the most part) of asteroids would join into a single silicate planet with the mass and dimension in the range between the Moon and Mercury, or even Mars.
When considering the issue of origin of giant planets, we tried to clear up the question about distances between these planets in the distant past. At that, we found out that if one “shifts” the giant planets into the past and farther from the Sun, using their modern values of relative deceleration, then the distances between planets would become level to a certain period.
It might seem that the terrestrial planets, since they, according to this hypothesis, are of the same origin (though different from that of giant planets), should shift into the past and farther from the Sun in such a way that the distances between them become level. However, as a matter of fact, the picture is somewhat different. If we draw up the table similar to the one made for the giant planets, using the modern values of relative decelerations of terrestrial planets, we would have the following values of distances of these planets from the Sun.
The second column contains the modern values of relative decelerations of terrestrial planets. The third one represents the modern distances of planets from the Sun. The following rows contain the distances of planets from the Sun in the past, at that, the last column – the largest and the oldest distances.
The fourth column shows us that Mercury once was farther from the Sun than Venus. From this, one can draw a conclusion that Mercury became a planet not so long ago; apparently, it entered a circumsolar orbit from an orbit around Venus.
From the fifth column we can see that the paths of Venus and Earth crossed near the modern orbit of Mars. Hence, at that time, either one of these planets did not exist at all, or one of them (apparently, Earth) was smaller by mass and dimension than it is today and, consequently, had larger relative deceleration and, as a result, was located far from the first planet.
Finally, the sixth column shows us that Mars was in 3.26 AU from the Sun, i.e. in the place where modern Ceres is located.
If we are guided by this scheme, then the origin of modern terrestrial planets can be explained in the following way. The first terrestrial planet, existing so far, to descend in the zone of asteroid belt (about 4 AU of somewhat farther from the Sun) was Venus; during its origin, it had the dimension and mass of modern Mercury or Mars. However, at first it was as big as the Moon, and still earlier – as Ceres, etc. But, with every galactic winter, its mass and dimension grew rapidly, though they grew during galactic summers as well at the expense of collisions and association of asteroids.
When Venus was in 3 AU from the Sun, a new planet arose in the asteroid belt that, although having a relatively big mass, was by far smaller than Venus having become bigger by that time. That was Mercury. Its relative deceleration was bigger than that of Venus, so it gradually approached the latter. Finally, it had approached Venus so that it had been captured onto an orbit around it. At that, Mercury had changed the direction of its circulation from direct to reverse one and, circulating Venus in reverse direction (like modern Titan does), slowed down the axial rotation of the latter. As a result, Venus not only ceased to rotate in forward direction, but even began to rotate slowly in reverse direction under the influence of powerful tidal friction caused by the reverse motion of Mercury. As we have seen above, Mercury, being the only satellite of Venus, could not make Venus rotate in reverse direction and move away from it at the same time. Therefore, we have to suppose that one more small planet had been formed before Mercury that, like Mercury, was later captured by Venus, approached it and fell onto its surface, thereby making it rotate in reverse direction. After that, Mercury, being a satellite of Venus, began to move away from Venus, since its period of circulation became longer than the period of rotation of Venus, and the direction of circulation of Mercury began to coincide with the direction of rotation of Venus (clockwise). At that, Venus slowed down its rotation; the period of it increased more and more, having reached the value of 243 days by present time.
It is possible that some more small planets appeared both before and after Mercury, their masses and dimensions being in the range between the Moon and Mercury; but all of them, having approached Venus, fell onto its surface (unlike Mercury) and increased its mass several times. Besides, Venus had captured a great number of small and large asteroids. All those planets and asteroids forced Venus to rotate in reverse direction.
After the origin of Mercury and other small planets, that joined Venus, one more (possibly, a large) asteroid ring gave birth to Earth with the mass equal to that of Mercury or Mars. Earth, having smaller mass than Venus with Mercury as its satellite, began to approach them gradually; after Earth, other smaller planets appeared, their masses being in the range from less than that of the Moon to that of Mercury. All of them, one by one, as well as a great number of asteroids, overtaking Earth and being captured by it, fell onto its surface and increased its mass (however, the question arises here: why haven’t they made Earth rotate in reverse direction?)
With every such fall of small planets or large asteroids, and, possibly, large satellites, great changes took place on Earth. Powerful earthquakes, volcanic eruptions happened; lithosphere broke into platforms; new mountains rose; the surface and biosphere of the planet undergone abrupt changes.
One of these small planets had been captured by Earth onto its orbit and became its satellite. At first, the Moon circulated Earth, apparently, in reverse direction, but then its orbit turned around. The Moon has been slowing down the rotation of Earth under the influence of tidal friction in Earth’s lithosphere, hydrosphere and atmosphere caused by the Moon’s attraction; but this deceleration is by far weaker than Mercury’s influence over Venus’ rotation, since the mass of the Moon is 81 times smaller than that of Earth, while the mass of Mercury is only 15 times less than that of Venus. It is quite possible that Earth had also other satellites in the past, but they had approached Earth in the course of time and fell onto its surface. Maybe, Venus also had other satellites in the past.
On the heels of Venus, Mercury, Earth, the Moon and other small planets (that later found themselves on the surfaces of Venus, Earth and, probably, Mercury), one more big asteroid ring generated Mars, the mass of which was and is smaller than that of Earth. Having bigger relative deceleration than Earth, it approaches gradually to the latter; in the future, Mars will either overtake it, fall onto its surface and join with it into one big planet, that will rotate in reverse direction, or expand at the expense of other smaller planets and asteroids up to such dimensions that its relative deceleration will become equal to that of Earth (or even smaller, as it was the case for Earth). Previously, Earth had greater relative deceleration than that of Venus, and so the former overtook the latter. Then their relative decelerations became level and the distance between them did not change for a certain period. Later, owing to quicker expansion of Earth, its relative deceleration had decreased even more and it began to fall behind Venus (to simplify the picture, we do not regard the relative accelerations of the planets here).
It’s not unlikely that, after the origin of Mars, several more small planets (of about the Moon’s size) appeared, but soon all of them found themselves on the surface of Mars. At last, the currently existing asteroid ring appeared; in the “near” future, it will generate one more terrestrial planet with the mass in the range from the Moon to Mercury (at present, the biggest asteroid – Ceres – has the mass 50 times smaller than that of the Moon). Simultaneously, or before that, Mercury, having moved away from Venus, entered a circumsolar orbit under the influence of powerful gravitational attraction of the Sun. In such a way, the significant eccentricity of the orbit of Mercury (0.206) appeared, that is difficult to be explained otherwise.
The above pattern of origin of terrestrial planets can quite satisfactorily explain the values of their eccentricities. Since Venus was the first terrestrial planet to be formed, its eccentricity has decreased the most of all – down to 0.0068 by present time. Earth is a “younger” planet, and so its eccentricity is somewhat bigger – 0.0167. Mars is still younger; it was formed after Venus and Earth, therefore, it has a still larger eccentricity of 0.0934. Mercury, as a planet, is the youngest of all – it entered a circumsolar orbit from the orbit around Venus – and so it has the biggest eccentricity of 0.206.
This pattern does not conflict with other parameters of the planets. Venus and Earth, having been formed before Mars, are 8 to 9 times more massive than Mars. Mercury and the Moon have the least masses, since Mercury was a planet satellite and the Moon remains such; therefore, they have acquired only a little of cosmic precipitations in the form of solid celestial bodies: asteroids and meteorites. Earth is somewhat bigger than Venus by mass; this could be explained, first, by the fact that the former was, possibly, formed from a larger asteroid ring than the latter, and, second, by the fact that Earth has captured a greater number of asteroids and small planets than Venus, the former being a sort of shield for the latter. Mercury and Venus have smaller slopes of equatorial planes to the orbital planes: 1° and 2° respectively, while Earth and Mars have 23°26’ and 24°48’ correspondingly. This scheme, apparently, does not conflict with inclinations of orbital planes of terrestrial planets to the equatorial plane of the Sun. However, it absolutely cannot explain the fact that Venus rotates in reverse direction, while Earth – in forward one. Besides, the paces of growth of the masses of terrestrial planets are, obviously, excessively high in comparison with those of giant planets. It seems to the author that the hypothesis of origin of Venus, Earth and, possibly, Mars from the silicate cores of giant planets, and Mercury, the Moon and, perhaps, large asteroids – from the satellites of giant planets is more preferable.
If the terrestrial planets have descended from the cores of giant planets indeed, then one might suppose that they, when being the cores, had greater densities than they have today owing to monstrous pressure of tremendous atmospheres. In the course of loss of atmospheres, the process of expansion and decompression of the cores took place. If this expansion happened slowly enough, then, even before the complete decompression of the cores, the hard lithosphere could be formed in the outer regions of the cores; during the subsequent decompression and expansion of silicate cores (later – silicate planets) this lithosphere could be broken into parts, i.e. lithospheric plates. In such a way, the continents and oceans could be formed; the latter increased later in process of expansion of planets owing to the fall of cosmic precipitations.
When considering the issue of origin of satellites, we have said that the largest satellites of the planets, except Triton, are located on the middle of the sequences of planet satellites. We can see the same for the sequence of planets: the largest planet – Jupiter – is located in the middle of the planets. And the explanation of such a phenomenon is the same: the nearby planets lost a significant part of their substance, like satellites, and became multiply smaller, the more so as they, in contrast to the satellites, lost not only ice, but also gaseous component: hydrogen and helium.
But if we consider the terrestrial planets only, then we would find the same regularity: the largest planet (Earth) is located in the middle of the sequence of terrestrial planets, and not in the beginning of it, near the Sun, where it would seem to be. If we proceed from the assumption that all the terrestrial planets are formed from asteroids, or if Venus and Earth had been generated from silicate cores of giant planets and then expanded at the expense of asteroids, while Mercury, the Moon and Mars were formed from satellites (the latter two – from the satellites of Jupiter), then the explanation is quite simple; we have discussed it above.
The difficulty appears, if we suppose that Mars had been formed from silicate core of a giant planet as well. This could be explained, apparently, by the fact that the terrestrial planets expand quicker than the silicate cores of giant planets do, since the density of gas-dust matter during galactic winter increases in the course of approaching the Sun. That is why the masses of Venus and Earth are by far larger than that of Mars that became a terrestrial planet and approached the Sun relatively recently. And the expansion of terrestrial planets at the expense of asteroids takes place quicker with the increase of the distance to the Sun. Therefore, the mass of Earth is more than that of Venus. In the future, Mars, being a younger planet, will expand quicker than Earth and Venus; it will overtake them by mass and dimension. Besides, all the Solar System will expand in the course of time, so that when, for example, Jupiter loses all its gaseous and ice component and turns to the fifth terrestrial planet, it will have a slightly greater mass than Mars had, being born out of a giant planet. And when Saturn becomes the sixth terrestrial planet, it will have a little greater mass than the new-born Jupiter; the latter fact could, at least – partially, explain why Earth has a greater mass in comparison with Venus.
7. Origin of comets
We have seen above that the terrestrial planets descend from the giant planets or their satellites or asteroids, while the giant planets – from the ice planets. The ice planets and asteroids, as well as the small satellites descend from comets. Consequently, comets are the initial stage of development of all the celestial bodies. So where do they themselves come from?
One might suppose that there are two ways of origin of comets in the Solar System. Small comets are being formed predominantly within the Solar System, mainly at its periphery, where the number of them amounts, apparently, to many billions and trillions. Comets, circling the Sun in different directions with different orbit inclinations and eccentricities, often collide with one another, being split into smaller pieces. This process of disaggregation of celestial bodies is, of course, a secondary one together with the main process of consolidation of celestial bodies, but it plays an important role in the evolution of the celestial bodies. As a result of splitting the comets, a number of smaller formations – tiny comets and meteoric bodies – appear; the latter, expanding gradually at the expense of scooping the diffuse matter, grow and turn to new comets. In such a way, comets secure their new generation.
However, we might assume that, along with tiny and small comets at the periphery of the Solar System, there are also big comets that, probably, could give birth to a part of ice planets. These comets could be of another origin. They could enter the circumsolar orbits from the orbits around the centre of Galaxy owing to deceleration in gas-dust environment during galactic winters.
A galaxy could be regarded as a giant star-planet system, around the centre of which, together with stars, a great number of other, smaller bodies circulate. At that, in the Galaxy, like in any other star-planet system (including the Solar System), there is a regularity that the number of smaller celestial bodies is greater than the number of larger ones.
This regularity is confirmed by the following facts. First, the number of silicate planets and large satellites in the Solar System is greater than the number of giant planets, while the number of asteroids and comets is by far greater than the number of planets and large satellites. Second, in all the galaxies, the number of stars of medium mass, like the Sun, is multiply greater than that of large stars of 5 to 10 Sun masses. Still smaller is the number of giant stars of several dozen Sun masses. On the contrary, there are a lot of dwarf stars. The smaller are the stars by mass and dimension, the greater is the number of such stars.
From this, one can draw a conclusion that in the Galaxy, along with visible stars, there exist a great number of invisible small and tiny bodies; dwarf infrared stars and giant planets, ice planets and comets. At that, the number of infrared dwarfs is greater than that of all the visible stars. The number of giant planets is greater than that of all the visible and infrared stars taken together. Still larger is the number of ice planets, but the greatest of all is the number of comets and meteoric bodies.
Some of these comets move along the orbits around stars and planets in various star-planet systems. But the overwhelming majority of comets and planets of the Galaxy move along independent orbits around its centre.
Getting to the gas-dust environment during galactic winters, comets begin to approach the galactic centre quicker than other celestial bodies do. They overtake larger bodies, cross their orbits and leave them behind, continuing their way to the centre of Galaxy. However, not all the comets manage to perform such an overtaking. Many of them, during this maneuver, pass too close to the large bodies – stars and planets – and fall onto their surfaces increasing their masses. But some comets could enter the orbit around the large body, being overtaken, the same way as some celestial bodies of the Solar System, approaching the Sun, transfer from a circumsolar orbit to an orbit around one or another planet, turning to its satellites.
Comets can also transfer from the orbits around the centre of Galaxy to the orbits around the Sun and other stars. It is possible that some part of comets (especially large ones) and, perhaps, some planets of the Solar System are of this very origin.
Since the celestial bodies in the part of Galaxy, where the Solar System is located, circle the galactic centre at the same angular velocity, the comets, changing galactic orbits for circumsolar ones, may change the direction of their circulation, but may not do this, in contrast to the celestial bodies of the Solar System that, apparently, necessarily change their directions of circulation in the course of such transitions. It seems that about one half of comets, changing the galactic orbits for circumsolar ones, should change the direction of circulation. At that, comets should have the most various inclinations of their orbits to the ecliptic plane. This fact can explain the wide diversity of inclinations and eccentricities of comet orbits.
One might suppose that the celestial bodies of the Solar System, that circulate the Sun in reverse direction or did it in the past, have come to the Solar System from galactic orbits. Along with a number of comets, these bodies include Uranus.
But let’s turn to comets. As we have said above, comets can be of two different origins. Smaller comets with forward circulation around the Sun descend predominantly in the Solar System from the smallest bodies being formed as a result of splitting comets during their collisions. Some part of the other, more massive comets with reverse circulation around the Sun, possibly, has come to the Solar System from the galactic orbits located near that of the Sun. The orbits of comets with reverse direction of circulation gradually turn around, their inclinations decrease. And the majority of ice planets, descending from the large comets in the course of growth of the latter, have already forward direction of circulation. Only the reverse direction of axial rotation of some ice planets tells us that these bodies previously circulated the Sun in reverse direction.
8. Origin of the Sun
When considering the issue of evolution of the Sun, we have said that the Sun had descended from an infrared dwarf that, in its turn, appeared from a giant planet. Still earlier, this giant planet had descended from an ice planet, while the latter – from a comet. This comet was born at the periphery of the Galaxy in one of two ways of origin of comets at the periphery of the Solar System. The comet, from which the Sun was formed many billions years later, was either generated as a result of splitting larger comets or ice planets during their collision, or came to our Galaxy from intergalactic space.
It is well-known that all the visible galaxies move. At that, they circulate around the centre of cluster of galaxies. Many galactic clusters may form their family – still larger star-planet system, than single galaxies and their clusters.
Between the galaxies, circulating around the joint centre of gravity, there are a lot of other celestial bodies, though their number is, apparently, less than that in the galaxies. These celestial bodies – stars, planets and comets – circulate, like galaxies, around their joint centre of gravity along their independent orbits. When, during their orbital motion, they sink into gas-dust environment, they begin to approach the joint centre of gravity along the spiral owing to the deceleration in this environment. However, they have different speeds of this approach. The larger are the bodies, the smaller are their speeds of approach. The largest is the speed of comets. As a result, comets overtake galaxies and single independent star-planet systems. Having overtaken them, comets either leave them behind, or are being captured by them. In the latter case, comets and other celestial bodies from intergalactic space either fall onto the surfaces of large celestial bodies: stars and planets, or enter new orbits – around the centers of galaxies or single star-planet systems, becoming their satellites.
In such a way, the periphery of the Galaxy periodically accept a great number of small celestial bodies (especially – comets) from intergalactic space, thereby compensating the lost of celestial bodies of the Galaxy as a result of capture of smaller bodies by larger ones. Therefore, in spite of the fact that all the stars gradually approach the centre and the plane of Galaxy, where, owing to this process, the concentration of stars is larger than that at the periphery, there are a huge number of stars and smaller celestial bodies at the periphery of the Galaxy.
One of such celestial bodies, having come to the Galaxy from intergalactic space, could give birth to our Sun. At that, “the Sun” of that period not necessarily represented a comet. The “ancestor” of the Sun, during its arrival into our Galaxy from intergalactic space, could be a comet, a planet, or even an infrared dwarf.
However, considering the mass of the Sun and its distances from the centre and the edge of Galaxy, we can suppose that the Sun turned from a comet to a planet at the periphery of Galaxy, not in intergalactic space. Then, in the course of its expansion, the comet turned to an ice planet, a giant planet, etc.
The comet, that later gave birth to the Sun, could also be formed inside the Galaxy from a small piece of a larger comet or an ice planet as a result of a collision of celestial bodies. But is such a collision possible?
If we take the overall number of stars in the Galaxy, this number being estimated at hundreds of billions, and divide it by the radius of Galaxy, we would get the medium distance between the two neighbouring star orbits. This distance is strikingly small in comparison with the distance between two neighbouring stars. For example, the distance between the Sun and its nearest stars – Proxima and Alpha Centauri – is about four light years. It is a huge distance. But the medium distance between two neighbouring star orbits is … 2 to 3 million kilometers only. If all the stars are located at their orbits in one and the same direction from the centre of Galaxy, they would almost touch each other by their edges.
Meanwhile, along with the stars, there is a huge number of invisible celestial bodies in the Galaxy; this number is multiply larger than that of the stars, at that, not only by number itself, but, apparently, by aggregate mass as well. And they circulate around the centre of Galaxy with different eccentricities and inclinations, as well as different directions of circulation, especially at the periphery of Galaxy. Besides, the celestial bodies at the periphery of Galaxy circulate at different angular velocities and, consequently, have different periods of circulation around the centre of Galaxy. But, the main point, all these celestial bodies approach the centre of Galaxy at different speeds, the latter being dependent on their relative decelerations. It is clear that the collisions between celestial bodies of the Galaxy should happen quite often, especially in the periods of galactic and metagalactic winters. These collisions result in both agglomeration and fragmentation of celestial bodies. Small pieces of larger celestial bodies give rise to new celestial bodies, including the smallest ones: tiny comets and meteors, that later generate new large comets. These comets, getting larger, turn to ice planets, then – to giant planets. The latter, expanding more and more, turn to infrared dwarfs that, in their turn, become visible stars, one of each being our Sun.
An interesting question may arise: are there large celestial bodies at the periphery of the Solar System, such as the giant planet Jupiter, or a still larger super-giant planet, or an infrared dwarf (one or several)? It seems that this question should be answered affirmatively. In fact, in the Galaxy, among the visible stars, there should be a great number of infrared dwarfs, as well as giant and super-giant planets, circling the centre of Galaxy along their circumgalactic orbits. There are such celestial bodies near the Sun as well, in particular on the outside, looking from the centre of Galaxy. Some of them could get inside a galactic branch together with the Sun. Since the infrared dwarfs and giant planets are subject to stronger deceleration in the gas-dust environment of the branch, they will slow down and approach the centre of Galaxy more rapidly, than the Sun. And so, the distances between them and the Sun will decrease. During a severe galactic winter, some of them will inevitably enter the sphere of attraction of the Sun and become its satellites.
[Table of contents] [Foreword]
[COSMOGONICAL HYPOTHESES] [EXPANSION OF CELESTIAL BODIES]
[DEEP DIFFERENTIATION OF SUBSTANCE. ORIGIN OF CONTINENTS AND OCEANS] [DECELERATION OF CELESTIAL BODIES IN GAS-DUST ENVIRONMENT]
[EVOLUTION OF THE SOLAR SYSTEM] [ORIGIN OF THE SOLAR SYSTEM]