The Mars Gap Hypothesis

I have thought of a way to estimate the amount of matter that must have been in the Asteroid Belt at one time.

Our Solar System was formed from a star that exploded into a supernova. Most of the debris from the explosion condensed into our sun. Most of the rest, composed mostly of heavier elements that had been cooked up in the star from the original lighter elements of the universe by fusion, condensed into the planets. Matter that was thrown in all directions by the explosion began orbiting the sun in orbits that were perpendicular to each other gradually came together by collision and gravitational capture until the planets were formed and one general plane of planetary rotation around the sun became predominant.

Logic tells us that it would be a small planet that would form closest to the sun. This is because this closest planet would experience a stronger pull of gravity from the sun than more distant planets. The distance from the center of the planet at which the pull of the sun's gravity would be less than that of the planet's gravity would be shorter than it would be for the other planets. Thus, much matter in space that would have become part of the planet if it were further from the sun would be prevented from doing so by the gravity of the sun.

This means that planets should increase in size as we move outward from the sun because the gravity of the sun will be less competition and also because the outer planets sweep over a wider area of space in their orbits, enabling them to come in contact with more matter that can be captured by gravity. On the other hand, debris will become more and more scarce as we move away from the site of the supernova explosion so that planets should become larger going away from the sun before reaching a certain peak and then diminishing in size.

Indeed this is exactly what we observe in the Solar System.

Moving outward from the sun, the planets get progressively larger in size until we reach Jupiter. Then, they get progressively smaller. Notice that the size ratio of Venus to Earth before the peak is almost identical to that of Uranus and Neptune after the peak. Keep in mind that we must count planets and their moons together and that the outer planets would not be so large if they were closer to the sun because their vast oceans of liquid methane and ammonia would boil away in the heat of the sun. You may notice that our Solar System fits this model perfectly with the exception of one planet, that of Mars.

The Kuiper Belt, debris in the outer reaches of the Solar System, exists because the lack of gravity there slows down formation. In a similar way, the Asteroid Belt, between the orbits of Mars and Jupiter, represent the early Solar System frozen in time by Jupiter's gravity. Most asteroids are much closer to Mars than to Jupiter.

I see a different origin for the icy bodies in the Kuiper Belt and Oort Cloud, in the outer reaches of the Solar System, as we saw in the posting on this blog "New Thinking About The Origin Of Comets And Water". The ice of the outer reaches of the Solar System originated from a nova, the blasting off of the outer layers of the star which preceded the sun, before the entire star exploded from the center as a supernova and scattered it's matter across space. Much of the mass came back together by gravity to form the sun, which we know is such a second-generation star, and the Solar System. But the icy matter of the outer reaches of the Solar System originated with the lighter molecules, such as water and salt, that were scattered from the higher starting point of the nova which preceded the supernova.

In the model of the Solar System that I am presenting here, the asteroids must be considered as the matter which would have been a part of Mars, if not for the gravity of Jupiter preventing it from coalescing. Mars should have actually been larger than the Earth-Moon System and it's two small irregularly-shaped moons, Phobos and Deimos, must be asteroids that were captured by Mars' gravity.

Mars is composed of those asteroids which were far enough from Jupiter that it's gravity did not prevent them from coalescing into a planet. The asteroids are far enough from Jupiter that they are not pulled in by it's gravity but close enough that it's gravity can prevent them from coalescing into a planet. Mars is further from Jupiter than the asteroids and is far enough that it's component fragments were not prevented from coalescing into a planet by the gravity of Jupiter.

This is exactly the same pattern that can be seen in the rings of Saturn. There is an imaginary line around Saturn called the Roche Limit. Outside this limit debris coalesced into Saturn's moons. But inside this limit, pieces of ice and other matter was prevented from coalescence by the planet's gravity and was gradually lined up in the same plane by mutual collision. The result is the spectacular rings of Saturn. The three other largest planets all have much fainter rings for the same reason.

The Asteroid Belt is not permanent. the orbits of asteroids can be destabilized by Jupiter's gravity when they are ahead of Jupiter in the orbital trek around the sun. Many former asteroids have struck the Earth or Moon after their orbits have been destabilized in such a way.

This hypothesis gives us a way to estimate how much matter must have been in the Asteroid Belt originally. According to my calculations, if Mars were as much bigger than the Earth-Moon System as the Earth-Moon System is bigger than Venus, Mars would be 7.8 times it's present volume. I take this to mean that the amount of matter that was once in the Asteroid belt could be estimated to be about 6.8 times the present volume of Mars.