Research suggests Mars formed in the asteroid belt
Earth and Mars are very different planets right now, but they are both small, rocky planets in the inner solar system. However, a new study suggests that Mars may also have origins other than Earth. Researchers at the Tokyo Institute of Technology say analysis of the composition of Mars supports the idea that it originally formed in the asteroid belt, then migrated to the inner solar system . It could change much of what we know about the early eons of our little corner of the cosmos.
The team, led by planetologist Ramon Brasser, began to study this based on the fact that Mars has a different isotope ratio than Earth; in particular chromium, titanium and oxygen. This could indicate that he originated from outside the inner solar system where he now resides.
From what we currently understand, the solar system formed when the disk of gas and dust around the young sun was compressed by gravity. Eventually, planets, asteroids, and comets developed. Scientists believe rocky planets exist closer to the sun because the solar wind blew most of the gas into the outer solar system where we see gas giants. It is not known whether the planets migrated to different orbits during this process, but evidence from exoplanets suggests it is possible. There are a lot of “hot Jupiters” out there – gas giants that orbit near their stars.
To assess Mars as a candidate for migration, the team first considered its makeup. They compared the analyzes of Mars with those of the Earth, the Moon and the asteroid Vesta. Mars, it seems, is very similar in composition to objects found in the asteroid belt between Jupiter and the current orbit of Mars.
This is not sufficient to support the claim that Mars migrated inward, so the physics of such a maneuver had to be taken into account. If Mars had formed in the asteroid belt, it would have encountered many objects smaller than itself. Simulations indicate that Mars would have reached its current size five to ten million years after the formation of the solar system. Interaction with the asteroids in the belt would have been a net loss of energy for Mars, and simulations predict that it would have slipped into a narrower orbit around the sun after around 100 million years. The rest of the planet’s history would have unfolded as we currently understand it: the sun is getting more intense, Mars is losing its atmosphere, and most of the surface water is drying up.
The next step is to run more simulations to see if any of them can better match the properties of Mars that we are currently observing. If scientists take Martian migration for granted, it could tell us a lot about the formation of all the rocky planets.