Scientists from the Japanese space agency JAXA spotted two large red rocks in the asteroid belt between Mars and Jupiter that should not be there. The rocks have been described as having organic matter on their surfaces that could have come from an area past Neptune. That’s a long distance away from the asteroid belt, so how did they get there?
When our Solar System first formed around 4.5 billion years ago, it was very disorderly with tons of space rocks flying around – most of which ended up in the asteroid belt between Mars and Jupiter. But two of those rocks, which JAXA astronomers have named 203 Pompeja and 269 Justitia, are quite peculiar and very different from other rocks in the belt. Measuring 70 miles and 30 miles across, they were found orbiting approximately 2.7 and 2.6 times the distance of Earth to our sun.
The rock named 203 Pompeja looks as though it is structurally intact, while 269 Justitia appears as though it is just a piece of a once-larger object. Based on the stability of their circular orbits, it is believed that they have been in the asteroid belt for a very long time.
It was their red coloration that really caught the attention of astronomers as they are the only two red rocks in the asteroid belt. Space rocks that are located in the inner part of our Solar System reflect more of a blue light, while those in the outer areas are red due to a large amount of organic matter.
In an interview with The New York Times, MIT's Michaël Marsset described the organic matter on the rocks by explaining, “In order to have these organics, you need to initially have a lot of ice at the surface,” adding, “So they must have formed in a very cold environment. Then the solar irradiation of the ice creates those complex organics.”
As for how they ended up in the asteroid belt, there are several different theories such as when Jupiter traveled inwards while Saturn, Uranus and Neptune moved outwards over hundreds of millions of years, some space rocks (possibly bits of planets) were thrown all over the place and ended up in the asteroid belt. If this is correct, this would provide astronomers with proof of planetary migration during our Solar System’s early years.
The research was published in The Astrophysical Journal Letters where it can be read in full.