Two weird crimson asteroids someway migrated from the Kuiper Belt to the principle asteroid belt

When asked what color asteroids would be in the asteroid belt, most people probably cannot think of red. But that is exactly the color of two new asteroids that Hasegawa Sunao from JAXA and an international team of researchers have found. The catch is that the objects don’t seem to have come from the asteroid belt at all, but are most likely Trans-Neptunian objects that were somehow transported into the asteroid belt. How exactly they got there is still up for debate.

The two asteroids, known as 203 Pompeja and 269 Justitia, were originally thought of as D-type asteroids, are rich in silicates and carbon, and make up the majority of the Jupiter Trojan asteroids orbiting behind the giant planet. There is a group of these types of asteroids called the Kybeles, which form their own separate group of asteroids a little further outside the larger belt.

Distribution curve of the locations of different groups of asteroids.
Credit – Astronomical Image – NASA, Ryugu Image – JAXA, Hasegawa et al.

However, the spectral lines of the two new asteroids were “too steep”, which made them much more similar to the “centaurs” – a body larger than an asteroid but smaller than a planet orbiting between Jupiter and the Kuiper Belt. The reddish color they reflect indicates that there are organic compounds present on their surface, which is one of two different categories that centaurs can be – the other is “blue”.

These spectra make 203 Pompeiia and 269 Justitia unique in the asteroid belt, but they resemble their asteroid neighbors in other ways, such as their size (110 km diameter for Pompeiia and 55 km diameter for Justitia) and their orbit, which makes them exactly in the centers in the traditional asteroid belt. But why a Trans-Neptunian centaur should immigrate to the asteroid belt remains a mystery.

Artistic concept of NASA’s OSIRIS-REx spacecraft preparing to touch the surface of the asteroid Bennu.
Credits: NASA / Goddard / University of Arizona

One way to solve this puzzle could be to pay a visit. Hayabusa-2 and OSIRIS-REx are two recently successful missions that have visited asteroids and returned valuable material samples from their surfaces. Another mission to these unique asteroids would not be out of place as it could both provide a glimpse of how they landed there and help collect samples of examples of objects that otherwise only exist much further out in the solar system .

Currently, the discoveries are so timely that there are no plans for such a visit. However, there is still plenty of remote sensing force to guide them in making plans. There might be even more of these reddish objects in the belt that might be noticed first, given the increased attention this recent discovery received.

Learn more:
JAXA – When we’re ready to explore, how about these goals? Discovery of very red bodies in the asteroid belt that resemble trans-Neptunian objects.
NYT – 2 red objects were found in the asteroid belt. You shouldn’t be there.
Engadget – Two red objects between Mars and Jupiter could explain how the solar system was formed
Gizmodo – Astronomers discover two unusually red objects in the asteroid belt

Mission statement:
The spectra of the two red objects show a different curve than other objects in their vicinity in the asteroid belt.
Credit – Hasegawa et al.

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