Although Mars is much smaller than Earth, it has two moons. Deimos and Phobos were probably asteroids captured by Mars’ gravity. The red planet has also captured nine other small celestial bodies. These asteroids do not orbit Mars directly, but instead, orbit stable points of gravity on either side of the planet known as Lagrange points. These are called trojans, and they travel along Mars’ orbit about 60 ° ahead or behind Mars. Most of these trojans appear to have originated on Mars and were formed from asteroid effects on Mars. But one of the trojans seems to have a different origin.
We can understand the origin of small objects by looking at the spectrum of light emitted from their surface. Since each type of molecule has a unique spectrum, it is possible to identify the chemical fingerprints of each organism. For example, the Martian trojan all contains a mineral called olivine. Olivine is rare among asteroids but is relatively common on Mars. Therefore, the trojan is most likely originated from Mars.
But one of the trojans, simply named 101429, has a different spectrum. When a team of researchers recently looked at the infrared spectrum of 101429, they noticed it had traces of a mineral called pyroxene. This mineral is also found on the surface of the Moon. Given its spectral resemblance to that of the Moon’s Spectrum, it is most likely derived from the Moon.
Although that may seem a bit far-fetched, but it can be done. For example, we know that Mars’ debris was produced by effects that have drifted into Earth over time. There are a few meteors that are thought to have originated from Mars. In the early solar system, the Moon was bombarded, and fragments of the Moon may have reached Mars.
That said, we should be cautious when it comes to conclusions. Spectral comparison is not accurate enough to confirm the origin of the moon. Other bodies are also known to have pyroxene on their surface. All we know for sure is that 101429 has a different origin than other trojans on Mars.
Trojan asteroids exist near other worlds, such as Jupiter and Neptune. Together with Mars trojans, these celestial bodies can provide clues about the origins and history of the solar system. With this latest research, we know that even after planets form, there is a dynamic exchange of matter between worlds.
References: Polishook, David, et al. “Mars origin for Trojan asteroids on Mars.” Natural Astronomy 1.8 (2017): 1-5.
References: Christou, Apostolos A., et al. “Composition and origin of the L5 Trojan asteroid on Mars: Insights from spectroscopy.” Icarus 354 (2020): 113994.