The Trojan asteroids of Mars, which travel with it around the Sun, may be the remnants of another planet that has not been able to form completely.
The young solar system was a much more hectic place than it is today. The star itself was not so stable, many more comets and asteroids, dust, planetesimals and the planets themselves moved around it. The remains of a small "extinct" planet were discovered by astronomers of the Northern Ireland planetarium Apostolos Christou and Galin Borisov.
In an article published by the Monthly Notices of the Royal Astronomical Society, scientists draw attention to the populations of Mars' Trojan asteroids. Gravitationally associated with the planet, they move with it in an orbit around the Sun, remaining at the points where the gravitational pull of the planet and the Sun is mutually balanced. Trojans are known from Jupiter, Earth and other planets, and a little less than a dozen of them have been found on Mars.
Hristo and Borisov used the X-SHOOTER spectrograph installed on the VLT telescope in Chile, as well as the Bulgarian Rozhen telescope for observations. The objects for work were the Martian Trojans (385250) 2001 DH47 and (311999) 2007 NS2, which scientists compared with another large object of this group - (5261) Eureka.
Eureka is the only Trojan asteroid on Mars to remain at L5 and orbit slightly behind the planet; the remaining 7-8 asteroids are in L4 and move ahead of Mars. They are separated by millions of kilometers, however, the composition of all three bodies turned out to be extremely close. The spectrum obtained in the visible, as well as near infrared and ultraviolet ranges, made it possible to classify the objects as asteroids of a rather rare class A, rich in olivine.
The authors of the article speculate about the possible reason for this proximity. Most likely, it is associated with the common origin of all three asteroids. All of them may be the remnants of a planetesimal - the "embryo" of the planet, which was formed once in the inner regions of the solar system, but could not grow to a full-fledged planet, and fell apart even before Mars itself was formed. Some of these fragments have survived to this day, as fossils of a species that did not survive any extinction.
Sergey Vasiliev