The paths traced by the known Martian Trojans around L4 or L5 (crosses) relative to Mars (red disk) and the Sun (yellow disk). The dotted circle indicates the average Sun-Mars distance. Right: Enlargement of inset (dashed rectangle) showing the paths of the 8 L5 Trojans: 1998 VF31 (marked as “VF31” – blue), Eureka (red) and the 6 objects identified as family members (amber). The filled disks indicate the relative sizes of the asteroids. Eureka, the largest member, is about 2 km across. Figure credit: Apostolos Christou (E-mail: aac@arm.ac.uk)

Trojan asteroids are a fascinating thing. Whereas the most widely known are those that orbit Jupiter (around its L4 and L5 Lagrange Points), Venus, Earth, Mars, Uranus and Neptune have populations of these asteroids as well. Naturally, these rocky objects are a focal point for a lot of scientific research, since they can tell us much about the formation and early history of the Solar System.

And now, thanks to an international team of astronomers, it has been determined that the Trojan asteroids that orbit Mars are likely the remains of a mini-planet that was destroyed by a collision billions of years ago. Their findings are detailed in a paper that will be published in The Monthly Notices of the Royal Astronomical Society later this month.

For the sake of their study, the team – which was led by Galin Borisov and Apostolos Christou of the Armagh Observatory and Planetarium in Northern Ireland, examined the composition of Marian Trojans. This consisted of using spectral data obtained by the XSHOOTER spectrograph on the Very Large Telescope (VLT) and photometric data from the National Astronomical Observatory‘s two-meter telescope, and the William Herschel Telescope.