Mars may have appropriated our lunar twin: how did it happen?



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The asteroid in question, called (101429) 1998 VF31, is one of all Trojan asteroids that share the orbit of Mars.

The Trojan is a celestial body that falls in gravitationally balanced regions of space near other planets at an angle of 60 degrees in front of and behind it.

Most of the Trojan asteroids we know share the orbit of Jupiter, but also other planets, including Mars and Earth.

(101429) 1998 Asteroid VF31 follows Mars as it orbits the Sun. Astronomers at the Armagh Observatory and Planetarium (AOP) in Northern Ireland discovered that the latter Trojan is different from the L5 Mars Trojans, which belong to the so called Eureka family.

Using a spectrograph called the X-SHOOTER on the 8m very large telescope (VLT) of the European Southern Observatory in Chile, the team studied how sunlight is reflected by relatives 101429 and L5 of the Eureka family of asteroids. It now appears that the 101429 and Eureka families are unrelated and spectral analysis shows that asteroid 101429 is much closer to home.

“The spectrum of this particular asteroid appears to be an almost lifeless ring for those parts of the Moon where there is an open base, such as craters and mountains,” explains Galin Borisov, AOP astrochemist.

While we can’t yet be sure why this is the case, the researchers say it is likely that this Martian Trojan originated somewhere far from the Red Planet and 101429 was an “original hard lunar crust relic fragment” .

If this is true, how long ago did the lost lunar twin become a trojan associated with Mars?

“The early solar system was very different from what we see today,” explains Apostolos Christou, the study’s lead author, astronomer AOP.

“The space between the newly formed planets was full of garbage and collisions were normal. Large asteroids constantly hit the Moon and other planets. The fragment of such a collision may have reached the orbit of Mars while the planet was still forming and was trapped in its cloud of Troy.

It’s an interesting idea, but scientists say it’s not the only explanation for 101429’s past. It is also possible, and perhaps more likely, that this Trojan is a fragment of Mars formed during a similar event, or it could simply be a normal asteroid that resembles the Moon due to radiation from the Sun and Earth’s atmosphere.

Further observations with even more powerful spectrographs can help to learn more about this spatial parenting problem.

The results of the study are published in Icarus.



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