The Absolute Cosmos: This asteroid could be our Moon’s long lost twin

An international team of scientists has discovered an asteroid trailing behind Mars with a composition strikingly similar to that of our Moon. The space rock could be a bit of ancient debris resulting due to massive impacts that created Moon and other rocky planets of solar system.

The asteroid is called (101429) 1998 VF31 and it is part of a group of Trojan asteroids, following the orbit of Mars.

Trojans are type of asteroid that are trapped within gravitationally balanced regions of space around celestial bodies (planets or moons), located 60 degrees in front of and behind the celestial body.

Mostly, the known Trojan asteroids share Jupiter’s orbit, but other planets such as Mars and Earth also have them. It is much easier to look for Trojans of Mars than our planet Earth, as they always lie close to Sun in the sky where it is hard to detect them.

About ten years ago NASA’s WISE space telescope found an Earth Trojan 2010 TK7, but later it was revealed to be a temporary visitor from the asteroid belt between Mars and Jupiter.

Trojans are of significant importance to scientists as they are the leftover products of our solar system’s early evolution and formation. Scientists have been studying Mars Trojans to understand more about the terrestrial planets (inner planets) of our solar system.

To measure the composition of Trojans of Mars, the team used X-SHOOTER spectrograph installed on European Southern Observatory’s (ESO) Very Large Telescope (VLT) in Chile.

X-SHOOTER is used to examine the reflectance spectrum of an asteroid, i.e. how the surface of the asteroids reflect sunlight of different colors.

One such Trojan observed by team was asteroid 1998 VF31. Scientists combined the data collected by VLT with that of previous data collected by NASA’s Infrared Telescope facility in Hawaii.

The team found that 1998 VF31’s spectrum did not match with any specific type of asteroid, instead, to much of their surprise it showed a spectral match with our very own natural satellite- Moon.

According to scientists asteroid 1998 VF31 looks exactly same for lunar parts where there is exposed bedrock such as mountains and crater interiors.

However, they aren’t sure from where such an unusual object have come? There are quite a few possibilities about the origin of the asteroid.

First- It is possible that asteroid 1998 VF31 could be just another piece of space rock which became similar to Moon because of exposure to solar radiation.

Second- it may have actually came from Moon, as scientists’ explain- the early solar system was lot different from today’s solar system. At that time collisions were quite common as the space between newly formed planets was full of debris.

Large asteroids/planetesimals were continuously colliding with moon and other planets. A piece from one such collision could have reached Mars orbit and got trapped in its Trojan clouds, when the red planet was still evolving.

Third- and perhaps the most likely case is that asteroid 1998 VF31 came from Mars itself. The spectrum analysis of 1998 VF31 shows that it is rich in pyroxene mineral. Pyroxene is found in outer layers(crust) of planet sized objects.

In the early history of solar system Mars was also hammered by impacts, much like Earth and Moon. Those impacts could have easily pushed 1998 VF31 to the planet’s L5 Lagrange point.

While 1998 VF31 is pyroxene rich, the other asteroids (collectively called Eureka family) at Mars’ L5 are mostly olivine mineral, which is found deep in a planetary mantle.

According to scientists there could be more asteroids out there that look exactly like 1998 VF31. Further and more powerful observations will shed more light on its origins and compositions.

The study was published in Icarus.

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