Scientists discover Moon-like asteroid hiding behind Mars

Scientists from the Armagh Observatory and Planetarium (AOP) have discovered a Moon-like asteroid hiding behind Mars

The international research team, led by scientists at the Armagh Observatory and Planetarium (AOP), supported by the UK Science and Technology Facilities Council (STFC), believe the asteroid known as (101429) 1998 VF31 dates back to the early years of the solar system and the giant impacts that formed our Moon and substantially re-shaped the Earth.

Researchers involved in the discovery have been studying Mars’ Trojans, including the lunar-like asteroid, to understand if there are Trojan asteroids orbiting the Earth.

Trojan asteroids

Trojans are a large group of asteroids that share an orbit with a planet or moon and are of great interest to scientists because they represent leftover material from the formation of the planets and can tell scientists a great deal about how the planets came into being.

To their surprise, the team found that 101429’s best spectral match was not with other small bodies but with our nearest neighbour, the Moon.

The mini Moon’s origin

Though the unusual object’s origin is still a mystery, the researchers have a few theories. One of those is why the asteroid looks like the Moon – because it came from the Moon.

Lead author Dr Apostolos Christou, from AOP, explains:

“The early solar system was very different from the place we see today. The space between the newly-formed planets was full of debris and collisions were commonplace.

“Large asteroids – we call these planetesimals – were hitting the Moon and the other planets. A shard from such a collision could have reached the orbit of Mars when the planet was still forming and was trapped in its Trojan clouds.”

However, the more likely scenario is that the object came from Mars itself. Mars was pummelled by impacts early in its history and a colossal impact could have sent the lunar-like asteroid into Mars’ orbit.