A giant impact solves the mystery of Mars' moon formation.
Unlike Earth, Mars has two moons, Phobos and Deimos. Both are small – the larger of the two, Phobos, is only 14 miles across while the other one, Deimos, is only 8 miles across, making them amongst the smallest moons found in our solar system.
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Because of their odd shapes and unique characteristics, Martian moons were widely believed to be asteroids. They might have nudged into the Mar’s orbit by the gravity of another planet, allowing the planet to capture those asteroids. Two separate and complementary studies, however, deny this theory. One suggests that Phobos and Deimos were created as a result of a giant collision between Mars and a protoplanet one-third its size. The second study explains how exactly these two natural satellites were formed after the collision.
The origin of Martian moons has been a longstanding mystery. The existing theory that these moons are captured asteroids is apparently convincing but it is unable to provide answers to several questions such as how did Mars made them orbit almost circular and equatorial after capturing them and how exactly they entered the Mars’ orbit.
Using cutting-edge technology, a team of international researchers has now presented a complete and logical scenario for the formation of Martian moons for the first time. Researchers suggest when the protoplanet hit Mars, it would have formed a very wide disk of debris around it. In the inner part of the disk, which was densely packed, large moons up to hundreds of miles in diameter clumped together. In contrast, in the outer part of the debris ring which was composed of primarily thin gas, it was difficult for this material to form moons.
At that time, Mars was surrounded by a group of approximately ten small moons and one enormous moon. But a few million years later when the debris disk dissipated, the gravitational tugs from one or more large moons from the inner ring caused most of the moons to back away including the very large moon. This left behind only two small distant moons, Phobos and Deimos. This explains why debris from such an impact created two small moons instead of one enormous like the Earth.
The other study supports the collision scenario on the basis of compositional diversity. The composition of Mars moons is not compatible with the matter of the planet and has signatures of outside materials.
Researchers suggest that the collision between the Mars and the primordial body took place 100 to 800 million years after the beginning of planet’s formation.
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