This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The Earth got its moon when a small planet collided with our planet more than 4 billion years ago. This impact hurled molten rock into space, which eventually coalesced to form the satellite we can see every night from across our planet.
But what of our neighbor, Mars? The red planet has two small, irregularly shaped moons called Phobos and Deimos. There are several theories on how these natural satellites formed, but no clear front-runner.
Soon, a Japanese-led space mission called Martian Moons Exploration (MMX) will begin its hunt for the answer. On Monday, Oct. 19, MMX is due to lift off on an H3 rocket from Tanegashima Space Center in southern Japan. The mission will aim to land on Phobos and collect a sample of soil.
The spacecraft will then send this payload to Earth for study in laboratories. Of the two Martian moons, Phobos is the larger and orbits closer to the planet. It has a mean diameter of 22.2km (13.8 miles) and a mass of 10,637 million million kg.
Deimos has a mean diameter of 12.5km (7.8 miles) and a mass of 1,480 million million kg. The moons were discovered during a six-day window in 1877 by the American astronomer Asaph Hall, who was working at the U.S. Naval Observatory in Washington, D.C.
Two main hypotheses dominate discussions of how Mars got these moons. The giant impact theory proposes that a celestial object a third of Mars' size hit the planet early in its history, ejecting material into space. The general mechanism is similar to how scientists think Earth's natural satellite formed.
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