Mars atmosphere may lie on the surface of its moon Phobos

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Martian moon Phobos may hold some secrets about how Mars was formed. According to the new study, The moon's orbit of Mars gradually degrading over the aeons brings it through charged molecules (ions) of oxygen, carbon, nitrogen and argon that Mars has been shedding from its atmosphere for billions of years. Some of those ions might remain on Phobos surface.

The study was based on observations from NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission. The spacecraft also crosses the orbit of Phobos five times every Earth day.

MAVEN's Suprathermal and Thermal Ion Composition (STATIC) instrument measured Martian ions in the orbit of Phobos, allowing scientists to then estimate how deeply these ions would plummet into Phobos surface if they were to collide with the Martian moon. The researchers estimated that the ions dug no more than a few hundred nanometers deep, or 250 times shallower than the width of a human hair.

Researchers says that, we knew that Mars lost its atmosphere to space, and now we know that some of it ended up on Phobos. If somebody could study Phobos up close no one has been able to get there yet ion studies there could shed more light on the mystery of why Mars has lost so much atmosphere, and the associated question of when water stopped flowing on the planet's surface. Water is a key ingredient of life, and resolving the debate will help scientists better understand the Red Planet's chances for life. While MAVEN has been looking at atmospheric loss on Mars for years, Phobos would provide another perspective.

According to NASA, Phobos is tidally locked to Mars, like Earth's moon is locked to Earth, thus always showing the planet only one side. As a result, the rocks on the near side of Phobos have been bathed for millennia in Martian atoms and molecules. Nénon's research shows that the uppermost surface layer of Phobos near side has been subjected to 20 to 100 times more wayward Martian ions than its far side.

According to the NASA statement, Studying Phobos for clues about the Martian atmosphere has precedent, a lot closer to home. Earth's moon also has a record of atoms from both the sun and the Earth, which showed up in samples from the Apollo human landing missions of the 1960s and 1970s.

Phobos is a airless moons such as twin Martian moon Deimos, and Earth's moon are subject to little erosion since there is no substantial atmosphere, or surface processes like wind and water. This slowly changing surface of these moons thus provides a precious record of solar system history.

Besides looking at the atmosphere of Mars, MMX may also help scientists understand the origin story of Phobos and Deimos. The tiny moons may be asteroids captured by Martian gravity, satellites of Mars formed at the same time as their parent planet, or leftovers from a cosmic collision.

A paper based on the new study was published Feb. 1 in Nature Geoscience.