Mars moon may be an asteroid that was caught in the Red Planet's gravitational pull. At least one of the moons of the planet Mars, may not be a true moon but one of the asteroids from the belt between Mars and Jupiter, that got caught in the planet's orbit billions of years ago.

Scientists theorize that the moons of Mars, Deimos and the larger Martian moon, Phobos, could be asteroids that were captured by Mars billions of years ago. New research suggests that Mars' larger moon, Phobos, is likely an asteroid that trapped by Mars' gravitational pull. This is not far-fetched. Asteroids often break free from their host asteroid belts. Asteroids can be knocked from their normal orbits by collisions, gravitational perturbations and other random interactions.

Recently, astronomers matched the chemical makeup of the Mars moon Phobos' surface to a meteorite that struck Canada. The scientists believe that the moon of Mars has its origin as a carbon-rich, "D-type" asteroid. The scientists theorize that the asteroid drifted too close to Mars. One of the moons of Mars may be an asteroid that caught in the Red Planet's orbit. Recent scientific models of Phobos, one of the Mars moons, show that it may be a captured asteroid.

The two moons that orbit mars, Phobos and Deimos, were discovered in 1877. The origins of the moons of Mars have remained elusive. The surface of the Mars moons hint that the two moons might not have the same origin. The orbits of the two Mars moons are also different. Both of Mars' moons, Phobos and Deimos, are among the smallest moons in the solar sytem. There are two main schools of thought about where the pair of potato-shaped moons came from. Asteroids are a popular explanation in part because Mars sits at the edge of the solar system's asteroid field.

The models that are being studied were put together by an international team of astronomers using ultraviolet light reflected from the surface of Phobos. The scientists compared that to two asteroids that were found on earth, the asteroid 624 Hektor and the Tagish Lake meteorite, which exploded over Canada in 2000. So far, the studies show that the Mars moon has strong similarities to both asteroids.

In an email to Space.com, Maurizio Pajola of the University of Padova in Italy wrote "This provided more additional support for compositional similarities between Phobos and D-type asteroids."

Phobos is a tiny inner moon. It has a 7 mile radios. It orbits close to the planet. It runs very fast, circling Mars twice a day. The orbit is nearly circular, like it's siser moon, Deimos. Phobos has a very low density. This could mean that it has a highly porous interior. The scientists theorize that Phobos formed in orbit around Mars, possibly after an impact to the planet.

Studies of Phobos and Deimos surfaces show that they are similar to asteroids found in the asteroid belt between Mars and Jupiter that circle the sun. Phobos and Deimos are lumpy and disfigured, not spherical. This suggests they might resemble the chunks of rock in the asteroid belt.

Scientists postulate that Phobos and Deimos could have been captured by the Martian gravity.  most commonly help theory, based on the best evidence we have, is that our Moon formed when a large object impacted the Earth early in its formation. This impact caused a large amount of mass to be ejected into outer space.

Investigator Maurizio Pajola said "As you can see, the surface is showing one possible origin, while the orbit and maybe the interior are showing a different orbit."

The astronomers compared studies taken by the European Space Agency's Rosetta spacecraft and data from the USSR Phobos 2 spacecraft with the asteroid 624 Hektor. Pajola said, "I wanted to make a comparison between our Phobos spectra and a well-known D-type spectral behavior asteroid, like 624 Hektor is." 

The astronomers also compared the spectrum with models of the Tagish Lake meteorite. The meteorite also provided strong insights into D-type asteroids. Pajola said "The scientific community accepts Tagish Lake to be a D-type meteorite." The studies "present one more hint pointing toward Phobos being a possible D-type, captured-by-Mars asteroid."

Pajola said "I think that the final demonstration for Phobos being a captured asteroid or not will be only with a spacecraft dedicated to its complete and detailed study, and not only through spacecrafts dedicated to Mars studies, which then use their Mars-dedicated instruments to study Phobos when they have the possibility to orbit close to it."

Pajola has not offered the same conclusions to Deimos, pending studies. The next step would be to analyze a sample of the Mars moon itself. In October, Russia announced it intends to send a probe to Phobos by 2022.

The research was published in the Nov. 10 issue of the Astrophysical Journal.