Unsolved mystery: Astronomers have put forward a new theory regarding the origin of Mars' moons (photo).

Scientists believe that the moons Phobos and Deimos are remnants of an asteroid that approached too close to the Red Planet and was torn apart by Mars' gravity. This new explanation for the origins of the Red Planet's moons may resolve a long-standing debate regarding their formation. The study has been published in the journal Icarus, as reported by IFLScience.

The origins of Phobos and Deimos, Mars' two moons, have long puzzled researchers. One theory suggests that they are asteroids captured by Mars' gravitational pull. Another theory posits that a large asteroid collided with the Red Planet, sending debris into space from which the two moons formed. However, both theories have their shortcomings.

The authors of the new study, based on computer simulations, concluded that a very large asteroid passed extremely close to Mars in the distant past. As a result, the planet's gravity tore it apart, and Phobos and Deimos formed from some of the debris of this asteroid.

This explanation addresses the main issues of the two existing theories regarding the origins of Mars' moons. Phobos and Deimos are composed of material that resembles that found in asteroids more than the crust of Mars. On the other hand, the moons have circular orbits aligned with Mars' equator, which is quite unusual for objects captured by the planet's gravity.

Scientists believe that if a very large asteroid destroyed Mars, a ring of debris similar to Jupiter's rings would have formed around the planet. All this debris would orbit in a circular pattern and have a similar composition. Although some asteroid debris, as shown by the simulations, was still ejected further into space or fell onto the surface of the Red Planet.

Initially, the debris collided with each other, breaking apart while orbiting Mars, but over time, gravity caused some of these fragments to start clumping together, leading to the formation of Mars' two moons.

In 2026, the Japanese spacecraft Martian Moons eXploration (MMX) will be sent to study Phobos, which is expected to provide more information about the composition of this moon. The spacecraft will also investigate Deimos, albeit to a lesser extent.

The authors of the study state that if new data show that both moons have very similar compositions, the proposed theory will be confirmed.

Although simulations also indicate that only one moon could have formed from the asteroid debris around Mars, which then collided with the planet, and from the ejected material, a new disk of debris was created. From this disk, Phobos and Deimos emerged. In this case, their composition may include some elements of the Martian crust.