Phobos and Deimos, the mysterious moons of Mars
Representation of Mars and its two moons: Phobos and Deimos
Discovered only a few days apart, Phobos and Déimos are true twin sisters, with very different destinies: if Déimos emancipates itself from Mars by moving away from it, its little sister Phobos tends rather to approach it… dangerously.
If their etymology is well known, Phobos "fear" and Deimos "terror" being the twins that Ares (Greek counterpart of the Roman god Mars) had with Aphrodite, their origin is a source of disagreement between scientists around the world. Their common characteristics with type C asteroids, primitive bodies dating from the genesis of the solar system, are numerous: their albedo, the amount of light they reflect, is very low and their density is very similar. This has long led scientists to believe that Phobos and Deimos were two early celestial bodies that were pulled to Mars from the asteroid belt with the help of Jupiter's gravitational pull. However, their overly circular orbit does not match that of a captured object,
Recently, an international team of researchers came up with a completely different cosmogonic answer to the origins of the two moons, published in the Journal of Geophysical Research: Planets . These hypotheses advance the argument of the collision of Mars with a giant celestial body as the origin of Phobos and Deimos. A more violent birth, imaged by the impact of this object the size of Ceres, sending debris of rocks and dust into space. This rubble would then have gathered under the gravitational effect of the red planet to form Phobos and Deimos.
If they were born from the same event, these two moons, which are among the smallest in the solar system, do not have much else in common: the paths they take are very different. For one of them, the future would even be just as tragic as her birth.
PHOBOS, A TWIN WITH A CRUEL DESTINY
Average diameter: 22 km
Martian altitude: 9,000 km
Orbital speed: 7,700 km/h
Revolution around Mars: 8 hours
It was discovered on August 18, 1877 by the American astronomer Asaph Hall, a few days later than its big sister Deimos. Traveling 6,000 km above the Martian surface, Phobos is the closest satellite to its planet in the entire solar system. Its surface, which does not have a completely circular shape, is covered with a dusty powder about 1 meter thick and is dotted with craters and scars, caused by impacts of meteorites. The best known is the Stickney Crater , whose name refers to Asaph Hall's wife, Angeline Stickney, and which sees its diameter reach 9.5 km. The other grooves strewn on its ground are for the scientists the beginnings of multiple cracks of the moon, whose fate seems already sealed .
Representation of the Stickney crater, on the surface of Phobos.
While the forces of gravity lead our Moon to gradually move away from the Earth, for example, Phobos is in rebellion: it approaches Mars by about two meters every 100 years. A study carried out by NASA suggests that this rapprochement will cause the destruction of Phobos within 30 to 50 million years. The Martian moon will burst into pieces, its fragile structure not resistant to the deformations caused by the tides and the gravity of Mars, and will come crashing down on the red planet.
Source :websites