On August 12, 1877, Washington-based astronomer Asaf Hall discovered the first of two satellites of Mars - a little later, this huge shapeless piece of stone will be named Deimos, "horror." A few days later, on August 18, a second, flying closer to the planet, Phobos, "fear", will appear in his telescope. So for earthlings, these satellites have an anniversary - 140 years.
A couple of old potatoes
In fact, Phobos and Deimos are somewhat older - they are not 140, but at least 4.5 billion years old, and they are most likely older than Mars itself. They are not “native” children of Mars, but adopted children - large asteroids that fell into the planet's gravity zone and could not get out of it. And the mythological Phobos and Deimos are the sons of the god of war Ares and the goddess of love Aphrodite; it is interesting that their sister was Harmony - the goddess of harmony and a happy marriage.
Deimos and Phobos in ancient Greek representation
The size of Deimos is small - on the longest side it is 15 km, the distance from the Moscow Ring Road to Lobnya. The shape of its companion most resembles an ugly potato. Phobos is bigger and rounder - 27 km, the road to Ramenskoye.
Deimos. Photo: NASA
Phobos is gradually approaching Mars and will soon fall on it. There are two main versions - that the fall will occur in 43 million years and that the poor fellow "Fear" will fall to pieces in 10-11 million years due to gravitational disturbances from Mars. But his cautious brother "Horror", on the contrary, is gradually moving away from the red planet.
Promotional video:
The Opportunity rover watches Phobos pass in front of the sun's disk. The satellite is so close to Mars that it looks huge. Animation: NASA
Jump to Mars
It is because of its unusual orbit and high rotation speed that Phobos has long been considered … hollow inside, that is, artificial! Subsequently, however, the unusual physical properties of the satellite were explained by the tidal action of Mars. But there is still a large group of amateurs who believe in the hollow Phobos left here by aliens. They call the stripes on Phobos welds and patches.
Globe of Phobos. Museum of Cosmonautics, Moscow. Photo: Dmitry Gabyshev / Wikimedia.org
A person can never stand on Phobos, looking at Mars overhead. The fact is that from the side of Mars there is no gravitational force on the satellite - more precisely, the small gravity of the satellite and the significant gravity of the planet are balanced. This leads to weightlessness. Thus, with a good push off, it is theoretically possible to jump from Phobos to Mars.
And they finished their flight in the Pacific
The fact that Mars has two satellites was first described not by astronomers, but … by writers. First, in the story "Micromegas" Voltaire mentioned the two moons of Mars, "eluding the eyes of earthly astronomers." And then Jonathan Swift in "Gulliver's Travels" through the lips of scientists on the flying island of Laputa reported about two satellites, indicating even the period of their revolution around Mars - inaccurate, but quite close to reality.
The Flying Island Laputa from Gulliver's Travels was itself an entertaining celestial body. Drawing by Jean Granville
Deimos seems so smooth because it is completely covered in regolith - a "stone blanket" of fine dust. In fact, it is dotted with craters from the constant bombardment of small asteroids. And not very small: the diameter of the Voltaire crater is almost two kilometers! A body of this magnitude falling to Earth would cause a worldwide catastrophe, but lifeless Deimos doesn't care. But even more impressive is the 9-kilometer Stickney crater on Phobos.
Stickney Crater. Photo: NASA
All expeditions to Phobos so far have ended in failure. The Soviet "Phobos-1" and "Phobos-2", designed to deliver the descent vehicles to the satellite, did not reach their goal. In 2011, the Russian "Phobos-Grunt" could not reach the calculated trajectory and for several weeks frightened the entire planet, circling above it in a low unpredictable orbit. Now its fragments rest in the Pacific Ocean.
Model of the late "Phobos-2" in the Moscow Polytechnic Museum. Photo: Vladimir Galin / Wikimedia.org
DROZDOV PAVEL
