The two galaxies, Phobos and Dimos, were both discovered in 1877 and are named in Greek mythology after the sons of Aris (the Roman god of Mars, who was called Ares in Greek). Phobos means fear or panic and Dimos means fear.
They have long been thought to be asteroids captured by the planet’s gravity. Both appeared Carbonaceous chondrite in a combination that makes the asteroid black. However, scientists realized that the moons are in almost the same plane as the equatorial region of Mars. This means that they formed Mars at about the same time about 4.4 billion years ago.
Although they are both irregular, Dimos is a little more strange than Forbes – its orbit is tilted by two degrees.
“The orbit of Dimos with the equatorial region of Mars was not exactly in the plane, this was considered unimportant and no one tried to explain it,” said Matija said, lead author and researcher at the STI Institute. “But once we got a whole new idea and we looked at it with new eyes, Dimos’s orbit revealed his big secret.”
The cyclical fate of the moon on Mars?
Researchers looked to Forbes, which over time began to lose height as it interacted with Martian gravity. Eventually, its orbit will be very short and Mars will essentially tear it to pieces which form a ring around the planet. It is estimated that this will happen within 50 million years.
What if Mars once had another moon with the same fate? Over time, the rings will form new, more small moons in the seemingly endless cycle.
Something caused Demos to move away from the planet and it tilted – like interacting with another large moon.
Slightly larger than Dimos, Forbes Martian is just 3,700 miles above the surface – no moon in our solar system is close to its planet. Being so close, Forbes completed three orbits around Mars on one Earth day, and Demos, which is farther away, took about 30 hours to complete one orbit.
But if Forbes didn’t always exist, would Phobos? What if it gets bigger at once and goes through a few cycles where it goes from a moon to a ring and comes back again?
Researchers believe that Phoebus once had a grandfather 3 billion years ago who was known as Proto-Phobos – the small moon is now probably 20 times larger massive during a few lunar cycles, it becomes Phobos – this will explain why some researchers Believe that it was created about 200 million years ago.
A prominent ring around Mars pushed Proto-Phobos away from the planet. It also affected the resonance of Proto-Phobos orbits with Dimos and pushed it further away from Mars.
The Japanese space agency Jaxa planned to send a spacecraft to Phobos in 2024 to collect samples from the surface and return them to Earth. It may reveal more about the past of the moon.