According to a new study, the two moons of Mars, Phobos and Deimos, may have originated from a much larger moon that orbited the Red Planet billions of years ago.
There have been several theories over the years as to where the moons originated from. One popular hypothesis was that they were originally asteroids (because of the large amount of craters on their surfaces) that got caught by Mars’ gravitational pull. However, many questions arose over that theory because if they really were asteroids, they wouldn’t have an almost-circular orbit around the equator of the planet.
Another well-known hypothesis was that the moons may have been formed from a disk consisting of rocks and dust that could have orbited Mars when it was a very young planet. But again, there are more questions than answers regarding that idea as well, such as if there was a disk around Mars, one large moon instead of two smaller ones would make much more sense. Furthermore, if the disk was caused by a large cosmic impact that caused the massive Borealis Basin on Mars, it would have occurred during the early stages of our Solar System, and if Phobos was created during that time, it would have already crashed into the planet.
Phobos is moving towards Mars while Deimos is traveling further away. According to calculations, in about 39 million years, Phobos may crash into Mars or get ripped apart by the planet’s gravitational pull.
And now, a new theory has been presented that suggests Phobos and Deimos were created from the remains of a much larger shattered moon. Based on data collected by NASA’s InSight Lander, experts were able to look at the moons’ orbits and it is believed that they may have intersected sometime between 1 billion and 2.7 billion years ago which would suggest that they both came from a larger moon that shattered from a possible massive impact.
In an interview with Space.com, Amirhossein Bagheri, who is a planetary science researcher at the Swiss Federal Institute of Technology in Zürich as well as the lead author of the study, said, “I find the idea that Mars used to have a larger moon, which was hit by one of the many objects that has been rushing towards it, quite exciting and surprising.”
In addition to forming the two smaller moons, some of the shattered pieces from the larger body may have crashed down on Mars. “Mars’ surface is peppered with impact craters and many of them are estimated to have ages within the time period we compute for the disruption event of the earlier moon,” Bagheri explained.
The study was published in the journal Nature Astronomy where it can be read in full.