이 에피소드에 관해
The tiny moons of Mars are hard to explain. Scientists aren’t sure how they formed and how they wound up in their current orbits. But a Japanese mission that launched this month could settle the conundrum.
The mission is MMX – Mars Moons Exploration. It will scan both Phobos and Deimos – chunks of rock the size of a small city. And it will land on Phobos, gathering samples for return to Earth.
Both moons are dark, like a class of asteroids. In fact, astronomers long suspected they were captured asteroids. In this scenario, rocky “leftovers” from the birth of the planets flew close to Mars. The planet was surrounded by a cloud of gas and dust. As Phobos and Deimos passed through it, the cloud acted as a brake, slowing them enough for Mars to grab them.
But it’s not easy for a planet to capture an asteroid. And the orbits of the moons aren’t like those of the captured asteroids of the giant outer planets.
So scientists came up with another model: a giant impact. A massive space rock could have slammed into Mars, blasting out material that formed a ring around the equator. The debris coalesced to form several small moons. Phobos and Deimos are the only survivors.
In yet another scenario, Mars captured a single large asteroid. It was sheared apart by Martian gravity, creating a ring that gave birth to Phobos and Deimos. MMX will arrive at Mars next year – a big step toward solving the mystery of the Martian moons.
Script by Damond Benningfield
