火星上空的火卫一
2023年7月31日 Phobos over Mars Image Credit: ESA, DLR, FU Berlin, Mars Express; Processing & CC BY 2.0 License: Andrea Luck Explanation: Why is Phobos so dark? Phobos, the largest and innermost of the two Martian moons, is the darkest moon in the entire Solar System. Its unusual orbit and color indicate that it may be a captured asteroid composed of a mixt...