The cameras on NASA’s Curiosity rover usually look down at the rocks on Mars, divining clues in the minerals of what the planet was like billions of years ago.
Sometimes though, the rover also looks up, and in March it spotted two eclipses (eclipsi?).
Eclipses on Mars are not as total as those on Earth where the moon completely blots out the sun. The two moons of Mars are tiny. Phobos is 7 miles wide while Deimos is even tinier, just 1.5 miles in diameter. They only partially block the sun when they pass in front of it.
The camera on Curiosity’s mast is equipped with solar filters that allow it to look directly at the sun and photograph eclipses. On March 17, Curiosity observed Demios eclipsing the sun. Nine days later, it also spotted Phobos passing in front.
The observations by Curiosity, and by earlier NASA Mars rovers, Spirit and Opportunity, enable more precise pinpointing of the moons’ orbits, which are jostled around by the gravity of Mars, Jupiter, and even each other.
Although Phobos and Deimos are small, the details of their formation are of considerable scientific interest. Japan’s space agency plans to send a spacecraft to the two moons within the next decade. The Mars Moon Exploration probe, or MMX, will collect samples and return them to Earth for study. A panel of scientific experts recently approved the sample-return phase of the mission.