Here’s What a Solar Eclipse Looks Like on Mars
Solar eclipses on Earth are rare and wonderful events. The August 21, 2017 total eclipse didn’t reach totality over my own home, but it was still an impressive sight. Scientists from NASA have published images of what a solar eclipse looks like on Mars, where they happen and look quite different than they do here.
On Earth, solar eclipses can be partial, annular, or total. The reason this can occur on Earth is that the Moon and the Sun are almost the same apparent size in our sky, despite being vastly different in both actual size and distance from the planet. This means that when things line up properly, the Moon can briefly block the Sun.
On Mars, this can’t happen. While the Sun’s apparent size is smaller on Mars, Mars’ moons of Phobos and Deimos are proportionally far smaller than our own Moon. Phobos is the larger moon, but its radius is just 11.2km. The Moon’s radius, in comparison, is 1079 miles. Both Deimos and Phobos have equatorial orbits around Mars, which means they transit across the sun nearly every day. Deimos is even smaller than Phobos, with a mean radius of 6.2km. Neither moon has any gravity to speak of.
That’s Phobos, which orbits Mars more quickly than Mars itself rotates. The moon is only expected to survive for between 30-50 million years. Eventually, atmospheric drag will decelerate it enough to strike the surface of the planet. Deimos, in contrast, will eventually escape Mars altogether and be flung into space.
The Deimos transit. Like Phobos, Deimos may be a rubble pile or contain a high amount of ice.Phobos moves much more quickly than Deimos and is much closer to Mars.
Mars is the only other rocky planet in our solar system to have moons, but the differences between Phobos, Deimos, and Luna are quite large. The two Martian moons could be asteroid captures or objects that coalesced around the forming planet, or they might have formed in orbit after Mars impacted a planetesimal. Research into the formation of the planet’s moons is still ongoing. Overall, the two moons closely resemble C- or D-type asteroids. NASA continues to take regular observations of the moons to better understand Martian orbital dynamics, including the impact of Jupiter and the changes the two moons make to each others’ orbit.
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