Mars doesn’t have much in the way of moons—just two small, lumpy objects called Phobos and Deimos. But those tiny natural satellites can still make their presence felt.
On September 13 NASA’s Curiosity rover documented a brief passage of Phobos, the larger of the Martian moons, in front of the sun. Phobos just grazed the edge of the solar disk from Curiosity’s vantage point, but the rover clearly captured the moon’s shadow in a series of photographs. This animated GIF comprises nine frames taken by Curiosity’s telephoto camera, the 100-millimeter Mastcam, through a solar filter.
Curiosity’s suite of weather instruments, known as the Rover Environmental Monitoring Station, also registered the event. The rover measured a roughly 5 percent dip in ultraviolet solar radiation during the eclipse, according to a NASA prepared statement.
In a September 19 teleconference with reporters, rover co-investigator Mark Lemmon of Texas A&M University explained that such partial eclipses, or transits, are not mere novelties. “With the transits we can measure [the moons’] orbits very precisely,” Lemmon said. By observing transits of Phobos and Deimos, Curiosity will also supply planetary scientists with data on the how the satellites’ orbits are changing due to tidal interactions with Mars, which, in turn, provides information on the interior structure of the Red Planet.