NASA's Curiosity rover has captured two stunning videos of solar eclipses from the surface of Mars, including one that shows the Red Planet's skies darkening dramatically above the 1-ton robot.
Curiosity recorded the two Mars solar eclipse videos on back-to-back days last month, Aug. 19 and Aug. 20. In both cases, Phobos — the larger of Mars' two tiny moons — blotted out much of the sun's disk.
Mission team members created the two eclipse videos, which NASA released Thursday, by stitching together photos Curiosity snapped with its workhorse Mast Camera — 52 images for the Aug. 19 eclipse and 89 pictures for the event one day later.
Curiosity's video of the Aug. 19 eclipse, however, also includes five frames captured by the car-size rover's rear hazard-avoidance camera. These images, taken 58 seconds apart, show the Martian landscape dimming markedly and then brightening again as Phobos completes its trek across the sun's face.
Phobos is just 14 miles (22 kilometers) wide on average, but it still manages to take a pretty big bite out of the sun during an eclipse seen from Mars. That's because the tiny satellite orbits very close to the Red Planet's surface — just 3,700 miles (6,000 kilometers) away.
For comparison, Earth's moon is about 2,160 miles (3,476 km) wide but zips around our planet at an average distance of 239,000 miles (384,600 km). That's just the right combination of size and distance to completely cover the sun's face, creating a total solar eclipse here on Earth when the alignment works out right.
Scientists think both Phobos and Mars' other minuscule satellite, Deimos, are former asteroids captured by the Red Planet's gravity long ago.
Phobos orbits Mars every eight hours, while the more far-flung Deimos (average orbital distance: 12,470 miles, or 20,070 km) completes one lap every 30 hours or so. But neither moon will be in its current orbit forever; Deimos is speeding up, while Phobos is slowing down.
Curiosity's eclipse observations should help refine scientists' understanding of the two moons' orbits, mission team members have said.
The Curiosity rover landed inside Mars' huge Gale Crater in August 2012 to determine if the Red Planet has ever been capable of supporting microbial life. In March, rover scientists announced that an area near the mission's landing site called Yellowknife Bay was indeed habitable billions of years ago.
Curiosity is now embarked on a long drive to the foothills of the towering Mount Sharp, whose many layers preserve a record of Mars' changing environmental history over time.
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