Phobos is no slowpoke. Given its size, angle, and orbital pattern, the moon makes a full-circle around Mars roughly once every 7.6 hours. This frequency also makes it far more likely to pass in front of the Sun compared to Earth’s solar eclipses. If you were hypothetically at the right location at the right time on Mars, you could glimpse the small, potato-shaped satellite briefly turning the Sun into a giant googly eye. NASA’s Mars Perseverance rover captured just such an event back in February—and it managed to photograph another eclipse barely seven months later.
NASA recently showcased the latest Phobos eclipse seen on September 30th from the rover’s vantage point on Mars’ Jezero Crater. Once again, the googly eye’s lifespan lasted barely 30 seconds, making Earth’s minutes-long eclipse events seem lengthy in comparison. Like its last documentation, the Phobos footage was captured using Perseverance’s Mastcam-Z, an instrument co-designed and overseen by Arizona State University.
Astronomer Asaph Hall discovered the two Martian moons in 1877, naming them Phobos and Deimos after the twin Greek gods of fear and dread. While their origins are still unclear, experts theorize the pair originated either as asteroids that got caught by Mars’ gravitational pull, or as debris leftover from the Solar System’s formation.
[Related: A Martian solar eclipse turns the sun into a giant googly eye.]
At just 17-miles-wide, Phobos is about 157 times smaller than Earth’s moon—although both are slowly traveling in opposite directions. Whereas the moon is currently moving further away from Earth at a rate of about 1.5 inches per year, both Phobos and Deimos are being drawn closer to Mars by an estimated six feet every century. At that pace, the moons are predicted to either smash into their host planet in about 50 million years, or fragment into countless smaller pieces to form a Saturn-like ring.
Until then, however, there will be plenty more googly eye opportunities for Perseverance—and perhaps, one day, human visitors—to document.
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Source : Popular Science