2 worlds, 2 eclipses, 2 days

On August 12, the moon passed in front of the sun, producing a total eclipse along a narrow path in the northern hemisphere of Earth. On Mars, in a cosmic coincidence a day later, Perseverance watched a tiny potato-shaped moon pass in front of the same sun. On this episode of Mars Guy, for any given location on Earth, a total solar eclipse occurs on average about once every 373 years. On Mars, eclipses are way more frequent, but never total. That's because it has two moons, and they're really small. The larger of the two, called Phobos, is about 27 by 22 by 18 kilometers, and orbits much closer than Deimos, so it appears larger in the sky, but still, it can only cover about a quarter of the sun's disk, which makes for an annular eclipse rather than a total one. But because it orbits Mars every 7 hours and 39 minutes, most locations can see an eclipse several times per year. On August 13, at about 10.13 in the morning local time, Perseverance turned its Mastcam-Z camera at maximum zoom toward a small spot in the sky where scientists predicted Phobos would appear in front of the sun. Here you can see the orbits of Phobos and Deimos, which are inclined due to the tilt of the Martian spin axis relative to the plane it orbits the sun. And here's Phobos in all its potato-y glory. This visualization includes the shadow of Phobos, which is closing in on the location of Perseverance, slightly faster than real time. The shadow races across the surface at about 7200 kilometers per hour, which means an eclipse lasts only about 30 seconds. August 13 on Earth was Sol 1948 of the Perseverance mission, the Sol after it arrived in this location. Here's Mars Guy for scale, looking southeast toward the rim of Jezero crater. Perseverance aimed Mastcam-Z at a spot in the sky above the rim to observe the eclipse. And note that like observers on Earth, it protected its vision with a neutral density filter that blocks 99.9999% of the sunlight. Mastcam-Z shot one frame about every 7 tenths of a second, starting at about 1013 a.m., 12 seconds before Phobos first entered the disk of the sun. Here I'm showing it in real time, without any smoothing between the frames, which is why it looks so jerky. Unlike totality during an eclipse on Earth, you can't take off your protective glasses watching an eclipse on Mars, and the duration of the transit is much shorter, about 30 seconds versus the typical 2-3 minutes of an eclipse on Earth. Note that the sun also rises as Phobos descends, not due to Hemingway, but instead due to the rotation of Mars. And there you have it, an eclipse that will never rival the otherworldly beauty of a total eclipse on Earth, but one that is by definition otherworldly. Back-to-back eclipses on Earth and Mars is indeed a cosmic coincidence, but an even more remarkable one is that Earth's moon is just the right diameter and just the right distance from Earth to give us a profound experience that can't be had anywhere else in the solar system, or maybe even in the galaxy.