Thursday, 31 October 2024

Eclipse observed on Mars.

NASA's Perseverance Rover has observed an eclipse from the surface of Mars, caused by the moon Phobos passing in front of the Sun. Phobos is significantly smaller than our Moon, only 17 km in diameter compared to 3475 km, but orbits much closer to Mars than the Moon does to Earth, an average of 9376 km compared to 384 400 km, which combined with the smaller apparent size of the Sun seen from Mars, which is roughly 1½ times as far from the Sun as the Earth is, means that eclipses are still an observable phenomenon. 

Solar eclipse on Mars, caused by the moon Phobos passing in front of the Sun, recorded by the Perseverance Rover. Images are at 10 second intervals, with the whole event lasting much less time than an eclipse on Earth, due to the closer orbit of Phobos, and the correspondingly higher speed of the Martian moon, which takes only 7.6 hours to orbit the planet. NASA.

The eclipse, which occurred on 30 September 2024, was the second such eclipse observed by Perseverance this year, with the Curiosity and Opportunity rovers also having Martian eclipses. These eclipses are common because, unlike that of our Moon, the orbit of Phobos has very little tilt, effectively remaining above the planet's equator at all times.

An eclipse caused by the passage of Phobos in front of the Sun recorded by the Perseverance Rover on 8 February 2024. NASA.

Mars's second moon, Deimos, does not cause such obvious eclipses, as it is only 6.2 km in diameter, and orbits at an altitude of 23 460 km, making it almost invisible from the planet's surface.

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