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Category Archives: Moons

THEMIS Takes Deimos’ Temperature

Infrared image of Deimos by THEMIS on Feb. 15, 2018 (NASA/JPL-Caltech/ASU/SSI)

Can you feel the heat? NASA’s Mars Odyssey can see it! This is an image of Mars’ smaller moon Deimos, captured with Odyssey’s THEMIS (Thermal Emission Imaging System) instrument on Feb. 15, 2018. Part of the 7-mile-wide Moon was in shadow, but the sunlit surface area reached temperatures up to 200 K (that’s still pretty cold for us, though… –100ºF / -73ºC!)

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Have No Fear, Phobos is Here!

Mars and Phobos imaged by Hubble on may 12, 2016. Credits: NASA, ESA, and Z. Levay (STScI), Acknowledgment: J. Bell (ASU) and M. Wolff (Space Science Institute).

On May 12, 2016, the Hubble Space Telescope captured a series of images of Mars and in them the planet’s moon Phobos can be seen appearing from behind the western limb. This was just 10 days before opposition which, in 2016, was the closest Mars had been to Earth since 2005, lending particularly good opportunity for picking out its largest—yet still quite small—moon.

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These Are Our Best Pictures of Mars’ Smallest Moon

Mars’ smallest moon Deimos imaged by HiRISE on Feb. 21, 2009. (NASA/JPL/University of Arizona)

Mars isn’t a planet well-known for its natural satellites but it actually does have two small moons. The larger, Phobos, is an irregularly-shaped, heavily grooved and cratered world only about 17 miles (27 km) across at its widest. It orbits Mars so closely that it completes 3 orbits every day, and isn’t even visible from some parts of the planet. But Phobos has an even smaller companion in orbit: Deimos, which at the most 7.5 miles across is half Phobos’ size. Deimos orbits Mars much further away as well, taking about 30 hours to complete one orbit.

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This is Jupiter Seen from Mars

Jupiter and its four largest moons imaged by the HiRISE camera in orbit around Mars on Jan. 11, 2007. (NASA/JPL/University of Arizona)

Jupiter and its four largest moons imaged by the HiRISE camera in orbit around Mars on Jan. 11, 2007. (NASA/JPL/University of Arizona)

The HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter (MRO) is specifically designed to take super high-resolution images of the surface of Mars but it also does a pretty darn good job capturing pictures of other objects too—like Jupiter and its Galilean moons, several hundred million miles away! The image above was captured in expanded color (that is, it includes wavelengths in infrared) by HiRISE on January 11, 2007, and shows the giant planet from Mars orbit.

Mars and Jupiter were at opposition at the time, only about 345 million miles apart.

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Hail Hydra: Pluto’s Moon is Covered in Almost Pure Water Ice

One of Pluto's smaller moons Hydra, imaged by New Horizons on July 14, 2015 from a distance of about 143,000 miles (231,000 km). (NASA/JHUAPL/SwRI)

Hydra, one of Pluto’s smaller moons, imaged by New Horizons on July 14, 2015 from a distance of about 143,000 miles (231,000 km). Credit: NASA/JHUAPL/SwRI.

Discovered in June 2005, distant Pluto’s outermost moon Hydra it thought to have formed during the same collision four billion years ago that created the Pluto-Charon system that we see today. Yet despite its age this 31-mile (50-km) -long moon appears remarkably clean and bright,  as witnessed by New Horizons during its close pass through the Pluto system in July 2015.

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