Categories: Mars

Phobos and Deimos Together At Last!

ESA’s Mars Express orbiter took images last month of Mars two moons, Phobos and Deimos. This is the first time the moons have been imaged together in high resolution, but as Emily Lakdawalla points out on Planetary Blog, not the first time the two have been imaged together: the Spirit rover did it back in 2005! But these new image definitely provide a ‘wow’ factor, as well as helping to validate and refine existing orbit models of the two moons.

Phobos and Deimos together for the first time in high resolution. Credits: ESA/DLR/FU Berlin (G. Neukum)

“It doesn’t happen very often that both Martian moons are right in front of the camera, directly one behind the other,” said Harald Hoffmann from the German Aerospace Center (DLR).

“During the now more than six-year long project, we have had several opportunities to photograph the two moons together,” said Klaus-Dieter Matz, who worked with Hoffmann to plan the acquisition of these images. “The geometry of the constellation during Orbit 7492 on 5 November 2009 was especially favorable, so this time we wanted to try taking a sequence of photographs – and this first attempt has delivered the expected result!”

The geometrical relationships between Mars, its moons and the Mars Express probe at the time of the sequence. Credit: DLR

Phobos, the larger of the two moons, orbits closer to the Red Planet, circling it every 7 hours and 39 minutes. It travels faster relative to Mars than the Moon relative to Earth. It was 11,800 km from Mars Express when the images were taken. Deimos was 26,200 km away.

The images were acquired with the Super Resolution Channel (SRC) of the High Resolution Stereo Camera (HRSC). The camera took 130 images of the moons on 5 November at 9:14 CET over period of 1.5 minutes at intervals of 1s, speeding up to 0.5-s intervals toward the end. The image resolution is 110 m/pixel for Phobos and 240 m/pixel for Deimos — since Deimos was more than twice as far from the camera.

Sources: DLR, ESA

Nancy Atkinson

Nancy has been with Universe Today since 2004, and has published over 6,000 articles on space exploration, astronomy, science and technology. She is the author of two books: "Eight Years to the Moon: the History of the Apollo Missions," (2019) which shares the stories of 60 engineers and scientists who worked behind the scenes to make landing on the Moon possible; and "Incredible Stories from Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos" (2016) tells the stories of those who work on NASA's robotic missions to explore the Solar System and beyond. Follow Nancy on Twitter at https://twitter.com/Nancy_A and and Instagram at and https://www.instagram.com/nancyatkinson_ut/

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