A brief spacecraft encounter with the Martian moon Phobos shows off the tiny world's surface in detail.
The European Mars Express mission, in orbit around the Red Planet, recently glimpsed Phobos as the moon passed by at a distance of 1,500 miles (2,400 kilometers). While that's a faraway look, Mars Express is the only spacecraft that can get a glimpse of Phobos right now.
Mars Express snagged 41 images of Phobos on Nov. 17, showing craters, marks, and even long furrows or scratches on the surface. "The image sequence shows Phobos at a number of angles — the moon can be seen rotating and slowly lightens up before it begins to darken again," the European Space Agency said in a statement. (The image sequence also shows a slight oscillation from spacecraft movements.)
Clearly visible are a number of features. One is Stickney Crater, which takes up nearly half of Phobos' 16-mile (26 km) diameter. The spacecraft also imaged the furrows, in hopes of further unveiling how these features formed. The current thinking is that debris or the tug of Mars' gravity on Phobos could have made these scratches.
The science team said it was especially pleased that Mars Express nabbed images of Phobos from several "phase angles," meaning the angle between the light source (which was the sun) and the observing spacecraft.
"Images acquired across a range of phase angles … are incredibly useful for scientists," ESA added. "Different shadows are cast as the sun's position changes relative to the target object: This illuminates and highlights the surface features and enables calculations of feature height, depth and relief and reveals much about the roughness, porosity and reflectivity of the surface material itself."
The spacecraft will get its next chance to capture images of Phobos in such direct solar light in April and September.
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