Odd Craters on Mars

Last October, the HIRISE instrument aboard the Mars Reconnaissance Orbiter grabbed this picture of a crater in the northern Arabia Terra region of Mars. This crater and several others in the same region contain oddly shaped deposits usually on the south side of the craters. All the odd craters are large, at least 600 m in diameter. The best guess (so far) is that the features were formed by the sublimation of water from ice-rich material stirred up by the substantial impacts which created the craters.

Image Credit: NASA

Look on the Sunny Side

sunny_sideThis view of Mercury’s horizon was taken by the MESSENGER spacecraft in orbit around the planet. It was acquired looking from the shadows toward the sunlit side of the planet.A 120-km impact crater stands out near the center. The crater has several chains of secondary craters which gouge linear tracks radially away from it. While this crater does not appear to be of recent origin (its rays have faded), its secondary crater chains are more prominent than most similar craters.

Once per week, MESSENGER captures images of Mercury’s limb, with an emphasis on imaging the southern hemisphere limb. These limb images provide information about Mercury’s shape and complement measurements of topography made by the spacecraft’s laser altimeter of Mercury’s northern hemisphere.

Image Credit: NASA

An Elliptical Crater

ellipticalcraterMost craters are more or less circular. This is Hovnatanian crater on Mercury, named for Armenian painter Hakop Hovnatanian. The crater’s elliptical shape and the bright rays’ butterfly pattern indicate the whatever hit the planet causing the crater came in at a very shallow angle. The brightness of the rays indicates that they are relatively young features on Mercury’s surface.

This image was acquired by the MESSENGER spacecraft, the first to orbit Mercury. MESSENGER has acquired over 150,000 images and other extensive data sets, and should continue orbital operations until early 2015.

Image Credit: NASA

UPDATE—Cabin Boy Bill Schmalfeldt likes this picture. He tweets:

RadioWMS ‏I don’t know about you, but I enjoy these closeup pictures of Hoge’s complexion.
3:26 PM – 3 Aug 13 GMT