Yesterday, the much-anticipated comet ISON made its closest pass by Mars. Mars Reconnaissance Orbiter's HiRISE camera is the first to achieve a positive detection of the somewhat-fainter-than-expected comet in its photos.
The International Association of Geomorphologists' "planetary geomorphology image of the month," contributed by Joe Levy, features water tracks on Earth and compares them to recurring slope lineae on Mars.
The fictional world Tatooine, scene of action in the Star Wars movies, is named after a town in Tunisia, where parts of the movies were filmed. The desert backdrops against which the movies were filmed are real terrestrial landscapes, which prove to be perhaps unexpectedly dynamic.
ESA celebrated the tenth anniversary of Mars Express' launch with a several-day science meeting during which they issued lots of press releases and numerous spectacular photos. My favorite of them all is this enormous image of Kasei Valles on Mars.