Mars

http://www.nature.com/news/2007/070226/full/070226-2.html

Published online: 26 February 2007; | doi:10.1038/news070226-2
Mars - worth a detour
Europe's Rosetta mission is still years from its cometary target, but has sent home some pretty pictures of Mars en route

The images sent back - such as this one taken the day before the close flyby at a distance of 240,000 kilometres - were used mainly to check Rosetta's onboard instruments. Mars Express, the European Space Agency's current Mars mission, was also taking measurements at the same time, allowing comparisons and calibrations to be made. Because Mars Express was built from spare parts some of its instruments are identical to Rosetta's, which helped the process. The ability to produce accurate pictures will be crucial once Rosetta finally reaches Churyumov Gerasimenko and finds a safe place to set down its lander, Philae. 

This image of clouds in the martian atmosphere was taken by Rosetta's OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) camera. Most of the instruments on Rosetta itself were powered down during the closest parts of the flyby because the spacecraft was flying through Mars's shadow and its solar panels thus couldn't provide power.