Mars has lost an ocean’s worth of water, but to find where it all went will take satellites and computer models working in conjunction. Water ice is known to be lurking under the martian surface, while vestiges of carbon dioxide can be found in the polar ice cap and in certain mineral deposits. But many scientists expect that a large fraction of the water-soaked atmosphere was sucked “up” into space. The current loss rate of martian atmosphere is estimated to be around 100 tons per day, but this is based on incomplete data. The upcoming NASAMAVEN mission, planned to fly to Mars in 2013, will measure all aspects of atmospheric escape – helping astrobiologists understand what happened to Mars’ water.