NASA's Mars Reconnaissance Orbiter has captured stunning images of a patch of frozen water and deep gouges from landslides that have left no visible debris behind, in the first few days of its main phase of science observations.
The MRO landed in Mars in March 2006, but spent its first few months skimming in and out of the Martian atmosphere to tighten its orbit around the Red Planet. It then underwent a period of instrument testing, followed by a hiatus beginning in mid-October when the Sun was too close to Mars, for reliable radio communication.
The MRO began its primary science phase only after November 7.
Among the pictures captured by the MRO's High Resolution Imaging Science Experiment, the most powerful camera ever sent to Mars, are images of gullies carved in the sides of sand dunes in the Russell Crater.
These gullies were first imaged by Mars Global Surveyor and are puzzling because they do not have deposits of debris at their ends, unlike any other gullies seen on Mars.
Scientists have previously suggested that these gullies might form when sunlight heats the dunes, causing frozen carbon dioxide or water ice mixed in with the sand to suddenly evaporate, loosening up the sand and causing it to flow downhill.
"But it is still puzzling that there is no accumulation of material at the bottom of the channels. However, the new images show the gullies in much better detail than ever before, and may eventually help scientists solve the mystery," the New Scientist quoted HiRISE chief scientist Alfred McEwen as saying.
Another image shows part of the frozen "lake" of water ice imaged by ESA's Mars Express spacecraft in 2005.
McEwen says, despite its appearance, the ice is not flat, but mound shaped.
"The mound is at 700 north in latitude, which is far enough from the North Pole to make the survival of ice at the surface surprising, especially since other craters of similar size in the same area do not contain water ice," McEwen says.
"There might be something special about this crater that has led water ice to accumulate there. Maybe there's a source of water vapour from the subsurface," he adds.
A third image further shows a very unusual crater on Mars called Ada Crater. The crater walls show clear signs of erosion, exhibiting gullies and scalloped edges.
"That's surprising because this is clearly a very, very young crater," McEwen further says.
According to McEwen, the camera has already taken hundreds of images of the Martian surface and the instrument will obtain about 5000 for every year till 2010, till which the mission is expected to run.
