Well, nuts. A little over a year ago, NASA announced it had found strong evidence of liquid water flowing, at least temporarily, on the surface of Mars. Pictures taken a few years apart showed flow-like gullies in the sides of craters, and there were a few different pieces of evidence that these were due to sudden flooding of liquid water downhill. Here are the original shots:
However, a new study just released says that these images fit better with being dry grains flowing downhill. The researchers, led by Jon D. Pelletier of The University of Arizona, used HiRISE, the very high-resolution camera on board the Mars Reconnaissance Orbiter, to look at the same regions as observed before. By taking images at different angles, they could establish a digital elevation model, a topographical map of the same crater shown in the earlier announcement. They then modeled the way liquid water would ...
