Water on Mars?

The question of whether there is water on Mars is a major one, for several reasons:

• Human Mars explorers will need a source of water.
• Any life on Mars, past or present, would need water.
• The possible terraforming and settling of Mars will require water.

There is evidence that water has flowed on Mars, and may still be there. We have detected water in the atmosphere and under the polar ice caps. From orbit, we have seen geological features that look like river valleys and water erosion. On Earth, rain flowing down a volcanic ash layer formed the alcove, channel and apron you see below. Similar features have been seen on the Martian gullies.

Photo courtesy NASA/JPL/ Malin Space Science Martian gullies (left) and Earth gullies (right)

Furthermore, because of the extreme cold of the Martian surface, there may be large deposits of water in the form of permafrost under the Martian surface. We see permafrost in the polar latitudes on Earth, so the same could be true for Mars. Further robotic exploration of Mars could provide those answers.