Data from NASA's Curiosity rover on Mars has left scientists scratching their heads. On the one hand, the bot appears to have found evidence that water once flowed on Mars, but on the other hand, the readings suggest there couldn't have been.
The problem stems from carbon dioxide, or rather the lack of it. Curiosity has been trundling across the unforgiving dust world for nearly five years now, and so far it has found no carbonates. This potentially blows a hole in boffins' theories about the Martian atmosphere.
Current thinking is that about 3.8 billion years ago, Mars had running water on the surface. The Sun back then wasn't strong enough to warm the Martian surface to a temperature that would cause liquid water to form, so scientists postulated that there was enough carbon dioxide in the atmosphere to heat the surface using a greenhouse effect.
If that was the case, Martian rocks should be studded with
carbonate material. Instead, Curiosity hasn't found any evidence of this after drilling into what is thought to be the bed of what was once a giant lake in the Gale Crater, according to new research to be published in the
Proceedings of the National Academy of Science.
