On Mars, some of the most likely places to look for traces of ancient life may also be the least likely to preserve those traces.
This is the result of a recent study that simulated exposing important building blocks of life called "lipids" to cosmic rays pummeling the surface of Mars. And, in short, the exposed material appeared to break down very quickly under the bombardment of radiation from space — and even faster when there was salt mixed in with the sediment, which is the case in many of the places we consider the most likely ancient habitats on Mars.
