"The amazing thing about the geologic record and the fossil record is that sooner or later some piece of research, some amazing find, sheds light on things that you think are absolutely unanswerable, and really changes the whole picture, " said Professor Sereno.

BBC: NEWS | Science/Nature | Golden age of dino finds forecast

Layered rock and layered polar deposits on Mars may also preserve a comparable record of that planet's geologic and environmental history.

BBC: Mars south pole