Mars discovery: how did the organic matter end up there? – video

Nasa's Curiosity rover has found complex organic matter buried and preserved in ancient sediments that formed a vast lake bed on Mars more than 3bn years ago. Nasa expert Jennifer Eigenbrode explains how that matter might have ended up there and what the source could be: biological processes in the lake itself, meteorites or a natural rock-forming process. But, as Eigenbrode explains, there is not yet enough information to tell what the source is and how it got in there.