Mars rover finds traces of possible ancient life

Nasa's Curiosity rover has found the largest organic compounds ever seen on Mars, raising tantalising questions about whether life emerged on the red planet billions of years ago.

- Ian Sample

The compounds were detected in a 3.7bn-year-old rock sample collected in Yellowknife Bay, an ancient lakebed that harboured all the necessary ingredients for life in the planet's warmer, wetter past.

Tests onboard the rover found that the rock contained long-chain alkanes, organic molecules thought to be remnants of fatty acids. The compounds can be made by lifeless chemical reactions, but are crucial constituents of cell membranes in all living organisms on Earth.

The researchers do not claim to have found a biosignature - a smoking gun indicating life was once present - but one expert said the material represented the best chance scientists had ever had for identifying remains of life on Mars.