NASA's Curiosity rover has discovered 21 organic molecules in a soil sample taken from Gale Crater (a vast impact basin on Mars formed over 3.5 billion years ago), including seven never previously detected on the planet. Among the compounds identified is a nitrogen-containing molecule structurally similar to DNA precursors, as well as benzothiophene, a carbon-sulphur compound commonly found in meteorites. NASA stresses the find is not evidence of past life — the molecules could have formed through geological processes — but says it represents the most chemically diverse collection of carbon-based molecules ever found on Mars and reinforces that the planet once had the right chemistry to support life.