A miniature laboratory that can spot a tell-tale chemical signature of life is set to be part of NASA’s 2009 Mars mission. The device will look for amino acids, the molecular building blocks of proteins. “Amino acids are the best molecules to look for if you want to find evidence of life that existed a long time ago. Unlike DNA, they could last for millions of years on Mars without changing,” says Alison Skelley, a chemist at University of California, Berkeley, who helped build the ‘life chip’.