The American space agency's Mars rover Curiosity has recorded its largest measurement yet of methane. The robot frequently "sniffs" the Red Planet for the gas but has never before seen so high a concentration - of 21 parts per billion (ppb). The observations are fascinating because on Earth, methane is produced in large part by living things. That's not necessarily the case on Mars; geological processes are very capable of making it as well. Through the course of its mission, Curiosity has noticed a number of spikes in methane , and it senses a background level that appears to have a seasonal pattern to it . But although the robot's big onboard chemistry lab - the Sample Analysis at Mars (SAM) instrument - can detect the gas's presence, it can say nothing about the source. "With our current measurements, we have no way of telling if the methane source is biology or geology, or even ancient or modern," said SAM Principal Inv...
