During the Viking missions to mars, three experiments were done to search for traces of life. The pyrolytic-release, labeled-release and gas exchange experiment. The PR showed positive, and non positive on the control on the first cycle, then the rest were inconsistant. The LR showed positive on all cycles and negative on controls. The GR showed results that were mysterious, but pointed to weird chemistry more likely than biology. They couldn't detect organic molecules, but the technology couldn't detect enough parts per billion ton assume detection of the ones involved in the findings under the biology assumption anyways. The labeled-release experiment has yet to be reproduce on earth with chemistry or biology. There is debate among those who carried out the experiments and other biologists on the significance. The viking missions were the first to land on mars and since others in more recent times have done so. But I have not heard of any similar follow up experiments done. Does anyone know of recent biology detection experiments done since. I understand that the labeled release experiment has yet to be explained as a non biological chemical process. My information comes from "To the Red Planet" by Eric Burgess. He is was a prominent Science writer for NASA at the time. Modern attempts to disprove the biology explanation include a theoretical super-oxide which has not been discovered. I see lots of publication about mars trips and the search for life, but none that detail any experiments on detection. What has been done since viking to follow up.