Interesting read, just what I consider the key excerpt:

Many of the Viking experiments involved applying water to the soil samples, which may explain the puzzling results. Perhaps the putative Martian microbes collected for the labelled release experiments couldn’t deal with that amount of water and died off after a while. Most of the runs for the pyrolytic release experiment were conducted under dry conditions, contrary to the other experiments. The first run was positive for life when compared to a control run conducted later, which was designed so that no biology could have been involved. Interestingly, the only run conducted under wet conditions had less of a signal than the control.

Agreed with @[email protected], this probably isn’t as dramatic as it might sound at first. Unless life on Mars was dying out anyways, and we accidentally stomped the last survivors, there will be plenty of these to discover elsewhere.