False and True Positives (IMAGE) NASA/Goddard Space Flight Center Caption Left: Ozone molecules in a planet's atmosphere could indicate biological activity, but ozone, carbon dioxide and carbon monoxide -- without methane, is likely a false positive. Right: Ozone, oxygen, carbon dioxide and methane -- without carbon monoxide, indicate a possible true positive. Credit NASA Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.