Here's how NASA is going to search for alien life in future

NASA has said that astronomers searching the atmospheres of alien worlds for gases that might be produced by life can't rely on the detection of just one type, such as oxygen, ozone, or methane, because in some cases these gases can be produced non-biologically.

The researchers in the NASA Astrobiology Institute's Virtual Planetary Laboratory simulated the atmospheric chemistry of alien worlds devoid of life thousands of times over a period of more than four years, varying the atmospheric compositions and star types and found that in some cases, there was a significant amount of ozone that built up in the atmosphere, despite there not being any oxygen flowing into the atmosphere.

Shawn Domagal-Goldman of NASA's Goddard Space Flight Center in Greenbelt, Maryland said that this has important implications for our future plans to look for life beyond Earth, however their research strengthens the argument that methane and oxygen together, or methane and ozone together, are still strong signatures of life and they tried really, really hard to make false-positive signals for life, and did find some, but only for oxygen, ozone, or methane by themselves.

This study demonstrated that both molecular oxygen and ozone can be made without life when ultraviolet light breaks apart carbon dioxide (a carbon atom bound to two oxygen atoms) and the findings suggest this non-biological process could create enough ozone for it to be detectable across space, so the detection of ozone by itself would not be a definitive sign of life.

The study was published in the Astrophysical Journal.