Confidence of Life Detection Scale (CoLD) is a numerical scale developed by NASA astrobiologists to assess possible biosignatures of extraterrestrial life. It was suggested in 2021.[1][2][3] The scale is designed similar to NASA’s technological readiness scale.[4]
It is a seven-step scale:
Detect possible signal
Rule out contamination
Make sure biology is possible
Rule out non-biology
Find additional independent signal
Rule out other hypothesis
Independent confirmation
The Cheyava Falls rock, found by the Perseverance rover on Mars in 2024, is an example of a step one on the CoLD scale, a detect of a possible signal.[5] If methane will be found on Mars, it would be assessed as level four of the scale.[6]
CoLD scale was criticized as a useless tool that doesn't solve existing issues in scientific reporting: "CoLD scale is an inapt and easily abused tool that will do little to address the misleading terminology and sensational narratives that plague both public and scientific communications from the astrobiology community."[7]
