Confidence of Life Detection Scale

File:Confidence of Life Detection Scale.png

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.{{cite journal |last1=Green |first1=James |last2=Hoehler |first2=Tori |last3=Neveu |first3=Marc |last4=Domagal-Goldman |first4=Shawn |last5=Scalice |first5=Daniella |last6=Voytek |first6=Mary |title=Call for a framework for reporting evidence for life beyond Earth |journal=Nature |date=October 2021 |volume=598 |issue=7882 |pages=575–579 |doi=10.1038/s41586-021-03804-9 |url=https://www.nature.com/articles/s41586-021-03804-9 |access-date=10 February 2025 |language=en |issn=1476-4687}}{{cite journal |last1=Vickers |first1=Peter |last2=Cowie |first2=Christopher |last3=Dick |first3=Steven J. |last4=Gillen |first4=Catherine |last5=Jeancolas |first5=Cyrille |last6=Rothschild |first6=Lynn J. |last7=McMahon |first7=Sean |title=Confidence of Life Detection: The Problem of Unconceived Alternatives |journal=Astrobiology |date=November 2023 |volume=23 |issue=11 |pages=1202–1212 |doi=10.1089/ast.2022.0084 |url=https://www.research.ed.ac.uk/files/369788519/Vickers_et_al_accepted.pdf |issn=1557-8070}}{{cite journal |last1=Green |first1=James |last2=Hoehler |first2=Tori |last3=Neveu |first3=Marc |last4=Domagal-Goldman |first4=Shawn |last5=Scalice |first5=Daniella |last6=Voytek |first6=Mary |title=Moving toward a framework for communicating the confidence of life detection |journal=Nature Astronomy |date=January 2024 |volume=8 |issue=1 |pages=2–3 |doi=10.1038/s41550-023-02135-1 |url=https://www.nature.com/articles/s41550-023-02135-1 |access-date=10 February 2025 |language=en |issn=2397-3366}} The scale is designed similar to NASA’s technological readiness scale.{{Cite web|url=https://nap.nationalacademies.org/read/26621/chapter/5|title=Read "Independent Review of the Community Report from the Biosignature Standards of Evidence Workshop: Report Series—Committee on Astrobiology and Planetary Sciences" at NAP.edu|via=nap.nationalacademies.org}}

It is a seven-step scale:

1. Detect possible signal
2. Rule out contamination
3. Make sure biology is possible
4. Rule out non-biology
5. Find additional independent signal
6. Rule out other hypothesis
7. 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.{{cite web |title=NASA’s Perseverance Rover Scientists Find Intriguing Mars Rock |url=https://www.jpl.nasa.gov/news/nasas-perseverance-rover-scientists-find-intriguing-mars-rock/ |website=NASA Jet Propulsion Laboratory (JPL) |access-date=10 February 2025}} If methane will be found on Mars, it would be assessed as level four of the scale.{{Cite web|url=https://www.scientificamerican.com/article/how-scientists-could-tell-the-world-if-they-find-alien-life/|title=How Scientists Could Tell the World if They Find Alien Life|first=Jonathan|last=O'Callaghan|date=August 2, 2022|website=Scientific American}}

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."{{Cite journal|url=https://www.nature.com/articles/s41550-023-02031-8|title=Communicating astrobiology in words not numbers and with facts not fiction|first1=Adrian|last1=Lenardic|first2=Johnny|last2=Seales|first3=William B.|last3=Moore|first4=A. Mark|last4=Jellinek|date=September 10, 2023|journal=Nature Astronomy|volume=7|issue=9|pages=1009–1009|via=www.nature.com|doi=10.1038/s41550-023-02031-8}}