In 1997, Levin published his conclusion that a 1976 Viking lander had discovered living microorganisms on Mars. He is noted for still claiming that his experiment on board the 1976 Viking Mars landers to detect microscopic life on Mars rendered a true positive result. On 12 April 2012, an international team including Levin reported, based on mathematical speculation through cluster analysis of the Labeled Release experiments of the Viking program, that may suggest the detection of "extant microbial life on Mars."
He is one of the scientific advisers of the International Committee Against Mars Sample Return.
- Bianciardi, Giorgio; Miller, Joseph D.; Straat, Patricia Ann; Levin, Gilbert V. (March 2012). "Complexity Analysis of the Viking Labeled Release Experiments". IJASS. 13 (1): 14–26. Bibcode:2012IJASS..13...14B. doi:10.5139/IJASS.2012.13.1.14. Archived from the original on 15 April 2012. Retrieved 15 April 2012.
- Life on Mars Found by NASA's Viking Mission?
- Spie (2014). "Gilbert Levin: Mars microbes -- proof from the Viking missions?". SPIE Newsroom. doi:10.1117/2.3201403.03.
- ICAMSR Advisors, retrieved 2013-7-16
- Richard Stenger Mars sample return plan carries microbial risk, group warns, CNN, November 7, 2000
- A Natural Way to Stay Sweet, NASA, retrieved 2009-09-02.