International Journal of Astrobiology

Research Article

A possible biogenic origin for hydrogen peroxide on Mars: the Viking results reinterpreted

Joop M. Houtkoopera1 and Dirk Schulze-Makucha2

a1 Center for Psychobiology and Behavioral Medicine, Justus-Liebig-University of Giessen, Otto-Behaghel-Strasse 10F, D-35394 Giessen, Germany e-mail:

a2 School of Earth and Environmental Sciences, Washington State University, Pullman, WA 99164, USA e-mail:


The adaptability of extremophiles on Earth raises the question of what strategies putative life might have used to adapt to the present conditions on Mars. Here, we hypothesize that organisms might utilize a water–hydrogen peroxide (H2O–H2O2) mixture rather than water as an intracellular liquid. This adaptation would have the particular advantages in the Martian environment of providing a low freezing point, a source of oxygen and hygroscopicity. The findings by the Viking experiments are reinterpreted in light of this hypothesis. Our conclusion is that the hitherto mysterious oxidant in the Martian soil, which evolves oxygen when humidified, might be H2O2 of biological origin. This interpretation has consequences for site selection for future missions to search for life on Mars.

(Received November 03 2006)

(Accepted March 29 2007)

(Online publication May 22 2007)