Microbial Survivability of Ionizing Radiation on Mars: Considerations for Sample Return

-As the goals of Mars exploration expand to include returning samples, it becomes important to protect Earth from potential sources of extraterrestrial contamination. Likewise, it is important to avoid confusing terrestrial life with native life brought back from Mars. In a new study, scientists examine the effects of desiccation and freezing on the survivability of microbial ionizing radiation on Mars. The study is published in the peer-reviewed journal Astrobiology. Click here to read the articles now.

Corresponding author Michael Daly, PhD, of the School of Medicine at the Uniformed Services University of the Health Sciences, and his colleagues sought to better understand the impact of the Martian surface on microbial dormancy and survivability. By imitating conditions on Mars, they tested the influence of desiccation and freezing on the survival to ionizing radiation of six model microorganisms: the vegetative cells of two bacteria, a strain of yeast, and the vegetative cells and the endospores of three Bacillus bacteria. Investigators found that desiccation and freezing increased the radiation survival of vegetative microorganisms.

“We report that desiccated and frozen cells of the bacterium D. radiodurans can survive amazing ionizing radiation,” the investigators said, “at exposures equivalent to hundreds of millions of years of background radiation on Mars.”

The investigators concluded that “if Martian life ever existed, even if viable life forms are not now present on Mars, given that all viable life D. radiodurans cells can survive the equivalent of 280 million years in the frozen Martian subsoil, so their macromolecules would survive much, much longer. This reinforces the likelihood that, if life ever evolved on Mars, it would reveal itself in future missions.

Astrobiology Editorial board member John Rummel noted that “the work proposed by Michael Daley and his colleagues represents a comprehensive overview of the interactions between desiccation, freezing, and radiation survivability in one of our most more tenacious, Deinococcus radiodurans. The potential of D. radiodurans or other terrestrial microbes to survive the current conditions on Mars draws attention to the need for complex analysis regarding the very real possibility of terrestrial microbes contaminating specific landing sites on Mars, and even some of them they – as qualified Martian survivors – show up in our studies after returning to Earth in a sample that returned from Mars.

About the journal

Astrobiology, led by Managing Editor Sherry L. Cady, PhD, at Pacific Northwest National Laboratory’s Marine and Coastal Research Laboratory (MCRL), and a top international editorial board of leading scientists in the field, is the authoritative peer-reviewed journal for the latest information and perspectives on new research findings and exciting discoveries emanating from interplanetary exploration and Earth-based field and laboratory research programs. The Journal is published monthly online with Open Access options and in print. Full tables of contents and a sample issue can be viewed on the Astrobiology website. The 2021 Journal Impact Factor is 4.045.

About the editor

Mary Ann Liebert, Inc. editors are known for creating authoritative, peer-reviewed journals in many promising areas of biomedical science and research. Its magazine specializing in biotechnology, GEN (Genetic Engineering and Biotechnology News), was the first in its field and is today the most widely read industry publication in the world. A complete listing of the company’s more than 100 journals, books, and newsmagazines is available on the Mary Ann Liebert, Inc. Publishers website.

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