Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Bachelor of Science

Degree Level

Undergraduate

Department

Biological Sciences

Advisor/Mentor

Kral, Timothy

Committee Member/Reader

Lessner, Daniel

Committee Member/Second Reader

Magnetti, Brenda

Committee Member/Third Reader

Clay, Matt

Abstract

The question of whether life has ever existed on Mars – either in the past or currently – has been pursued for decades. This debate has been prompted by a variety of discoveries regarding similarities between Mars and Earth and more recently concerns over human extinction. Mars, like Earth, once had large amounts of water, a key ingredient for life. H2O exists on Mars in various forms now, and it is theorized that there is liquid water beneath the surface as well. Mars also contains salt and is very cold at its surface, pointing researchers towards the idea of subsurface life. Methanogens – methane-producing archaea – are candidate/model organisms for the Life on Mars debate since they are anaerobic, non-photosynthetic, and often found in extreme environments on Earth. They have also been shown to survive and grow in various Martian conditions. The discovery of methane on Mars further entrenched methanogens in this debate.

This experiment analyzed the effect of 1% NaCl, 1% MgSO4, 2% NaCl, and 2% MgSO4 on the metabolism of Methanothermobacter wolfeii, Methanosarcina barkeri, and Methanobacterium formicicum when incubated at their ideal growth temperatures and sub-ideal temperatures. All of the methanogen species were able to grow in 1% and 2% salt concentrations at their ideal temperature, however growth was inhibited when incubated at a cooler temperature. M. formicicum displayed the most tolerance to higher salt conditions coupled with low temperatures. The presence of NaCl and MgSO4 therefore does not eliminate the possibility of methanogens are Mars, and the inhibition of growth linked with changes in temperature further reinforces the argument for subsurface Martian life. Though the surface is subfreezing, subsurface temperatures would be more hospitable for life, including for methanogens.

Keywords

Astrobiology; Methanogens; Life on Mars

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