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, 18 (7), 923-933

Lack of Microbial Diversity in an Extreme Mars Analog Setting: Poás Volcano, Costa Rica

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Lack of Microbial Diversity in an Extreme Mars Analog Setting: Poás Volcano, Costa Rica

Brian M Hynek et al. Astrobiology.

Abstract

The Poás volcano in Costa Rica has been studied as a Mars geochemical analog environment, since both the style of hydrothermal alteration present and the alteration mineralogy are consistent with Mars' relict hydrothermal systems. The site hosts an active volcano, with high-temperature fumaroles (up to 980°C) and an ultra-acidic lake. This lake, Laguna Caliente, is one of the most dynamic environments on Earth, with frequent phreatic eruptions, temperatures ranging from near-ambient to almost boiling, a pH range of -1 to 1.5, and a wide range of chemistries and redox potential. Martian acid-sulfate hydrothermal systems were likely similarly dynamic and equally challenging to life. The microbiology existing within Laguna Caliente was characterized for the first time, with sampling taking place in November, 2013. The diversity of the microbial community was surveyed via extraction of environmental DNA from fluid and sediment samples followed by Illumina sequencing of the 16S rRNA gene. The microbial diversity was limited to a single species of the bacterial genus Acidiphilium. This organism likely gets its energy from oxidation of reduced sulfur in the lake, including elemental sulfur. Given Mars' propensity for sulfur and acid-sulfate environments, this type of organism is of significant interest to the search for past or present life on the Red Planet. Key Words: Mars astrobiology-Acid-sulfate hydrothermal systems-Extremophiles-Acidic-High temperature-Acidiphilium bacteria. Astrobiology 18, 923-933.

Figures

<b>FIG. 1.</b>
FIG. 1.
(left) Location map of central Costa Rica and Poás volcano. (right) Google Earth image of Laguna Caliente and surrounding features of interest. Note the lack of vegetation to the west of the crater due to volcanic emissions and dominant easterly winds.
<b>FIG. 2.</b>
FIG. 2.
The active Poás crater and Laguna Caliente. Arrow represents the biological sampling site.
<b>FIG. 3.</b>
FIG. 3.
Clumps of elemental sulfur floating on Laguna Caliente observed during the March 2017 field season. The longest clump is ∼6 cm in length.
<b>FIG. 4.</b>
FIG. 4.
Bacterial diversity at Laguna Caliente, Poás crater, Costa Rica. See text for details.

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