Curiosity rover Mastcam photograph of a plateau in the < 3.7 Ga Gillespie Lake Member, Mars. Credit: NASA/JPL-Caltech/MSSS

Curiosity rover Mastcam photograph of a plateau in the < 3.7 Ga
Gillespie Lake Member, Mars.
Credit: NASA/JPL-Caltech/MSSS

Photographs from NASA’s Curiosity Mars rover clearly show sediment deposits resembling those found in modern evaporite (salty) settings at Portsmouth Island, N.C., and Bahar Alouane, Tunisia (Africa); in playa lake sediments cropping out of the Mediterranean coast in Tunisia; and in Archean salt deposits of the Pongola Supergroup in South Africa and the Dresser Formation in Australia.

Yes, a picture is worth a thousand words…and in this case it adds up to a 24-page research paper in the Astrobiology journal.

Microbial terrestrial erosional remnant photographed at a modern site at Carbla Point, Western Australia. Courtesy: Nora Noffke

Microbial terrestrial erosional remnant photographed at a modern
site at Carbla Point, Western Australia.
Courtesy: Nora Noffke

Nora Noffke, in the Department of Ocean, Earth and Atmospheric Sciences at Old Dominion University in Norfolk, Virginia reports that: “Sandstone beds of the <3.7 Ga (billion year old) Gillespie Lake Member on Mars have been interpreted as evidence of an ancient playa lake environment. On Earth, such environments have been sites of colonization by microbial mats from the early Archean to the present time.”

Noffke explains that terrestrial microbial mats in playa lake environments form microbialites known as microbially induced sedimentary structures (MISS). On Mars, three lithofacies of the Gillespie Lake Member sandstone display centimeter- to meter-scale structures similar in macroscopic morphology to terrestrial MISS.

Geological evidence

As a geobiologist, Noffke has in the past produced sedimentary evidence that prokaryote biofilms existed on Earth billions of years ago. Now she is focusing efforts on showing that similar colonies of bacterial life may have existed on Mars at about the same time.

Noffke reported last year that the structures found in Australia might also provide scientists with clues about geologic evidence of microbial life that exists, or might have existed, on Mars.

Although Mars today is much colder than Earth and seems only to have water in ice and vapor forms, scientists believe that it must have been a very different place 3.7 billion years ago – warmer, wetter and with a much thicker atmosphere.

Past climate of Mars

Why the climate then was more hospitable to life is puzzling, but perhaps could have been caused by volcanoes or large asteroid impacts.

Still, she acknowledges that any remote analysis of imagery has its drawbacks.

“Without any evidence for life on Mars detected in returned rock samples, reconstructing microbial ecosystems on the Red Planet is pure speculation,” she writes.

One section of the journal article examines possibilities that the structures shown in the NASA photos could be also caused by “abiotic” – non-life – processes such as weathering.

Hypothesis

The Astrobiology article suggests a hypothesis that the structures seen on the Mars images may be ancient MISS; the preliminary evidence presented in her report may be sound enough to warrant more investigation by NASA.

Noffke calls for the Curiosity mission and other astrobiology-focused missions to Mars to dedicate specific photography and data collection assignments to the search for MISS. In her research paper, she proposes a strategy for detecting, identifying, confirming, and differentiating possible MISS.

“The sedimentary structures in the Gillespie Lake Member, Mars, constitute a promising set of potential biosignatures that compel further analyses by Mars rovers, including future sample return missions from Mars,” Noffke concludes.

Check out this impressive “Hypothesis Article” – “Ancient Sedimentary Structures in the <3.7 Ga Gillespie Lake Member, Mars, that Compare in Macroscopic Morphology, Spatial Associations, and Temporal Succession with Terrestrial Microbialities” – by going to:

http://online.liebertpub.com/doi/full/10.1089/ast.2014.1218

One Response to “Potential Signs of Ancient Life in Mars Rover Photos?”

Leave a Reply

Griffith Observatory Event