Microbial Nitrate Dependent Fe2+ oxidation. A Potential Early Mars Metabolism

Description:
Develop skills in microbiology and geochemistry
Understanding biogeochemical cycling in hydrothermal environments
Identify potential bio-signatures for life detection on Mars
The surface of present-day Mars is cold and dry. These conditions are considered inhospitable for
life; yet, the geological record contains evidence that liquid water did occur on the surface of early
Mars, suggesting that the planet was warmer, wetter and more hospitable to life. The persistence of
water is unclear (Carr 2006); however, it is likely that hydrothermal systems may have developed due
to volcanic systems or impact craters and warm/hot water may have been long-lived.
On Earth, hydrothermal systems are thought to be a logical candidate for the emergence of life.
Phylogenetic evidence suggests that modern hyperthermophiles (microbes that live at high
temperature) are closer related to a common ancestor than any other form of life (Woese et al 1990).
Therefore, it is inevitable that hydrothermal systems on Mars are potential target sites for life
detection missions.
The Mars Science Laboratory (MSL) has focused its search for habitable environments in Gale
Crater. Impact craters create a wealth of potential habitats for life. As water seeps from the sub surface, a temperature gradient occurs, from high temperatures near the impact rocks to cold surface
temperatures. At the surface, an impact lake can be sustained until evaporation occurs.
Finding evidence for life is dependent on detecting bio-signatures. For example, microbial activity
can effect secondary mineral formation and increase leaching of bio-essential ions. Yet there are a
number of questions that are unanswered, such as, what bio-signatures could be used to identify sub surface activity in hydrothermal systems? How would temperature affect these bio-signature? What
is their fate on the surface of Mars? The aim of this studentship is to identify potential bio-signatures
for life detection in impact craters on Mars.
The specific objectives are:
To identify potential signatures for biological activity in a hydrothermal system. This will be
achieved by culturing microbes isolated from a hydrothermal system and using geochemical
analysis.
To use geochemical modelling to determine the effect of temperature on bio-signatures.
This will be accomplished using the modelling program CHIM-XPT.
To determine the possibility of detecting bio-signatures on the surface of Mars using
environmental simulation chambers.