MISSes on Mars? Let’s look

January 22, 2008 / Posted by: Shige Abe

The January 2008 issue of the journal Geobiology is dedicated to the subject of microbially induced sedimentary structures (MISSes), a topic of interest in astrobiology. Nora Noffke, a Principal Investigator in the Exobiology and Evolutionary Biology Program, is guest editor of this special issue.

Noffke is an associate professor in the Department of Ocean, Earth, and Atmospheric Sciences at Old Dominion University in Norfolk, Virginia. Noffke’s research interests include, in addition to astrobiology, the biosedimentary dynamics of siliciclastic marine environments and the co-evolution of sedimentary systems and benthic bacteria. She is studying ancient fossil MISSes at a site in South Africa.

In a presentation to scientists at the National Museum of Natural History in Washington, D.C., on January 10, 2008, “Turbulent lifestyle: cyanobacteria in sandy beaches today and 3 billion years ago,” Noffke reported on her own Earth-based studies of MISSes and her interest in using MISSes as a biosignature for past or present life on Mars.

Noffke reviewed the ABCs of MISSes, explaining what they are (not stromatolites), how they form (see below), why she is studying them (as a record of climate conditions, storm frequencies, tidal oscillations…), where they are found (the extreme environment of tidal flats), and how modern and ancient MISSes compare (for one thing, they look exactly the same). She said she has identified 21 different types of MISSes thus far.

The MISS formation process involves the following steps, Noffke said. Initially, cyanobacteria in tidal environments form biofilms around individual grains of sand. If the biofilms continue to grow, they eventually form microbial mats. If the sedimentary process in the environment is chemical, stromatolites form. If the process is physical, MISSes form. During periods of latency in these tidal environments, when neither deposition nor erosion is occurring, the cyanobacteria engage in processes called binding and leveling, communicating with each other by a process not yet understood to make mats. Different sorts of latencies yield different types of mats. Different types of mats react to erosion with different modes of biostabilization.

Noffke described her own ongoing field study of 2.9 billion year old fossil MISSes in the Pongola Supergroup of South Africa. She also highlighted the potential for using MISSes as a biosignature in the search for evidence of life on Mars. She mentioned that with researchers at the Carnegie Institution, she has tested geochemical methods for detecting MISSes on Mars.