Evaluation of Microbial Diversity in Ophiolite-Hosted Cold Springs as an Analog to Martian Environments

Abstract

The exploration of ophiolites,as an analog to Martian environments,may be useful in devising a search strategy for life on Mars. Oceanic settings, dominated by mafic and ultramafic rocks interacting with seawater and other fluids, are thought to be similar to early Earth and Martian environments. Ophiolite suites, sections of oceanic crust that have been emplaced onto continental crust, allow ready access to these terranes. Today, these ophiolite suites are permeated with cracks and veining through which fluids have flowed in a previous geologic period. Spring waters emanating from these modem ophiolites reflect a mixture of meteoric water and the host-rock chemistry. Martian soil has a composition similar to ophiolite suites because of its high iron content and, in some areas, an abundance of the mineral olivine. We are particularly interested in chemosynthetic species in the community, because photosynthesis in subterranean habitats is highly unlikely. To characterize the microbiological communities in the ophiolite environment, water and microbial mat samples were collected from surface and subterranean environments in Del Puerto Canyon, California. It is thought that presentday Martian microbes, if they exist, will likely be subterranean due to the lack of water at the planet's surface. The microbial constituents of these materials were analyzed using PCR amplification, DGGE analysis, and DNA sequencing. We detected bacterial DNA in all environments analyzed; however, archaeal DNA was not found in any of the environments. Cyanobacterial DNA was present in the microbial mat samples tested. Our data indicates there could be bacterial life present in a similar environment on Mars.