Utilizing active mid-infrared microspectrometry for in situ analysis of cryptoendolithic microbial communities of Battleship Promontory, Dry Valleys, Antarctica

摘要

We have constructed an active mid-infrared Fourier transform micro-spectrometer capable of analyzing mineralogy and organic chemistry of specimens in the field. While of great utility for terrestrial studies, the instrument has also been designed for potential use on future robotic missions to Mars. The device operates in the spectral range of 650 cm^-1 (15 µm) to 3800 cm^-1 (2.6 µm) and has a 4 cm^-1 spectral resolution. The spectrometer is coupled to a microscope yielding a spatial resolution on the sample of approximately one millimeter. Mounted to the spectrometer are two motors that allow for spatial scanning of the sample. Maximum scanning range in both X and Y directions is approximately 2.5 centimeters. During a recent field campaign (Jan-Feb. 2005), our instrument successfully detected cryptoendolithic microbial communities in the Dry Valleys of Antarctica. Colonized rocks of Beacon sandstone in the Battleship Promontory formation were examined non-invasively both from the surface and in cross-section. Samples characteristic of the various communities (lichen, cyanobacterial) were analyzed. Detection of C-H bands on the surface, indicative of possible biology below, was successful. Several organic functional groups, characteristic of microorganisms, were detected in both lichen and cyanobacterial-dominated communities. In addition, the vertical distribution of inorganic compounds suggests that the organisms may play an active role in rock weathering.