Biology
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufm.p51d0959h&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #P51D-0959
Biology
0406 Astrobiology And Extraterrestrial Materials, 0424 Biosignatures And Proxies, 0448 Geomicrobiology, 0456 Life In Extreme Environments
Scientific paper
We have analyzed both the surface expression and depth profile of cryptoendolithic microbial communities at Battleship Promontory, in the Dry Valleys of Antarctica. Data was collected on site with an active mid-infrared Fourier transform microspectrometer (2.6 - 15 um), a near-infrared spectrometer (0.9-1.8 um), and a visible spectrometer (0.4-1 um). The trio of instruments are connected to microscopes that yield ~1 mm2 spatial resolution on the sample and they are mounted on two perpendicular motorized stages that allow for spatial scanning over an area of ~2cm2. Here we present results on the surface expression of the subsurface microbes in these three spectral regions and we present results on the analysis of a colonized sample examined in cross section. The former case has direct application to the remote, robotic detection of life within the rocks of Mars and the later case provides fundamental insights into the geological and biological interactions that make the Antarctic cryptoendolithic ecosystems possible. Non-invasive surface detection of cyanobacterial dominated communities was possible through the observation of several distinct bands: the carbon-hydrogen stretching modes (symmetric and asymmetric) for CH, CH2, and CH3 in the regions of 3.3-3.6 um and 3.6-3.7 um; the NH2 scissoring and C=O stretch near 6.0 um; the amide I of beta-pleated structures at ~6.1 um; and the 6.4 um - 6.6 um bands of N-H in plane bend of the amide II functional group. In combination, these bands make a strong case for carbohydrates and proteins associated with life. Not surprisingly, as the integrity of the amorphous silica surface varnish improved, our ability to detected the subsurface biosignature decreased. We note, however, that by utilizing the JPL rock crusher in Antarctica, a device designed to fly on the Mars Science Laboratory mission, the mid-infrared biosignature was easily detected. In the cross-section analysis the mid-infrared data provide a depth profile tracking the presence of hydrocarbons, amide bonds, and the mineralogical transition from amorphous quartz to crystalline sandstone. Mapped onto this are the changes in the oxidation states of iron, as recorded by the visible and near-infrared spectrometers. Together, this data set allows us to track the role of biologically produced compounds, such as oxalic acid, in the chelation and leaching of iron compounds from the surface through the rock and into the deposition zone below the colonized subsurface region.
Anderson Malcolm
Calrson R.
Hand Kevin Peter
Levy Ran
Sun Handong
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