Biology – Quantitative Biology – Biomolecules
Scientific paper
Mar 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004aps..mar.g1002p&link_type=abstract
American Physical Society, March Meeting 2004, March 22-26, 2004, Palais des Congres de Montreal, Montreal, Quebec, Canada, MEET
Biology
Quantitative Biology
Biomolecules
Scientific paper
These diverse topics exploit optical properties of micron-size particles in ice. AMANDA (Antarctic Muon and Neutrino Detector Array) searches for astrophysical sources of high-energy neutrinos by recording arrival times of Cherenkov light from their interaction products (muons and cascades) at phototubes in the 0.1 km^3 array in deep ice at the South Pole. Using pulsed lasers and LEDs in the array, we found that absorptivity and scattering of light in ice depend on dust concentration, which varies with depth due to dependence of dust concentration on global temperature at the time of deposition. Knowing dust concentration vs depth in AMANDA, we can fit muon tracks and locate neutrino sources to 1 arcdegree. As an AMANDA spinoff, we invented the Dust Logger, a new paleoclimatological instrument that emits laser light into glacial ice surrounding the borehole down which it is lowered. It records light that reenters the borehole after being partially absorbed and scattered by dust in the ice. This signal serves as an accurate proxy for global temperature as a function of time over a million years. The Dust Logger obtains a detailed time sequence of glacial and interglacial periods and of abrupt temperature changes that occur at millennial intervals. Occasional eruptions of nearby volcanoes punctuate the dust record with cm-thick ash layers in ice. We infer that strong volcanic eruptions lead to millennial-scale global coolings, most likely by dumping soluble iron- and acid-rich grains into nutrient-limited southern oceans, thus stimulating rapid growth of phytoplankton, which sequester carbon dioxide, a major greenhouse gas, from the atmosphere. Microbial cells are similar to dust in size and contain biomolecules that autofluoresce. We invented a BioSpectraLogger, which emits 224-nm laser light into ice and searches for fluorescence by microbes able to live in liquid veins in ice. It can be used in lakes, oceans, ice, and permafrost. A miniaturized version can search for life in Martian permafrost.
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