Biology
Scientific paper
Oct 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007dps....39.4003l&link_type=abstract
American Astronomical Society, DPS meeting #39, #40.03; Bulletin of the American Astronomical Society, Vol. 39, p.492
Biology
Scientific paper
Solid H2O and CO2 are present on Mars, some Galilean satellites, comets, and interstellar ices. Laboratory work on frozen H2O-CO2 mixtures shows that they produce H2CO3, carbonic acid, when exposed to either high-energy radiation (keV, MeV) or vacuum-UV photons (eV). While this molecule readily dissociates at 298 K, its stability below about 250 K suggests that it should exist in extraterrestrial environments. Unfortunately, little is known of solid-phase carbonic acid at temperatures relevant to planetary science.
Recently we have studied some of the thermodynamic properties of carbonic acid. To synthesize this compound, we first injected a KHCO3 solution onto a substrate, pre-cooled to 15 K, to make a thin icy film. On top of this, an HBr solution was injected to make a second icy film. The substrate then was heated to about 200 K to initiate an acid-base reaction between KHCO3 and HBr, and to sublime the water present into a vacuum chamber. The resulting formation of carbonic acid was confirmed by recording infrared (IR) spectra of the samples before and after warming. The ices then were further heated to 240 - 255 K, and spectra recorded over time. Decreases in carbonic acid's IR bands near 1300 and 1500 cm-1 allowed the vapor pressure of the compound to be measured at several temperatures, from which an enthalpy of sublimation was determined. Comparisons were made to the heats of sublimation for formic and acetic acids, both those measured by us and those already in the literature.
This work was supported by the Mars Fundamental Research Program and Goddard Center for Astrobiology. The first author was supported by an award from the Summer Undergraduate Internship in Astrobiology program.
Cooper Paul D.
Hudson Reggie L.
Lewis Ariel S.
Moore Marla H.
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