2000 Annual Science Report
NASA Jet Propulsion Laboratory Reporting | JUL 1999 – JUN 2000
Impact Frustration and Subsequent Generation of Biologically Tenable Climates on Earth and Mars
We are developing a system to measure position or negative ions. The speciation of gases produced by impact devolatilization of target rocks in large impact events can have significant environmental implications which affect life on planets such as the Earth and Mars. The presence of anhydrite in the sediments at Chicxulub means that SO2 and SO3 were released in large quantities during the K/T impact, resulting in the formation of a stratospheric sulfuric acid layer sufficiently opaque to cool the earth and interupt photosynthesis. Atmospheric SO3 is very rapidly converted to sulfuric acid, whereas SO2 is converted to sulfuric acid on longer timescales (~ years), extending the environmental influence of the devolatilized anhydrite to possibly a ~10 year time-scale of drastic global climatic change. Thus, the ratio of SO2 to SO3 is a key factor in the extent of cooling following the K/T impact.
We are also currently constructing experiments employing a pulsed electron gun to virtually completely ionize all neutral gas species produced by a given shock pressure on a mineral sample are in progress and will likely yield a more complete and quantitative mass spectrum of volatilized species. Systematic study of the speciation of the impact-induced vapor upon impact of the biogenetic related CO2,SO2 and H2O-bearing minerals is being conducted.
In order to address the issue of sulfur speciation in an impact, we are developing mass spectrometry methods associated with performing laboratory impact experiments on natural anhydrite samples using Dr. Hörz’s 4 ns pulsed N2 laser (337 nm) as the energy source for UV-visible emission and time-of-flight mass spectrometry (TOFMS) experiments. The UV-visible emission experiments were performed in air using a system that was built for study of the calibration of the Cosmic Dust Analysis instrument, and have thus far yielded spectra dominated by Ca and CaO emissions but without lines from any sulfur species. The lack of detectable sulfur species may be due to the relatively weak visible emission intensities of these species compared to Ca species. Time-of-Flight Mass Spectrometer (TOFMS) experiments were carried on in vacuum at 10 -15 on an instrument in Dr. Beauchamp’s laboratory with a 1 meter pathlength and a 15 kV target plate voltage. In addition to the low ionization potential metals (Na+, K+, Ca+, Mg+, etc) several sulfur species were observed including SO4+, CaS+, and CaSO2+.Notably, ions of SO3 were not observed in these experiments. Therefore the results obtained do quantitatively constrain the SO2/SO3 ratio to ~10.
PROJECT MEMBERS:Thomas Ahrens
RELATED OBJECTIVES:Objective 11.0
Determine (theoretically and empirically) the ultimate outcome of the planet-forming process around other stars, especially the habitable ones.
Define climatological and geological effects upon the limits of habitable zones around the Sun and other stars to help define the frequency of habitable planets in the universe.
Determine the resilience of local and global ecosystems through their response to natural and human-induced disturbances.