Radiation-Formed Color Centers of Sodium Chloride on Inner Solar System Bodies
Dr. Michael Bramble, JPL Postdoctoral Fellow
Thursday, November 10th @ 12:00 pm (PT) 180 – 101 and via WebEx
Abstract: Radiation-formed color centers of alkali halides are a powerful tool for identifying these minerals that are otherwise featureless in remote sensing spectroscopic data. Previously, this has mostly notably been demonstrated at Europa, where analyses of spacecraft and telescopic data at visible and ultraviolet wavelengths have identified radiation-formed color centers of halite (NaCl). We report on the identification of radiation-formed color centers of halite on Ceres and Mars using spectroscopic imaging data collected by the Dawn spacecraft and Mars Reconnaissance Orbiter. The irradiated halite was identified by visible-wavelength radiative transfer modeling of spacecraft observations and mixture modeling using laboratory reference spectra. At Ceres, the irradiated halite was identified most notably at Cerealia Facula and Ahuna Mons. At Mars, the irradiated halite was identified as co-located with the chloride salt-bearing deposits. The presence, abundance, and distribution of halite on these two bodies leads to novel identifications and interpretations of active geological processes. We performed tests in an attempt to differentiate between Solar energetic particles or Galactic cosmic rays (GCRs) as the radiation source. Both worlds do not present evidence for Solar influences, and the observations point to GCRs as the radiation source. Therefore, radiation-formed color centers may be common throughout the Solar System and reveal previously invisible compositional information about salty surfaces.
About the speaker: Michael Bramble is a JPL Postdoctoral Scholar in the Small Bodies group of the Planetary Science section, and he is a geochemist and spectroscopist in JPL's Ocean Worlds Laboratory. Michael is interested in the remote sensing of materials at extreme environmental conditions, and explores spectral alterations due to cold, irradiated, and vacuum conditions. He uses remote spectral data to characterize mineralogy, geological history, and surface processes on planetary surfaces, and is interested in the development of quantitative analytical techniques and instrumentation in the geological sciences. Michael graduated from Brown University with a PhD in Earth, Environmental, and Planetary Sciences where his dissertation focused on advancing thermal emission spectroscopy of cold, airless planetary surfaces. Michael received a B.Sc. in Planetary Science from Western University, and he also has a B.Mus. degree from the Memorial University of Newfoundland and originally hails from New Brunswick, Canada.
WebEx Info: https://jpl.webex.com/jpl/j.php?MTID=m11c09106842ed41a74b08beab09688d4
Meeting number (access code): 2762 786 0315
Meeting password: PHjdDcHY465
