Astrophysics Seminar

Jupitar’s icy moon Europa is continuously bombarded by solar photons as well as energetic electrons, protons, and ions from the magnetospheric torus of Jupiter. Depending upon the energy, electrons can penetrate up to one meter on the icy surface of Europa, chemically alter the surface, and eject sputtered radiation products into the atmosphere. Investigating the radiation sputtering on the ice surface is important to understand the exchange between Europa’s surface and its atmosphere. Upon sputtering, different types of materials emit specific sputtered products. Any unique sputtered product can be used to link the local surface composition with Europa’s atmosphere. If biotic or abiotic organics are present near the surface of Europa, the radiation products are expected to be sputtered into Europa's tenuous atmosphere and potentially detected by in-situ mass spectrometers on board the Europa Mission spacecraft. The detection of any unique evolved gaseous species during these reactions may provide clues to the type of organic material being irradiated at Europa’s surface. Our goal is to determine whether different classes of organic matter (e.g., hydrocarbon, alcohol, acid and more biologically relevant amino acid) embedded in ice produce different unique signatures under radiation, to begin to understand whether these might be detectable through spacecraft instrumentation. To mimic Europa’s surface conditions at JPL's Ice Spectroscopy Lab (ISL), I used an ultrahigh vacuum system with a 2keV electrons source to study the radiation sputtering of organics at different Europa surface temperatures from 80 K to 120 K, corresponding to the range of temperatures experienced by Europa. I investigated the electron sputtering of water ice containing the above-mentioned organics to understand how differences in chemical structure influence the observed sputtered byproducts. Sputtered organics are detected by a quadrupole mass spectrometer. The results from this work determine that the production of different sputtered byproducts (such as CO2) depends on organic type, temperatures and radiation exposure. Although it is unknown what carbon-containing compounds would be present on the surface of Europa, these experiments provide an important reference point for evolved gas signature detection, to determine the types of molecules that can be produced with a surrounding ice water matrix. Our laboratory data is critical for the upcoming Europa Clipper mission (launching in October 2024) and for defining the requirements for sample collection and analysis. Also, the data from this work on the radiation effects at Europa’s surface could significantly influence the interpretation of data collected from the Europa clipper instruments.