DIX Planetary Science Seminar

ZACHARIAH MILBY - The tenuous atmospheres of the Galilean satellites are sputtered and/or sublimated from thevolatile ices that make up their surfaces. When electrons from Jupiter's rapidly-spinningmagnetosphere impact these atmospheric gases, they produce auroral emission similar toEarth's northern lights. By studying both the absolute brightnesses of the aurora and therelative brightnesses at different wavelengths, we can determine the constituent atomic andmolecular species in the satellite atmospheres, their column densities and their relative mixingratios. To date, most observations of aurora in the Galilean system have been at far-ultravioletwavelengths. However, there are only a few emission lines in this wavelength region, so theconstraints they provide can be limited. We've expanded these observations to opticalwavelengths covering 500 to 900 nm using several nights of data taken with the High ResolutionEchelle Spectrometer (HIRES) at the Keck I telescope on the summit of Maunakea. This additionalwavelength range adds several more potentially-observable emission lines, which coupled withthe cadence of our observations allows us to provide more robust constraints on theatmospheric composition of the Galilean satellites. With these observations, we were able toreport the first statistically-significant detection of optical aurora at Ganymede and Callisto.

YU YU PHUA - Geomorphological evidence such as valley networks, and fans and delta deposits indicate thatliquid water once flowed on the surface of Mars. Spectroscopic observations from orbit showdiverse range of hydrated minerals such as hydrated silica, sulfates, and phyllosilicates,indicating water-rock interaction that resulted in the partitioning of water into hydratedminerals. Landed in situ investigations can ground truth orbital spectroscopic observations andprovide more constraints to understand the evolution of the surface environment. Mostrecently, the Mars 2020 Perseverance rover landed and has been exploring the Jezero craterfloor and western fan units. In this work, we used SHERLOC, a Raman spectrometer payload onMars 2020, to directly detect hydration signatures at high spatial resolution (100 micrometer),and examine the variability in alteration phases as well as hydration carrier phases across therocks in the crater floor and western fan units. We find that hydration phases are observed insome targets in the crater floor and western fan, with sulfates being the likely hydration carrierphase in all targets. Perhaps surprisingly, hydrated silicates have not yet been detected, but thismay be an effect of the Raman measurement approach. Spectral features such as peak positionsand band shapes appear to vary within and across geologic units, indicating variable degree ofhydration and changing fluid environments across time/space in the Jezero system.