The Nature of Europa's Surface and Ocean from New Infrared Spectroscopy

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Jupiter's moon Europa may harbor a global water ocean of approximately 100 km in depth, having 2 to 3 times the volume of all the liquid water on Earth. Despite almost a decade of observations from the Galileo spacecraft, it is still not clear whether Europa is merely a passive ice shell with a thin surface layer of active chemistry, or a geologically active body with a chemically rich ocean. One key to resolving the issue is determining the relationship between the icy surface and the interior ocean chemistry. Recent models suggest hydrated sulfuric acid created by ion bombardment should be abundant in the trailing hemisphere, with hydrated salts deposited by ocean evaporation more dominant elsewhere. Galileo data are of insufficient spectroscopic resolution to constrain the models in detail; but modern infrared spectrographs with adaptive optics systems on large ground based telescopes are capable of mapping the surface chemistry. The Principal Investigator and collaborators will observe Europa using the adaptive optics system on the Keck telescope to obtain unprecedentedly high spectral resolution and moderate spatial resolution from the near infrared through the thermal infrared, and will chemically map the surface of Europa, identifying salts and radiation products and determining their spatial distributions. They will construct a comprehensive model of the sources and sinks of chemical species on Europa's surface, disentangle indigenous and exogenous materials, and begin to explore the chemical composition of the unseen ocean beneath the icy crust. The project will constitute the Ph.D. dissertation work of a graduate student, and an undergraduate student will be involved in the project through the Summer Undergraduate Research Fellowship program. The Principal Investigator will communicate research results to the public through a variety of outreach activities.