Ice Seismology

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Cutway of the interior of Europa. The ice crust is 10-30 km thick, with a 100 km deep ocean of liquid water. The mantle is rocky, and there may be a small iron core.

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Icy satellites are some of the most dynamic worlds in our solar system, displaying active tectonics, eruptions of ice and water, and more heat than even their terrestrial counterparts. Many of these satellites may have had subsurface liquid water oceans at some point in their past and some are suspected to harbor oceans today. Those whose surfaces display recent geologic activity are particularly suggestive of subsurface oceans. Icy satellites are perhaps the most potentially habitable spaces in the Solar System. Our group combines seismoligcal model with investigations of Earth analogs to understand the geological processes observed on icy satellites, identify those satellites that likely possess oceans in the present day, and help propel forward the search for extraterrestrial life.

Theoretical seismic models of the Europan interior. There is a significant difference between models with a cold and hot interior. Adapted from Cammarano et al., 2005.

To study the icy crusts of the outer satellites, we are using the ice shelves and ice sheets of Earth as analog environments to study the deformation of ice and propagation of seismic waves in such environments. Many features on the outer satellites are related to tidal stresses, thus it is expected that seismicity will be closely coupled to the tidal periods of these satellites. By using the redundant information provided by repeat seismicity, we are modeling what a future seismometer on a tidally active outer satellite might image. The goal of such approaches is to determine if such information can be used to illuminate the deeper interior, putting constraints on the size of the core, mantle, and ocean layers (if present).

Additionally, recent drilling experiments in eastern Greenland revealed that there is a significant amount of seasonal water that is stored in the surface firn layer. To determine the structure of this acquifer with depth, our research group will be deploying geophones onto the surface of the ice sheet to refine the depth extent and volume of the firn acquifer. The amount of melt water present in the firn is significant and may account for a substantial amount of previously unrecognized melt.

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Measuring the seismic wave velocity of the firn in Greenland with an active source geophone line.

Relevant Papers:

Forthcoming!

This research is supported by NSF Arctic Research Office Grant #PLR-1417993.

© Nicholas Schmerr 2014