Seismometer to Investigate Ice and Ocean Structure (SIIOS)

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Northwest Greenland Active Source Seismic Experiment

Line Starting Position (lat/long): 78.05494 -68.43001 Line Ending Position (lat/long): 78.06791 -68.36563In summer of 2018, the Seismometer to Investigate Ice and Ocean Structure (SIIOS) team conducted a geophysical field investigation on the Greenland ice sheet in northwestern Greenland at a location where a previous airborne radar survey by Palmer et al. (2013) had detected the signatures of a subglacial lake. The field site is located approximately 50 km north of the town of Qaanaaq. This site was chosen for the SIIOS project as it provides an opportunity for studying how a lander station could be used to detect subsurface water at an icy-ocean world. The purpose of the investigation was to confirm the presence of the subglacial lake and to measure its physical properties such as seismic impedance, as well as to estimate its depth and volume. One component of the investigation consisted of an active source seismic survey that was used to create a reflection image of the lake, as well as to measure the ice-bottom reflection coefficient. The survey was conducted along a roughly northeast oriented traverse, which started above the subglacial lake and crossed the lake’s eastern boundary.Funding for this work was provided by the NASA Planetary Science and Technology Through Analog Research (PSTAR) Grant # 80NSSC17K0229

SIIOS in Alaska: Testing an "In-Vault" Option for a Europa Lander Seismometer Experiment

The icy moons of Europa and Enceladus are thought to have global subsurface oceans in contact with mineral-rich silicate interiors, likely providing the three ingredients needed for life as we know it: liquid water, essential chemicals, and a source of energy. The possibility of life forming in their subsurface oceans relies in part on transfer of oxidants from the irradiated ice surface to the sheltered ocean below. Constraining the mechanisms and location of material exchange between the ice surface, the ice shell, and the subsurface ocean, however, is not possible without knowledge of ice thickness and liquid water depths. In a future lander-based experiment seismic measurements will be a key geophysical tool for obtaining this critical knowledge. The Seismometer to Investigate Ice and Ocean Structure (SIIOS) field-tests flight-ready technologies and develops the analytical methods necessary to make a seismic study of Europa and Enceladus a reality. We have been performing small-array seismology with a flight-candidate sensor in analog environments that exploit passive sources. Determining the depth to a subsurface ocean and any intermediate bodies of water is a priority for Ocean Worlds missions as it allows assessment of the habitability of these worlds and provides vital information for evaluating the spacecraft technologies required to access their oceans

The Deployment of the Seismometer to Investigate Ice and Ocean Structure (SIIOS) in Northwest Greenland: An experiment to study icy ocean world seismic deployments

In anticipation of future spacecraft missions to icy ocean worlds, the Seismometer to Investigate Ice and Ocean Structure (SIIOS) was funded by NASA to prepare for seismologic investigations of these worlds. During the summer of 2018, the SIIOS team deployed a seismic experiment on the Greenland Ice Sheet situated approximately 80 km north of Qaanaaq, Greenland. The deployment included one Trillium 120 s Posthole (TPH) broadband seismometer, thirteen Silicon Audio flight-candidate seismometers, five Sercel L28 4.5 Hz geophones, and one HTI 60-min hydrophone. Seismometers were buried 1 m deep in the firn in a cross-shaped array centered on a co-located TPH, hydrophone, and Silicon Audio instrument. One part of the array consisted of Silicon Audio and Sercel Geophones situated 1 m from the center of the array in the ordinal directions. A second set of four Silicon Audio instruments situated 1 km from the center of the array, in the cardinal directions. A mock-lander spacecraft was placed at the array center and instrumented with four Silicon Audio seismometers. We performed an active-source experiment and a passive-listening experiment that lasted for approximately 12 days. The active-source experiment consisted of 9-12 sledgehammer strikes to an aluminum plate at ten separate locations up to 100 m from the array center. The passive experiment recorded the ice-sheet ambient background noise, as well as local and regional events. Both datasets will be used to quantify differences in spacecraft instrumentation deployment strategies and for evaluating science capabilities for single-station and small-aperture seismic arrays in future geophysical missions. Our initial results indicate that the flight-candidate seismometer performs comparably to the TPH at frequencies above 0.1 Hz and that instruments coupled to the mock-lander perform comparably to ground-based instrumentation in the frequency band of 0.01-10 Hz. For future icy ocean world missions, a deck-coupled seismometer would perform similarly to a ground-based deployment.NASA PSTAR Grant #80NSSC17K0229 and NASA NESSF # 80NSSC18K126