Winter 2021

Fridays at 12:00 PM

Zoom information can be found on the EPS advising Google calendar

January 22, 2021

Speaker: Alexis Cartwright-Taylor, University of Edinburgh, School of GeoSciences

Title: Damage localization and catastrophic failure of brittle rocks – what can we learn from combining in-situ x-ray microtomography with acoustic emissions?


January 29, 2021

Speaker: Ronald Ballouz, Lunar and Planetary Laboratory, University of Arizona

Title: The strength of solid asteroids constrained by craters on asteroidal boulders and Near-Earth Object population estimates


February 5, 2021

Speaker: Nathaniel Miller, USGS

Title: Fault roughness and earthquake rupture at plate boundary scales


February 12, 2021

Speaker: Xian Shi, Max Planck Institute for Solar System Research

Title: Near-nucleus activities of comet 67P/Churyumov-Gerasimenko observed by Rosetta/OSIRIS

Abstract: Between August 2014 and September 2016, ESA's Rosetta spacecraft rendezvoused with its target comet 67P/Churyumov-Gerasimenko and accompanied it through its perihelion passage. During the over-two-year operation, the scientific camera system on board Rosetta, OSIRIS, acquired more than 70,000 images of the comet with unprecedented resolution and coverage. In this talk, I will introduce our work on investigating gas and dust activities in the ambient coma of 67P's nucleus. Our analyses of the imaging data, combined with thermophysical and gas/dust dynamic models, show how water-ice sublimation could drive both nominal and uncommon cometary activities.


February 19, 2021

Speaker: Brad Lipovsky, Harvard University

Title: Cracking the case of ice shelf fracture

February 26, 2021

Speaker: Claire Nichols, University of Oxford

Title: The Geometry of the Ancient Lunar Magnetic Field

Abstract: Paleomagnetic studies of Apollo samples indicate that the Moon generated a core dynamo lasting for at least 2 billion years. However, the geometry of the lunar magnetic field is still largely unknown because the original orientation of nearly all Apollo samples are unconstrained. Determining the direction of the lunar magnetic field over time could elucidate the mechanism by which the lunar dynamo was powered, whether the magnetic field underwent reversals, and whether the Moon experienced true polar wander. I will present measurements of the lunar magnetic field at 3.7 Ga as recorded by Apollo 17 mare basalts 75035 and 75055. These samples formed as part of basalt flows that make up wall-rock within Camelot crater in the Taurus-Littrow valley. Using layering in the parent boulder for 75055, we inferred its original paleohorizontal orientation on the lunar surface at the time of magnetization. We find that 75035 and 75055 record mean paleointensities of 37.3 ± 5.4 µT and 43.6 ± 4.6 µT, respectively. Furthermore, 75055 records a paleoinclination of 34 ± 11°. This inclination is consistent with, but does not require, a selenocentric axial dipole. Additionally, although true polar wander is also not required by our data, polar wander inferred from independent studies is consistent with our reported paleoinclination.


March 5, 2021

Speaker: Manoochehr Shirzaei, Virginia Tech

Title: Earth-Observing Satellite Boom and Emerging Hazards in the Era of Climate Change

Abstract: With the global population surpassing 7.8 billion people in 2021, the impacts of human activities on the environment are noticeable almost everywhere on our planet. The consequences of these impacts are still elusive, particularly when trying to quantify them at larger scales. It is essential to trace environmental changes from a local to a global scale over several decades. This task is increasingly fulfilled by Earth-observing (EO) satellites, in particular, radar imaging instruments. Synthetic Aperture Radar (SAR), a cloud-penetrant microwave imaging system, provides unique day-night and all-weather monitoring capabilities. The availability of repeated SAR acquisitions with similar imaging geometry allows performing interferometric SAR (InSAR) processing. InSAR uses radar to illuminate an area of the Earth's surface and measures the change in distance between satellite and ground surface, as well as the returned signal strength. Such measurements are suitable for generating high-resolution digital elevation models and accurate terrain deformation maps. Here, I discuss some of the recent advances in developing modern multitemporal InSAR algorithms. Next, I present examples demonstrating the value of high-resolution Radar EO satellite data for mapping surface deformation with implications for sea-level rise, coastal flooding hazards, and quantifying droughts' impact on groundwater resources. Firstly, I report on high-resolution vertical land motion measurements along the U.S. coast obtained from InSAR, spanning 2003-2020. The findings include subsidence rates of up to several millimeters per year affecting different parts of the U.S. West and Gulf coasts, particularly deltas, wetlands, artificial landfills, and Holocene mud deposits. For instance, a subsidence rate of 2-10 mm/yr affects most coastal areas along San Francisco Bay. Furthermore, it is estimated that between 4.3-8.7 million people in California's coastal communities are exposed to subsidence. In combination with future projections of sea-level rise under different climate warming scenarios, it is estimated that in San Francisco Bay and Houston, an area of 125 km2-429 km2 and 186 km2-1157 km2, respectively, will be subject to inundation and flooding by 2100. Secondly, I present results from an interdisciplinary study of the response of aquifer systems in California's Central Valley to the drought periods of 2007-2010 and 2012-2015. The findings show that during droughts, the land subsidence modulated with a seasonal variation independent of the winter precipitation. The subsidence continues beyond the drought periods, although the groundwater levels have already stopped declining. It is estimated that maximum subsidence rates in the southern San Joaquin Valley are up to ~25 cm/yr and ~35 cm/yr for the 1st and 2nd droughts, respectively. Also, the groundwater loss of 21.3±7.2 km3 for the entire Central Valley during 2007-2010 and 29.3±8.7 km3 for the San Joaquin Valley during 2012-2015 is obtained. The subsidence-based estimates of groundwater loss are consistent with that of GRACE gravimetric satellites, considering uncertainty ranges. It is also found that due to overdraft, the aquifer system storage capacity was permanently reduced by up to 5%. These sets of case studies highlight the importance of EO satellite data for developing management, adaptation, and resilience plans.


March 12, 2021

Speaker: Shannon Mackenzie, Johns Hopkins University

Title: Lakes, evaporites, and sand: Investigations into the sedimentary cycle on Saturn’s moon Titan

Abstract: Saturn’s moon Titan hosts the only active hydrological cycle outside of Earth’s and, thus, an associated sedimentary cycle where surface materials are modified and redistributed with the ebb and flow of liquid hydrocarbons. In this talk, we’ll discuss some recent efforts to understand the history of Titan’s lakes and seas, their associated organic deposits, and how these processes manifest across the surface, especially as might be observable by NASA’s next New Frontiers Mission, Dragonfly.