A5078151990- Planetary Science and Exploration
- Astro and Planetary Science
- Geology and Paleoclimatology Research
- Space Exploration and Technology
- Landslides and related hazards
- Geological formations and processes
- Cryospheric studies and observations
- Hydrology and Sediment Transport Processes
- Soil erosion and sediment transport
- Methane Hydrates and Related Phenomena
- Maritime and Coastal Archaeology
- Climate change and permafrost
- Isotope Analysis in Ecology
- Hydrology and Watershed Management Studies
- Fire effects on ecosystems
- Granular flow and fluidized beds
- Space Science and Extraterrestrial Life
- Aeolian processes and effects
- Geological Studies and Exploration
- Marine and environmental studies
- Archaeology and Natural History
- Geotechnical and Geomechanical Engineering
- Hydrology and Drought Analysis
- Space Satellite Systems and Control
- Mercury impact and mitigation studies
Dartmouth Hospital
2020-2025
Dartmouth College
2017-2025
University of California, Berkeley
2010-2020
California Institute of Technology
2015-2018
Planetary Science Institute
2010-2016
The Curiosity rover discovered fine-grained sedimentary rocks, which are inferred to represent an ancient lake and preserve evidence of environment that would have been suited support a martian biosphere founded on chemolithoautotrophy. This aqueous was characterized by neutral pH, low salinity, variable redox states both iron sulfur species. Carbon, hydrogen, oxygen, sulfur, nitrogen, phosphorus were measured directly as key biogenic elements; inference, is assumed available. probably had...
Ancient lake system at Gale crater Since 2012, the Curiosity rover has been diligently studying rocky outcrops on Mars, looking for clues about past water, climate, and habitability. Grotzinger et al. describe analysis of a huge section sedimentary rocks near crater, where Mount Sharp now stands (see Perspective by Chan). The features within these sediments are reminiscent delta, stream, deposits Earth. Although individual lakes were probably transient, it is likely that there was enough...
Observations by the Mars Science Laboratory Mast Camera (Mastcam) in Gale crater reveal isolated outcrops of cemented pebbles (2 to 40 millimeters diameter) and sand grains with textures typical fluvial sedimentary conglomerates. Rounded conglomerates indicate substantial abrasion. ChemCam emission spectra at one outcrop show a predominantly feldspathic composition, consistent minimal aqueous alteration sediments. Sediment was mobilized ancient water flows that likely exceeded threshold...
Abstract Catchment travel time distributions reflect how precipitation from different storms is stored and mixed as it transported to the stream. can be described by mean shape of distribution around mean. Whereas times have been quantified in a range catchment studies, only rarely has estimated. The affects both short‐term long‐term response pulse input soluble contaminant. Travel are usually estimated conservative tracer concentrations streamflow, which analyzed using time‐domain...
Abstract Debris flows are typically a saturated mixture of poorly sorted particles and interstitial fluid, whose density flow properties depend strongly on the presence suspended fine sediment. Recent research suggests that grain size distribution (GSD) influences excess pore pressures (i.e., pressure in predicted hydrostatic pressure), which turn plays governing role debris behaviors. We report series controlled laboratory experiments 4 m diameter vertically rotating drum where coarse...
Abstract The landing site for the Curiosity rover is located at distal end of Peace Vallis fan in Gale Crater. covers 80 km 2 and fed by a 730 catchment, which drains an upland plains area through 15 wide gap crater rim. Valley incision into accumulated debris delivered sediment relatively low density valley network to main stem channel fan. An estimated total volume 0.9 3 matches calculated removal due (0.8 ) indicates mean thickness 9 m. profile weakly concave up with slope 1.5% lower...
Abstract The quantification of lake levels in Gale crater is important to define the hydrologic and climatic history experienced by sedimentary deposits found Curiosity . We propose that there were at least three major stands within Gale, each persisted >1000 years, all occurred after Mount Sharp reached close its current topographic form. Deltaic off southern rim derived from incision Farah Vallis, corresponding flank highest level, which had a mean depth 700 m. Canyons similar form...
Abstract We describe preliminary results from the first 100 sols of ground temperature measurements along Mars Science Laboratory's traverse Bradbury Landing to Rocknest in Gale. The data show long‐term increases mean that are consistent with seasonal evolution. Deviations expected trends within diurnal cycle observed and may be attributed rover environmental effects. Fits measured amplitudes using a thermal model suggest surfaces have inertias range 265–375 J m −2 K −1 s −1/2 , which values...
Abstract This paper characterizes the detailed sedimentology of a fluvial sandbody on Mars for first time and interprets its depositional processes palaeoenvironmental setting. Despite numerous orbital observations landforms surface Mars, ground‐based characterization such deposits has not previously been possible. Results from NASA Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale sedimentary architecture palaeomorphology environment Mars. work describes...
Abstract Soils are a principal global reservoir of mercury (Hg), neurotoxic pollutant that is accumulating through anthropogenic emissions to the atmosphere and subsequent deposition terrestrial ecosystems. The fate Hg in soils remains uncertain, however, particularly what degree re-emitted back as gaseous elemental (GEM). Here we use fallout radionuclide (FRN) chronometry directly measure accumulation rates soils. By comparing these with measured atmospheric fluxes mass balance approach,...
Abstract The Curiosity rover has analyzed various detrital sedimentary rocks at Gale Crater, among which fluvial and lacustrine are predominant. Conglomerates correspond both to the coarsest sediments least modified by chemical alteration, enabling us link their chemistry that of source on Crater rims. In this study, we report results six conglomerate targets Alpha‐Particle X‐ray Spectrometer 40 ChemCam. bulk derived instruments suggests two distinct end‐members for compositions. first group...
Amplified warming of high latitudes and rapid thaw frozen ground threaten permafrost carbon stocks. The presence modulates water infiltration flow, as well sediment transport, on soil-mantled slopes, influencing the balance advective fluvial processes to diffusive hillslopes in ways that are different from temperate settings. These shape landscapes also impact stored via temperature, saturation, slope stability such stocks landscape morphometry should be closely linked. We studied <mml:math...
Abstract We have assessed the characteristics of clasts along Curiosity's traverse to shed light on processes important in genesis, modification, and transportation surface materials. Pebble‐ cobble‐sized at Bradbury Landing, subsequently Yellowknife Bay, reflect a mixing two end‐member transport mechanisms. The general clast population likely represents material deposited via impact processes, including meteorite fragments, ejecta from distant craters, impactites consisting shocked...
Abstract Deltaic deposits mapped along the Martian crustal dichotomy boundary scarp have been suggested to delineate an ancient ocean in northern lowlands of Mars. Using recently acquired orbital data, we expanded delta inventory and performed updated analysis front elevations, a proxy for paleo‐water levels. Our focused near Gale crater, home Curiosity rover. We found that elevations vary by approximately 2,400 m, but these elevation variations do not correspond modeled deformation from...
Abstract Steep, rocky landscapes often produce large sediment yields and debris flows following wildfire. Debris can initiate from landsliding or rilling in soil-mantled portions of the landscape, but there have been few direct observations flow initiation steep, landscape that lacdk a thick, continuous soil mantle. We monitored first-order catchment burned San Gabriel Mountains, California, USA. Following fire, prior to rainfall, much hillslope mantle was removed by dry ravel, exposing...
On many frozen hillslopes, subsurface water above permafrost is routed through regularly spaced, linear features known as tracks. We test whether tracks form thermal channelization, where heat from viscous dissipation in flowpaths deepens the active layer, creating a preferred flow path that attracts more water. derive equations for suprapermafrost Darcy and, using stability analysis, we calculate growth rates and obtain wavelength selection this system, which compare to observed track...
Geologists have long debated the erosive power of glaciation. At one extreme, glaciers and ice sheets been viewed as non-erosive protective blankets, while at other they are considered among Earth&#8217;s most potent forces. As such, question whether or rivers are, on average, more effective agents remains contentious. This problem is further complicated by &#8220;Sadler effect,&#8221; which describes how erosion deposition rates appear to decrease timescale observation...
Thaw-induced permafrost landslides, or thaw slumps, exemplify the alarming potential of rapid Arctic climate change to couple with unstable geomorphic feedbacks and escalate landscape hazards, sediment solute fluxes, carbon emissions. An emergent hot spot slump activity in western Canadian provides an opportunity understand context that predisposes some regions extreme sensitivity. Previous research suggests concentration this region may result from postglacial incision ice-cored moraine...
Abstract Steep mountain streams have channel morphologies that transition from alternate bar to step‐pool cascade with increasing bed slope, which affect stream habitat, flow resistance, and sediment transport. Experimental theoretical studies suggest bars form under large width‐to‐depth ratios, step‐pools in near supercritical or when width is narrow compared grain size, morphology related debris flows. However, the connection between these process variables slope—the apparent dominant...
Earth’s topography and climate result from the competition between uplift erosion, but it has been debated whether rivers or glaciers are more effective erosional agents. We present a global compilation of fluvial glacial erosion rates alongside simple numerical experiments, which show that “Sadler effect,” wherein geological an inverse relationship with measurement timescale, comprises three distinct effects: thickness bias, bias redeposition, introduced by not observing quiescent...