Publications

Ventifacts, rocks abraded by wind-borne particles, are found in Gale Crater, Mars. In the eastward drive from “Bradbury Landing” to “Rocknest,” they account for about half of the float and outcrop seen by Curiosity's cameras. Many are faceted and exhibit abrasion textures found at a range of scales, from submillimeter lineations to centimeter-scale facets, scallops, flutes, and grooves. The drive

Remote sensing data acquired during Dawn’s orbital mission at Vesta showed several local concentrations of high-albedo (bright) and low-albedo (dark) material units, in addition to spectrally distinct meteorite impact ejecta. The thermal behavior of such areas seen at local scale (1-10 km) is related to physical properties that can provide information about the origin of those materials. We use Da

A suite of eight rocks analyzed by the Curiosity Rover while it was stopped at the Rocknest sand ripple shows the greatest chemical divergence of any potentially sedimentary rocks analyzed in the early part of the mission. Relative to average Martian soil and to the stratigraphically lower units encountered as part of the Yellowknife Bay formation, these rocks are significantly depleted in MgO, wi

The oldest compiled U–Pb zircon ages for the Acasta Gneiss Complex in the Northwest Territories of Canada span about 4050–3850 Ma; yet older ca. 4200 Ma xenocrystic U–Pb zircon ages have also been reported for this terrane. The AGC expresses at least 25 km2 of outcrop exposure, but only a small subset of this has been documented in the detail required to investigate a complex history and resolve d

A recent study by Schmidt et al. (2011) suggests that Thera Macula, one of the “chaos regions” on Europa, may be actively forming over a large liquid water lens. Such a process could conceivably produce a thermal anomaly detectable by a future Europa orbiter or flyby mission, allowing for a direct verification of this finding. Here, we present a set of models that quantitatively assess the surface

Twenty small new impact craters or clusters have been observed to excavate bright material inferred to be ice at mid and high latitudes on Mars. In the northern hemisphere, the craters are widely distributed geographically and occur at latitudes as low as 39°N. Stability modeling suggests that this ice distribution requires a long-term average atmospheric water vapor content around 25 precipitable

Global maps of the macroscopic thermal neutron absorption cross section of Vesta's regolith by the Gamma Ray and Neutron Detector (GRaND) on board the NASA Dawn spacecraft provide constraints on the abundance and distribution of Fe, Ca, Al, Mg, and other rock-forming elements. From a circular, polar low-altitude mapping orbit, GRaND sampled the regolith to decimeter depths with a spatial resolutio

The southwesterly course of the probably pre–early Miocene and possibly Oligocene Crooked Ridge River can be traced continuously for 48 km and discontinuously for 91 km in northern Arizona (United States). The course is visible today in inverted relief. Pebbles in the river gravel came from at least as far northeast as the San Juan Mountains (Colorado). The river valley was carved out of easily er

We have measured the bidirectional reflectance of analogs of dry, wet, and frozen Martian soils over a wide range of phase angles in the visible spectral range. All samples were produced from two geologic samples: the standard JSC Mars-1 soil simulant and Hawaiian basaltic sand. In a first step, experiments were conducted with the dry samples to investigate the effects of surface texture. Comparis

Once considered dry compared with Earth, laboratory analyses of igneous components of lunar samples have suggested that the Moon’s interior is not entirely anhydrous. Water and hydroxyl have also been detected from orbit on the lunar surface, but these have been attributed to nonindigenous sources, such as interactions with the solar wind. Magmatic lunar volatiles—evidence for water indigenous to

The ChemCam instrument package on the Mars Science Laboratory rover, Curiosity, is the first planetary science instrument to employ laser-induced breakdown spectroscopy (LIBS) to determine the compositions of geological samples on another planet. Pre-processing of the spectra involves subtracting the ambient light background, removing noise, removing the electron continuum, calibrating for the wav

Rootless cones on Mars are a valuable indicator of past interactions between lava and water. However, the details of the lava–water interactions are not fully understood, limiting the ability to use these features to infer new information about past water on Mars. We have developed a model for the pressurization of a dry layer of porous regolith by melting and boiling ground ice in the shallow sub