Search Publications
VIRTIS emissivity of Alpha Regio, Venus, with implications for tessera composition
Gilmore, Martha S.; Helbert, Jörn; Mueller, Nils
The composition of Venus tessera terrain is unknown. The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) aboard Venus Express (VEx) collects data that yields the surface emissivity at ∼1 µm, which contains information convolving a number of surface properties, including composition. We examine the variation of emissivity in the vi…
Persistent aeolian activity at Endeavour crater, Meridiani Planum, Mars; new observations from orbit and the surface
Johnson, Jeffrey R.; Chojnacki, Matthew; Moersch, Jeffrey E. +3 more
Aeolian-driven bedform activity is now known to occur in many regions of Mars, based on surface and orbital observation of contemporary martian ripple and dune mobility events. Many of these sites have only been monitored with sufficient resolution data for the last few Mars years, when the High Resolution Imaging Science Experiment (HiRISE) began…
Age determination of linear surface features using the Buffered Crater Counting approach - Case studies of the Sirenum and Fortuna Fossae graben systems on Mars
Platz, T.; Michael, G. G.; Walter, S. H. G. +1 more
Buffered Crater Counting (BCC) offers a possibility to determine ages of linear/curvilinear surface features that provide no or only very limited surface areas for the conventional crater counting approach. In this study we applied the BCC analysis to two tectonic fault systems, Fortuna Fossae and a subsection of Sirenum Fossae. We compared BCC re…
Record-breaking storm activity on Uranus in 2014
de Pater, Imke; Sromovsky, L. A.; Fry, P. M. +3 more
In spite of an expected decline in convective activity following the 2007 equinox of Uranus, eight sizable storms were detected on the planet with the near-infrared camera NIRC2, coupled to the adaptive optics system, on the 10-m W.M. Keck telescope on UT 5 and 6 August 2014. All storms were on Uranus' northern hemisphere, including the brightest …
Detection of Callisto's oxygen atmosphere with the Hubble Space Telescope
France, Kevin; Feldman, Paul D.; Strobel, Darrell F. +3 more
We report the result of a search for evidence of an O2-dominated atmosphere on Callisto, using the high far-ultraviolet sensitivity of the Hubble Space Telescope Cosmic Origins Spectrograph (COS). Observations of Callisto's leading/Jupiter-facing hemisphere show, for the first time, variable-strength atomic oxygen (O I) emissions with b…
Mixtures of clays and sulfates within deposits in western Melas Chasma, Mars
Wray, James J.; Weitz, Catherine M.; Noe Dobrea, Eldar
We have utilized several data sets from multiple spacecraft that have been acquired over a continuous observation campaign across the southwestern Melas Chasma region of Mars. The blocky deposit observed on the chasma floor and on portions of the southern wallrock consists of mixtures of light- and medium-toned materials that exhibit displacement …
Thermal evolution of Venus with argon degassing
O'Rourke, Joseph G.; Korenaga, Jun
Decades-old measurements of atmospheric and elemental surface composition constrain the history of Venus. In this study, we search for a model featuring continuous evolution in the stagnant-lid regime that predicts the present-day atmospheric mass of radiogenic argon and satisfies the other available constraints. For comparison, we also consider t…
Dust devil height and spacing with relation to the martian planetary boundary layer thickness
Fenton, Lori K.; Lorenz, Ralph
In most remote and unmonitored places, little is known about the characteristics of daytime turbulent activity. Few processes render the optically transparent atmospheres of Earth and Mars visible; put more plainly, without clever instruments it is difficult to "see the unseen". To address this, we present a pilot study of images of martian dust d…
Lithospheric structure of Venus from gravity and topography
Ruiz, Javier; Jiménez-Díaz, Alberto; Kirby, Jon F. +3 more
There are many fundamental and unanswered questions on the structure and evolution of the venusian lithosphere, which are key issues for understanding Venus in the context of the origin and evolution of the terrestrial planets. Here we investigate the lithospheric structure of Venus by calculating its crustal and effective elastic thicknesses (T
A radar survey of M- and X-class asteroids. III. Insights into their composition, hydration state, & structure
Nolan, Michael C.; Springmann, Alessondra; Howell, Ellen S. +13 more
Using the S-band radar at Arecibo Observatory, we observed thirteen X/M-class asteroids; nine were previously undetected and four were re-observed, bringing the total number of Tholen X/M-class asteroids observed with radar to 29. Of these 29M-class asteroids, 13 are also W-class, defined as M-class objects that also display a 3-µm absorptio…