Search Publications
Climbing and falling dunes in Valles Marineris, Mars
Chojnacki, Matthew; Moersch, Jeffrey E.; Burr, Devon M.
Multiple occurrences of “wall dunes” are found several kilometers above the Valles Marineris canyon floor. Dune slip face orientation and bed form morphologies indicate transport direction and whether the wall dunes are climbing dunes or falling dunes. On Earth, these types of dunes form in a unidirectional wind regime and are strongly controlled …
Impact-induced overland fluid flow and channelized erosion at Lyot Crater, Mars
Harrison, Tanya N.; Malin, Michael C.; Cantor, Bruce A. +5 more
Lyot Crater is one of the youngest impact basins > 200 km in diameter on Mars. Although published hydrological models suggest that impact-related groundwater release might have occurred at Lyot, no geomorphic evidence for such activity has been previously identified. Here, we use images acquired predominantly by the Mars Reconnaissance Orbiter …
Sodium chloride as a geophysical probe of a subsurface ocean on Enceladus
Glein, Christopher R.; Shock, Everett L.
Recent data from the Cassini spacecraft suggest that an ocean exists inside Saturn's satellite Enceladus. Here, we show that the size of an ocean can be estimated if the NaCl concentration of the ocean is known. We find that concentrations of aqueous NaCl reported by Postberg et al. (2009) imply a relatively large ocean, comprising at least 17% by…
A strong high altitude narrow jet detected at Saturn's equator
Hueso, R.; Sánchez-Lavega, A.; García-Melendo, E. +2 more
Here we report the discovery at the upper cloud level of an extremely narrow and strong prograde jet, centered in the middle of the broad equatorial jet. Measurements from images obtained by the Cassini Imaging Science Subsystem (ISS) show that the jet reaches 430 ms-1 ± 16 m s-1 with a peak speed difference of 180 ms-1<…
Differences in solar wind cross-helicity and residual energy during the last two solar minima
Perri, S.; Balogh, A.
The minimum of solar cycle 23 exhibited anomalous characteristics with respect to its predecessors. Other than the differences in the standard indicators of activity, such as sunspots, polar magnetic fields were also found to be different. These differences had a range of effects in the solar wind. In this work we study the Alfvénicity and the res…
Venus OH nightglow distribution based on VIRTIS limb observations from Venus Express
Drossart, P.; Piccioni, G.; Gérard, J. -C. +1 more
The full set of VIRTIS-M limb observations of the OH Venus nightglow has been analyzed to determine its characteristics. Based on 3328 limb profiles, we find that the mean peak intensity along the line of sight of the OH(Δv = 1 sequence) is 0.35-0.21+0.53 MR and is located at 96.4 ± 5 km. The emission is highly variable and n…
Cassini imaging search rules out rings around Rhea
Hedman, Matthew M.; Burns, Joseph A.; Tiscareno, Matthew S. +1 more
We have conducted an intensive search using the Cassini ISS narrow-angle camera to identify any material that may orbit Rhea. Our results contradict an earlier and surprising inference that Rhea, the second-largest moon of Saturn, possesses a system of narrow rings embedded in a broad circum-satellite disk or cloud.
Escape of O+ through the distant tail plasma sheet
Sauvaud, J. -A.; Wurz, P.; Bochsler, P. +13 more
In February 2007, the STEREO-B spacecraft encountered the magnetosheath, plasma sheet and plasma sheet boundary layer from about 200 RE to 300 RE downtail. This time period was during solar minimum, and there was no storm activity during this month. Using data from the PLASTIC instrument, we find that even during quiet times,…
Groundwater processes in Hebes Chasma, Mars
Grindrod, Peter M.; Balme, Matthew R.
We describe a conceptual model of groundwater processes at Hebes Chasma, Mars, which can account for the distribution of hydrated minerals and their subsequent evolution. At Hebes Chasma, pressure gradients set up by the large central mound, Hebes Mensa, could cause groundwater to be sourced predominantly from beneath the central region, if such w…
Permittivity estimation of layers beneath the northern polar layered deposits, Mars
Orosei, Roberto; Cartacci, Marco; Cicchetti, Andrea +6 more
Martian Polar Layered Deposits, most likely dusty ice are transparent to radar waves. In the North Pole bedrock has been detected by MARSIS up to a depth about 2 Km, whereas in the South Pole such interface has been located at about 3.7 Km. The reflected signal is generally above the noise and can be used to estimate the dielectric properties of t…