Search Publications
Pumping out the atmosphere of Mars through solar wind pressure pulses
Barabash, S.; Futaana, Y.; Fränz, M. +6 more
We study atmospheric escape from Mars during solar wind pressure pulses. During the solar minimum of 2007-08 we have observed 41 high pressure events, which are predominantly identified as corotating interaction regions (CIR) while a few are coronal mass ejections (CME), in data from the Advanced Composition Explorer (ACE) upstream of the Earth. 3…
Near-tropical subsurface ice on Mars
Bibring, Jean-Pierre; Mustard, John; Forget, François +4 more
Near-surface perennial water ice on Mars has been previously inferred down to latitudes of about 45° and could result from either water vapor diffusion through the regolith under current conditions or previous ice ages precipitations. In this paper we show that at latitudes as low as 25° in the southern hemisphere buried water ice in the shallow (…
Evidence for present day gully activity on the Russell crater dune field, Mars
Hiesinger, H.; Erkeling, G.; Reiss, D. +1 more
On the basis of High Resolution Imaging Science Experiment (HiRISE) images of two successive years we observed changes of a gully on the Russell crater dune field. Within the first year the length of a ∼2 m wide incised gully channel grew about 50 m downslope, and ∼120 m within in the second year. Gully activity occurred in early spring between L<…
Precise mass determination and the nature of Phobos
Pätzold, M.; Rosenblatt, P.; Häusler, B. +4 more
We report independent results from two subgroups of the Mars Express Radio Science (MaRS) team who independently analyzed Mars Express (MEX) radio tracking data for the purpose of determining consistently the gravitational attraction of the moon Phobos on the MEX spacecraft, and hence the mass of Phobos. New values for the gravitational parameter …
Non-detection of impulsive radio signals from lightning in Martian dust storms using the radar receiver on the Mars Express spacecraft
Gurnett, D. A.; Morgan, D. D.; Farrell, W. M. +3 more
Here we report the results of a nearly five-year search for impulsive radio signals from lightning discharges in Martian dust storms using the radar receiver on the Mars Express spacecraft. The search covered altitudes from 275 km to 1400 km and frequencies from 4.0 to 5.5 MHz with a time resolution of 91.4 µs and a detection threshold of 2.…
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 …
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…
Overlapping ionospheric and surface echoes observed by the Mars Express radar sounder near the Martian terminator
Gurnett, D. A.; Morgan, D. D.; Duru, F.
Radar soundings from the Mars Express spacecraft occasionally show ionospheric and surface echoes that overlap in frequency. For specular reflection from a horizontally stratified ionosphere such a frequency overlap is not possible, since ionospheric and surface reflections can only occur at frequencies below and above the maximum ionospheric plas…