Search Publications
Assessing the mineralogy of the watershed and fan deposits of the Jezero crater paleolake system, Mars
Mustard, John F.; Goudge, Timothy A.; Head, James W. +2 more
We present results from geomorphic mapping and visible to near-infrared spectral analyses of the Jezero crater paleolake basin and its associated watershed. The goal of this study is to understand the provenance of the sedimentary deposits within this open-basin lake using a source-to-sink approach. Two fan deposits located within the basin have d…
The Martian atmospheric ion escape rate dependence on solar wind and solar EUV conditions: 1. Seven years of Mars Express observations
Barabash, Stas; Nilsson, Hans; Holmström, Mats +3 more
More than 7 years of ion flux measurements in the energy range 10 eV-15 keV have allowed the ASPERA-3/IMA (Analyzer of Space Plasmas and Energetic Ions/Ion Mass Analyzer) instrument on Mars Express to collect a large database of ion measurements in the Mars environment, over a wide range of upstream solar wind (density and velocity) and radiation …
Variability of the Martian thermosphere during eight Martian years as simulated by a ground-to-exosphere global circulation model
Forget, F.; López-Valverde, M. A.; García-Comas, M. +3 more
Using a ground-to-exosphere general circulation model for Mars we have simulated the variability of the dayside temperatures at the exobase during eight Martian years (MY, from MY24 to MY31, approximately from 1998 to 2013), taking into account the observed day-to-day solar and dust load variability. We show that the simulated temperatures are in …
Structural mapping of Enceladus and implications for formation of tectonized regions
Crow-Willard, Emma N.; Pappalardo, Robert T.
Global structural mapping of high-resolution Cassini images of Enceladus reveals a richly varied surface. Most notable are three main regions of deformation each containing multiple structural units. In addition to the well known "South Polar Terrain" (SPT), there are two other large regions of deformation that we term "Leading Hemisphere Terrain"…
Cooling of the Martian thermosphere by CO2 radiation and gravity waves: An intercomparison study with two general circulation models
Medvedev, Alexander S.; Yiǧit, Erdal; Hartogh, Paul +3 more
Observations show that the lower thermosphere of Mars (∼100-140 km) is up to 40 K colder than the current general circulation models (GCMs) can reproduce. Possible candidates for physical processes missing in the models are larger abundances of atomic oxygen facilitating stronger CO2 radiative cooling and thermal effects of gravity wave…
Morphometry of small recent impact craters on Mars: Size and terrain dependence, short-term modification
Watters, W. A.; Geiger, L. M.; Fendrock, M. +1 more
Most recent studies of crater morphometry on Mars have addressed large craters (D>5 km) using elevation models derived from laser altimetry. In the present work, we examine a global population of small (25 m ≤D≤5 km), relatively well-preserved simple impact craters using HiRISE stereo-derived elevation models. We find that scaling laws from pri…
Dynamics of Saturn's polar regions
Hueso, R.; Sánchez-Lavega, A.; Antuñano, A. +1 more
We analyze data retrieved by the imaging science system onboard the Cassini spacecraft to study the horizontal velocity and vorticity fields of Saturn's polar regions (latitudes 60-90°N in June-December 2013 and 60-90°S in October 2006 and July-December 2008), including the northern region where the hexagonal wave is prominent. With the aid of an …
Hot oxygen corona at Mars and the photochemical escape of oxygen: Improved description of the thermosphere, ionosphere, and exosphere
Bougher, Stephen W.; Combi, Michael R.; Tenishev, Valeriy +2 more
The Mars Adaptive Mesh Particle Simulator model is coupled with the Mars Global Ionosphere Thermosphere Model for the first time to provide an improved description of the Martian hot O corona based on our modeling studies of O2+ dissociative recombination. A total of 12 cases comprising three solar activity levels and four or…
Identification of Mars gully activity types associated with ice composition
Vincendon, Mathieu
The detection of geologically recent channels at the end of the twentieth century rapidly suggested that liquid water could have been present on Mars up to recent times. A mechanism involving melting of water ice during ice ages in the last several million years progressively emerged during years following the first observations of these gullies. …
Electron impact ionization in the Martian atmosphere: Interplay between scattering and crustal magnetic field effects
Lillis, Robert J.; Fang, Xiaohua
Precipitating electrons are typically the dominant source of energy input into Mars' nighttime upper atmosphere, with consequences for atmospheric and ionospheric structure, composition, chemistry, and electrodynamics. Mars' spatially heterogeneous crustal magnetic fields affect the fluxes of precipitating electrons, via both the magnetic mirror f…