Search Publications
The volcanic history of Mars: High-resolution crater-based studies of the calderas of 20 volcanoes
Hynek, Brian M.; Robbins, Stuart J.; di Achille, Gaetano
Determining absolute surface ages for bodies in the Solar System is, at present, only possible for Earth and Moon with radiometric dating for both bodies and biologic proxies such as fossils for Earth. Relative ages through cratering statistics are recognized as one of the most reliable proxies for relative ages, calibrated by lunar geologic mappi…
Sequence and timing of conditions on early Mars
Head, James W.; Fassett, Caleb I.
The geological record of early Mars displays a variety of features that indicate fundamental differences from more recent conditions. These include evidence for: (1) widespread aqueous alteration and phyllosilicate formation, (2) the existence of an active magnetic dynamo, (3) the erosion of extensive valley networks, some thousands of kilometers …
Accretion of Saturn’s mid-sized moons during the viscous spreading of young massive rings: Solving the paradox of silicate-poor rings versus silicate-rich moons
Dones, Luke; Charnoz, Sébastien; Crida, Aurélien +7 more
The origin of Saturn’s inner mid-sized moons (Mimas, Enceladus, Tethys, Dione and Rhea) and Saturn’s rings is debated. Charnoz et al. [Charnoz, S., Salmon J., Crida A., 2010. Nature 465, 752-754] introduced the idea that the smallest inner moons could form from the spreading of the rings’ edge while Salmon et al. [Salmon, J., Charnoz, S., Crida, A…
Transient surface liquid in Titan's polar regions from Cassini
Lorenz, R. D.; Wye, L. C.; Zebker, H. A. +12 more
Cassini RADAR images of Titan's south polar region acquired during southern summer contain lake features which disappear between observations. These features show a tenfold increases in backscatter cross-section between images acquired one year apart, which is inconsistent with common scattering models without invoking temporal variability. The mo…
The haze and methane distributions on Neptune from HST-STIS spectroscopy
Karkoschka, Erich; Tomasko, Martin G.
We analyzed a data cube of Neptune acquired with the Hubble STIS spectrograph on August 3, 2003. The data covered the full afternoon hemisphere at 0.1 arcsec spatial resolution between 300 and 1000 nm wavelength at 1 nm resolution. Navigation was accurate to 0.004 arcsec and 0.05 nm. We constrained the vertical aerosol structure with radiative tra…
Redefinition of the crater-density and absolute-age boundaries for the chronostratigraphic system of Mars
Werner, S. C.; Tanaka, K. L.
For the boundaries of each chronostratigraphic epoch on Mars, we present systematically derived crater-size frequencies based on crater counts of geologic referent surfaces and three proposed "standard" crater size-frequency production distributions as defined by (a) a simple -2 power law, (b) Neukum and Ivanov, (c) Hartmann. In turn, these crater…
Heavy ion escape from Mars, influence from solar wind conditions and crustal magnetic fields
Barabash, Stas; Lundin, Rickard; Nilsson, Hans +5 more
We have used more than 4 years of Mars Express ion data to estimate the escape of heavy ions ( O+,O2+ and CO2+) from Mars. To take the limited field of view of the instrument into account, the data has been binned into spatial bins and angular bins to create average distribution functions for different positions in the near Mars space. …
Plasma, plumes and rings: Saturn system dynamics as recorded in global color patterns on its midsize icy satellites
Johnson, Robert E.; Hamilton, Douglas P.; McKinnon, William B. +4 more
New global maps of the five inner midsize icy saturnian satellites, Mimas, Enceladus, Tethys, Dione, and Rhea, have been constructed in three colors (UV, Green and near-IR) at resolutions of 1 km/pixel. The maps reveal prominent global patterns common to several of these satellites but also three major color features unique to specific satellites …
Energy deposition and primary chemical products in Titan’s upper atmosphere
Lewis, G. R.; Coates, A. J.; Galand, M. +4 more
Cassini results indicate that solar photons dominate energy deposition in Titan's upper atmosphere. These dissociate and ionize nitrogen and methane and drive the subsequent complex organic chemistry. The improved constraints on the atmospheric composition from Cassini measurements demand greater precision in the photochemical modeling. Therefore,…
The mesosphere and lower thermosphere of Titan revealed by Cassini/UVIS stellar occultations
Sandel, B. R.; West, R. A.; Yelle, R. V. +5 more
Stellar occultations observed by the Cassini/UVIS instrument provide unique data that probe the mesosphere and lower thermosphere of Titan at altitudes between 400 and 1400 km. This region is a site of complex photochemistry that forms hydrocarbon and nitrile species, and plays a crucial role in the formation of the organic hazes observed in the s…