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Subsurface water and clay mineral formation during the early history of Mars
Murchie, Scott L.; Ehlmann, Bethany L.; Mustard, John F. +4 more
Clay minerals, recently discovered to be widespread in Mars's Noachian terrains, indicate long-duration interaction between water and rock over 3.7 billion years ago. Analysis of how they formed should indicate what environmental conditions prevailed on early Mars. If clays formed near the surface by weathering, as is common on Earth, their presen…
Map-projection-independent crater size-frequency determination in GIS environments—New software tool for ArcGIS
Neukum, G.; van Gasselt, S.; Kneissl, T.
Statistical analysis of crater size-frequency distributions (CSFDs) of impact craters on planetary surfaces is a well-established method to derive absolute ages on the basis of remotely-sensed image data. Although modelling approaches and the derivation of absolute ages from a given CSFD have been described and discussed in considerable depth sinc…
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…
Ion Energization and Escape on Mars and Venus
Fedorov, A.; Lundin, R.; Dubinin, E. +4 more
Mars and Venus do not have a global magnetic field and as a result solar wind interacts directly with their ionospheres and upper atmospheres. Neutral atoms ionized by solar UV, charge exchange and electron impact, are extracted and scavenged by solar wind providing a significant loss of planetary volatiles. There are different channels and routes…
Columbus crater and other possible groundwater-fed paleolakes of Terra Sirenum, Mars
Clark, R. N.; Wray, J. J.; Milliken, R. E. +11 more
Columbus crater in the Terra Sirenum region of the Martian southern highlands contains light-toned layered deposits with interbedded sulfate and phyllosilicate minerals, a rare occurrence on Mars. Here we investigate in detail the morphology, thermophysical properties, mineralogy, and stratigraphy of these deposits; explore their regional context;…
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 …
Formation timescales of large Martian valley networks
Hynek, Brian M.; Hoke, Monica R. T.; Tucker, Gregory E.
Assessing timescales for formation of the ancient Martian valley networks is key to interpreting the early climate on Mars. We determined the likely formation times for seven of the largest ancient valley networks on Mars using the Darcy-Weisbach equation for average flow velocity, three different sediment transport models, and a range of input pa…
The Induced Magnetospheres of Mars, Venus, and Titan
Szego, K.; Fraenz, M.; Edberg, N. +4 more
This article summarizes and aims at comparing the main features of the induced magnetospheres of Mars, Venus and Titan. All three objects form a well-defined induced magnetosphere (IM) and magnetotail as a consequence of the interaction of an external wind of plasma with the ionosphere and the exosphere of these objects. In all three, photoionizat…
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. …