Global mineralogical mapping of Mars by the Observatoire pour la Mineralogie, l'Eau, les Glaces et l'Activite (OMEGA) instrument on the European Space Agency's Mars Express spacecraft provides new information on Mars' geological and climatic history. Phyllosilicates formed by aqueous alteration very early in the planet's history (the "phyllocian" era) are found in the oldest terrains; sulfates were formed in a second era (the "theiikian" era) in an acidic environment. Beginning about 3.5 billion years ago, the last era (the "siderikian") is dominated by the formation of anhydrous ferric oxides in a slow superficial weathering, without liquid water playing a major role across the planet.

https://science.sciencemag.org/content/sci/312/5772/400.full.pdf

Global Mineralogical and Aqueous Mars History Derived from OMEGA/Mars Express Data

Calibration of the geological time scale is achieved by independent radioisotopic and astronomical dating, but these techniques yield discrepancies of ∼1.0% or more, limiting our ability to reconstruct Earth history. To overcome this fundamental setback, we compared astronomical and 40 Ar/ 39 Ar ages of tephras in marine deposits in Morocco to calibrate the age of Fish Canyon sanidine, the most widely used standard in 40 Ar/ 39 Ar geochronology. This calibration results in a more precise older age of 28.201 ± 0.046 million years ago (Ma) and reduces the 40 Ar/ 39 Ar method9s absolute uncertainty from ∼2.5 to 0.25%. In addition, this calibration provides tight constraints for the astronomical tuning of pre-Neogene successions, resulting in a mutually consistent age of ∼65.95 Ma for the Cretaceous/Tertiary boundary.

https://science.sciencemag.org/content/sci/320/5875/500.full.pdf

Synchronizing Rock Clocks of Earth History

Shock metamorphism of ordinary chondrites

[1] The Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO) is a Facility Instrument (i.e., government-furnished equipment operated by a science team not responsible for design and fabrication) designed, built, and operated by Malin Space Science Systems and the MRO Mars Color Imager team (MARCI). CTX will (1) provide context images for data acquired by other MRO instruments, (2) observe features of interest to NASA's Mars Exploration Program (e.g., candidate landing sites), and (3) conduct a scientific investigation, led by the MARCI team, of geologic, geomorphic, and meteorological processes on Mars. CTX consists of a digital electronics assembly; a 350 mm f/3.25 Schmidt-type telescope of catadioptric optical design with a 5.7° field of view, providing a ∼30-km-wide swath from ∼290 km altitude; and a 5000-element CCD with a band pass of 500–700 nm and 7 μm pixels, giving ∼6 m/pixel spatial resolution from MRO's nearly circular, nearly polar mapping orbit. Raw data are transferred to the MRO spacecraft flight computer for processing (e.g., data compression) before transmission to Earth. The ground data system and operations are based on 9 years of Mars Global Surveyor Mars Orbiter Camera on-orbit experience. CTX has been allocated 12% of the total MRO data return, or about ≥3 terabits for the nominal mission. This data volume would cover ∼9% of Mars at 6 m/pixel, but overlapping images (for stereo, mosaics, and observation of changes and meteorological events) will reduce this area. CTX acquired its first (instrument checkout) images of Mars on 24 March 2006.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2006JE002808

Context Camera Investigation on board the Mars Reconnaissance Orbiter

Results by Neukum et al. (2001) and Ivanov (2001) are combined with crater counts to estimate ages of Martian surfaces. These results are combined with studies of Martian meteorites (Nyquist et al., 2001) to establish a rough chronology of Martian history. High crater densities in some areas, together with the existence of a 4.5 Gyr rock from Mars (ALH84001), which was weathered at about 4.0 Gyr, affirm that some of the oldest surfaces involve primordial crustal materials, degraded by various processes including megaregolith formation and cementing of debris. Small craters have been lost by these processes, as shown by comparison with Phobos and with the production function, and by crater morphology distributions. Crater loss rates and survival lifetimes are estimated as a measure of average depositional/erosional rate of activity.

/pdf/cratering-chronology-and-the-evolution-of-mars-15gbue0bfh.pdf

Cratering Chronology and the Evolution of Mars

The SNC (Shergotty-Nakhla-Chassigny) meteorites have recorded interactions between martian crustal fluids and the parent igneous rocks. The resultant secondary minerals — which comprise up to ~1 vol.% of the meteorites — provide information about the timing and nature of hydrous activity and atmospheric processes on Mars. We suggest that the most plausible models for secondary mineral formation involve the evaporation of low temperature (25 – 150 °C) brines. This is consistent with the simple mineralogy of these assemblages — Fe-Mg-Ca carbonates, anhydrite, gypsum, halite, clays — and the chemical fractionation of Ca-to Mg-rich carbonate in ALH84001 “rosettes”. Longer-lived, and higher temperature, hydrothermal systems would have caused more silicate alteration than is seen and probably more complex mineral assemblages. Experimental and phase equilibria data on carbonate compositions similar to those present in the SNCs imply low temperatures of formation with cooling taking place over a short period of time (e.g. days). The ALH84001 carbonate also probably shows the effects of partial vapourisation and dehydration related to an impact event postdating the initial precipitation. This shock event may have led to the formation of sulphide and some magnetite in the Fe-rich outer parts of the rosettes.

/pdf/alteration-assemblages-in-martian-meteorites-implications-1akeyls42e.pdf

Alteration Assemblages in Martian Meteorites: Implications for Near-Surface Processes

Lunar meteorites represent a more random sampling of lunar material than the Apollo or Luna collections and, as such, lunar meteorite impact melt ages are the most important data in nearly 30 years with which to reexamine the lunar cataclysm hypothesis. Within the lunar meteorite breccias MAC 88105, QUE 93069, DaG 262, and DaG 400, seven to nine different impact events are represented with 40Ar-39Ar ages between 2.76 and 3.92 billion years ago (Ga). The lack of impact melt older than 3.92 Ga supports the concept of a short, intense period of bombardment in the Earth-moon system at approximately 3.9 Ga. This was an anomalous spike of impact activity on the otherwise declining impact- frequency curve.

https://science.sciencemag.org/content/sci/290/5497/1754.full.pdf

Support for the Lunar Cataclysm Hypothesis from Lunar Meteorite Impact Melt Ages

Xenon and other noble gases in shergottites

We show that the action of a CO2 suspended flow could have produced the recent small gullies on Mars, and, hence, that liquid water is not required. The model involves the build-up of a liquid-CO2 aquifer behind and below a dry-ice barrier (dam/cap rock) in the pore spaces a few meters into the rock from the cliff face and on order of a hundred meters below the top of the cliff brink surface. Seasonal (or obliquity-cycle-seasonal) heating causes pinching out of the dry-ice barrier and rapid release of the liquid CO2. Erosion of the gullies occurs as the rapid vaporization of the liquid CO2 with entrainment of rock and clathrate-hydrate ice produces a density flow analogous to a terrestrial nue ardente.

Liquid CO2 Breakout and the Formation of Recent Small Gullies on Mars

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000GL012496

Timothy D. Swindle

Papers

Alteration Assemblages in Martian Meteorites: Implications for Near-Surface Processes

Support for the Lunar Cataclysm Hypothesis from Lunar Meteorite Impact Melt Ages

Xenon and other noble gases in shergottites

Liquid CO2 Breakout and the Formation of Recent Small Gullies on Mars

Liquid CO2 breakout and the formation of recent small gullies on Mars