* Astronomy

Blobrana · L

RE: Martian Clays

Blobrana · L

Clays in Pacific lavas back drier early Mars

A study of rocks at an old A-bomb test site in the Pacific has led a team of scientists to conclude that early Mars was not so warm and wet, as many argue.
The rocks at Mururoa Atoll in French Polynesia contain clay minerals that look like those seen on the Red Planet.
But whereas the Martian clays are taken to be the products of weathering of rocks by liquid water, the atoll's clays have a very different origin.
These were precipitated directly from water-rich molten rock as it cooled.
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Blobrana · L

Martian Clay as Habitats for Life

Two small depressions on Mars found to be rich in minerals that formed by water could have been places for life relatively recently in the planets history, according to a new paper in the journal Geology.
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Blobrana · L

We report here on a formation hypothesis for carbonates detected in the Nili Fossae Region near Syrtis Major. Our favoured hypothesis is talc-carbonate hydrothermal alteration, similar to that seen in ultramafic units in Western Australia.

Title: Hydrothermal formation of Clay-Carbonate alteration assemblages in the Nili Fossae region of Mars
Authors: Brown, A. J.; Hook, S. J.; Baldridge, A. M.; Crowley, J. F.; Bridges, N. T.; Thomson, B. J.; Marion, G. M.; de Souza Filho, C. R.; Bishop, J. L.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) has returned observations of the Nili Fossae region indicating the presence of Mg-carbonate in small (<10 km²), relatively bright rock units that are commonly fractured (Ehlmann et al., 2008b). We have analysed spectra from CRISM images and used co-located HiRISE images in order to further characterise these carbonate-bearing units. We applied absorption band mapping techniques to investigate a range of possible phyllosilicate and carbonate minerals that could be present in the Nili Fossae region.
We also describe a clay-carbonate hydrothermal alteration mineral assemblage in the Archean Warrawoona Group of Western Australia that is a potential Earth analog to the Nili Fossae carbonate-bearing rock units. We discuss the geological and biological implications for hydrothermal processes on Noachian Mars.

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Blobrana · L

The OMEGA instrument on board ESA's Mars Express has found strong indications that liquid water must have been present, in a stable form, in Mars' early history, having implications for the planets climatic history, and questions of life in the past.

OMEGA (Observatoire pour la Mineralogy, l'Eau, les Glaces et l'Activite), is the visible and infrared mapping spectrometer on board ESA's Mars Express. It has been collecting data on Martian surface minerals for he last 18 months.
The instrument detected the presence of the hydrated minerals, 'phyllosilicates' and 'hydrated sulphates', in isolated but large areas on the surface.
Hydrated minerals, are so called because they contain water in their crystalline structure.
Both minerals are the result of a chemical alteration of rocks. However, their formation processes are very different and point to periods of different environmental conditions in the history of the planet.

A HRSC 3D perspective view of Candor Chasma (in false colours) characterised by the infrared images of OMEGA. It shows bright and brown deposits (red markers) that are rich in the mineral kieserite, a hydrated magnesium sulphate.

Phyllosilicates, have a characteristic structure of thin layers ('phyllo' = thin layer). They are the alteration products of igneous minerals (magmatic origin) sustaining a long-term contact with water. An example of phyllosilicate is clay.
Phyllosilicates were detected by OMEGA mainly in the Arabia Terra, Terra Meridiani, Syrtis Major, Nili Fossae and Mawrth Vallis regions, in the form of dark deposits or eroded outcrops.
Hydrated sulphates, the second major class of hydrated minerals detected by OMEGA, are also minerals of aqueous origin. Unlike phyllosilicates, which form by an alteration of igneous rocks, hydrated sulphates are formed as deposits from salted water; most sulphates need an acid water environment to form. They were spotted in layered deposits in Valles Marineris, extended exposed deposits in Terra Meridiani, and within dark dunes around the north polar region.

The detection and mapping of the hydrated minerals point to two major climatic episodes in the history of Mars: an early - Noachian - moist environment in which phyllosilicates formed, followed by a more acid environment in which the sulphates formed. These two episodes were separated by a Mars global climatic change.

Blobrana · L

Outcrops of clay rich crust in Mawrth Vallis, Mars, revealed by OMEGA and HRSC/MEX

D. Loizeau, N. Mangold (IDES-Orsay), F. Poulet, J.-P. Bibring, A. Gendrin, C. Gomez, Y. Langevin, B. Gondet (IAS-Orsay), V. Ansan, P. Masson (IDES-Orsay), G. Neukum (FU-Berlin), OMEGA Team, HRSC Team

The hyperspectral imager OMEGA aboard the Mars Express spacecraft has found hydrated minerals in the region of Mawrth Vallis, Mars, by the detection of the 1.9 nm hydration absorption band, caused by the H2O molecule inside the mineral structure.
For these hydrated minerals, the combination bands due to the Fe-OH bond at 2.3 nm and the Al-OH bond at 2.2 nm reveal the presence of clay minerals: ferric smectites and montmorillonites.
HRSC images indicate that the clays correspond to bright outcrops on the plateaus each side of Mawrth Vallis. These plateaus are part of highly cratered Noachian terrain (greater than 3.7 billion years).
On these bright clay rich outcrops, MOC images show light-toned layered deposits. The intense wind erosion of these outcrops implies that clays are not only surfacial, but that the bright sedimentary rock itself is made of clays.
The observation of such a large amount of clays in this region implies extensive alteration of igneous rocks by water, and the subsequent deposition of clays.

Adapted from source