Few news from Mars, but there is a disappointing study on Earth
Two weeks ago I wrote in this blog (Is there life on Mars?) on the Mars Science Laboratory mission of NASA with the famous Curiosity rover, which its main aim is finding possible signs of past life in the red planet.
Well, as expected, until now there are no spectacular news, as in all scientific studies, things take time. The Curiosity has been taking photos (see one here) and taking samples and analyzing them. Today there are 40 days since the landing and it has walked about 150 meters. As stated in the last NASA chronicle, Curiosity continues its work “in good health”. So keep waiting.
But today I want to comment some disappointing news regarding the possibilities that there had been life on Mars. It turns out that a recent study of French and American researchers (Meunier et al, 2012) provides evidences that Martian clays could have a direct magmatic origin and therefore they would not have made by contact of the basaltic crust with liquid water, as hypothesized until now. And so, the less likely the existence of liquid water on Mars in the past, less likelihood of living beings there.
Clays are hydrous silicates (of phyllosilicates group), mainly of aluminium (Al2O3 · 2 SiO2 · 2 H2O). They are minerals with granular structure, which originate on Earth mainly by decomposition of magmatic rocks containing silicate minerals such as the feldspar by the action of liquid water (this may contain carbonic acid and other compounds). Clays have been identified on Mars some years ago with the spectrometers of the OMEGA observatory carried by the Mars Express spacecraft of the European Agency, which is orbiting Mars (Bibring et al, 2006). It was believed until now that these clay minerals, abundant in Mars surface, would have been formed for a long time by interaction of liquid water with basaltic crust, decomposing the magmatic rocks, but early in Mars history, 3700 million years ago, at the same time that Earth life was beginning. The presence of liquid water would be a sign of warmer and wetter conditions on early Mars, and therefore more likely to carry life.
But the recent published work of Meunier et al. suggests a different mechanism that does not require prolonged reaction of rocks with water. Interestingly, evidence has been found on Earth, studying clays of Mururoa Atoll in French Polynesia, which are similar to Martians phyllosilicate clays. Using petrographic techniques (study of the mineral structures at the microscopic level), microanalysis of elements, and isotope ratio analysis, these researchers have found that the Mururoa clays, rich in Fe and Mg, are much richer in rare earth elements (lanthanides and other), and microscopic structures are very different from other more abundant clay on Earth, originated from aqueous weathering. The characteristics of the Mururoa clays assert that were originated by short pulses of degassing magma in the interstices of basalt, and the water contained in clays would be only of magmatic origin.
Meunier et al. have also studied clays of Martian meteorites and have found that some of them have similar characteristics as those of Mururoa. Especially the ratio of the isotopes carbon-13 and deuterium in Lafayette meteorite shows that their clay was formed by direct precipitation of magmatic fluid containing water, by degassing magma.
Therefore, if martian clays, very similar to those of Mururoa (at least in their spectra), are proved to be formed also by magmatic degassing, then the presence of liquid water in early Mars would be more difficult to prove, and this planet would not have had easy conditions of habitability, at the same early period when life began to flourish on Earth.
The place where Curiosity is walking around, the Gale Crater, is known to contain phyllosilicates, i.e. clays. So, we must therefore wait that this rover could find clays and analyze them, and wait for some news a little more optimistic.
Bibring, J-P. et al (2006) Global mineralogical and aqueous Mars histoy derived from OMEGA/Mars Express Data. Science 312, 5772, 400-404
Hynek, B. (2012) Planetary science: Unhabitable martian clays ? Nature Geoscience, News and Views, online 9 sept 2012: http://dx.doi.org/10.1038/ngeo1560
Meunier, A. et al (2012) Magmatic precipitation as a possible origin of Noachian clays on Mars. Nature Geoscience, online 9 sept 2012: http://dx.doi.org/10.1038/ngeo1572