Astronomy Picture of the Day
March 28, 2013

Martian Aqueous Environments
Martian Aqueous Environments

Credits: NASA/JPL-Caltech/Cornell/MSSS and Dr Paolo C. Fienga/LXTT/IPF for the additional process. and color.

This couple of images allows us to make a comparison between Rocks seen by the NASA - Mars Exploration Rover (MER) Opportunity and the NASA - Mars Exploration Rover - Mars Laboratory "Curiosity" at two (very) different sites of Mars: on the left (Sx) frame, in fact, you can see a relatively big Rocky Boulder - dubbed " Wopmay" - which was located inside Endurance Crater, in the Meridiani Planum Region of Mars (and that was photographed by the Opportunity Rover). On the right (Dx) frame, instead, you can see small Rocks belonging to the so-called "Sheepbed" Rocky Unit, which is located in an area inside Gale Crater that has been dubbed Yellowknife Bay (and which has been photographed by the Curiosity Rover and Laboratory).

The Wopmay Boulder is made of Sulphate-rich Sandstone. Scientists think that the Particles that, in time, created that Rock, were in part formed - and then cemented - in presence of Water. They also think that the Concretions (---> the Spherical Bumps almost evenly distributed all over the Rock) were formed in the presence of Water. Basically, the Rocks found in Meridiani Planum record an Ancient Aqueous Environment (or a "Wet Environment, like NASA often says) that (probably) was not habitable (obviously, by Earth-like Lifeforms) due the extremely High Acidity of the Water, its very limited Chemical Gradients (which would have restricted the amount of available energy to first create and then sustain said Earth-like Microbial Life), and the Extreme Salinity of the Water itself (which would have impeded the formation, and/or the development, of the metabolism of these Earth-like Microbial Lifeforms - if, again, Earth-like Microorganisms had ever been present over there).

On the other hand, in the Sheepbed image, these very fine-grained Sediments also represent the record of an Ancient Aqueous Environment, but this time, perhaps, a Wet Environment which might have been habitable by Earth-like Lifeforms. Furthermore, the Sheepbed Sediments were, most likely, deposited under Water. Scientists think the Water cemented the Sediments and also formed the Concretions. The Rock was, at some point, fractured and then filled-up with Sulphate Minerals when the Water flowed through the Subsurface Fracture Networks (---> the white thin lines running through the Rock). The data that have been obtained by several instruments onboard the Rover Curiosity - such as the Alpha Particle X-Ray Spectrometer, the Chemistry and Camera Instrument, the Chemistry and Mineralogy Instrument, the Mars Hand Lens Imager, the Mast Camera and, last but not least, the Sample Analysis at Mars Instrument - all support these interpretations: in other words, they indicate the presence of an habitable (still for some Earth-like Microbial Lifeforms), Wet Environment this time characterized by the presence of a Neutral pH, by the presence, also, of Chemical Gradients that would have created enough energy to allow the birth and subsequent survival of Microbial Lifeforms, and a definite Low Salinity of the Water (a fact, this last one, which would have helped to sustain the metabolism of these Earth-like Microorganisms - of course if they had ever been present there).

These pictures (which are two Original NASA - Mars Exploration Rover (MER) Opportunity (left - Sx) and NASA - Mars Exploration Rover - Mars Laboratory "Curiosity" (right - Dx), "White-Balanced" frames taken, respectively, during the 250th Sol of Opportunity's Mission to Meridiani Planum and during the 192nd Sol of Curiosity's exploration of Gale Crater, published on the NASA - Planetary Photojournal and identified by the joint ID n. PIA 16833) have both been additionally processed, calibrated and then re-colorized in Absolute Natural Colors (such as the colors that an average human eye would actually perceive if someone were near the NASA - Mars Exploration Rover (MER) Opportunity and/or near the NASA - Mars Exploration Rover (MER) - Mars Laboratory "Curiosity" and then looked ahead, towards, respectively, the Boulder known as "Wopmay" (Sx) and/or the Rocky Paving dubbed "Sheepbed" (Dx), both located in front of each of the two Rovers), by using an original technique created - and, in time, dramatically improved - by the Lunar Explorer Italia Team. Different colors, as well as different shades of the same color, mean, among other things, the existence of different Elements (Minerals) present on the Surface of Meridiani Planum and Gale Crater, each having a different Albedo (---> Reflectivity) and Chemical Composition.

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