Rover "Perseverance": First petrological results
along the traverse (sol 1 to 135 and so on)

Norbert Brügge, Germany
Dipl.-Geol.

Update:
23.09.2021
    
 Sol-136: The rover now moving towards a  -----> trench-like structure in the Jezero crater 

My latest Analysis

My new analysis is based on a number of new insights into the groundmass and texture of the rocks, captured by the rover's cameras.

The photos published so far by NASA allow the conclusion that the boulders and remains of it are all of igneous origin. The boulderss, which are chaotic deposited on the bottom and in the sandy elevations, are in a strongly varying stage of their disintegration. "Fresh" boulders are usually angular and have a dark groundmass. In the stage of disintegration  they dissolve columnar to friable. In the final stage of disintegration, the flat and brighly colored stones are in the ground, or it are remains of total crumbled boulders.
It has been found that in holes residues of decomposed olivine can be found in various distributions in boulders, but often there are only empty holes. The stones at the rover's landing place which I originally referred as deposits of pumice are in reality remnants of rocks in final stage of disintegration. In retrospect, the "holes" in the supposedly blistered structure are empty nests of decomposed olivine. Such holes in high concentration leads to the conclusion that olivine is also part of the groundmass.
A main component of the matrix in the boulders is dark hornblende (amphibole). This explains the many reflections that emanate from the crystal surfaces when light is incident. These reflections were referred before as mysterious "inclusions". Another component are obviously bright-colored high calcium-pyroxes. Strong concentrations of magnesium, aluminum and calcium are detected in a single spectrogram published so far.

 If the rocks are actually basalt, then is it a hornblende and olivine rich basalt. Attention: It could also be an ultramafic magma (kimberlite, peridotite ?), because the almost complete lack of quartz is noticeable.
Note: The rover  "Curiosity" found the same stones (olivine + hornblende).

 

First datasets from the Visible and InfraRed (VISIR) sensor and Raman spectrometer instruments of the SuperCam were now published. VISIR uses reflected sunlight to examine the mineral compositions of rocks and soils. The Raman spectrometer uses a green laser beam for its observations. The result: Clear peaks of Mg, Al and Ca were found in the spectrogram from an outcropd stone in the ground (Sol 12). It could be an indication of Ca- rich pyroxenes.
 

Zoom with the SuperCam on a stone in the ground that is identified
as basaltic (?). Clear peaks of Mg, Al and Ca were found in a spectrogram.


Source: NASA/JPL-Caltech/LANL/CNES/CNRS

    


S
eptember 10: After a long waiting now from NASA (JPL-Caltech) new datasets recorded with the instruments of the SuperCam from a abraded stone at "Artuby ridge".
 

The guesswork continues. According to the investigations, some of the bright inclusions in the "basalt" are supposed to be sulfate and phosphate "salts". Contrary to this assumption of NASA scientists, it is inconceivable, that secondary salts can form in the dense matrix of the crystalline rock if they are laying in the water of a lake. In addition, it has not been proven that they are salts. Only the elements sulfur and phosphor were detected, which is an indication of volcanism
Note: The high density of
calcium and aluminum in the rock is striking.

 

1.) Composition of groundmass and phenocrysts

Hornblende and Ca-pyroxe in the groundmass

                       
First published photos by the SherlocCams from the surface of unspecified stones shows some details from the groundmass, included dark areas therein.
 The probability that this dark areas are
hornblende is high. The bright parts in the matrix could be Ca-pyroxene and olivine


       
               
Reflexions on hornblende crystals when exposed to light

First great details from sol-160 (crumbly "Paving stones")


            

It are to see hornblende (dark brown), decomposed olivine (brownish) and probably Ca-pyroxene (bright) . The dark holes symbolize broken-out hornblende

The white parts are still a mystery.
 If it is actually high calcium-pyroxene, it would
be a surprise.
High calcium-pyroxe found e.g. in S-type asteroids:

The HCP mystery


           


Second great details from sol-185 (abraded solid boulder "of Artuby Ridge" )
 

The same composition:
Hornblende, olivine and the conspicuous bright parts, but all less weathered.

 






Further details from sol-206 (abraded solid boulder of "South Seitah")
 

The same composition as before:

Small white grains that are scattered everywhere and do not seem to belong to the matrix. They are still clearly visible in blurred photos of the abraded surface. The origin of these grains remains a mystery for the time being.  Perhaps it is reflective splinters of hornblende crystals that were created during the abrasion.



 



Olivine in the groundmass and as phenocrysts

An exposed rock (Sol-37) is described as puzzling. It has a smooth surface (almost vitreous) on which numerous rounded depressions can be seen. Upon closer inspection of the photo, I notice that some of the depressions still have a brownish (not secondary) filling. Obviously these are the typical remnants of decomposed olivine aggregates, which are already missing in most of the holes.

    

Sol-37 (Lava bomb !?)

Several holes from phenocrysts

Decomposed olivine






Decomposed olivine

High concentration of holes from decomposed olivine in the groundmass of debris

 

2.)  Stages of disintegration of the boulders

The different stages of the disintegration of the boulders suggest that these were included in the glacier moraine at different times. The youngest boulders (from the upper parts of the moraine) are still angular and "fresh". The oldest boulders, which are already in the final stages of disintegration, come from the lower parts of the eroded moraine. Disintegration and bleaching of the boulders could have been caused by chemical processes in the glacier moraine.
 

"Fresh" boulders


Columnar to friable disintegrated boulders









        


         


Boulders with "adherent crust" and their disintegrate products ?

But, the "crust" could be a different form of the disintegration of the groundmass and the small rounded parts on the ground are the final products.











Mineral aggregates in the final stage of decay

 

Puzzling:
Shreds of lava in the adherent crust?
It is a surprise. This photo was taken in the pile of boulders from sol-169. It are most likely shreds of lava.
For comparison, a piece of lava from sol-134.


Boulders in the final stage of disintegration
 It is complicate to explain the bright color of the remains of these very disintegrated ultramafic "paving stones". My guess is that it is the outcrop of an older moraine that is hidden in the subsurface or it is the bedrock in the crater (more likety).