The riddle of the "Paving Stones" in the Jezero Crater

Norbert Brügge, Germany
Dipl.-Geol.

It seems that NASA scientists have an increased interest in the paving stones that outcrop at the floor of the Jezero crater.
Numerous photos have been taken to identify the nature of these bright and heavily weathered stones, and at least one drill sample with accompanying analysis is planned. There is hope of finding traces (signatures) of life, because it is assumed that the former bottom of a lake was here.

Unfortunately, this assumption is not relevant. If there was a lake, sedimentary deposits from the lake would no longer exist. The P.S. are clearly of magmatic origin in their composition and are identical to the ultramafic stones from the moraine. The mineral composition (hornblende, olivine and Ca-pyroxene) is in the numerous close-ups of the P.S. to recognize.

The exclusively high degree of disintegration and the dense arrangement of the outcropping rock can lead to two conclusions:

  • It is the hidden part of an older, and partly still intact moraine with a high accumulation of boulders.

  • It is the outcropping weathered bedrock in the crater, what is very likely.

Still unanswered, however, is the question of whether and where a boundary can be established between the friable or holey disintegrated stones on the surface that occure together with the P.S., that are spreading out in other places. However, regardless of the degree of weathering, there are stones lying in the ground that do not belong to it and possibly come from younger parts of the former moraine.

First photos from the landing site

Current photos from the "paving stone" ground






 

Close up of the ultramafic rock that has weathered down to the ground. We can still see reflections from hornblende

..... and the close-up of a abraded drilling place

        

These "paving stones" are very crumbly. Therefore, no core could be extracted from the first drilling.