The Geology of Jezero Crater, Observations & Findings Options

[serpens]

....Knowing how the layering and dips were distributed across Seitah would probably be a valuable constraint...

Indeed. Sometimes you have to pull back a bit and observe the wood rather than concentration of the trees. The thing that has interested me John is that across Sietah the strike of the ridges is generally NW while the strike of the anomalous layering is around S45E. The RIMFAX plot seems to reveal that the width of the layering exposure is only some 45 metres and there does not seem to be any layering beneath the exposure designated T6. Seitah is an erosional remnant and from the strike of the ridges and the position of outlying delta remnants Occam's Razor would suggest that Seitah was part of the delta formation. It is now clear that the crater floor was covered in lava well after the lake dried and erosion had reduced much of the delta. Based on embayment of delta material and subsequent erosion the depth of the lava cover has been assessed as between 10 and 30 metres. This lava embayed Seitah and may well have been built up as sequential deposits. So there is the possibility that these layers are simply an onlap onto the Seitah remnant. Sequential layering would mean the probability of both igneous and sedimentary deposits across the surface exposure.

[JRehling]

This co-occurrence of igneous rocks, including olivine, and carbonate rings some bells, as the same thing (at least as far as those details go) was detected from orbit at Nili Fossae, which also happens to be a source of methane releases.

https://en.wikipedia.org/wiki/Nili_Fossae

The interlocking olivine-and-carbonate that we're seeing at sub-millimeter scales in Jezero might be very different from the way that the materials are physically situated in Nili Fossae, but the similarity – and the methane – certainly merits further attention.

[Bill Harris]

Exactly, jrehling.
Weathering of basalt can be serpentization, with formation of carbonates plus the evolution of methane.

Remember the rock (I think it was a gabbro) that Opportunity found on the way to Victoria Crater (I think) that appeared to be serpentinized. The rock was an erratic, thrown out as ejecta from a deep impact (apparently). It was so long ago that I barely remember details.

--Bill

[serpens]

The olivine carbonate deposits cover a large area of the Nili Fossae region including Jezero and its assessed catchment. While the olivine deposits would probably have a common provenance there are indications of a number of pathways for the associated carbonate formation. There are a number of papers addressing this but the link provides an interesting assessment.

https://www.sciencedirect.com/science/artic...019103518306067

[Julius]

Serpentinisation leading to formation of carbonate minerals from water interaction with olivine during a much more volcanically active Mars would have produced greater amounts of methane with more enhanced greenhouse warming on early Mars. The detection of methane in the present time could be a result of still ongoing same chemical process but at a much lesser rate ineffective to substantially warm the planet today.

[Bill Harris]

I look at this akin to the Lost City carbonate mounds (hydrothermal field) on the northwest Altlatic ocean on Earth. "Cold water" hydrothermal activity will do well. This is adjacent to the Syrtis (now called Nili?) Volcanic province, with an extensive fracture system from the Isis impact.
But the big story will be to study the deltaic facies of the Jezero Delta, and look for organic traces. We've gotten so tunnel-visioned with these first lake-bottom favors we've encountered.
I'm looking forward to the adventure of the forthcoming year!

--Bill

[JRehling]

Something I hadn't previously appreciated is how close Jezero is to the Nili Fossae region. While the largest fractures are about 200 to 600 km away, there are smaller fractures closer, and it may turn out that in at least some respects, Jezero is not an area similar to Nili Fossae but in fact part of the Nili Fossae region and phenomena. Certainly the geology varies on scales much smaller than 100 km, so any suggestion of homogeneity would have to be strongly qualified, but it seems at least plausible that some of the geological history in the two areas was shared – the same one phenomenon extending over a broader area that included them both, rather than the same type of thing occurring twice.

[serpens]

Rather than a one size fits all scenario for the formation of the carbonates it is probable that there were a number of pathways. The environment at the time is not clear and there are indications for marginal deposits, either for the Jezero lake or for the Northern ocean if it did exist, as seems likely. The extent of such an ocean in the Nili Fossae region, possibly with associated precipitation is uncertain.

Julius suggestion of methane as a key greenhouse gas on early mars is problematic as its absorption band peaks at 1300 cm−1, well above the the blackbody emission spectrum peak at 250–300 K and the contribution to warming would seem insufficient. There has been some discussion on whether CO2 –H2 and CO2 –CH4 collision-induced absorption could increase the effectiveness of the greenhouse effect. But the warming mechanism remains a mystery.

[Julius]

Rather than a one size fits all scenario for the formation of the carbonates it is probable that there were a number of pathways. The environment at the time is not clear and there are indications for marginal deposits, either for the Jezero lake or for the Northern ocean if it did exist, as seems likely. The extent of such an ocean in the Nili Fossae region, possibly with associated precipitation is uncertain.

Julius suggestion of methane as a key greenhouse gas on early mars is problematic as its absorption band peaks at 1300 cm−1, well above the the blackbody blackbody emission spectrum peak at 250–300 K and the contribution to warming would seem insufficient. There has been some discussion on whether CO2 –H2 and CO2 –CH4 collision-induced absorption could increase the effectiveness of the greenhouse effect. But the warming mechanism remains a mystery.

I would think the methane alone would not explain the complex evolution story of Mars...one has to factor in the presence of a magnetic field allowing for a thicker atmosphere, effects on climate due to a changing obliquity of Mars over thousands of years as well as the higher impact rates at Mars in the early solar system.

[Julius]

I look at this akin to the Lost City carbonate mounds (hydrothermal field) on the northwest Altlatic ocean on Earth. "Cold water" hydrothermal activity will do well. This is adjacent to the Syrtis (now called Nili?) Volcanic province, with an extensive fracture system from the Isis impact.
But the big story will be to study the deltaic facies of the Jezero Delta, and look for organic traces. We've gotten so tunnel-visioned with these first lake-bottom favors we've encountered.
I'm looking forward to the adventure of the forthcoming year!

--Bill

Are the fractures in Nili Fossae region a direct result of the Isidis impact or due to the emergence of Syrtis Major volcanic province? Isidis impact predates syrtis major?

[JRehling]

This is an informative take on the Nili Fossae region; almost certainly, Perseverance's discoveries will have some relevance in confirming or rebutting some of the suppositions found here.

https://marsnext.jpl.nasa.gov/documents/Lan...ossae_final.pdf

[Julius]

This is an informative take on the Nili Fossae region; almost certainly, Perseverance's discoveries will have some relevance in confirming or rebutting some of the suppositions found here.

https://marsnext.jpl.nasa.gov/documents/Lan...ossae_final.pdf

Thanks for the link.

[serpens]

A bit more information on analysis of the purple rock coatings has come to light.

https://www.hou.usra.edu/meetings/lpsc2022/pdf/2346.pdf and

https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/989148

The enriched Mg and possible H are indicative of a water influence. The question is when did these coatings from. All in all a work in progress.

In one of Tau's images it may be my overactive imagination but it looks as if there has been a degree of alteration around a couple of now absent clasts/crystals.

Attached thumbnail(s)

 

[Bill Harris]

A bit more information on analysis of the purple rock coatings has come to light.

snip

The compositional analysis from WATSON is wonderful information. Not only will there be continuing analysis of Martian specimens, there will be lab analysis of reference samples.
My initial take is that it seems similar to a "desert varnish" from compositional and mechanical properties, which opens a whole field of processes on it's formation, but still leaves the "biofilm" question floating.

--Bill

[moustifouette]

A summary of first year findings: Jezero is igneous


Nature of Perseverance