#AGU21 Press conference: Ten months of Perseverance: Jezero science - 15 Dec 2021
Presentations and questions answered by:

Ken Farley, California Institute of Technology
Sanjeev Gupta, Imperial College London
Briony Horgan, Purdue University
Eva Scheller, California Institute of Technology
Kelsey Moore, California Institute of Technology

Lots of discussion of these results in the "Finishing work in and around Seitah" topic, starting here, which would actually be more appropriate if moved to this topic.

After listening to the AGU press briefing, it seems the team themselves don't have a good explanation for the tilted layering seen in Seitah, and how to reconcile that with the apparently igneous textures that they see in the microscopic images, though they mention how igneous cumulate textures can mimic sedimentary textures. Knowing how the layering and dips were distributed across Seitah would probably be a valuable constraint- perhaps Ingenuity can help out by mapping more of Seitah?

John

Actually, John, the Arm-Waving and discussion of the incoming data from the Rover would be more apropos in the "Finishing Up in and Around" thread. We are observing bits and pieces of incoming information that could be interpreted as many things. Save this Geology topic for conclusive data and discussion of the results from research papers down the road.
Thus far the discussions of observed deltaic facies and features falls into a reasonable realm of reality
My two cents

--Bill

There are many lunar craters with floors filled by what seems to be the same lava flows seen in adjacent maria without the crater rim being visibly breached. It would seem possible (necessary?) that the layers in Jezero would have seeped in, like those lunar craters, laterally through the crater wall, then been tilted either by subsequent lava emplacement below that or the general tilting of the entire area as Syrtis Major formed?

The floor of Gusev Crater that Spirit traversed was "surprisingly" unaltered volcanic or volcaniclastic rocks... probably from intrusive fissures after the wallop of crater formation, and then since buried. The 'water' channels into Gusev brought hopes to find an abundance of clays and cobbles and other such lake and riverine materials. Exposed volcanic crater basements may be a feature and not a bug for non-tectonic aeolian Mars?

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.

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.

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

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

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.

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

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.

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.

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.

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?

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.

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.

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

A summary of first year findings: Jezero is igneous


Nature of Perseverance

The fact that the current floor of the crater is igneous was hardly surprising. Well before the landing it was identified as lava deposit(s) laid down after the lake dried up and significant erosion of the delta had occurred. Guillaumes grind (Roubion coring attempt) was at the bottom of a 16 metres dip well below all other grinds/samples and and still looks sedimentary to my tired old eyes.

Current literature:

https://www.science.org/doi/10.1126/sciadv.abo3399

A couple more very interesting contributions. Some indications that water in Jezero may have a long history, albeit cyclical.

https://www.science.org/doi/10.1126/science.abo2196

https://www.science.org/doi/10.1126/sciadv.abp8564

Hi,

Maybe we can add this one ?

https://www.science.org/doi/10.1126/science.abo2756

Good set of papers. Jezero crater has a long and varied history. .I'm looking forward to getting up on the delta surface, the floodplain and river channels. Mars as a whole has had a cyclical climate. Although Mars is presently dry and cold on the surface it is warm snd wet at depth.

--Bill

The models for the evolution of Séítah, Máaz etc are compelling. The only query I would have is the timeline for the beginning of cyclical inflow to the crater. That is, did this begin prior to basaltic emplacement because Guillaumes at the deepest exposure seems sedimentary.