Not sure where to post this- so, try the 'hot' posts and mods can move as needed-

It appears that the Juno probe's solar arrays inadvertently "sampled" Mars geology
The space probe was pummeled and pitted by "Zodiacal Dust" which seems to be streaming off Mars.

More amazing, Martian rocks are ground into fine dust, lifted by global Martian dust storms, tossed into space, constrained in a torus, only to spiral inward and float down to Earth.

Even more amazing, with a ballpark estimate of of 60 tons of "space dust" per day drifting down to earth,
https://www.popsci.com/60-tons-cosmic-dust-...arth-every-day/
that suggests Earth receives about 30 tons of Mars rock samples every day. They're just REALLY tiny and spread across the entire globe.

SHORT


LONG

To be fair, the authors say they know of no mechanism to do that, considering the escape velocity needed.

nice to see preliminary results already!

"Scientists were able to reveal that Máaz was basaltic, meaning it contained a substantial amount of magnesium and iron, BBC News reported. They are yet to discover whether the 'rock itself is igneous, ie volcanic, or perhaps if it is a sedimentary rock made up of igneous grains that were washed downriver into Jezero lake and cemented together,' said SuperCam chief investigator, Roger Wiens"

https://www.businessinsider.com/nasa-persev...lopments-2021-3
https://mars.nasa.gov/news/8885/perseveranc...-first-results/

Martian dust is not representative of martian rock.

https://mars.nasa.gov/MPF/science/lpsc98/1723.pdf

Moreover, martian meteorites are not representative of martian rock overall. There are selection biases based on altitude and durability.

Sedimentary rock may be very scarce or virtually absent from the dust/meteorites that leave Mars.

Currently the primary source of dust is the Medusae Fossae formation which is weakly cemented and likely volcanic ash with limited mixing from erosion of other areas. It takes a pretty large impact in the right place to eject material with an escape velocity and only some 260 meteorites of Martian origin have been identified. Sedimentary rock is comparatively fragile and if it did survive ejection would probably fragment on entering Earth's atmosphere.

[quote name='Marz' date='Mar 14 2021, 04:43 PM' post='250965']

"nice to see preliminary results already!"

For the next five days I'm going to be viewing the online sessions of the Lunar and Planetary Science Science Conference.
There are several good session about Perseverance with longer presentations on Tuesday so presumably more results. Only taken aback
a bit by the limit of 3 minutes on most talks. So I suppose i will read a lot more of the abstracts.

Program: https://www.hou.usra.edu/meetings/lpsc2021/...021_program.htm , Tuesday is all on Mars

While the channels leading into Jezero, the delta and the Jezero floor have been covered in great detail the outflow channel is something of an orphan. A lot of water flowed down that channel but what I am curious about is where did it go? Following the channel on https://www.arcgis.com/home/webmap/viewer.h...78.2144,20.7779 results in an intriguing puzzle. But the ESA image confirms that there was a significant flow.

Looks like width of the channel is about half a kilometer.

I am following https://twitter.com/hashtag/LPSC2021 a bit today to get a sense of the conference and found this first ground penetrating radar image (RIMFAX) intriguing as a first into the subsurface:

Click to view attachment

It looks like the profile was acquired on the long second, S to N drive, and units on the horizontal axis may be meters. There is this highly reflective shallow (down to 40cm or so) layer with a distinct discontinuity (unconformity ?) to less reflective material with potentially systematic but faint S dipping reflectors in the 0 - 20m section of the drive. I would associate the horizontal reflectors with the bright pediment in the area, and perhaps the slight bumps correspond to where it is better exposed on the surface. That would mean it is not very thick, which seems consistent with how it is punctured by small, dark craters.

HSchirmer: "500 MY old fossils of the same fish species that are in the river now indicates the rivers are over 500 million years old."

Where does this interpretation come from? Can you identify any species which lived 500 MY ago and today? I think this is completely wrong.

Phil

one interesting tidbit in this summary is that some of the rocks in the crater floor may show signs of aqueous erosion:
https://www.nature.com/articles/d41586-021-00698-5

Alas, it will likely take 2 more months to deploy Ingenuity and begin science ops in earnest. Maybe the heli should be called Patience? ;-)

(edited) It's about a 500 MY old fish lineage: the same genus and (IIRC species) in the same river valley, since the opening of the Atlantic ocean.

I may be wrong, or "misremember" a paper I read 30 years ago as a biochem Grad student. I'll check because river valley capture is a great topic when applied to Mars & Tharsis tectonics reversing drainage network gradients.

Here are the papers that give shorter time frames - I'll check on longer-
-

-https://www.researchgate.net/figure/Distribution-of-species-density-in-quadrats-of-the-Simpson-grid-Quadrat-numbers-record_fig1_266459830
-https://webapps.lsa.umich.edu/ummz/fishes/publications/pdf/2010%20NA%20fish%20diversity.pdf

I've read some articles such as this one talking about how most of Mars' water may be underground. What role could Perseverance have in confirming this? Would Perseverance's RIMFAX radar instrument be able to detect water and help answer this question at least regarding Jezero Crater?

A few essential ages: The Atlantic Ocean started to open about 200 Ma ago breaking up Pangea. Before Pangea, there was another ocean about 600 to 400 Ma bp , in a similar relative location, the Iapetus, which closed to form part of Pangea. 500 Ma was the time when complex life just had started. Fish developed later, in the Devonian (420 Ma), and later still got into freshwater (360 Ma). Most species including fish species became extinct at 66 Ma, the mass extinction event due to asteroid impact.

Hey, I was off on dates, but close on percentages.
The biome is ~300 million years old, the Atlantic is ~150 million years old.

GRIN- Since we're dealing with 250 MY precision, when was Jezro crater formed, and when was the delta laid down?

Good point. I thought I saw today in summary blog of a talk that the delta is at least 3500 Ma old but the crater floor (cratering?) age is 2600 Ma although the delta is supposed to sit on top of it due knickpoint elevation profile arguments. What is a few 100 M years here or there.

Mars's water underground is distributed quite differently according to latitude (especially) and longitude (to a secondary degree). Perseverance is not particularly likely to tell us something about the global distribution of subsurface H2O. Mars Odyssey already told us quite a bit; the Phoenix lander corroborated that; and, the Mars Exploration Ice Mapper should advance that considerably. A rover can't compete with an orbiter for telling us things about the planet overall.

Could you expand on that please Andreas as I would assume that the only knickpoints at the crater would be the penetrations through the crater wall by the north and South rivers. There have been a number of papers dating the Jezero MFU and results vary from 2.6 Ga (Shahrzad et al 2019) to 3.1 Ga (Marchi) although 2.6 Ga is widely accepted. The duration of the inflow channels and hence the lake can be assessed by the time that would have been needed to cut so deeply through an igneous basement, but even such assessments have a wide margin given the variable flows that would have been experienced 10,000 <>100,000 years. The age of the of the fluvial system by crater count again has a wide range of 3.2 to 3.6 Gy (Mangold et al 2020). So the MFU postdates the lake and the delta cannot 'sit on it'.

On the East Coast of the U.S., the Susquehanna is substantially older than other major rivers. I don't think there's any belief that it ever flowed in the opposite direction. Other major rivers in eastern North America are typically much younger.

Fish existed on Earth ~400 million years ago, and a very old fish fossil has been found in Pennsylvania but it would have been a marine species in rock that was once in an ocean, not a river.

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

Curious- (i.e. I don't expect and answer) what are the over / under "Los Vegas odds" for an early Mars ocean lapping the edges of Jezro?
Has this moved from "daft" to "draft" to "perhaps"?

https://twitter.com/MartinHajovsky/status/1...0700393478?s=20
https://twitter.com/MartinHajovsky/status/1...7477369856?s=20
https://t.co/g7VNDGJuW9?amp=1

The key question with respect to the Jezero region is where the water to feed the input rivers and their tributaries came from. The area to the South of the Southern river has been covered by Syrtis Major flow. Only remnants survive of the smaller tributaries from the North, But the flow was significant over a long period so precipitation bordering an ocean would seem probable. If there was an ocean encompassing Isidis with a coast near Jezero then the indications for or against this will be at the termination of the outflow channel.

This is good reading. It places some constraints on early martian climate, including precipitation.

https://agupubs.onlinelibrary.wiley.com/doi...29/2018GL079767

Very quick summary: Models don't predict the observed morphologies very well. Also well worth emphasizing: The topography around Jezero has significantly changed since the era of rivers.

Andreas, I had read the Quantin-Nataf et al paper but had some trouble with a key statement "The basal layer is about 40 m thick, finely
grained and layered, while a second upper layer is blocky, as is expected for a proximal ejecta blanket" I would have said that it was as expected from an igneous layer covering the lake floor sediment, with the more fragile ejected basal layer material having been readily eroded from the ejecta blanket.

JRehling, thanks for the link. Despite the massive number of erudite and conflicting papers on the early climate of Mars the bottom line is we do not know what the climate was like other than it was not dry and cold. The faint young sun hypothesis precludes liquid water on either Mars or Earth, but it is clear that this is wrong. So while models / simulations fiddle with the variables they all have qualitative as well as quantitative elements.

A few figures for future reference showing some interpretations of the relationships between delta fan sediments and crater wall and interior:

Quantin-Nataf et al:

Click to view attachment
(apparently from presentation, tweeted)
They explain the younger cratering age of the floor unit as an apparent, average exposure age after slow removal by wind erosion of a protective layer of tens of meters of presumably Lake sediments.

USGS geol. map cross-section:
Click to view attachment
Click to view attachment

The younger age of pink Njf below the blue NHjf2 fan is not discussed, I think.

To me, it appears that the delta fan is deposited on some crater floor and then on early lake sediments after relatively fast progradation. That crater floor and lake sediments may or may not be exposed currently. The Hartwell and Belva craters are potentially windows into deeper units. Quantin-Nataf et al show that there is clearly a high degree of variability in crater densities in the crater floor units. The very smooth, much less cratered nature of the crater floor just adjacent to the current delta limits was intriguing to me. I do not think it is just a statistical outlier but Quantin-Nataf et al may need to show that the spatial variability they measure is significant. The first order implication is that the units are younger. But we know from retreating delta erosion and missing Hartwell ejecta that there has been significant erosion and removal of some crater floor material. That may make it permissible to explain the younger cratering age as an exposure rather than an emplacement age.

Hmm, which way did the wind blow when there were rivers at Jezro?
I can't find any papers about early Mars and wind direction and atmospheric circulation. Anybody have suggestions?

Was Jezro was located at the Martian equivalent of "the Pacific Northwest" in a rain belt?
Did the weight of Tharsis wrench Mars and move Jezro to a different latitude?


Interesting- according to recent papers, the Arabia Ocean could have been lapping at the shores of Jezro, and the crater floor would be below sea level.
If the Deuteronilus Ocean was lower; wouldn't the location and morphology of the outflow channel change?

Andreas, While I am sure most here are around the USGS map unit designations perhaps some are not and the labels provide a lot of insight into the image. The initial capitals define the age of the unit (N, Noachian. H, Hesperian. A, Amazonian). The following lower case letters can identify position (j, Jezero cater or np Nili Planum); Stratigraphic relationship (l, lower; u, upper); landform (f, fan or floor), visual characteristics (b, bright. e, etched. r, rugged. s, smooth). The numerics indicate relative age of elements of the same unit (1, older. 2, younger).

One interpretation of the map image you posted could be that Nle and Nue units were laid down during the Noachian as part of an initial delta. A second, lesser influx occurred in the early Hesperian with sediment deposited over part of the Noachian delta. So delta unit NHjf2 could more properly be termed Hjf2. Subsequent erosion resulted in step back of the delta front leaving the Nle and Nue units and the few outliers with Hesperian deposits. The MFU subsequently embayed the Nle units and the outliers which are effectively kipuka.

While the map designates the crater floor as Njf, USGS indicate that they cannot determine the age due to so many conflicting assessments so in reality it should be NHA?jf. But it is clear that the MFU embayed the Northern Nle unit because it has eroded down below the level of the MFU. This could only happen if the MFU was laid down after the Noachian delta had eroded back and given that the remnant outliers have Hesperian deposits, after the Hesperian fluvial events and subsequent erosion.

Right. However, we also know that it transitioned from whatever its wettest, warmest past state into the one it's in now, so there was possibly a climate where snow predominated and rain was rare at some point. And in such a climate, the places with heaviest precipitation would likely be locations at high altitude and not, as on Earth, downwind of bodies of water.

Currently, the topography of Syrtis Major is a whopping 6.9km above Isidis. Even a fraction of that would allow for a substantial snowpack to form to the west. But that's speculative.

One of the seeming paradoxes of Mars is how so much of the surface is so ancient and yet so much change has occurred. And the resolution to that paradox is that many major topographical features have survived 4 GY, but not unaltered. We can see the remnants of early Mars, but there's a lot that's happened in the meantime to muddle the clues.

Early Mars would have been a pretty dynamic place, nothing at all like todays extremely benign environment. Despite the faint young sun it is clear that Earth and seemingly Mars had warm liquid water on the surface. A possible age related analogue for Jezero is the greenstone belt of the 3.5 - 2.8 GA Pilbara craton. For this area Archean water temperatures have been assessed as around 27 degrees Celsius which agrees pretty well with estimates from the Barberton craton greenstone belt. With respect to one of Perseverance's primary mission objectives the area of most interest would be the 3.3 Ga Strelley Pool Chert unit, where morphologically diverse Stromatolites have been preserved over a large area. This is not to say that we could expect Stromatolite equivalents or indeed microbiological mats to have developed in the Martian environment, but there is the possibility that the Jezero and Archean Pilbara craton environments were similar.

The diversity of rocks types next to Perseverance now is considerable.

http://www.unmannedspaceflight.com/index.p...st&p=251199

The Pliva Vallis outflow channel continues to intrigue me. The crater wall breach appears to be around 150m deep so the outflow, assuming the crater wall was overrun rather than infiltrated would be some 300 km^3 not counting replenishment. A significant amount of sediment would have been transported from the excavation of the crater breach and Pliva Vallis. 5 to 10 cubic km given the impossibility of establishing the extent of post fluvial fill. The termination of the outflow is a bit of a puzzle, disrupted by impacts and erosion and trying to identify the course of the flow and deposition from https://www.arcgis.com/home/webmap/viewer.h...78.2144,20.7779 is a challenge. I would be interested if anyone can provide insights into the termination area and potential deposition configuration.

First, general FYI - OP Lunch Talk #40: "Geologic Mapping of Jezero Crater on Mars" by Vivian Sun
https://youtu.be/lv3-ltFKuwo

Second, If the earlier paper about Tharsis & Isidis is partially correct, the area saw about a 2 km change in height, the rivers could have reversed course, OR Pliva Vallis could have spent some time as a submarine canyon

Interesting find from Vivian Sun's talk- The "regional carbonate unit" from 2015 Goudge et al 'Jezro crater and its watershed' is a surprisingly good match for the estimated ocean highstand from the Tharsis-Isidris paper

Conglomerate bed:

Click to view attachment

Some of the clasts are rather large.

excellent! That indicates that a main delta channel swept through at high flow and long enough duration to round the stones.

The clinothems seem to be built out of both sandy, cross-bedded material, and poorly sorted structureless conglomeratic material. This may reflect a subaqueous delta front environment that was characterized by lower-concentration sediment gravity flows that deposited the sandy material, and higher-concentration sediment gravity flows (debris flows) that deposited the coarser strata. I've thought we'd see evidence of antidune cross-strata, and it looks like some possible backsets peeking out. Fingers crossed!

Wow, a poorly sorted conglomerate with well rounded, seemingly huge clasts, somewhere midsection in the delta sequence. I think sampling the clasts would be very valuable if there is a way to get to a bed like this, since we know the source area, from the crater wall, tens of kilometers to the west. In a way, it is free delivery from a large area without having to travel.
Speculating, the bed could be the result of a catastrophic flooding event upstream (glacial dam breach ???) or a basal conglomerate of a transgression cycle, after a period of non-deposition or perhaps erosion.
Very cool.

Wondering if we now have any additional insight into the mechanics of the deposition of the delta given this new visual data.

Is there a possibility this delta formed as the result of glaciation - ice rather than water carrying the sediment? Would Mars' lower gravity make it easier for glaciers to flow or to retain the clastic material we see now in the delta?

However warm Mars was in the past, it wasn't that warm for a long long stretch of its history, and so isn't it more likely that any flow would have been in the form of glaciers? The amount of force required to breach the crater rim must have been immense. Is it possible that this force was generated by a massive glacier with somewhere (lower) to go. If it was a glacier, would the water ice have sublimed away during the erosion process, or should we see evidence of vestigial water ice within the delta?

It seems strange to me that these outlier remnants remain at km distance from the eroding delta front. Why did they not erode at the same rate? We also observe a lot of scouring on the top of the delta which seems to suggest to me some mechanical interaction between a glacier and the deposit. Perhaps the outlying remnants are the remnants of eskers rather than part of the original delta?

I know this is speculative, but is it possible?

Looking a little closer, and squinting mightily, I now think that the conglomeratic unit is crudely cross-stratified, with backsets! I could also believe there is some imbrication and alignment of clasts along the backsets. I would really like a little better idea of scale, but just eyeballing, I would now say that the sandy units may be characterized by cross strata from the migration of antidunes, and the coarser units by cross strata from the migration of cyclic steps. These don’t negate a delta front setting, but these kinds of features are also quite common in glaciolacustrine, and subglacial settings on earth. It does look like it was a very energetic setting, with supercritical flow conditions as the rule. I can post some references to similar cross-stratification formed in marine and glacial deltaic settings here on earth, if anyone is interested. I’ve specialized on identifying and interpreting these types of cross-stratification and the bedforms that create them for the past 8 years, so maybe I see them where they ain’t, too!

I definitely agree that there appears to be crossbedding in the coarse conglomerate, and would be interested in terrestrial analogues of a sedimentary environment that can generate a crossbedded, poorly sorted conglomerate with well rounded clasts, in a sandy delta, because this seems a bit out of the ordinary.

I had thought about a glacial lake at some distance upstream, at higher elevation. Such lakes are known to form behind icy dams which get eventually breached and can cause catastrophic flooding events. But it is intriguing to think about glaciation as a mechanism to initially erode the crater wall as well.

The conglomerate was deposited when the delta was well established, long after the crater wall was initially compromised. But the deep incision of the crater wall shows that it continued to be eroded representing a significant source of sediment, and therefore potentially of some of the clasts.

I agree that the preservation of the existing piece of the delta needs explanation. It reminds me of much larger scale escarpments of slightly tilted, Mesozoic sedimentary units which form a distinct landscape (Schichtstufen). It may suffice to have a somewhat more erosionally resistant unit at the top to form the step at the current limit of the preserved delta.

Perhaps it is worth stepping back and looking at the features in context (image from Neo56 below). Is it possible that this gravel/large cobble deposit could be scour fill? Certainly the size and rounding of some of the clasts indicates long transportation and deposition in a surge environment but whether this was an unusual event or the norm will need further investigation. The catchment area has been disrupted and eroded but I don't think there is evidence of glacial activity. A surge could be caused by an ice dam, melting of a snow pack by volcanic activity, collapse of an erosion resistant part of the input channel or a sudden increase in precipitation caused by impact into the purported ocean.

There has been significant erosion and step back of the delta front since the Hesperian deposits and the preservation of the remains is potentially due to the transition to a benign environment through loss of atmosphere.

Click to view attachment

Here is one of the terrestrial analogs I was thinking of, the Pleistocene Porta fan in Germany, worked by my friend and colleague Jorg Lang:

Lang and Winesmann, 2013

And here is another example that both Jorg and I, plus George Postma, Dave Hoyal, Juan Fedele, Vitor Abreu, and Keriann Pederson worked on, this one an Eocene fan delta from Spain:

Postma et al., 2020

Tim, harking back to your post link on the Jurassic Tank/XES experiment, the breaching of the crater wall by the outflow channel would have lowered the water level in the crater reasonably quickly which would seemingly have caused increased flow velocity and erosion of the delta at the time. Bit of a stretch I know but could this have resulted in concentration of a layer of gravel/cobbles through top down erosion, negating the need for surge from the inlet channels?

Per the mention of catastrophic events, we know that Syrtis Major, to the west and upslope, was very likely the source of some volcanic activity which could have contributed catastrophic flooding across the site. However, I'm not sure if that would show up in sediments created while the lake was present, or if that would have begun when the lake was no longer in existence. The minerals found in Meridiani by Opportunity suggest that perhaps aqueous environments that began before planetary volcanic activity increased might have continued in existence into a new epoch. So perhaps units formed in an aqueous environment in Jezero cover a really wide range of eras.

Yes, and entrenchment of the feeder channel system and reworking of previously deposited material. Depending on the speed of the level drop, and the sediment supply coming in, the shoreline/delta system could have 1) followed the water level down and deposited at lower and lower elevations (this is called a forced regression), 2) incised into the delta topsets and fixed the entrance into the lake in an incised valley, or 3) built an alluvial fan/new fan delta on the exposed delta topsets with its apex at the incised crater rim inlet. These are the types of stratal geometries that the XES experiments, and subsequent physical and numerical models, investigated by varying discharge, sediment flux, and base level changes. I did some numerical modeling looking at just these kind of upstream and downstream controls, and on the area in the system affected by both.

I was notified of this AAPG event:

https://aapg.zoom.us/meeting/register/tJElc...N5h3355itV2_zGX

on 4/22 noon CT, registration required.

I plan to attend if there is no conflict.

My first try to stitch Supercam images...

Sol 54 Supercam detail by Tomislav Bandin, on Flickr

Nice effort Tomislav.

charborob stitched together the Supercam panorama of the outlier:

http://www.unmannedspaceflight.com/index.p...st&p=251866

Much higher resolution than the zcam images. What appeared to be more massive foresets in the lower, and upper, sequence are actually sets of rather thin beds, intercalated with fine grained, perhaps shaly layers.