[X] My Assistant

[pbanholzer]

[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.

[Andreas Plesch]

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

[serpens]

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.

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[Blue Sky]

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

[Andreas Plesch]

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:



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.

[Phil Stooke]

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

[Marz]

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? ;-)

[HSchirmer]

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

(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-
-

Over 6,300 plant species are known from the region. The Appalachian Mountains are among the richest of temperate areas, providing habitat for over 250 birds, 78 mammals, 58 reptiles and 76 amphibians (Pickering et al. 2002)
https://www.landscapepartnership.org/cooper...est%20diversity.

-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

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[pioneer]

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?

[Andreas Plesch]

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.

[HSchirmer]

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 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?

[Andreas Plesch]

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.

[JRehling]

I've read some articles […]] 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?

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.

[serpens]

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'.

[JRehling]

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