The Geology of Jezero Crater, Observations & Findings Options

[nprev]

This thread is for those rockhounds among us to discuss the new terrain we'll see as Perseverance scoots around her new home. Let's get dirty & technical!

[Explorer1]

One of the papers I read (can't find it now) implied that speed is not about finishing before the retrieval mission arrives, but placing enough caches down in case something catastrophic happens years down the road, rendering any samples still inside Perseverance irretrievable. The fetch rover's job is difficult enough as is; no need to make it harder.

[vjkane]

One of the papers I read (can't find it now) implied that speed is not about finishing before the retrieval mission arrives, but placing enough caches down in case something catastrophic happens years down the road, rendering any samples still inside Perseverance irretrievable. The fetch rover's job is difficult enough as is; no need to make it harder.

The current plan is to double collect in Jezero. Half the collection is left on the rim in case Percy has a catastrophic failure on the way to Midway. Ideally, Percy collects new samples in Midway to supplement those retained from Jezero.

There doesn't seem to be a consensus yet on how to deal with samples carried from Jezero or collected in Midway. If they are retained by Percy and it has a catastrophic failure, the fetch rover can't remove them from Percy. If Percy deposits all of them in a cache at Midway and the fetch rover fails, Percy can't pick them up to deliver them to the MAV.

[MahFL]

...Percy can't pick them up to deliver them to the MAV.

I was under the impression once Percy drops the tubes on the ground it cannot pick them back up.

[JRehling]

One solution to this would be to fill about 3/4 (~24) of the sample tubes on the way up to the rim. At the top of the rim, drop ~16 of them, representing the whole trek up the delta, on the ground, and keep ~8 that also represent the trek up the delta. Then pick up ~8 more on the crater rim, and when that is complete, drop all ~16 in one spot.

That leaves you with ~16 representing the delta in one place and ~16 representing both the delta and the crater rim in another place. The return can choose which group of 16 to retrieve. If there were any failure in the return, there's another group of ~16 for a second try. If Perseverance failed after reaching the crater rim, there would be the first set of ~16 for a first and only retrieval attempt.

[vjkane]

One solution to this would be to fill about 3/4 (~24) of the sample tubes on the way up to the rim. At the top of the rim, drop ~16 of them, representing the whole trek up the delta, on the ground, and keep ~8 that also represent the trek up the delta. Then pick up ~8 more on the crater rim, and when that is complete, drop all ~16 in one spot.

That leaves you with ~16 representing the delta in one place and ~16 representing both the delta and the crater rim in another place. The return can choose which group of 16 to retrieve. If there were any failure in the return, there's another group of ~16 for a second try. If Perseverance failed after reaching the crater rim, there would be the first set of ~16 for a first and only retrieval attempt.

Phil Stooke at NASAspaceflight.com posted links to presentations from a recent sampling strategy workshop. Extremely interesting with lots of details on the notional traverses, notional sampling plan, and notional caching strategy

Link to Phil's post

First set of slides

Second set of slides

Third set of slides

These slides are from those presentations and represent a notional sampling strategy.

Attached thumbnail(s)

 

[Andreas Plesch]

Phil Stooke at NASAspaceflight.com posted links to presentations from a recent sampling strategy workshop. Extremely interesting with lots of details on the notional traverses, notional sampling plan, and notional caching strategy

Link to Phil's post

First set of slides

Second set of slides

Third set of slides

These slides are from those presentations and represent a notional sampling strategy.

Thanks, these slides provide a good summary of what I take is the current understanding of the crater and surroundings in terms of geology, traversability, and relevance to mission goals. It was the first time for me to delve a bit deeper into these planning steps. I have to say, it was surprising to me how much emphasis there is on getting out of the crater even given that it is clearly stated that the delta and the crater lake basin are the primary target. Why not really focus on that primary target ? I understand that the more diverse geology outside of the crater (Nili Planum) is tempting and that it could be explored but the criteria for not leaving the crater is either serious rover dysfunction or extremely exciting discoveries on the way (what ? a fossil ?). That leaves room for only one traversal up and along the delta. In effect, it gives the delta and crater interior the same weight as Nili Planum which does not sit quite right. So I think it will be important to make this one delta traverse count perhaps by attempting to cover all sides of the (remaining) delta. One could even argue one should stay in the delta until there is a sense of exciting discoveries, and only then leave, rather than leaving by default.

Another impression I had that there is rather high confidence that it is possible to plan a detailed traverse based on current remote sensing data. My very limited experience looking in detail at HiRISE imagery around the landing site (and even EDL imagery) and comparing it with rover imaging on the ground would make me much less confident to do such planning much in advance. The rover is only 3m or so, eg. a few pixels in these images. In other words, it will be critical to use on the ground imagery as it becomes available, with a willingness to revise existing plans freely. This seems perhaps obvious but with all the planning investment there may be a degree of inertia.

Considering this, I think there should be a lot of, almost exclusive emphasis on getting to and sampling the sediments about which we can know with a high degree of confidence that (a lot of) water was present. Apart from the potential for life, their composition is an indirect sample of the watershed area (at the time) which often leads to strong conclusions about geologic evolution. Imagine finding a conglomerate bed. The clasts could be dated.

[vjkane]

Thanks, these slides provide a good summary of what I take is the current understanding of the crater and surroundings in terms of geology, traversability, and relevance to mission goals. It was the first time for me to delve a bit deeper into these planning steps. I have to say, it was surprising to me how much emphasis there is on getting out of the crater even given that it is clearly stated that the delta and the crater lake basin are the primary target. Why not really focus on that primary target? ...

Another impression I had that there is rather high confidence that it is possible to plan a detailed traverse based on current remote sensing data. My very limited experience looking in detail at HiRISE imagery around the landing site (and even EDL imagery) and comparing it with rover imaging on the ground would make me much less confident to do such planning much in advance. The rover is only 3m or so, eg. a few pixels in these images. In other words, it will be critical to use on the ground imagery as it becomes available, with a willingness to revise existing plans freely. This seems perhaps obvious but with all the planning investment there may be a degree of inertia.

Considering this, I think there should be a lot of, almost exclusive emphasis on getting to and sampling the sediments about which we can know with a high degree of confidence that (a lot of) water was present. Apart from the potential for life, their composition is an indirect sample of the watershed area (at the time) which often leads to strong conclusions about geologic evolution. Imagine finding a conglomerate bed. The clasts could be dated.

From presentations I watched several years ago, the focus was always to get a good sample of Jezero from the crater floor to rim in the primary mission lasting one Martian year. Any extended mission is gravy.

A couple of thoughts on why to leave. The Great Cosmic God smiled on us and the top two places to sample Mars (as selected through a series of workshops bringing in much of the Mars science community) happen to be within driving distance. As I recall, Jezero won the vote of the workshop participants, but not by much. Not only does Midway likely contain a geologic record of key events, several of the proposed sampling sites could be locations of significant astrobiological interest. The science community *really* wants sample from both areas.

As for planning the traverse, I have experience with similar products to what I expect the mission planners have. From stereo HiRISE imaging, they likely have a highly accurate 1 m (or slightly better) digital terrain model. They also can tell a great deal about the likely surface of each location from both direct photo interpretation and from texture analysis of variance among adjacent pixels. They have been using these products to plan Curiosity's traverse for years now.

[Andreas Plesch]

From presentations I watched several years ago, the focus was always to get a good sample of Jezero from the crater floor to rim in the primary mission lasting one Martian year. Any extended mission is gravy.

A couple of thoughts on why to leave. The Great Cosmic God smiled on us and the top two places to sample Mars (as selected through a series of workshops bringing in much of the Mars science community) happen to be within driving distance. As I recall, Jezero won the vote of the workshop participants, but not by much. Not only does Midway likely contain a geologic record of key events, several of the proposed sampling sites could be locations of significant astrobiological interest. The science community *really* wants sample from both areas.

As for planning the traverse, I have experience with similar products to what I expect the mission planners have. From stereo HiRISE imaging, they likely have a highly accurate 1 m (or slightly better) digital terrain model. They also can tell a great deal about the likely surface of each location from both direct photo interpretation and from texture analysis of variance among adjacent pixels. They have been using these products to plan Curiosity's traverse for years now.

Thanks for the background. Concerning the planning products, of course they are very valuable for considering all options. I was just impressed how every twist and turn was shown on some of planning maps. Now, the map presented today seems to go out of the crater on another route, eg. straight through the main inlet, for now.

Looking at the slides, I did start to think that there are probably strong factions in the community for both the Delta and also Midland. In that case the planning discussion material makes more sense. Thinking ahead it is somewhat problematic that the expected lifetime (1-2 years) of the mission is so conservative, in light of the success of previous missions. It will be impossible to argue to go back into the crater once the rover left it.

[vjkane]

...Thinking ahead it is somewhat problematic that the expected lifetime (1-2 years) of the mission is so conservative, in light of the success of previous missions. It will be impossible to argue to go back into the crater once the rover left it.

Everyone hopes and probably expects that Percy will have a long life and will sample both Jezero and Midway. However, rovers/spacecraft do break, and any operations past the first Martian year also require that NASA approve an extended mission and that is funded. So the managers and science team want to make sure that the base mission requirements are met in that first year.