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!

[Andreas Plesch]

There are sedimentologists specializing in landscape evolution and numerical modeling, see for example https://agupubs.onlinelibrary.wiley.com/doi...1002/jgrf.20031 . Consequently, there are a large number of models, based on diffusion or advection concepts. Unfortunately, I am not such a modeler and do not have that insight. My inclination would be to treat lower gravity similar to a change in slope both acting on the erosional effect at the river base in similar ways. Slope is just one parameter besides flow rate, sediment load or potentially tectonic uplift or subsidence.

With that in mind I would expect that 0.38g would require a much steeper slope for a stream to develop similar erosional characteristics, other parameters being equal (which would be difficult to establish). The 2km relief over 100km intuitively feels rather steep and it should be possible to find longitudinal river profiles of similar length, for a direct comparison. A main difference is that the profile does not look like a textbook river profile on earth which has a steep initial gradient, an intermediate section, and a very gentle final gradient before entering a base line (a lake or ocean) which is considered an equilibrium profile where erosion at the source and aggradation at the sink are in balance.

I suspect that there have been attempts to understand such profiles on Mars, after the idea of an early wet history was getting (more?) widely accepted.

Looking more closely along the stream, there are what could be rather short tributaries, and perhaps drainage from the Hargraves crater region to the north.

Proposing a secondary inlet at the northern crater rim clearly requires some interpretation since it would be not very well preserved. I do think there are markers of channeling and meandering further upstream which seem to connect to it.

[edit] ah Thanks serpens, yes that is what I see as well. It is just not much of a system of tributaries.

[serpens]

....It is just not much of a system of tributaries.

While the catchment as it stands can be reasonably constrained, as HSchirmer alludes to the area has been subject to tectonic activity, cratering and erosion that makes the accurate assessment of the ancient drainage area and tributary flows challenging to say the least. While there are traces of the tributaries much has been erased. As I understand it the mineralogy of the Northern and Southern deltas vary, reflecting the mineralogy of the two separate catchment areas. All in all it is a pretty impressive drainage area which I suspect would have hosted an extensive tributary network.

[Andreas Plesch]

While the catchment as it stands can be reasonably constrained, as HSchirmer alludes to the area has been subject to tectonic activity, cratering and erosion that makes the accurate assessment of the ancient drainage area and tributary flows challenging to say the least. While there are traces of the tributaries much has been erased. As I understand it the mineralogy of the Northern and Southern deltas vary, reflecting the mineralogy of the two separate catchment areas. All in all it is a pretty impressive drainage area which I suspect would have hosted an extensive tributary network.

Undoubtedly, there has been substantial vertical tectonics (with some extensional rifting) as there is so much geologic time available. Nevertheless, today the crater floor is essentially horizontal and the main stream bed is well preserved, up to a 100 miles back. So the base assumption would be that first order tributaries would be preserved to a similar degree. I agree that together the Northern and Southern deltas were supplied from a large catchment. Since the main stream to me looks relatively starved to the west and south, perhaps at times there was major supply from the north.