Like yesterday reiterating the points pro and con of the Eberswalde Crater as landing site for MSL, today we are going to look at Holden Crater. What speaks for landing Curiosity there? What speaks against it? In this all we need to keep in mind that all of the landing sites were discussed with the following in mind of the scientist at landing workshops:
“What do we know; what do we just think we know?
In short: What is the quality of our knowledge of Mars?”
Using the most powerful cameras and spectrographic instruments ever sent to the red planet, the Mars Reconnaissance Orbiter (MRO) played a pivotal role in collecting data to help scientists evaluate many potential landing sites for the Curiosity rover in greater detail. The images by Malin Space Science Systems (MSSS) made with the cameras of the MRO are interspersed with the text, just as we showed yesterday. The more you zoom in the more interesting a site becomes. Looking at these images and the ones of yesterday, it drives home the fact that there is a good reason why there were 5 landing site workshops needed. As we all can see each and every landing site holds great promise of discoveries, of giving us an opportunity to understand not just Mars better, but our own planet better.
Overarching Hypothesis:
Holden crater preserves evidence of an evolving system of flowing water and a crater lake. This system was a sustained, habitable environment.
Pros:
- * Holden’s alluvial fans and layered rocks make up one of the largest and best preserved alluvial systems on Mars.The diverse and potentially weathered sediments likely record the environmental conditions responsible for their formation during the Hesperian perhaps into the Early Amazonian.
- * The targets can be related to the global stratigraphy of Mars since lots of crater counting has been done on the Holden area.
- * It’s a diverse site, with fan sediments, clay-bearing layered rocks, flood deposits (by Uzboi vallis), and mega-breccias in the crater walls/floor, and blocks of rock blasted into Eberswalde when the Holden crater formed.
- * The mineralogical diversity in the light-toned layered deposits and crater walls/floor include both altered and primary compositions.
- * The layered rocks might be lake beds, which are good for preserving organic molecules.
- * There are examples of all the key targets inside the ellipse, although better examples of some require a drive outside the ellipse to the south. Targets within the ellipse offer access to all major units for interrogation, though thicker sections of the light-toned layered materials and megabreccias occur farther to the south. Putative bottomset beds provide a target for evaluating any preserved organics.
- * Strata comprising the light-toned layered materials may be the equivalent of bottom set beds emplaced in a lacustrine (=lakelike) setting, which might preserve organics for interrogation by the MSL.
Uncertainties:
- * The outcrops of impact-crushed boulders (mega-breccia) in may suggest an impact-induced hydrothermal system.
- * Other than the fact that the layered rocks have nice, continuous layers, there isn’t much evidence that can help to tell how they formed from orbit. MSL could figure this out in-situ.
- * The layered rocks may be relatively young. Same uncertainty as Eberswalde: is that a bad thing for life?
- * The various science targets might record times spanning from very early mars to relatively recent.
Cons:
- * Has a lot of similarities to the other two crater sites, Eberswalde and Gale, but less stratigraphy than Gale and less evidence that the layered rocks formed in a lake than Eberswalde.
- * Lots of ripples in the landing ellipse might make traversing across the ripples time-consuming.
- * Relatively limited variety of phyllosilicate minerals known to preserve organics detected from orbit.
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