Crossing the Dunes at Murray Buttes, Sites 54-62, Sols 1353-1659, May 28 2016-Apr 6 2017 Options

[elakdawalla]

Some late-breaking discussion on the Ireson Hill caprocks from LPSC last week: these appear to be a new class ('Pogy') of basaltic sediment found within Gale Crater. They're unusual in that they're alkalic, but look like they have a different source region from similar rocks (e.g. Jake M) that have been studied previously. The Pogy rocks have a low potassium and nickel content, but are heavily enriched in calcium. So far these don't look like they were a major contribution to the Murray sedimentary system (if they even belong to it), and might represent a brief pulse of activity from another sediment source. Pogy-class rocks also have Fe/Mg ratio and CaO/Al2O3 ratios, which is similar to shergottites. That's about all I understood from the talks.

Cool! Was this a ChemCam talk?

[jccwrt]

It's a mix of information from ChemCam (John Bridges) and APXS/basalt chemistry modelling (Mariek Schmidt) talks.

[atomoid]

Sol 1648 Lmastcam view (no color correction). Notice the "pancake piles" on the left

mmm, Thanks for that, absolutely lovely pancakes! now serving stitch pair anaglyph salvaged from the ICE mess with a heaping helping of flapjacks on the side for parellel viewing

[PaulH51]

Curiosity Mission Update by Lauren Edgar: Sol 1651: Scoop #1 at Ogunquit Beach

Sol 1650 activities completed as expected, so it’s time to start scooping. Today’s plan is focused on acquiring Scoop #1 and dropping off a portion of the sample to SAM. This is the first of four intended scoops at this location, aimed at sampling different grain sizes and their composition. The plan begins with a Mastcam mosaic of “Kennebago Divide” to document some possible layering exposed by the wheel scuff on the right side of the workspace. We’ll also take several Mastcam images for change detection to monitor active sand movement. Then the arm backbone starts by retracting the arm and a vibe to clean APXS. After that we’ll take a few MAHLI documentation images of the “Flanders Bay” and Scoop #1 locations (prior to scooping), and a very close-up image of the “Avery Peak” ripple crest. Next up, we’ll acquire Scoop #1! The sample will be sieved, and the fine-grained portion (<150 microns) will be delivered to SAM. These are all very power intensive activities so there wasn’t much room for other science today, but tomorrow’s plan should accommodate more activities and context observations. In the meantime, sitting on “Ogunquit Beach” is providing a pretty great view.

[PaulH51]

Curiosity Mission Update by Lauren Edgar: Sol 1652: CheMin drop-off and SAM Analysis

Sol 1651 activities executed nominally, so today’s plan is focused on dropping off the fine-grained portion of “Ogunquit Beach” Scoop #1 (now named “OG1”) to CheMin, and SAM analysis of OG1. The plan kicks off with Mastcam multispectral imaging of the right and left wheel scuffs, as well as Mastcam change detection imaging. Then ChemCam will investigate “Tumbledown Mountain,” “Elephant Mountain” and “Canoe Point,” to characterize the composition of sand in different parts of the left wheel scuff. Navcam will also acquire an image to look at line-of-sight dust loading within the crater. Later in the afternoon, part of the OG1 sample will be dropped off to CheMin. Curiosity will stay busy overnight, with a SAM solid sample evolved gas experiment to analyze the fine-grained portion of OG1. I’m busy on the other side of the planet working operations for the Opportunity rover today, but it’s fun to hear many members of both rover teams jumping back and forth between telecons to help plan lots of great science activities for our hardworking robots.

[PaulH51]

1651 Focus merged MAHLI raw colour with added scale bar. Shows us some sub-millimeter a variety of well-rounded grains of Bagnold sands (slightly sharpened after adding the scale bar). Credit to Gerald for his MAHLI Ruler

[nprev]

Great shot!

Beginning to understand how the dunes can be so mobile in that exceedingly thin atmosphere.

[PaulH51]

Curiosity Mission Update by Lauren Edgar & Michael Battalio: Sol 1653: Targeted Science at Ogunquit Beach

Yesterday afternoon the downlink included some results of ongoing drill feed diagnostics that warrant a further look before proceeding with the dune campaign, so the arm activities from Sol 1652 were pulled from the plan and we did not drop-off to CheMin. But we did receive some beautiful images of scoop OG1, as shown in the above Mastcam image. Today’s plan is a great opportunity to do some targeted remote sensing activities that we haven’t been able to accomplish due to power constraints earlier in the week. The first science block includes ChemCam observations of “North Brother” and “Avery Peak” to investigate undisturbed sand and to look for changes in sand composition along a ripple crest. Then Mastcam will document the ChemCam targets and take several change detection observations. Later in the day, the GEO theme group requested a ChemCam observation of “Baxter Peak” to investigate changes in composition along another large ripple crest. We also planned two Mastcam mosaics to document sedimentary structures and changes in the Murray formation at nearby outcrops.
Meanwhile, the ENV theme group used the remote sensing sol to catch up on normal cadence activities, which had been partially suspended to provide as much time as possible for the dune campaign. ENV added a Navcam supra-horizon movie to try to capture cloud activity above the crater rim. Additionally, Mastcam was planned to capture a mid-week tau, to continue tracking changes in atmospheric dust between the usual weekend observations. The plan also includes a four-frame, Navcam dust devil survey to cover as wide an area across Gale as possible, and REMS and DAN observations were included as usual.

Animation of the Dune sand in the Scoop Link

[HSchirmer]

Great shot!

Beginning to understand how the dunes can be so mobile in that exceedingly thin atmosphere.

Agreed, neat to see how rounded the grains are.

Curious, is there any work estimating void space from scooping the sand?
Interesting to think about how much void space, "air space", there is in a dune;
and to appreciate how much adsorption area, surface area, there is inside a dune.

Odd to think about it that way, but what if, eh, 90% of the "surface area" of Mars is inside the dunes?

[AndyG]

Odd to think about it that way, but what if, eh, 90% of the "surface area" of Mars is inside the dunes?

Particle sizes are 0.1 to 0.25mm, more or less.
Void density <0.25. (~0.74 is 'optimally packed equal spheres'), but here smaller particles can fill in the gaps.

A quick dip into Excel suggests 'tens of thousands' of square metres of particle 'surface' per cubic metre of dune. Given ~1% of Mars is covered by dunes, I think it's easily safe to say the vast bulk of Mars' atmosphere/rock interface is within the dunes.

Andy

[Gerald]

Much of the reddish dust and (temporary) aerosols are on the micrometer scale while the grains in the dunes appear rounded or well-rounded and polished. This may change the numbers considering the active solid - gas interface. It depends much on the portion of fine dust embedded in the dunes. Since active dunes look dark, they may show a low dust/sand ratio. I wonder, whether SAM / CheMin will be able to determine this in more detail.

[jvandriel]

Dust on the deck on Sol 1653.

Jan van Driel

[serpens]

[quote name='Gerald' date='Apr 1 2017, 01:58 PM' post='235279']
.... Since active dunes look dark, they may show a low dust/sand ratio.....
[/quote
Mechanical and chemical weathering on Mars is extremely slow with minimal supply of sand and silt to replenish dunes and ripples. Without cohesion the dune material is constantly recycled. The wind velocity necessary for active dunes would ensure that any exposed silt sized particles would be winnowed and active dunes would be made up of well rounded, sand sized particles. As we have seen the influence of Mount Sharp provides significant local wind velocities confirming that its real name of Aeolis Mons was most appropriate. Outside the somewhat unique Gale Crater environment it is likely that dunes have a high basaltic glass content which would contribute to the dark colour.

[Guest_Actionman_*]

Dust on the deck on Sol 1653.

Jan van Driel

Static cling (as it were). It does not seem to "rain" dust.

[Art Martin]

[/quote
Mechanical and chemical weathering on Mars is extremely slow with minimal supply of sand and silt to replenish dunes and ripples. Without cohesion the dune material is constantly recycled. The wind velocity necessary for active dunes would ensure that any exposed silt sized particles would be winnowed and active dunes would be made up of well rounded, sand sized particles. As we have seen the influence of Mount Sharp provides significant local wind velocities confirming that its real name of Aeolis Mons was most appropriate. Outside the somewhat unique Gale Crater environment it is likely that dunes have a high basaltic glass content which would contribute to the dark colour.
[/quote]

Have there been experiments done to determine the wind velocity required to transport sand and dust in Mars rarefied atmosphere and lowered gravity? I know they can simulate zero gravity with diving airplanes so I would imagine they could do a similar thing but with a lower angled dive to create the same level of gravity you'd find there. Your experiment then could be in a partially evacuated wind chamber within the aircraft. Seems like we were rather surprised by the amount of transport in short periods of time. I suppose computer modeling has probably been done.