Dust Storm- Opportunity EOM, the end of the beginning of a new era in robotic spaceflight Options

[serpens]

The effect of dust storms is to loft water vapor into the middle atmosphere, with a significant decrease in absolute humidity near the ground. This reduction in the amount of water vapor means that the formation of films or brines is even less likely during a dust storm despite higher minimum temperature or minor variations in atmospheric pressure.

[marsophile]

...the formation of films or brines is even less likely during a dust storm....

I am more interested in the aftermath of the dust storm, when (hopefully) Opportunity will be able to observe changes in the resultant dust deposits. Is the above hypothesis still applicable at that point?

[mcaplinger]

Is the above hypothesis still applicable at that point?

I don't think there's really an appreciable pressure signature from dust storms, but this has been measured. Note that some of the graphs below are more about diurnal variation in pressure and less about absolute pressure.

https://www-k12.atmos.washington.edu/k12/re...ion/overlay.gif

https://mars.nasa.gov/resources/4902/atmosp...ing-dust-storm/

[marsophile]

https://mars.nasa.gov/msl/mission/instrumen...onsensors/rems/

Dates (2018) Mean Pressure (Pascals)

June 05--June 10
758 756 758 762 764 765
June 11--June 16
766 767 768 770 768 769
June 17--June 21
771 772 776 780 778

Looks quite suggestive. Of course it might be just the normal seasonal signal.

[djellison]

The effect of dust storms is to loft water vapor into the middle atmosphere, with a significant decrease in absolute humidity near the ground. This reduction in the amount of water vapor means that the formation of films or brines is even less likely during a dust storm despite higher minimum temperature or minor variations in atmospheric pressure.

And the maximum temperatures are also decreased, dramatically, during the storm. Rendering windows when such events might occur astonishingly small, if they existed at all.

[serpens]

I don't think there's really an appreciable pressure signature from dust storms, but this has been measured.

The second linked graph measures atmospheric pressure hundreds of miles from a dust storm and compares pressure changes above the daily minimum. Given the general atmospheric heating and the localised heating referred to wouldn't the minimum absolute pressure be different for each of the graphs, possibly implying that the absolute maximum temperatures would tend to align?

[mcaplinger]

wouldn't the minimum absolute pressure be different for each of the graphs...

Of course. Without finding the raw data I can only show what the team chose to plot. My only point in posting this was to indicate that the pressure was being measured and eventually we would be able to see those measurements (see http://pds-atmospheres.nmsu.edu/data_and_s.../Mars/Mars.html although if this page is right the REMS team is way behind on releasing data.)

Going back to the Viking 1 data would be the best way to look at the pressure through a dust storm as of today, probably.

[scalbers]

This simulated version shows the blue scattering surrounding the sun a bit better. Tau ranges from 0.5 to 10. I'll try to make a plot of the phase functions being used for this.

[Deimos]

Pressure is of course modified by the storm--but there is no measurable enhancement from the dust loading, the original question (I think). The modification is not as simple as a perturbation to the existing profile (e.g., shifting the absolute minimum pressure up or down or compressing/expanding the range of variation).

There are many modes, and they interfere. There's a diurnal tide--the surface gets warmer and heats the air, warm air rises, circulation happens--that can be diminished by the the diminished temperature cycle, but also by more complex interactions (VL1 diurnal tide went away, http://science.sciencemag.org/content/213/4506/437--at least the abstract can be seen). There's a semi-diurnal tide from heating by dust in the air and can be seen from orbit and the ground (http://www.planetary.org/blogs/guest-blogs/2013/mysterious-tides-martian-atmosphere.html). It increases in amplitude significantly when there is a lot of dust in the hemisphere or globe (Fig. 2 in https://journals.ametsoc.org/doi/full/10.1175/JAS3718.1)

The tides are enhanced in Gale as opposed to Meridiani; they correlate with dust as seen by Curiosity--two pay-walled papers discuss this: https://www.sciencedirect.com/science/artic...0531?via%3Dihub and https://www.sciencedirect.com/science/artic...5850?via%3Dihub. It might be cool if Scott (or Scot) would do a blog post at Planetary Society.

To visualize the modes, see Figs. 3, 9, 10 in http://sirius.bu.edu/withers/pppp/pdf/with...014atmo_v02.pdf.

So, there is no particular effect from the dust mass; but there will be a substantial impact from the dust heating and cooling effects, and those would be expected to significantly alter the shape of the pressure wave, based on how much the first two modes would be expected to change with tau>5 over possibly large regions.

[marsophile]

https://mars.nasa.gov/mer/home/

Opportunity at Meridiani
Sol: 5127 Time: 12:51

Spirit at Gusev
Sol: 5148 Time: 14:18

http://www.planetary.org/multimedia/space-...lakdawalla.html
This doesn't seem right---Opportunity is at the opposite side of the planet from Spirit, so the LST times should be around 12 hours apart. Having the correct local time for Oppy is useful for checking the DSN Now comm schedule.

[marsophile]

Pressure is of course modified by the storm--but there is no measurable enhancement from the dust loading,

According to this article
http://curious.astro.cornell.edu/physics/6...re-intermediate
the atmospheric dust in a Martian dust storm would correspond to a layer about 3mm thick if deposited on the surface.

Assuming the dust has a density of about 1.5 gm/cc, a 3mm layer over 1 cc of surface would weigh about 1.5 x 1/3 x 3 x 1/10 = 0.15 gm on Mars. Thus, all else being equal, the pressure due to dust loading should be about 0.15 gm per sq. cm, which is equal to about 0.15 x 98 = 14.7 pascals. That is small but it should be measurable by the REMS instrument.
[EDIT: Perhaps the article linked above is confusing mm with microns (mu-m). Indeed a layer only 3 microns thick would not contribute significant loading.]
[EDIT: As a clarification, the "1/3" factor in the formula "1.5 x 1/3 x 3 x 1/10" is the correction for Mars gravity (with a slight abuse of units).]

[mcaplinger]

0.15 x 98 = 14.7 pascals.

On Mars, 0.15*38 = 5.7 pascals, I believe, unless you tried to compensate for this in your gram number (improperly, since a gram is a unit of mass, not weight.)

The article you linked cites https://www.sciencedirect.com/science/artic...2855?via%3Dihub which is behind a paywall, although I guess I could walk upstairs and get a copy from the author I think unit confusion is likely.

[xflare]

For amateur observations and updates on Mars during the dust storm, keep an eye on these sites:

https://britastro.org/node/10908
http://alpo-j.asahikawa-med.ac.jp/indexE.htm

[Deimos]

Note that the Cornell link got to the estimate of a few mm thick using dust diameter of 3 mm. Using a more traditional 3 microns, you can take the result down 3 orders of magnitude. I get close to 1 mPa per unit optical depth (order of magnitude), which ends up in the same ballpark.

Even at a few Pa, I'd be skeptical--certainly REMS could measure a few Pa, but I'm not sure it could measure a few Pa of dust. There are many thermal perturbations. There are tidal perturbations, changing stationary and traveling waves. The polar cap sublimation rate and mass transport rate in the atmosphere may be affected.

[For tau=1, there is 0.5 m^2 per m^2 of dust (dust area fraction) given a likely extinction efficiency of ~2. Volume is roughly cross-sectional area times 4/3 R. So, tau=1 implies 1 micron thickness for dust that is uniformly 3 microns in diameter. Being generous, since we're talking cohesive dust particles, not the actual thickness a powdery pile would have, 3000 kg/m^3 implies 0.003 kg/m^2, or 0.001 Pa in Mars gravity.]

[xflare]

https://mars.nasa.gov/mer/home/


http://www.planetary.org/multimedia/space-...lakdawalla.html
This doesn't seem right---Opportunity is at the opposite side of the planet from Spirit, so the LST times should be around 12 hours apart. Having the correct local time for Oppy is useful for checking the DSN Now comm schedule.

This site http://www.dmuller.net/spaceflight/realtim...amp;mode=planet lists the current time as Sol 5127, 23:32. The MER site has Sol 5128, 22:51