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Dust Storm
RoverDriver
post Aug 4 2018, 05:20 PM
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IIRC once the clock is lost (which is a likely event) the BCB needs at least a 2A current from the array and 27V on the batteries before attempting to beep.

Paolo


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marsophile
post Aug 5 2018, 01:48 AM
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The sporadic nature of the Martian dust storms reminds me of the sporadic occurrences of wildfires (which are currently raging here in California). Apologies if this seems like a far-out idea, but I'm wondering if combustion ever occurs on Mars and whether it might be related in some way to the dust storms.

The regolith is now known to contain organics and perchlorate, which may build up over time. This might conceivably form a combustable mixture in some places. Given the frigid Martian temperatures, combustion would be rare but perhaps a meteor strike could trigger ignition? Combustion could raise dust (and smoke) into the atmosphere which might be enough to trigger a positive-feedback process. Such events would tend to be self-limiting, though, given the depletion of the consumable resource.

Of course, this suggestion could easily be falsified by Maven observations, which presumably could detect the products of combustion.
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RoverDriver
post Aug 5 2018, 04:38 AM
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My chemistry is not so hot (pun intended), but combustion doesn't it require an oxidizer?

Paolo


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marsophile
post Aug 5 2018, 06:04 AM
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https://en.wikipedia.org/wiki/Perchlorate

The perchlorate serves as the oxidizer.
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nprev
post Aug 5 2018, 08:28 AM
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Open question as to whether deposits of organics of sufficient mass in close proximity to large concentrations of perchlorates exist anywhere on Mars for this to occur to say nothing of the probability of an ignition event, but I gotta rate such a confluence of favorable circumstances as unlikely to the point of 'ain't gonna happen' (yes, that's a technical term wink.gif ).

Moving on...


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dvandorn
post Aug 5 2018, 04:23 PM
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Thanks, guys. The technical discussions thus far available had not been much help for me to understand what the thresholds are for a MER re-animation after a major dust storm event. I've got a much better idea now. This is exactly the discussion I was hoping to see, again much thanks.

And yes, we don't know the dust loading, but as Mike pointed out, it's got to be between 0 and 1, thus providing a range on a graph that must, when added to the tau range and the minimum charge required for the rover to start up again, define the conditions required to get to a re-activation of Oppy.

In my mind's eye, there is a graph, sort of a Venn diagram, of those three sets -- tau, dust loading and resultant power -- and the area where they overlap is the area in which we can expect a successful re-activation. And it would surprise me no end if such a graph does not exist for all you JPL types to see. I was just trying to get some insight on what the ranges are in each of the major categories, and how each sort of generally plots against time, is all.

But, yeah, planetary exploration via Venn diagramming... smile.gif


p.s. -- Even with all the times lately (and yet upcoming) I have had to undergo surgeries, and get another few million brain cells whacked by the anesthesia, I am still swift enough to understand that there is not a magic date on a calendar beyond which the situation goes from "we're confident and optimistic" of recovery to "let's declare Oppy finally dead and have a wake for her". Like I say, I was just trying to get the shape of that Venn diagram I mentioned straight in my head. Again, thanks!


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djellison
post Aug 5 2018, 05:43 PM
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QUOTE (dvandorn @ Aug 5 2018, 09:23 AM) *
.... the area where they overlap is the area in which we can expect a successful re-activation. And it would surprise me no end if such a graph does not exist for all you JPL types to see.


Power models are run based on presumed battery voltage ( all we know is it is < power fault voltage ) dust loading (which we don't know with any accuracy ), presumed Tau ( which we don't know either - we can sort of infer from MSL, and MARCI when MER gets occasional updates from that team ) - but they're little more than educated guesses.

You could run the numbers and argue the vehicle should have woken up last week, or not until October. It's almost as bad as running the Drake Equation. You put in the numbers to get the answer your want.

Moreover - tau varies, a lot, during a storm decay. We might see enough power on the arrays on one day to start charging the battery back up but not hear anything...but then have three days of worse conditions. There are also fault recoveries where we might be listening at the wrong time, etc etc etc.

In short - tomorrow is better than today, generally speaking. The story only really gets worse when next winter arrives - many, many months from now.
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dvandorn
post Aug 7 2018, 04:02 PM
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Thanks much, Doug! smile.gif


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marsophile
post Aug 12 2018, 01:20 AM
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https://mars.nasa.gov/msl/mission/instrumen...onsensors/rems/

Some new readings from REMS. The pressure now seems to be running about 30 pascals lower than the average for previous Mars years.
Perhaps due to a further increase in altitude by Curiosity?
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Explorer1
post Aug 12 2018, 02:56 AM
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Something to do with the dust storm, perhaps? How much higher has the rover climbed since landing? I recall seeing a 'side chart' detailing this somewhere on the board a while back...
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PaulH51
post Aug 12 2018, 04:07 AM
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QUOTE (Explorer1 @ Aug 12 2018, 10:56 AM) *
....How much higher has the rover climbed since landing?....


I believe the landing elevation was in the order of -4501 meters. The current elevation (reached on sol 2132) is shown as -4170 meters on the JPL traverse map. However the rover drove downslope from its higher elevation on the ridge to reach this drill target. So are you looking for the max elevation or current elevation.


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serpens
post Aug 12 2018, 09:06 AM
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The month 11 weather report attributes the drop in pressure compared to last year to Curiosity's increased elevation and also notes the effect on pressure of the reduced temperature range due to the dust storm.
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marsophile
post Today, 06:32 AM
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Is anything known about the after-effects of a major dust storm on the global distribution of dust? For example, would it tend to move dust from lower elevations to higher elevations or vice versa?
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