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Recent research into dust devils

darker99 3 years ago updated by Tyler Owen (Lead Developer) 2 years ago 9

Quite recently a paper on dust devils on Mars was published: https://arxiv.org/abs/1708.00484


Three quotes that could be of special interest to you (Brian Jackson et al. 2017):


"Instead, we can adapt their formulation for our estimated typical, actual diameter of 13 m (Figure 9), which gives an occurrence rate ten times higher, 1 event per sol per km2. [...] This estimate includes detection biases and a population average should be used instead of typical values, but these results are roughly consistent with terrestrial field studies that estimate 40% of dust devils lift visible amounts of dust (Lorenz and Jackson, 2015)."


"Figure 8 (b) shows the resulting Γobs distribution. Consistent with estimates of the distributions of dust devil widths (e.g. Reiss and Lorenz, 2016), wider devils are less common than narrow devils, and Figure 8 (b) shows a power-law model for the differential distribution with index -1.6 provides a reasonable fit.
The distribution also declines for dust devils narrower than [...]18 m, seemingly at odds with the results of Reiss and Lorenz (2016), which conducted a visual survey of dust devil tracks and reported a population dominated by devils with a diameters < 10 m. However, the apparent decline on the narrow-end of the distribution is likely the result of selection bias in Ellehoj et al. (2010). Given the typical wind velocity of 5 m/s measured at the Phoenix site, a devil with a width ∼ 10 m would produce a signal with only a ∼2-s duration."


"For example, the devils with the deepest pressure profiles seem to occur preferentially around mid-day local time both on Mars Ellehoj et al. (2010) and the Earth Jackson and Lorenz (2015)."


Which means that for the 25 sq mile map (about time you Americans finally switched to metres now that even Myanmar and Liberia are converting) there should be around 64*0.4=25.6 visible dust devils per sol, skewed towards midday. They should be generally small at around 10m diameter or less, although a rare one might reach a width of around 100m. They should move at a speed of some 5 m/s on average.



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There was a bug that was making dust devils much rarer than they should be. The coming update should fix this to be more in line with what you've quoted from this paper.

Could this change somehow have regressed between 0.61 and 0.62? In 0.62b1/0.62 I've seen only 2 dust devils in 12 sols, while In 0.61 I've seen at least one, but usually more than one, per sol.


It also feels as if there were much fewer dust clouds than before. I've explored more than half the map by now, and hardly have seen any areas where they were present.

Dust clouds have not been reduced, but I did reduce the instances of dust devils again. Not as rare as they used to be, but I didn't want you to see them every time you go out on an EVA. I want them to feel special and somewhat awe-inspiring. Not common and forgettable.

Yes, I actually felt them being a bit too common at the previous frequency, but maybe it could go just a little bit higher than the current rate. Something that would (if the mechanism makes it possible to estimate it in this manner) result in one possible sigthing in 2-3 sols on average?


Is the visibility/occurence of dust clouds affected by the graphics quality setting? I had to drop that to 4 from 5 due to a combination of a new high resolution display and a really old video card, so if they are, that might be the reason why I seem to get them less often than before.

I don't think graphics settings should affect the blowing dust clouds. I might double check them though.

I still feel dust devils have gotten way too rare with that change to their frequency back a few months. I hardly ever see any, in my current game I've seen the first (and so far only) one after 11 sols.

I could try making them slightly more common, but I still would like them to be relatively rare.

Just a question regarding dust devils... is seeing them also dependent on distance?


I've actually seen a good number of dust devils over a span of several SOL's. My computer is high speed low drag, so I keep everything at maximum or ultra settings for all of my games.


I don't know if lower performing systems are unable to see these dust devils unless they are a hundred km away... Because I can see them out there several hundred km away, even saw two way north and another way south eastern of my position during exploration.

They are fairly well randomized so that could just be your luck, but generally speaking they are not dependent on your computer. Some scenarios could make them more difficult to see at a distance, but they are spawned with the same parameters for everyone, but those parameters have a large degree of randomization.