How can Mars have dust storms with such a thin atmosphere?

Question

Mars, as I understand, has a very thin atmosphere. However, it still has weather like this:

What causes the thin atmosphere to move fast enough to cause such a monster wave of dust?

Answer 1

Mostly a product of two environmental factors, I would wager:

• Lack of in-air humidity or liquid water on the ground keeping dust fine grained and not sticking together to form larger mass particles, and
• Relatively low surface gravity of roughly 1:2.6 when compared to the sea-level gravity on the Earth keeping them suspended in atmosphere for longer periods of time.

So while there might be low atmospheric pressure on the surface of Mars and winds not having much strength at all, even if they are moving fast over its surface, what we'd consider a mere breeze here on Earth, can produce in relative terms hurricane force long-lasting dust storms and local dust devils lifting the fine grain dust off the Mars' regolith and suspend them in the thin atmosphere for a long time, before they finally settle with the winds subduing.

We have observed similar phenomena here on the Earth with the Chelyabinsk Meteor's mostly silica based dusty plumes lingering in the upper atmosphere (with similar atmospheric conditions than that of Mars' surface, i.e. low humidity, low atmospheric pressure, low temperatures, e.t.c.) for months and circling the globe:

    

    ^{Chelyabinsk's dust plume circled Earth in just four days, as shown in this image based on modelling. (Source: NASA Goddard)}

Answer 2

The answer is that the solar radiation heats the thin atmosphere of Mars but hot air rises up and it also lift its small dust (since Mars has low surface gravity of 3.711 $m/s^2$ they are almost weightless) and dust-storms begin to form, swirling at great speeds due to the thin atmosphere probably due to formation of different pressure in the atmosphere (what we call in earth as hurricane) The greater the temperature, the better chance of dust storm.

External Sources

http://curiosity.discovery.com/question/mars-dust-storm-causes

http://www.universetoday.com/14892/mars-dust-storms/

Answer 3

Dust on Mars, and on the moon, is very, very fine. There's no water, so there's no clumping or mud, no washing into basins to form clay or sedimentary rocks. On the Apollo missions, moon dust got through zippers, through filters, it got into everything and became a hazard. If you look at the famous footprint picture you can see how fine it is, like flour, perfectly reproducing the pattern of the boot. Mars dust would blow around a lot more easily than Earth dust does.

https://medium.com/@adammann930/the-problem-with-dust-on-the-moon-and-mars-2a916162b864

Answer 4

Although I'm a Mars Dust Devil researcher, my work is mostly conducted on terrestrial desert analogs (so I'd want to check my details if this were crucial). My understanding is that:

1. The dust is re-cycled so much it's now very fine clay (2-4 μm), dry and often recently draped over surface roughness elements.

2. Meanwhile, weathered quartz leads to fine sand which "sticks up into the wind" relative to the tiny dust motes.

3. Once a breeze starts moving the sand (always the first grain size to start transport), it can saltate and bounce/slam into the surface dust drape and splash it into the wind.

4. Furthermore, Greeley once calculated (late 1990's LPSC abstract) that merely the dust draped on rocks rising above the Martian surface (and into the wind) was enough on its own to account for much of the dust loading in the regional/global dust storms.

Given the small dust grain size range and the fluid dynamics and density of the atmosphere, I don't think Mars' reduced gravity plays any significant role. Simply put, although thin by our standards, the Martian atmosphere is plenty thick enough to erode and carry dust.