Image Credit: NASA/JPL-Caltech/Cornell [via 8]

This log covers how dust storms originate, their speed, size, and duration. Additionally, what a Martian dust storm visually looks like, a weather overview, additional information, and all the sources for this. Click on 'Read More' to see the entire log.

Information about Martian Dust Storms

Image credit: NASA/JPL-Caltech

Why do Mars dust storms occur?	James Shirley, a planetary scientist at NASA's Jet Propulsion Laboratory, Pasadena, California has found that solar system dynamics play a role in global-scale dust storms on Mars (see paper here). “Shirley found that global dust storms tend to occur when the momentum is increasing during the first part of the dust storm season. None of the global dust storms in the historic record occurred in years when the momentum was decreasing during the first part of the dust storm season.” [5] “The radiative heat of sunlight reaching the surface of the planet is what drives these dust storms. As sunlight hits the ground, it warms the air closest to the surface, leaving the upper air cooler. As in thunderstorms on Earth, the warm and cool air together become unstable, with warm air rising up and taking dust with it. Rising plumes of warm air create everything from small dust devils, similar to those that form in deserts on Earth, to larger continent-sized storms. These larger storms sometimes combine into the global storms, which cover the entire planet in atmospheric dust.” [2]
What is challenging about Mars dust storms?	“When global storms hit, surface equipment often has to wait until the dust settles, either to conserve battery or to protect more delicate hardware.” [2] “remain difficult to predict with climate models because the mechanisms of their onset and evolution are not well known and involve many subtle positive or negative feedbacks between the circulation and heating.” [4]
What qualifies as a dust storm?	Area > 10^5 km^2 and that are visually distinguishable from the surface [1] There are also dust devils too
Do the storms have electricity (lightning)?	Yes. “The storms might also crackle with electricity, which may produce reactive chemicals that build up in the Martian soil” [3]
Do storms have rain?	“the height at which water condenses to form clouds increases during the storm, leading to more water vapor in the upper atmosphere.” [4]
When do Mars dust storms occur?	During the southern hemisphere’s summer, as that is when the planet is closer to the sun and significantly hotter [2] “Once every three Mars years (about 5 ½ Earth years), on average, normal storms grow into planet-encircling [global] dust storms” [2]
How long do Mars dust storms last?	Weeks at a time, and bigger storms cal last weeks to months [2] 3-5 sol period as observed during the mid-northern winter [12 via 11] Some storms have shown a 24 hour life-cycle. This one in particular, shows further evidence that some Martian weather phenomena are highly repeatable interannually. [20 via 11]
How many dust storms on Mars have there been?	14,974 over 8 Mars years [1] For global dust storms, “The Red Planet has been observed shrouded by planet-encircling dust nine times since 1924, with the five most recent planetary storms detected in 1977, 1982, 1994, 2001 and 2007” [5]
Where are Mars dust storms happening?	Northern hemisphere: Acidalia, Utopia, and Arcadia Planitiae Southern hemisphere: Aonia-Solis-Valles Marineris and Hellas Basin [1]
How strong are the winds on Mars?	“the strongest Martian storms top out at about 60 miles per hour, less than half the speed of some hurricane-force winds on Earth” [2]
Why can the wind speed on Mars be misleading?	“The atmosphere on Mars is about 1 percent as dense as Earth’s atmosphere.” [2]
How fast do the dust storms travel?	Depends on the specific storm. As one example, a dust storm in the noth polar region around June 29, 2002 extended over 1900 km in length, reaching as far north as the perennial ice cap. [10 via 11] As another example, one of the fastest moving local dust events ever observed by MOC was over 45 m/s (100 mph) [13 via 11] 32 m/s [17 via 11]
How far do the dust storms travel?	Depends on the specific storm. For example, the same storm as mentioned above lasted for 2 days, and moved slowly eastward at 5 m/s. [10 via 11]
How large are storms?	There can be multiple scales, from global to regional to local. One example extended 3000 km (equivalent to the distance from the Great Lakes to southern California) [19 via 11] Another example is one dust storm extending from Erythraeum which stimulated dust activity as far south as Argyre Basin. [18 via 11]
What height do the dust storms reach?	Some have reached over 15 km, but most occur in the lower scale of height around 3-6 km. [14 via 11] 16-24 km [17 via 11]
Do large (sub-regional) storms break into smaller (local) events?	Yes. “There was a south polar storm that continued for several days, then abruptly partitioned into a number of small, local events scattered throughout the antarctic.” [16 via 11]
Does the pressure change during a dust storm?	Yes, before a dust storm the pressure peaks. During the dust storm, it subsides. Image credit: NASA/JPL-Caltech/CAB(CSIC-INTA)/FMI/Ashima Research [29]

What does a Martian dust storm visually look like?

Image credit: NASA/JPL-Caltech [27]

“This animation shows the evolution of the 2018 Mars global dust storm from late May to September. The animation shows the optical depth tau -- a measure of how much light is being blocked by atmospheric dust as measured by the Mars Climate Sounder instrument onboard NASA's Mars Reconnaissance Orbiter.” [27]

Image Credit: NASA/JPL-Caltech/MSSS [22]

“Two 2001 images from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter show a dramatic change in the planet's appearance when haze raised by dust-storm activity in the south became globally distributed. The images were taken about a month apart.” [23]

Image credit: NASA/JPL-Caltech/TAMU “This series of images shows simulated views of a darkening Martian sky blotting out the Sun from NASA’s Opportunity rover’s point of view, with the right side simulating Opportunity’s current view in the global dust storm (June 2018).” [6]

“Each frame corresponds to a tau value, or measure of opacity: 1, 3, 5, 7, 9, 11.” [7]

Image Credit: NASA/JPL-Caltech/Cornell [via 8]

“This image is a time-lapse composite where each horizon-survey image has been compressed horizontally (but not vertically) to emphasize the sky.” [9]

Martian Weather Overview

“The average temperature is about minus 80 degrees Fahrenheit (minus 60 degrees Celsius), although it can vary from minus 195 F (minus 125 C) near the poles during the winter to as much as a comfortable 70 F (20 C) at midday near the equator.” [25]

“At times, it even snows on Mars. The Martian snowflakes, made of carbon dioxide rather than water, are thought to be very small particles that create a fog effect rather than appearing as falling snow. The north and south polar regions of Mars are capped by ice, much of it made from carbon dioxide, not water.” [25]

There is seismic activity (marsquakes) as detected by InSight

Daily weather measurements:

MSL Curiosity
InSight (temporarily suspended)
MRO MARCI Weekly Weather Reports (no longer updating)

Image courtesy: NASA/JPL-Caltech/Cornell/NMMNH [28]

Additional Information

Image credit: NASA / JPL / additions by Sky & Telescope

Mars dust storms near Jezero crater (where Perseverance will be landing):

MRO-MARCI daily global mapping images from 16 November 2006 (Ls = 111.4°) through 15 July 2017 (Ls = 33.5°), covering portions of seven consecutive Martian years (MY 28 – MY 34) [26]
A total of 1321 dust storms (1228 local, 93 regional) were observed. (Across all 3 potential landing sites) [26]
Storms were observed in all seasons, but showed distinct seasonal trends [26]

Water vapor:

“researchers found an increase in water vapor by more than a hundred-fold in the middle atmosphere during that global storm.” [24]
“Dust storms play a role in the ongoing process of gas escaping from the top of Mars' atmosphere. That process long ago transformed wetter, warmer ancient Mars into today's arid, frozen planet.” [21]
“At times, it even snows on Mars. The Martian snowflakes, made of carbon dioxide rather than water, are thought to be very small particles that create a fog effect rather than appearing as falling snow.” [25]
“Baroclinic waves” means polar cold front (dust events). About 8 m/s. [15 via 11]

Electrified Martian dust storms:

“Dust particles could become electrified in Martian dust storms when they rub against each other as they are carried by the winds, transferring positive and negative electric charge in the same way you build up static electricity if you shuffle across a carpet.” [3]
“The researchers calculated that electric fields generated by the swirling dust are strong enough to break apart carbon dioxide and water molecules in the Martian atmosphere.” [3]

Mars Dust Activity Database (MDAD)

Dataset: https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi:10.7910/DVN/F8R2JX

"Mars Year","Mission subphase","Sol","Ls","Centroid longitude","Centroid latitude","Area (square km)","Member ID","Sequence ID","Maximum latitude","Minimum latitude","Confidence interval","Missing data"