by Richard A. Kerr on 5 April 2012, 2:06 PM
Earth may have terrifying tornadoes, but when it comes to dust devils,
Mars has us beat. A camera onboard the Mars Reconnaissance Orbiter has
captured a stunning example of a swirling funnel of dust spinning up to an altitude of 20 kilometers. (The animation above provides a side view.) On
Earth, tornadoes often reach such heights, but dust devils seldom reach up more than a few hundred meters. That's because dust devils only draw their
energy from the solar heating of the surface; tornadoes also tap the heat energy from the condensation of water vapor in a tornadic storm.
Mars is too dry for that, but the thinness of its air allows dust devils to soar, even on their restricted energy diet. Astronauts wouldn't be knocked off of their feet if caught in one, but martian dust devils are strong enough to play many roles. They loft dust high into the atmosphere between major dust storms.
Some Mars scientists suspect dust devils generate enough static electricity to produce bleach-like chemicals that consume any organic matter—and any living thing—in martian soil. And dust devils have certainly lent NASA a hand; they occasionally blow the dust off a rover's solar cells, letting it power back up and keep on truckin'.
ScienceNOW, the daily online news service of the journal Science
EDITOR'S NOTE: There is a discrepancy in the reported height of the dust devil. The text says about 20 kilometers, the video about 0.5 mile. When asked if he could clear up the matter, the video's narrator, NASA scientist Dr. Rich Zurek, emailed the following to The Huffington Post:
"The animation was based on a high-resolution MRO HiRISE color strip which included some, but not all, of the dust column. We estimated the height conservatively by matching curves in the column with curves in the ground shadow to get a height estimate, saying that the column did indeed reach above 1 km."
"The estimate for the much higher altitude comes from a bore-sighted context image (MRO CTX) which has a wider field of view. As I understand it, analysis of that image says the continuous dust column extended several kilometers above the ground with a more diffuse dust haze extending another several kilometers above that (for the total of 20 km)."
"I too await more details of the analysis."
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