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Dust devils like this one form frequently at Eldorado Valley. (Planetary Science Institute)

Devils’ Advocates

Some people go to Las Vegas to gamble, others to learn about Mars.

“Three, two, one, now!” Just seconds ago Asmin “Oz” Pathare was sitting under a beach umbrella in the baking heat, gazing off into the distance—now he has jumped to his feet behind his camera tripod and is on his walkie-talkie with fellow scientist Steve Metzger, who’s a couple hundred yards away. At the count of zero, they both trigger their shutters to get a stereo picture of the devil headed our way.

Me, I’m riding shotgun in a pickup truck with a bunch of scientific instruments duct-taped to the roof (a temporary backup—the team normally uses a specially equipped vehicle). In the driver’s seat is Matt Balme of the Planetary Science Institute in Tucson, Arizona. He’s an expert on dust devils—the little whirlwinds that form in dusty parking lots and ballfields, picking up whatever sand and grit lie in their path. Except that the dust devils here, on this dry lakebed outside Las Vegas, aren’t so little.

Which is good.

Balme guns it, and off we race, dodging rocks, ruts, and creosote bushes as he tries to maneuver the truck into the devil’s path. At the last second he turns hard and jerks to a stop. The dust devil passes through us, the blast of sand audible against the metal of the truck. We glance down at the dust particle counter and Balme records the number. The other instruments have captured wind speed and direction, atmospheric pressure, humidity, and temperature.

“That was awesome,” Balme says. Then we sit back and wait for the next one, just as he and his colleagues have been doing all day, every day, for two weeks. Here at Eldorado Valley, the dust devils, some of which rise hundreds of yards into the pitiless desert sky, form every few minutes.

What sounds like a lark for teenage off-roaders is actually NASA-funded research into an atmospheric phenomenon common on Mars. Temperatures there are much colder than in Nevada, of course, and the air is thinner. But no matter—in both settings, it’s the temperature differential between the ground and the air that fuels dust devil formation.

Balme and his colleagues want to know the basic physics and meteorology of dust devils, including how much material they pump into the atmosphere. The scientists don’t think devils cause the global dust storms that occur frequently on Mars, but they may contribute to the day-to-day dustiness of the atmosphere; that’s something the team hopes to determine.

Planetary researchers are good at finding cheap ways to simulate Mars on Earth, and other scientists have tagged along on this trip, including a team from the Open University in Milton Keynes, England (where Balme is also a research fellow), who are testing an ultraviolet sensor intended for Europe’s ExoMars rover, scheduled to launch in 2018. It’s hot, dusty work, and though Balme admits the driving is fun, he says that after a month in the field, here and in Arizona, he’ll be glad to get home.

Then a call comes over the walkie-talkie, and we’re off chasing another dust devil. So far that makes something like 500 here at Eldorado alone.

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