Martian dust devils are so big that they dust the planet's atmosphere, giving the atmosphere its reddish-brown hue, and so big that Mars Global Surveyor cameras have photographed them from orbit.

Now an international team of 20 space scientists and engineers are conducting an ambitious field test of equipment this week to study dust devils swirling over the Santa Cruz flats near Eloy, Ariz.

The "Matador" experiment, led by Peter Smith of the University of Arizona Lunar and Planetary Laboratory and funded by NASA's Human Exploration and Development of Space enterprise, will help define instruments needed for studying much larger dust devils on Mars later this decade, possibly in 2007.

Earth dust devils can be 10 meters to 20 meters in diameter and 1,000 meters (a kilometer or six-tenths of a mile) high, Smith said. Mars dust devils are typically a kilometer in diameter and 10 kilometers (6 miles) high.

Smith, whose Imager for Mars Pathfinder camera returned a trove of famous photos from the surface of Mars where it landed July 4, 1997, was among a group of scientists who recently briefed the National Research Council on hazards to humans on Mars. He also is co-investigator for Beagle 2, the lander part of the 2003 "Mars Express" mission, Europe's first mission to the Red Planet.

"We are going to get experience in measuring the physical and electrical properties of dust devils," Smith said. "We want practice tracking dust devils with LIDAR. And we may find that we'll need to make measurements that we haven't thought about yet."

Starting Monday, June 4, the Matador team is conducting daily operations near plowed but uncultivated agricultural fields in the desert near Eloy.

Using LIDAR at their fixed station, researchers are tracking speed and direction of the moving dust storms, then driving their instrument-laden pickup "mobile station" into the paths of any dust devils they can intercept.

Video crews in another vehicle and at the fixed station are recording dust devils as they hit the instruments deployed from the pickup.

LIDAR, which bounces a laser beam to measure distance to the dust storm, is being used to track moving dust devils and to get density profiles of dust in the twisters.

The suite of instruments for the field test also includes cameras, a laser doppler anemometer for gauging wind speed, temperature and pressure sensors, magnets, high frequency and low frequency radios and electric field antennae, a dust counter, an "electric field mill" made by Global Atmospherics of Tucson (it measures changes in Earth's electric field that averages around 100 volts per meter but shoots up to 2,000 or 3,000 volts per meter, e.g, during lightning strikes), and MAOS, the Mars Atmospheric Oxidant Sensor, a chemistry experiment to discover the source of oxidation (corrosion) on Mars.

Portable GPS units are attached to the scientists' rugged field laptop computers.

Team scientists include Smith and others from the UA Lunar and Planetary Lab; John Marshall of NASA Ames Research Center, an expert on dust properties; William Farrell of NASA Goddard Space Flight Center, an expert on the electrical properties of dust devils; Greg DeLory of the University of California-Berkeley, who is managing the data system during the experiment; Allan Carswell of Optech, Ontario, Canada, who will operate the LIDAR; Barry Hillard of the NASA John Glenn Research Center, who will be using the electric field mill; Nilton Renno of the UA departments of atmospheric sciences and planetary sciences, an expert on Earth's dust devils, and others.

[Contact: Peter Smith, Nilton Renno]

06-Jun-2001