ANN ARBOR, Mich. -- University of Michigan scientists have found clues that dust devils on Mars might have high-voltage electric fields, which means the so-called mini-tornados could be hazardous for both human and robotic space explorers.
NASA and university researchers discovered that dust devils on Earth have unexpectedly large electric fields, in excess of 10,000 volts per meter, and can generate magnetic fields as well. If Martian dust grains have a variety of sizes and compositions, dust devils on Mars should become electrified in the same way as their particles rub against each other, according to the team.
This research supports NASA's Vision for Space Exploration by helping to understand what challenges the Martian environment presents to explorers, both robotic and eventually human.
"Two ingredients, present on both Earth and Mars, are necessary for a dust devil to form: rising air and a source of rotation," said Nilton Renno, associate professor in atmospheric, oceanic and space sciences and an expert on the thermodynamics and fluid dynamics of dust devils. Renno is the principal investigator of a National Science Foundation project that supported the 2002 field campaign to track and measure dust devils here on Earth. The goal of Renno's ongoing NSF research is to study the role of dust devils on aerosol transport in the Earth's atmosnphere.
"Dust devils are common on Mars, and NASA is interested in them as well as other phenomena as a possible nuisance or hazard to future human explorers," said Dr. William Farrell of NASA's Goddard Space Flight Center in Greenbelt, Md. "If Martian dust devils are highly electrified, as our research suggests, they might give rise to increased discharging or arcing in the low-pressure Martian atmosphere, increased dust adhesion to space suits and equipment, and interference with radio communications."
Dust devils are like miniature tornadoes, about 10 to 100 meters wide with 20- to 60-mile-per-hour (32- to 96-km/hr) winds swirling around a hot column of rising air.
"Complex tracks, generated by the large Martian dust devils, are commonly found in many regions of Mars, and several dust devils have been photographed in the act of scouring the surface," said Peter Smith of the University of Arizona (Tucson) who led the 2002 MATADOR (Martian Atmosphere and Dust in the Optical and Radio) activity, that studied dust devils on Earth, with Renno. "These Martian dust devils dwarf the 5- to 10-meter terrestrial ones and can be greater than 500 meters in diameter and several thousand meters high. The track patterns are known to change from season to season, so these huge dust pipes must be a large factor in transporting dust and could be responsible for eroding landforms."
Dust particles become electrified in dust devils 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.
The team MATADOR includes researchers from NASA Goddard, NASA Glenn (Cleveland, Ohio), NASA Jet Propulsion Laboratory (Pasadena, Calif.), University of Arizona (Tucson), University of California (Berkeley), SETI Institute (Mountain View, Calif.), University of Washington (Seattle), University of Michigan (Ann Arbor), and Duke University (Durham, N.C.).
NASA - Goddard Space Flight Center story -- http://www.gsfc.nasa.gov/topstory/2004/0420marsdust.html
American Geophysical Union story -- http://www.agu.org/pubs/crossref/2003/2003GL017879.shtml
NASA Jet Propulsion Laboratory -- http://marsrovers.nasa.gov/home/index.html
Nilton Renno -- http://aoss.engin.umich.edu/go/index1.php?id1=10&id2=1&id3=35**
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