- News Home
5 December 2013 11:26 am ,
Vol. 342 ,
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
- 5 December 2013 11:26 am , Vol. 342 , #6163
- About Us
Dusty Ponds in Space
26 September 2001 7:00 pm
Pockets of drifting dust have cropped up on the airless surface of an asteroid called Eros. But with no wind to push the dust around, researchers weren't sure how it gathered into smooth patches. Now, thanks to stunning images from a craft that landed on the asteroid, scientists have proposed an exotic explanation: electrostatic levitation, triggered by sunlight.
Until recently, planetary geologists thought asteroids were barren rock, because, they reasoned, jolting collisions with other objects would propel any soil or dust into space. But images from the NEAR-Shoemaker spacecraft are dispelling that notion. The craft, which began orbiting Eros in February 2000, spied a jumble of deposits on the asteroid's surface, including oddly smooth "ponds" inside craters. On 12 February 2001, controllers guided the explorer to land on one such pond. Photos revealed details as small as 1.2 centimeters across--by far the closest scrutiny of an asteroid.
NEAR researchers examined these and thousands of other images to explain the ponds. Their report--part of a suite of papers on Eros in the 27 September issue of Nature--points to sunlight as the driving force. Sunlit dust particles near the asteroid's equator build up an electrostatic charge compared to their shadowed neighbors. Spectral analysis suggests that many grains are much less than 50 micrometers wide; that's light enough for the charges to briefly levitate the grains in the weak gravity of Eros. Each time they are aloft, the particles gradually migrate to the low parts of craters to form ponds in a process that may take millions of years to unfold, says planetary geologist and NEAR team member Mark Robinson of Northwestern University in Evanston, Illinois.
A similar suspension probably occurs on the moon, where astronauts saw dust wafting above sunlit zones, says planetary scientist Erik Asphaug of the University of California, Santa Cruz. "It's exciting to see these fine, loose soils on an asteroid," Asphaug says. "Levitation is a great possibility," although impacts also may shake dust into motion, he notes. One consequence, Asphaug adds, is that future asteroid landers may need to cope with a problem faced by astronauts on the moon: coatings of charged dust on their instruments.