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through the enclosure floor. The young females, who didn’t yet have
sex organs, showed no interest in mating,but they evidently were impressed by themales who sought them. When the femalesreached adulthood, they were twice as likelyto mate with males with the leg color of theoriginal suitor than with males with legs ofthe alternate color. The suitor look-alikeswere also half as likely to be eaten by theirfemale partners.
The laboratory finding that female spi-ders are sexually impressionable whenyoung, “opens up a lot of questions aboutsocial learning,” says Gail E. Stratton of theUniversity of Mississippi in Oxford, whodiscovered the species. —S. MILIUS
Out of HidingLost asteroid reappears,bringing surprises
A team of astronomers has spotted Her-mes, an asteroid that disappeared into thenight after a close flyby of Earth in 1937.Ever since, some researchers have won-dered—and worried—about the asteroid’spath. Last month, scientists finally foundHermes, and they now know what to expectfrom it.
“Within the astronomical community,people were almost obsessed with findingthis thing,” says Tim Spahr of the Smith-sonian Astrophysical Observatory in Cam-bridge, Mass.
Early in the morning of Oct. 15, BrianSkiff of Lowell Observatory in Flagstaff,Ariz., spotted a possible near-Earth aster-oid. He alerted Spahr, who posted the find-ing on the Internet. Observers in Californiasaw the asteroid within 30 minutes andsent additional positional data to Spahr.
Reviewing recent images of the sky, hecould follow the asteroid and make roughcalculations of its orbit around the sun. Thetrajectory he came up with convinced himthe asteroid was Hermes. Within hours ofthe original sighting, Spahr announcedHermes’ reappearance in an Internet cir-cular of the International AstronomicalUnion (IAU).
“We’ve kind of expected that it could befound sooner or later,” comments Alan Har-ris of the Space Science Institute in Boul-der, Colo. “We’ve been waiting, and finallythey’ve got it.”
The precise calculation of Hermes’ paththrough space was made by Steven Chesleyand Paul Chodas of NASA’s Jet PropulsionLaboratory in Pasadena, Calif. Usually,astronomers there use programs to predictwhether or not an asteroid might slam intoEarth. In this case, Chesley and Chodas ransuch a program backwards to determineHermes’ path for the past 66 years.
They calculated that the asteroid made31 unobserved circuits around the sun dur-ing this time. Six times, Hermes must havecome within 9 million kilometers of Earth,or 24 times the Earth-moon distance. In1942, Hermes came within 640,000 km, amere 1.6 times the distance to the moon.
This year, Hermes will be at its clos-est—a comfortable 7 million km away—on Nov. 4. By extrapolating the orbit intothe future, the astronomers verified there’sno chance of Hermes hitting Earth withinthe next 100 years, which is as long intothe future as astronomers typically predictfor asteroids.
Hermes is “fairly large and capable ofmaking close approaches to Earth,” saysSpahr. “It’s nice to know where it is now.”
Beyond knowing Hermes’ orbit,researchers were interested in the aster-oid itself. Using the Arecibo Radar Tele-scope in Puerto Rico, Jean-Luc Margotof the University of California, Los Ange-les was able to tell that Hermes consistsof two gravitationally tied pieces, eachabout 300 to 450 meters across and orbit-ing the other.
“What was particularly surprising wasthat it was a binary with equal components,”says Margot, who presented the finding inan Oct. 20 IAU circular. Most binary objectshave a primary body with a smaller satel-lite, he says. The unusual arrangementcould help astronomers better understandhow asteroids break into two and how onecomponent influences the motion of theother. —K. RAMSAYER
Stone AgeCode RedScarlet symbols emerge in Israeli cave
The Qafzeh Cave in Israel contains skele-tal remains of modern Homo sapiens thatare more than 90,000years old, as well asmore-recent signs ofhuman occupation.Investigators now saythat red ocher foundin Qafzeh Cave’soldest sections sup-ports the controver-sial theory that sym-bolic thinking, ahallmark of modern-dayhuman thought, arosedeep in the Stone Age.
Archaeologists tradition-ally have held that theassigning of separate mean-ings to certain items or col-ors emerged no more than
50,000 years ago, with the appearance ofUpper Paleolithic cultures.
In the Middle East and Eurasia, how-ever, “many symbolic behaviors that areconsidered modern existed for a time[before the Upper Paleolithic] and thendisappeared, to be reinvented time andagain,” contends Erella Hovers of theHebrew University of Jerusalem, whodirected the Qafzeh project.
Her argument hinges on the discoveryof 71 pieces of red ocher, a form of ironoxide typically used as a pigment, as wellas ocher-stained stone tools, near severalof Qafzeh’s oldest H. sapiens graves. Thesame sediment holds the remains of largehearths and, intriguingly, scattered shellsof inedible mollusks
Preliminary chemical analyses indicatethat the ocher had been heated.
In the August-October Current Anthro-pology, Hovers and her coworkers pro-pose that, more than 90,000 years ago,lumps of ocher from nearby sources werebrought to the cave, carefully heated inhearths to yield specific hues of red, andused with the shells in possibly symbolicactivities related to burying the dead.
Evidence of similar ocher use nearhuman graves doesn’t appear again atQafzeh Cave until 12,700 years ago, thescientists say.
The precise meanings of the ocher-based practices remain unknown, Hov-ers notes. Many nonindustrial societiestoday regard the color red as symbolic offertility or vitality.
Prehistoric artwork and other symbolicexpressions commonly occurred in largepopulations that stayed for extended peri-ods at resource-rich locations, Hoverssays. In the small, nomadic groups typi-cal of Stone Age Middle East, a capacityfor symbolic behavior would have sur-faced only for special activities at desig-nated sites, such as the interment of thedead at Qafzeh Cave, she argues.
Several commentaries appear with thenew report and offer mixed reactions toHovers’ analysis of the Qafzeh artifacts.
According to Sally McBrearty of theUniversity of Connecticut in
Storrs, for example, ocher pro-cessing at Qafzeh adds to
evidence of “the verygreat antiquity of the
color red as a sym-bolic category.”Engraved ocher
dates to 77,000years ago in South
Africa (SN: 1/19/02, p. 40), she notes.
However, Richard G.Klein of Stanford Uni-versity argues thatocher use representedmerely a step toward
HUE CLUE An ancient lump ofred ocher excavated at QafzehCave contains evidence ofscraping by stone implements.
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advanced symbolic culture, which he saysH. sapiens established around 50,000years ago. —B. BOWER
Blame the Sea?Ocean may be melting iceshelf from below
Significant portions of a large Antarcticice shelf just south of one that suddenlybroke apart in February 2002 are rapidlythinning and may suffer a similar, cata-strophic demise in less than a century, sci-entists say.
Satellite observations collected between1992 and 2001 suggest that the upper sur-face of the Larsen C ice shelf dropped asmuch as 27 centimeters per year duringthe period. About a quarter of that shrink-age, or 7 cm, may have resulted from snowpacking down into denser material calledfirn, says Andrew Shepherd, a glaciologistat the University of Cambridge in Eng-land. Uncertainties about such factors asthe height of ocean tides and the temper-ature and the salinity of water beneath theice shelf would account for no more thana small fraction of the remaining loss inheight above water, says Shepherd.
Therefore, he notes, as much as 20 cmper year of the upper surface’s drop stemsfrom melting. About nine-tenths of anymass of floating ice lies below the water’ssurface, suggesting that Larsen C is thin-ning overall by as much as 2 meters eachyear. Shepherd and his colleagues reporttheir analysis in the Oct. 31 Science.
The likely cause of the thinning, saysShepherd, is relatively warm waterbeneath the ice shelf. Although water at adepth of 300 m just offshore of the iceshelf ’s edge is about –1.5°C, that’s about0.65°C above the melting point for ice atthat depth. Many factors, including salin-ity and pressure, affect ice’s melting tem-perature.
Even a small temperature increase inthe water below an ice shelf can make a bigdifference in the overlying ice’s meltingrate, says Eric J. Rignot, a glaciologist atNASA’s Jet Propulsion Laboratory inPasadena, Calif. His research suggests thateach 0.1°C rise in water temperature can,in a year’s time, melt away about 1 m ofshelf ice.
In February 2002, 3,250 square kilo-meters of the Larsen B ice shelf splintered
into thousands of icebergs (SN: 3/30/02,p. 197). Shepherd says his team’s data sug-gest that during the previous decade,Larsen B, which was about 200 m thickwhen it collapsed, was thinning at an aver-age rate of about twice that of Larsen C.
Larsen C is stable and isn’t sheddingmore icebergs than normal, says Shep-herd. However, at the ice shelf ’s currentrate of thinning, Larsen C could reach a200-m thickness, and therefore be sus-ceptible to disintegration, in 70 years orso. If the waters in the region continue towarm, the ice shelf ’s demise could occureven sooner. —S. PERKINS
Water RepellencyGoes NanoCarpet of carbonnanotubes cleans itself
The amazing water-shedding ability ofthe lotus leaf has long inspired materialsscientists. The leaf ’s wax-coated microstruc-tures cause rain droplets to bounce off thesurface, carrying away with them dust par-ticles and other contaminants. In trying toreproduce this so-called lotus effect in thelab, chemical engineers have fabricated asimilar self-cleaning material out of forestsof carbon nanotubes.
Led by Karen Gleason of the Massachu-setts Institute of Technology (MIT), theresearchers first created arrays of tinyislands of nickel on a surface of silicon.From these islands, the researchers grewvertically aligned carbon nanotubes. “Sortof like a bed of pins” is how coinvestigatorKenneth Lau describes the result.
The minuscule pillars, each measuring50 nanometers in diameter and standing2 micrometers, form a rough surface.Because there are air pockets between thenanotubes, when a drop of water landson the surface, “it’s essentially held up byair,” says Lau.
Using a technique called chemical-vapor deposition, the researchers coatedthe top of each carbon nanotube withpoly(tetrafluoroethylene), otherwiseknown as Teflon. Not only did thisarrangement stabilize the nanotube for-est, but it also boosted the surface’s water-repelling properties. When water dropletssqueezed from a syringe hit the Teflon-coated nanotube carpet, the dropletsbounced from and rolled off the surface.
Because the spacing between nan-otubes was less than a micron, the mate-rial could repel tiny droplets of water justa few micrometers in diameter. Theresearchers describe the new material in
a forthcoming issue of Nano Letters. Materials such as these are called super-
hydrophobic because of their ability torepel water so completely. On more stan-dard hydrophobic surfaces, such as thehood of a car, water droplets form flatter-bottomed spheres that might not roll off.
Researchers throughout the world havebeen striving to invent superhydrophobicmaterials for products such as antifoulingpaint, self-cleaning garments, or coatingson airplanes to prevent ice buildup. Inpursuit of that goal, investigators havetried a variety of polymer fibers andspheres (SN: 3/1/03, p. 132). So far, how-ever, the resulting materials have been toofragile to be practical.
To join the competition, the MIT groupturned to one of nanotechnology’s postermaterials, carbon nanotubes. “Coatingthe nanotubes with [Teflon] is very neatand novel,” says A. Levent Demirel, a
chemist at Koç University in Istanbul,Turkey. Without the Teflon, the waterdroplets would eventually seep throughthe material.
David Quéré, a chemist at the Collègede France in Paris, says the nanotuberoute to superhydrophobic materials isattractive, but he isn’t yet convinced it willlead to commercial products. Even thoughthe Teflon coating stabilizes the nan-otubes, he says, “if you press your thumbon them, you immediately destroy thestructures.” —A. GOHO
SCIENCENEWSThis Week
NANOSTYLE WATERPROOFING Top:A water droplet forms a sphere on asuperhydrophobic surface. Bottom: Amicroscopic view of that surface reveals a forest of carbon nanotubes.
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