Teen Passengers a Driving Risk

Federal researchers have confirmed what parents and police officers have long suspected: Teenage drivers tend to take more risks and drive more dangerously when other teenagers -- particularly boys -- are sitting in the passenger seat.

The risk-taking is greatest when teenage drivers of either sex are accompanied by a teenage boy, said researchers who carried out detailed observations near 10 high schools in suburban Washington.

According to observers stationed a quarter- to a half-mile away from school parking lots, fully a quarter of all teenage drivers they spotted with a male passenger exceeded the speed limit by at least 15 mph.

Of the teenage boys who were observed driving dangerously, one in every five had a male passenger, but only one in 20 had a female. Overall, 14.9 percent of teenage boys and 13.1 percent of teenage girls were seen driving dangerously, which included speeding and tailgating.

Researchers from the National Institute of Child Health and Human Development published their results last week online in the journal Accident Analysis & Prevention.

The researchers noted that while teenage boys tended to become slightly safer drivers in the presence of a female companion, teenage girls took more risks when accompanied by either male or female passengers.

"The most surprising finding is that females would have a moderating effect on male teen driving," said lead researcher Bruce G. Simons-Morton.

As to why having boys as passengers prompted drivers to take more chances, Simons-Morton said the question would have to be explored in subsequent studies. It is possible that teenage drivers, especially boys, feel they must show off and drive more recklessly when they have a male companion, or it could be that the male passenger actively applies peer pressure on the driver, he said.

In all, the researchers tracked 471 teenage drivers and compared their driving with a large sample of adult drivers. Simons-Morton said the study showed parents are well advised to be extra vigilant when their teenage children are driving with other teenagers in the car.

-- Shankar Vedantam

Robot Tested for Mars Study

Hoping to develop technologies that could at some time look for signs of life on other planets, researchers are exploring Chile's Atacama desert, the driest on Earth, with an experimental robot.

Named Zoe, it is a solar-powered, independently functioning rover developed at Carnegie Mellon University in Pittsburgh. It is equipped with instruments to detect and identify microorganisms and study their habitats.

In its second year of field testing, Zoe will explore three diverse regions during a two-month stay that began last week. NASA's Ames Research Center, the universities of Arizona, Iowa and Tennessee, and Chile's Universidad Catolica del Norte are also taking part.

The rover can make observations, take scientific measurements and map the distribution of life forms it finds.

"This desert has similar conditions like the planet Mars, where you have dry, cold and low temperatures," said Alan Waggoner, professor of biological science at Carnegie Mellon. "It has large regions where you can't see any evidence of life. . . ."

Project leader David Wettergreen said, "The research team wanted an extreme environment where organisms survive in the desert and where there is high ultraviolet radiation, just like Mars."

While the twin NASA rovers that have been exploring Mars are equipped mainly to search for signs of water, Zoe carries a wide variety of sensors and cameras. "It has a visible-near-infrared spectrometer for mineralogy, and fluorescence imager for identification and localization of organic molecules," Wettergreen said.

Zoe is capable of navigating several kilometers a day, stopping periodically to deploy its instruments. The robot is guided by an operations center in Pittsburgh and a rover team in Chile.

The project is funded with a $3 million, three-year NASA grant.

-- Michael Zimmerman

Core Spins Faster Than Earth

The giant iron ball at the center of Earth appears to be spinning a bit faster than the rest of the planet.

The solid core that measures about 1,500 miles in diameter is spinning about one-quarter to one-half degree faster annually than the rest of the world, scientists from Columbia University's Lamont-Doherty Earth Observatory and the University of Illinois at Urbana-Champaign reported in Friday's issue of the journal Science.

The spin of Earth's core is an important part of the dynamo that created the planet's magnetic field, and researcher Xiaodong Song said he thinks magnetic interaction is responsible for the different rates of spin.

The faster spin of the core was proposed in 1996 by two of the current study's authors, Paul G. Richards of Lamont-Doherty and Song, now an associate professor at Illinois.

The researchers studied the travel times of earthquake waves through Earth, analyzing what are called couplets. Those are earthquakes that originate within a half-mile or so of one another but at different times.

They analyzed 30 quakes occurring in the South Atlantic and measured at 58 seismic stations in Alaska, and found differences in the travel times and shape of the waves, indicating differences in the core as the waves passed through the center of Earth. Analyzing those differences, they calculated that the core is spinning slightly faster than the rest of the planet and is a bit lumpy.

That solid inner core is surrounded by a fluid outer core about 4,200 miles across.

-- Associated Press