Dissecting a Meteoric Moment

About 50,000 years ago, a gigantic boulder crashed into Earth, creating what is known today as Meteor Crater near Winslow, Ariz. Now, scientists think they have a better idea of the circumstances surrounding the event.

Elizabetta Pierazzo of the University of Arizona and her colleagues conducted a detailed chemical analysis of tiny bits of the 60,000-ton, 100-foot-wide rock left in and around the resulting crater, which is about 4,200 feet wide and 570 feet deep.

Based on the analysis and mathematical models, the researchers determined that the meteor slammed into Earth at about 45,000 miles an hour. Most of the boulder melted upon impact, spraying molten material in every direction, the researchers reported in the July 2 issue of the journal Science. A small fraction of the meteor survived to form tiny particles called "spheroids."

How Bugs Fly: Mystery No

More Scientists have long been perplexed about how insects manage to fly. According to current aerodynamical wisdom, insects' relatively small wings shouldn't be able to provide enough lift to keep them aloft.

But most of the knowledge of how things fly comes from studying fixed wings like those on airplanes. Insect wings, in contrast, are constantly moving and changing their tilt. So Michael H. Dickinson of the University of California at Berkeley and his colleagues built a pair of 10-inch-long Plexiglas wings modeled on the wings of a fruit fly and studied them as they spun.

The experiment, described in the June 18 issue of the journal Science, showed that the wings produce lift in three different ways.

"Delayed stall" occurs when the insect sweeps its wings forward at a high angle, creating a "leading edge vortex" on the top surface of the wing to create lift.

The wing also produces "rotational circulation," which occurs as the wing rotates backward near the end of its stroke, creating backspin and adding lift like backspin on a tennis ball.

Finally, the wing employs "wake capture." If the wing rotates before starting its return stroke, the wing intersects its own wake, recapturing energy to provide added lift, the researchers concluded.

Ancient Insect Communication

German scientists have unearthed the oldest known fossils of ancient insects that show how the bugs communicated 55 million years ago.

Jes Rust of the University of Gottingen in Germany and colleagues discovered the well-preserved fossilized remains of ancient bushcrickets, commonly known as katydids, in Denmark.

An analysis of 11 left and right male forewings and three forelegs shows that the insects communicated in much the same way as their counterparts do today--by rubbing their wings together to produce a chirping noise. The researchers also found evidence of the insects' "ears," which are located on their legs, very much the way they are today.

"As the fossil bushcrickets could therefore presumably hear at least low ultrasound, they should also have been able to hear the echolocation calls of bats, which first occur in the fossil record at the same geological age," they wrote in the June 17 issue of the journal Nature.

Tales of Amnesia and Compulsion

Some people who suffer from amnesia not only have lost memories, but also have a tendency to "confabulate"--make up incredible stories. Now, new research suggests the reason for this behavior may be that they actually can't control their memories.

Armin Schnider and Radek Ptak of the University Hospital in Switzerland studied 18 amnesiacs, comparing six confabulators with 12 nonconfabulators. The subjects were shown sequences of designs and asked to identify those that had occurred earlier in the same sequence.

The confabulators performed more poorly on sequences in which designs from earlier sequences were mixed in, indicating that they were unable to prevent the intrusion of previously acquired mental associations.

"Our findings indicate that spontaneous confabulators specifically fail to suppress mental associations that do not pertain to the present; memories thus seem to be as real and pertinent for present behavior as representations of current reality," the researchers wrote in the July issue of Nature Neuroscience. "It is conceivable that the weaker a patient's ability is to suppress even distant mental associations, the more bizarre and fantastic the confabulations appear."

The researchers also found that the parts of the brain damaged in the study's confabulators were different than those of the nonconfabulators, indicating that a part of the brain known as the anterior limbic system is involved in controlled thinking and behavior in the "present reality."

Reproductive Clues to Longevity

A key to a long life may lie in our gonads. At least, that's what's suggested by a new study of longevity of a tiny worm commonly used to study the fundamental basis of aging in the laboratory.

Honor Hsin and Cynthia Kenyon of the University of California at San Francisco found that signals from the equivalent of sperm and eggs shorten lifespan in the nematode roundworm C. elegans, while signals from the part of the reproductive tissue that surround the worm's "germ cells" lengthen lifespan.

When the researchers removed the germ cells, the worms tended to live about 60 percent longer than normal, the researchers reported in the May 27 issue of the journal Nature.

The researchers speculated that the competing signals from the cells allow the animal to regulate its rate of aging so that it produces offspring when it is still young.