Helping store biodata for millions of years.

• Position: Asteroids and Comets - Impact glasses

Asteroid and comet impacts can cause widespread ecological havoc, killing off plants and animals on regional or even global scales, but research from Brown University, Providence, R.I., shows that impacts also can preserve the signatures of ancient life at the time of an impact.

A research team led by geologist Pete Schultz has found fragments of leaves and preserved organic compounds lodged inside glass created by several ancient impacts in Argentina. The material could provide a snapshot of environmental conditions at the time of those impacts. The find also suggests that impact glasses could be a good place to look for signs of ancient life on Mars.

The scorching heat produced by asteroid or comet impacts can melt tons of soil and rock, some of which forms glass as it cools. The soil of eastern Argentina, south of Buenos Aires, is rife with impact glass created by at least seven different impacts, according to Schultz. One of those impacts, dated to around 3,000,000 years ago, coincides with the disappearance of 35 animal genera, as reported in the journal Science a few years back.

"We know these were major impacts because of the shocked minerals trapped inside with plant materials," Schultz explains. "These glasses are present in different layers of sediment throughout an area about the size of Texas."

Within glass associated with two of those impacts--one from 3,000,000 years ago and one from 9,000,000 years ago--Schultz and his...