Source: Reuters (via Ndunlks)
Date: Dec 10, 1998
Written by: Peter Schultz

W A S H I N G T O N, Dec. 10: It’s clearly an asteroid that hit. The earth does get hit just as the moon gets hit.

Scientists said today they have evidence a killer asteroid smashed to earth in southeastern Argentina about 3.3 million years ago, possibly causing climate changes that wiped out 36 species of animals.

They said glassy fragments found in the soil in the region, part of Argentina’s vast pampas, suggest an intense heating that could only have come from an asteroid hitting the earth. The glass resembles similar materials found in known craters.

It’s clearly an asteroid that hit, said Peter Schultz, a planetary geologist at Brown University who led the study. The earth does get hit just as the moon gets hit.

This study, published in the journal Science, adds evidence to the theory asteroids have struck the earth throughout history, sometimes causing extreme changes in the climate.

Killing Locally, Not Globally

While this asteroid did not bring on global devastation like the one scientists think landed 65 million years ago and killed off the dinosaurs, it was still deadly locally because it probably brought on cooler temperatures and distinct seasons.

Giant armadillos, ground sloths and a large-beaked carnivorous bird were some of the animals that were unable to adapt to the colder environment and soon died out.

The big asteroid 65 million years ago, known as K-T to geologists, is believed to have kicked up dust that sent the planet into many years of year- round winter.

K-T was a killer - this was a wound, said Schultz, who pointed out the K- T asteroid would have been 10 to 15 miles across, while this smaller one measured only about one mile in diameter.

Melted Glass Provides a Clue

But the greenish-colored glassy material in the area, called escoria, was the key evidence pointing toward an asteroid hit, Schultz said. Scientists had been aware of the materials for a long time but thought either a volcanic eruption or human fire had left the fragments in the earth.

But in analyzing the deposits found across a broad area, the researchers discovered unusually high levels of minerals including magnesium oxide, iridium and chromium, and found the mineral zircon had been broken down by the heat. This was something neither a volcano nor human fire could have done.

Without the escorias we would not have any idea, Schultz said in a telephone interview. You don’t get this naturally and this is one of the key signatures of an impact.

Soon after the asteroid hit, local climate and ocean conditions quickly cooled and some animal species disappeared.

Direct Link to Climate Changes

These coincidences suggest that the impact may have directly induced regional faunal extinctions or triggered broad environmental changes leading to ecosystem collapse in Argentina, Schultz’s team wrote in their report.

We were surprised to find that the appearance of the glasses and the turnover of the fauna coincided with a temperature drop, Schultz added in a statement.

The impact from the speeding asteroid, which was moving 25 times faster than a rifle bullet, could have roiled the ground and sent dust and water particles up into the atmosphere and triggered the fatal temperature drop, Schultz said.

When you toss materials into the earth’s atmosphere it can cause change, he said.

However, the international team of scientists has still not located the actual crater where the asteroid landed. This could be because the coast has eroded inland.

But further study of the asteroid impact is helpful in understanding other natural events, like El Nino and volcanic eruptions, that can also cause climate change and sudden stress on the earth, Schultz said.

This is one of those events that is another type of tweak in our earth’s system, he said.

Copyright 1998 Reuters. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

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