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Scientists Find Signs of Meteor Crash That Led to Extinctions in Era Before Dinosaurs
by Kenneth Chang
February 23, 2001
Dr. Becker, Dr. Poreda and their colleagues had previously found buckyballs at an impact crater in Sudbury, Canada, and in two meteorites. They have also found buckyballs containing similar types of gases in sediments dating from the dinosaur extinctions.

In the experiments, the scientists extracted buckyballs -- not just the typical sphere consisting of 60 carbon atoms, but also larger versions with up to 160 atoms -- from the sediments with organic solvents.

They then opened the buckyballs to release the helium and argon inside them. The nuclei of most helium atoms consist of two protons and two neutrons. A few -- one out of 700,000 helium atoms in the atmosphere -- are a lighter version, with only one neutron. For the helium in the buckyballs, a much larger fraction -- one out of 5,000 -- was the lighter version, similar to the ratio produced by fusion in stars.

The argon indicated a similar story, with low concentrations of a version that is commonly produced on Earth from the radioactive decay of potassium.

"I think the argon isotope ratio measurement is very convincing," said Dr. Kenneth A. Farley, a professor of geochemistry at the California Institute of Technology. "That's very hard to understand if it's not extraterrestrial."

Asteroid 'destroyed life 250m years ago'
by Dr David Whitehouse
Friday, February 23, 2001
Earth's biggest mass extinction 251 million years ago was triggered by a collision with a comet or asteroid, US scientists say. They have reached this conclusion by looking at atoms from a star trapped inside molecular cages of carbon...

In rock layers laid down at the time, there is a much higher concentration of complex carbon molecules called fullerenes that have different types, or isotopes, of helium and argon trapped inside them. These molecules could only have been delivered from space, the researchers say...

The researchers believe these particular fullerenes are extraterrestrial because the gases trapped inside have an unusual ratio of isotopes that indicate they were made in the atmosphere of a star that exploded before our Sun was born...

The telltale fullerenes were extracted from sites in Japan, China and Hungary, where the sedimentary layer at the boundary between the Permian and Triassic periods had been exposed...

The research was made difficult because there are few 251-million-year-old rocks left on Earth. Most rocks of that age have been recycled through the planet's tectonic processes...

Researchers estimate the comet or asteroid was six to 12 km (3.7 - 7.4 miles) across, or about the size of the asteroid believed responsible for the extinction of the dinosaurs 67 million years ago...

The mass extinction of 251 million years ago was the greatest on record.