Buckyballs Teach Some History

About 250 million years ago, 90% of life on earth was destroyed in some sort of cataclysmic event. This event, which ended the Permian period and began the Triassic (the P-T boundary), is the most devastating mass extinction in the earth s history— far surpassing the catastrophe 65 million years ago that wiped out the dinosaurs (the K-T boundary). 

In 1979 geologist Walter Alvarez and his Nobel Prize-winning physicist father Luis Alvarez suggested that unusually high concentrations of iridium in rocks laid down at the K-T boundary meant that an asteroid had hit the earth, causing tremendous devastation. In the last 20 years much evidence has accumulated to support this hypothesis, including identification of the location of the probable crater caused by the impact in the ocean near Mexico. 

Recall that fullerenes include spherical C6o carbon molecules ( buckyballs ) whose cavities can trap other atoms such as helium and argon. (See the accompanying figure.) The scientists postulate that the fullerenes originated in the collapsing gas clouds of stars where the noble gas atoms were trapped as the fullerenes formed. These fullerenes were then somehow incorporated into the object that eventually hit the earth. Based on the isotopic compositions, the geochemists estimate that the im- 

A space-filled model of Q0 containing a caged methanol molecule. 

One factor that had previously cast doubt on an asteroid collision as the cause of the P-T catastrophe was the lack of iridium found in sediments from this period. However Becker and other scientists argue that this absence probably means the impacting object may have been a comet rather than an asteroid. It is also possible that such a blow could have intensified the volcanism already under way on earth at that time, delivering a one-two punch that almost obliterated life on earth, according to Becker. 

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CHEMICAL IMPACT Buckyballs Teach Some History 80... 

It is ironic that buckyballs, which made big news when they were recently synthesized for the first time in the laboratory, actually have been around for millions of years and have some very interesting history to teach us. ... 

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