Impact forensic evidence announced

Jeff Poling

Scientists reported in the December 3, 1997, issue of the journal Nature forensic evidence about the heavenly body that slammed into the Yucatan Peninsula at the end of the Cretaceous, 65 ma ago.

When the object from space slammed into the earth, it punched a hole in the ground that, within minutes, rebounded to hurl superheated rock and steam back into the atmosphere. Some of the material was blown into space, while the rest fell to earth creating a parabolic swath of destruction that incinerated North America (see "K-T extinction event mystery may be solved" and "More evidence for asteroid impact found"). Mike Warner of Imperial College, London, and scientists from Cambridge, Leicester, Canada, Mexico and Texas felt that it was the size of the initial hole, before the rebound, that would tell the most about the projectile itself.

Using seismic instruments to measure ballistics more than a kilometer below the Yucatan, the scientists found evidence that the initial crater gouged by the object was around 100 km in diameter. From this, the scientists concluded the object was 10 to 14 km across. They estimate that if the object was an asteroid, it was moving at 20 km/s. If it was a comet, it slammed into the earth going 65 km/s.

The devastation from the impact was horrendous; however, scientists continue to debate the long term effects. Much life went extinct at the time, including the non-avian dinosaurs, and the impact is one clue in the mystery of why. However, many things were happening on the planet at the time, including global cooling, falling sea levels and volcanism. None of these factors, including the impact, can fully account for all the extinctions nor, just importantly, for why the species that came through the extinction event survived.