Instead, the strata within it center would be complexly and distinctly folded, tilted, and faulted as a result of an extraterrestrial impact.

According to popular accounts, visitors to the Kebira Crater have repeatedly failed to find any evidence of an extraterrestrial impact.

Shoemaker's discovery is considered the first definitive proof of an extraterrestrial impact on the Earth's surface.

Further, an iridium anomaly - often an indicator of extraterrestrial impact - observed in Spain is far too small to denote a comet impact.

Another group, including many paleontologists, believes the evidence that extraterrestrial impacts caused mass extinctions is too weak to accept as conclusive.

Schindewolf was also the first to suggest, in 1950, that mass extinctions might have been caused by extraterrestrial impacts or nearby supernova.

Moreover, Mr. Eldredge sees no evidence that extraterrestrial impacts might have caused any of the other four major extinctions.

Various theories have attributed the wave of extinctions to human hunting, climate change, disease, a putative extraterrestrial impact, or other causes.

But the scientists say that the Pathfinder evidence points strongly to small extraterrestrial impacts as having a role.

Recent published research disputes the quality of the evidence of an extraterrestrial impact.