In the upcoming issue of 'Earth and Planetary Science Letters', South African scientists are to present new evidence of a major impact event which took place some 28mln years ago in what is now Egyptian Sahara.

The jewelry found on the mummy of King Tut contains small pieces of a yellowish material resembling glass. Little stones of this kind have been found in Sahara for millennia - mainly within a circular field measuring some 80 kilometers across. Scientists believe this glass-like material came into being after and an exploding cosmic impactor - an asteroid or a comet - melted desert sand.

Exploring the same area lately, South African scientists discovered black pebbles with tiny diamonds inside them. They hypothesized that the pebbles are the rocky remains of an impacting comet, and the diamonds, the product of a high-temperature transformation of carbon-containing components of the impactor.

Indeed, comet nuclei are known to contain frozen carbon dioxide and methane, which also go into comet tails. Overall, however, the chemical composition of comets is largely a mystery.

We have an opinion from Dmitry Vibe of the Astronomy Institute of the Russian Academy of Sciences:

"Asteroids regularly send us samples of their material in the form of meteorites. With comets, we only possess a single small sample, the one retrieved by NASA's Stardust probe. Our knowledge of the chemistry of comets leaves much to be desired."

Other scientists believe that only graphite can be the raw material from which cosmic impactors create diamonds. They mention rich diamond fields to be found inside the Popigai Crater located in the Arctic belt of Central Siberia. This giant crater, measuring some 100 kilometers across, sits on layers of graphite which gave rise to diamonds when the bolide struck about 35mln years ago.

Many other cosmic impacts or near impacts are not known to have left diamonds. One of them is the Tunguska Meteorite that struck in 2008 in the central part of Central Siberia.

Dr Vladimir Surdin is an astronomer at the Physics Department of Moscow State University:

"It was a comet exploding at an altitude of 7 to 8 kilometers. There is no crater, and only a radial pattern of ripped-up trees can still be observed. Small meteorite dust discovered at the site cannot be linked to the 1908 event with any degree of certainty. It might have settled on the surface much, much earlier."

"Any cosmic impact will instantly generate very high

Source: Voice of Russia