First Evidence Found of a Comet Strike On Earth

mdsolar writes in with a story about evidence of a comet explosion over Egypt 28 million years ago. "Saharan glass and a brooch belonging to King Tut provide the first evidence of a comet directly impacting Earth, a new study claims. The finding may help unlock some of the mysteries surrounding the birth of our solar system. About 28 million years ago a comet exploded over Egypt, creating a 3600F (2000C) blast wave that spread out over the desert below. The fiery shockwave melted the sand, forming copious amounts of yellow silica glass scattered over 2,300 square miles (6,000 square kilometers) of the Sahara. Polished into the shape of a scarab beetle, a large piece of this glass found its way into a brooch owned by the famed Egyptian boy king Tutankhamen. 'Because there is no sign of an impact crater, it has been a mystery as to what kind of celestial event actually could have caused this debris field, but a small, black stone found lying in the middle of the glass area caught our attention,' said study co-author David Block, an astronomer at Wits University in Johannesburg, South Africa."

Not necessarily.

[C0R1D4N]

Tunguska [wikipedia.org] is believed by some to be a comet not an asteroid, and since this is hardly confirmed, this is therefore the second "possible comet strike" recorded.

Update?

[Dunbal]

'Because there is no sign of an impact crater, it has been a mystery as to what kind of celestial event actually could have caused this debris field'

Are these people dim-witted? We had firsthand video footage of what happens when a big chunk of rock burns into the atmosphere. You get a huge multi-megaton blast like in Chelyabinsk as the meteorite breaks apart due to wanting to move faster through the atmosphere than the air can actually move out of the way... This blast IS NOT NECESSARILY THE IMPACT SITE [wikimedia.org]. It would be a rare thing for a meteorite to be headed perpendicular to the earth's surface. Extrapolating this mechanism to even larger chunks of rock, you'd expect fused sand and little lumps of meteorite, but you wouldn't expect to see the main part of the meteorite where the sand is. That thing landed far away from the blast site. Same for Tunguska - they never found anything because the "crater" is the epicenter of the shock wave, not the actual impact with the ground. All these theories of mysterious "evaporating comets" should be re-evaluated in the face of this new, modern evidence.

Re:Desert 28 Million Years Ago?

[stjobe]

Wikipedia [wikipedia.org] is only a few key-presses away, you know:

The climate of the Sahara has undergone enormous variations between wet and dry over the last few hundred thousand years.[15] This is due to a 41000 year cycle in which the tilt of the earth changes between 22 and 24.5.[16] At present (2000 AD), we are in a dry period, but it is expected that the Sahara will become green again in 15000 years (17000 AD).
During the last glacial period, the Sahara was even bigger than it is today, extending south beyond its current boundaries.[17] The end of the glacial period brought more rain to the Sahara, from about 8000 BC to 6000 BC, perhaps because of low pressure areas over the collapsing ice sheets to the north.[18]

(emphasis mine)