The mind reels when speculating how creationists and other Old Testament literalists might spin this one. For the rest of us, it’s just fascinating scientific detective work: geo-astronomers have confirmed a healthy sized comet lit Egypt on fire millions of years ago. If they’re right it would have made the 1908 Tungaska Event look like a shoe-bomb:
C/net — It may not have been the one that killed off the dinosaurs, but a massive comet soared into Earth’s atmosphere about 28 million years ago and exploded upon entry, raining down a “shockwave of fire” that killed off everything in its path and created a sea of silica glass spread out over a 6,000 square kilometer area in the Sahara desert. This discovery marks the first ever definitive proof of a comet striking Earth, says a team of South African scientists and international collaborators that plans to announce its findings Thursday.
The discovery was made after years of chemical analyses were conducted on a black pebble that was found by an Egyptian geologist among the shards of silica left by the comet’s blast. The blast had heated the sand beneath it to about 2,000 degrees Celsius when it impacted with Earth. The sea of silica was a well-known area of study as its glass was found in highly valuable jewelry, including a brooch of the Egyptian pharaoh Tutankhamun.
I played around with the Purdue University Earth Impact Simulator to see if we could get an idea of what would have done this kind of damage. Using an object made of low density ice hitting at 45 degrees at 20 km/sec with a diameter of about 4000 meters (2.5 miles) seems to be in the ballpark. From 200 miles away the airburst fireball would be 20 times larger than the sun and so bright and hot it would ignite anything flammable in the line of sight. That would have been a bad day in North Africa.