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Eltanin - part 2 of 2

Hi folks, I think that's it for tonight - I am on a collision course
with Mr. Sandman :-) Yaaawn !

Astronomy, March 1998, p. 30 (Collision With Earth: An Impact on the
Weather):

Frank Kyte, who discovered the impact of the Eltanin asteroid in 1981
when he was a graduate student, now believes that the planetoid may have
been large enough to have devastated Earth's climate.
Writing in the November 27, 1997, issue of Nature, Kyte and his 12
co-authors report that additional ocean-bottom sampling completed
recently suggests that instead of being an estimated 0.5 kilometer in
diameter, the asteroid was at least 1 km and possibly as large as 4 km
across. That's big enough to have caused global "devastating
megatsunamis," or 120-foot-tall tidal waves, after the object struck the
Southern Ocean about 2.15 million years ago.
"This was right before a significant cooling event, " said Kyte, a
geochemist with UCLA's Institute of Geophysical and Planetary Physics.
"Whether this impact was just a coincidence we can't say, but no one has
looked."
There are about 140 known terrestrial impacts of asteroids, but 60
percent of Earth is covered by oceans. Water impacts would leave little
evidence behind other than pulverized pieces of the asteroid buried
under more recent sediments, terrestrial evidence of ancient tsunamis,
or other subtle clues.
In the mid-1960s, the crew of the USNS Eltanin, an American research
ship looking for evidence of ancient glacier activity, punched one of
many 20-meter "piston cores" into the floor of the Southern Ocean about
1,400 km (900 miles) west of the southern tip of South America. The
ocean bottom often is deeply covered with recent sediment but,
fortunately, the ship passed above an area with little sediment when the
fateful core sample was taken. The sample extended deep enough into the
sea bottom to pierce a layer of asteroid debris. However, that core
sample sat undisturbed on a shelf until Kyte examined it and discovered
that it contained a region rich in iridium, a signature element of
asteroids.
"I just got lucky to find this one," said Kyte. "The labs of
sedimentologists and paleontologists all over the world have processed
sediments from deep-sea cores, and I wonder how many (asteroid) impacts
are sitting on the back of people's shelves."
Some 2 million years ago, an asteroid at least 1 km across smashed into
Earth, perhaps triggering global cooling. In this supercomputer
simulation of a similarly sized comet hitting water, the energy of 300
billion tons of TNT vaporizes the comet and large amounts of water and
sends it flying across the globe.


Best wishes,

Bernd


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