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Saturday, September 18, 2004
 
It Ain't The Size Of The Rock ...

Scientists have recently uncovered evidence of a massive
series of meteor and/or cometary strikes
in the southern
hemisphere. There's nothing surprising about that; in the geological
sense, our Earth gets whacked upside by giant falling rocks on a
depressingly regular basis.


Rather, the shocking news is not that the asteroid storm
hit, but
when it did
:


Scientists using satellites have
mapped huge craters under the Antarctic ice sheet caused by an
asteroid as big as the one believed to have wiped out the dinosaurs
65m years ago.


Professor Frans van der Hoeven,
from Delft University in the Netherlands, told the conference that
the evidence showed that an asteroid measuring between three and
seven miles across
had broken up in the atmosphere and five large
pieces had hit the Earth, creating multiple craters over an area
measuring 1,300 by 2,400 miles.


The effect would have been to melt
all the ice in the path of the pieces, as well as the crust
underneath. The biggest single strike caused a hole in the ice sheet
roughly 200 by 200 miles, which would have melted about 1% of the ice
sheet, raising water levels worldwide by 60cm (2ft).


But the climatic conditions were
different at the time of the strike — about 780,000 years
ago
— from when the asteroid that is believed to have wiped
out the dinosaurs struck Yucatan in Mexico.


Despite the fact that the collective mass of this extraplanetary
material is comparable to that of the infamous “dinosaur
killer” Rock of Doom, this particular event obviously didn't
have nearly the global impact. Nobody's noticed any mass extinction
event coming out of the fossil record of the time, and nothing in the
rock strata indicates that any great conflagration was visited upon
the planet then, either.


Although human evolution appears to have bumped ahead a bit right
around 780,000 years ago (from homo
erectus
to heidelbergensis).
That's also the same time as the earliest
fossil evidence
we have of tool-using hominids (homo
antecessor
) showing up in western
Europe
.


And those guys were quite voracious cannibals,
too. All of which, to me, is at least circumstantial evidence that
the ecosphere may have been unusually stressed right around then. But
only circumstantial.


As it turns out, scientists know a bit more than usual about what
was going on around the planet 780,000 years ago; the last time
Earth's
magnetic poles shifted
(i.e from south to north) was at
that time
, allowing for a handy
way
for us modern hominids to collate anything that happened on
that moment in prehistory. As the first article points out, the two
events (the meteor strike and the pole shift) happening at the same
time is probably not a coincidence.


Nevertheless, it's remarkable to consider that this stellar drama
was unfolding right over the sloping foreheads of our immediate
hominid predecessors
. Who knows what would have happened to those
poor, lumpish little hairy fellers had the meteor held itself
together right up until deep impact, or hit the earth at a different
angle, or hurled itself into another — perhaps more vulnerable
— section of our planet?


If, as recent evidence suggests, a mere
volcanic eruption
was enough to nearly wipe
our species
off the face of the Earth just
70,000 years ago
, I imagine that the effects of a Yucatan-style
impact would be quite a bit more final. Which, by the way, helps to
explain why we are such a freakishly inbred
species
when compared to other
mammals
.


Then again, nothing that's happened since the rise of life on
Earth compares to
the monster rock
that may
have caused
the great
Permian
Extinction
. Anything that could blow
a hole in the planet
the size of Scandinavia must have been
friggin' huge.



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