🚀 go-pugleaf

This is something that might interest some of the newsgroup readers
who have been discussing comet Swift-Tuttle's possible collision with
Earth in 2126. It is condensed from a story I wrote about a year ago,
and it has been worded around comet Swift-Tuttle to make it a little
more timely. The original story was 8 pages long and much of the
condensing involved generalizations. I still think it gets the point
across.


        WHAT MIGHT HAPPEN IF COMET SWIFT-TUTTLE HIT EARTH

Chances are P/Swift-Tuttle, if it were to collide with Earth, would
not reach the surface of Earth in one piece. Since a comet's nucleus
is not a solid rock, but a mixture of rock and ice, the scenario of a
comet of this size striking our atmosphere would probably go like this.

Upon reaching the atmosphere, the comet would begin heating up as do
meteoroids and space craft. Like the Tunguska object of 1908, the
outer layers of the comet would begin heating up and a large trail
of dust would begin forming behind the nucleus and hanging in the
sky. If at night, this dust trail would exceed the Milky Way in
brightness, while in daylight the trail would appear grayish against
the blue sky.

Somewhere around 20-40 miles above the surface of Earth, the comet
nucleus would explode. At this point, the Tunguska object, which has
been theorized as perhaps 100 feet across, may have been completely
vaporized and a shock wave circled the Earth twice. On the ground,
a forest was hit by the downward moving shockwave and was leveled for
a distance of 50 miles in every direction. In other words, a 100-mile
circle of trees was laid flat. The evidence leading to the belief
that the Tunguska object was vaporized was the lack of any apparent
craters. The shock wave from P/Swift-Tuttle should be tremendously
larger, though I have no means of computing exactly how large.

There is still a small problem remaining after P/Swift-Tuttle explodes,
Where the threat of a single object six miles across hitting the Earth
has now been eliminated, the likelihood of the comet being completely
vaporized is slim and the sky will now be filled with objects ranging
in size from dust particles to chunks a couple hundred feet across.
Being so low in the atmosphere, some of the largest chunks would
probably reach the surface of Earth, but many objects on the order of
tens of feet across and even hundreds of feet across will probably
reach temperatures great enough to cause them to explode, but at a
much lower altitude.

If over a major body of water at the time, the shock waves would
probably not cause a significant tidal wave, but if any objects in
the tens of feet range hit the water, a tidal wave would be
inevitable. Over a land mass, the devastation would far exceed that
caused by an atomic explosion. Forests would be laid waste. Buildings
would be obliterated. No life would exist at ground zero. All of this
after the initial explosion. The secondary explosions would simply
extend the devastation zone, which ultimately would appear as an
elliptical scar from high altitude.

And then there are the chunks which would reach Earth's surface. If
a 50-foot wide piece hits the surface, the resulting crater would be
more than 300-feet across, and the only remnants of man-made structures
would be twisted bits of metal along the crater bottom and walls.

Finally, where the Tunguska object shattered windows over 100 miles
from the "impact" point, Swift-Tuttle's initial explosion would
possibly cause damage of this type to a distance of nearly 1000 miles.

Perhaps it is comforting to know that we are aware of the chances
for Swift-Tuttle hitting the Earth in 134 years. Maybe sometime in
the future something could be done to help protect Earth from this
comet, like a couple of space probes carrying nuclear warheads which
could destroy the comet if its recovery in 2125 or 2126 reveals the
threat of collision with Earth still exists. But the scary part
about the above scenario is that it could happen at any time. We have
seen the results of the Tunguska object in 1908. We saw an object at
least as big as the Tunguska object skip off Earth's atmosphere in
1972. And since 1976, there have been at least a half dozen asteroids
that have made some of the closest approaches to Earth on record,
nearly all of which were discovered at the time of or shortly after
closest approach.