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Extinction Near Miss: Fragments From Billion-Ton Comet Missed Earth by a Hair in 1883

Extinction Near Miss: Fragments From Billion-Ton Comet Missed Earth by a Hair in 1883

Written by Michael Graham Richard

We Need to be More Careful About Low-Probability/High-Risk Events
There are some very serious risks to life on Earth that most environmentalists don’t talk about nearly enough, in my opinion, and I think it’s because they seem very unlikely to happen at any point in time. Nuclear war, super-volcanoes, near Earth objects hitting us, deadly plagues, etc. While these things are improbable on any single day, their negative consequences would be so huge that they have to be taken seriously. After all, what’s the point of doing our best socially and environmentally and such if it all gets wiped out by some mega-huge natural disaster? Especially if it’s something we could have avoided with enough forethought…

Which brings me to near Earth objects, like comets and asteroids. It might not be possible for us to do much about the Yellowstone super-volcano, but we can definitely monitor the orbits of asteroids and comets and, with enough lead-time, figure out how to make them change course.

Concrete Example of this Threat
Back in 1883, the Mexican astronomer José Bonilla made a very strange observation: Over two days, some 450 objects, each surrounded by a kind of mist, passed across the face of the Sun. Strangely, other observatories around the world did not see them. At the time, there were various theories to try to explain the observation, but none very conclusive. It was only over a hundreds years later that scientists figured out what probably happened, and it’s a scary thought:

Today, Hector Manterola at the National Autonomous University of Mexico in Mexico City, and a couple of pals, give a different interpretation. They think that Bonilla must have been seeing fragments of a comet that had recently broken up. [...]

They point out that nobody else on the planet seems to have seen this comet passing in front of the Sun, even though the nearest observatories in those days were just a few hundred kilometers away.

That can be explained using parallax. If the fragments were close to Earth, parallax would have ensured that they would not have been in line with the Sun even for observers nearby. And since Mexico is at the same latitude as the Sahara, northern India and south-east Asia, it’s not hard to imagine that nobody else was looking.

Manterola and pals have used this to place limits on how close the fragments must have been: between 600 km and 8000 km of Earth. That’s just a hair’s breadth.

600 to 800km is absolutely nothing when it comes to astronomical distance. It’s like a bullet grazing your head so close it shaves off some hair.

The scientists estimate that the objects ranged in size from 50 to 800 meters, and that the parent comet must have been in the billion-plus-ton range, close to the size of the famous Halley’s comet.

So how close did Earth come to catastrophe? Very close:

Bonilla observed these objects for about three and a half hours over two days. This implies an average of 131 objects per hour and a total of 3275 objects in the time between observations.

Each fragment was at least as big as the one thought to have hit Tunguska. Manterola and co end with this: “So if they had collided with Earth we would have had 3275 Tunguska events in two days, probably an extinction event.”

For those of you not familiar with the Tunguska event, it was a large explosion over northern Russia in 1908; it flattened an estimated 80 million trees down over 2,150 square kilometres (830 sq mi). The explosion was caused by what is believed to be a meteroid or comet fragment. Its power is estimated to have been in the 5 to 30 megaton range, which is about three orders of magnitude more than the nuclear bomb that was dropped on Hiroshima during World War II! Now imagine hundreds or thousands of these all hitting Earth within a couple of days, and that makes for a very, very bad weekend.


NASA/Public Domain

What Can We Do?
That’s a whole other article, but there are things we can do to greatly reduce the risks. The first thing to do is to find and monitor near Earth objects above a certain size. NASA is already doing a pretty good job with that, but the work is not over as they are still finding more and more every year. Calculating their orbits far in the future is the next step, and if any seem to be coming a bit too close to Earth, we need to monitor them extra-closely and refine orbits until we are sure one way or the other.

The second part is having the capabilities of rapidly deflecting an inbound object. Ideally we would have all this stuff tested and ready to go within a relatively short time frame, rather than having to actually do the R&D and build the stuff after we’ve discovered a dangerous orbit. You don’t want your test-run to have millions, if not billions, of lives hanging in the balance…

This post was originally published by TreeHugger.

 

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106 comments

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6:25PM PST on Jan 17, 2013

Thanks for the interesting article.....love and appreciate

6:13AM PST on Dec 18, 2012

Thank you TreeHugger, for Sharing this!

6:17PM PST on Dec 10, 2012

Nobody knows what will come on Dec 21, 2012, but the mere fact that several ancient societies all documented the same date deserves a better look. Our knowledge of this planet and our science is Juvenile at best. I cannot ignore that these ancient cultures knew of planets and moons in our solar systems thousands of years prior to our modern science accepting that the earth is not flat and we are not at the center of the universe, much less the existing bodies. I am more than convinced that mankind has been on this planet much longer than we have thought and that societies have been technologically advanced, especially in ways we cannot understand as of yet. What I fear is a routine cycle of technological growth and then a planetary event that wipes it out in a cycle, and we are starting just now to realize that this planet has cycles of growth and destruction. I hope that nothing is going to happen, but I have to remind myself of just how long we are overdue for a major catastrophe on this planet, and we are right at that magic 10-12K year Iceage/Extinction time frame. It could be a million things that could happen and preparing for any one event would be futile, but not being prepared to live for a few weeks if the grid goes down would be stupid, actually, it would be our modern society. I personally feel that something is going to happen, what I have no idea, but my personal belief is that the earth wobble is in for a correction due to magnetic shifts, not a pole reversal,

10:55PM PST on Dec 7, 2012

Colin, that's because the Spaniards conquered them (the Mayans) before they finished their calendar!

11:34AM PST on Dec 7, 2012

Have fun with that Ann, the Mayan Calendar's long count is only going to reset for the 13th time. There will even be a 14th, 15th and 16th long count. No mention of global catastrophe on their calendar though.

7:01PM PST on Dec 6, 2012

Well I just read about the Mayan calendar prediction for the end of the world--and now this "near miss" article-- so I'm off to buy a sports car and a lottery ticket and a mansion. Might as well go out smiling.

4:51AM PST on Dec 6, 2012

Fascinating.

4:49AM PST on Dec 6, 2012

Noted, thank you.

4:48AM PST on Dec 6, 2012

Noted, thank you.

3:54AM PST on Dec 6, 2012

If a comet takes us out then we won't be aware of it so just be happy and enjoy every day we have on this amazing planet, taking care to tell those we love just that!

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