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Asteroids and Us

By Bill Nye | Published: February 15, 2013 – 4:00 pm

My O my, wow… the 7,000-ton meteor over the Chelyabinsk region slammed into our atmosphere at 15,000 km per hour (33,000 miles an hour). Witnesses could see the flash of light 500 kilometers away. It was probably 15-meters (50 feet) across. When these things hit the atmosphere they just blow up. It’s not combustion, at least at first; it’s a rock slamming into something air so hard, that it disintegrates. Its energy becomes a pressure wave, a shock. This is to say, the molecules in the air get slammed into moving faster than their natural speed (at a given temperature). They form a shock wave turning the rock’s energy of motion into a wave of pressure and the energy of heat…in an instant. The pressure wave blasted windows and doors. The flying glass and falling building material injured over a thousand people— in an instant. The heat combined with atmospheric oxygen incinerated most of the rock— in a few moments. Rock hounds and scientists will no doubt scour the area for meteorites and for clues. The more we learn about these things the better, because it sure could happen again.

On top of the drama, what a remarkable phenomenon it was in Russia on the eve of the flyby of Asteroid 2012 DA14, which was discovered by astronomers funded in part by The Planetary Society http://planetary.org. This asteroid is somewhat larger at 45-meters, and it missed us completely, but wow is there a lesson to be learned for all of us humans.

When I was in 2nd grade, our teacher, Mrs. McGonagle told us that the reason the ancient dinosaurs went extinct was that their brains were small. This enable mice and rabbits to take all of the dinosaurs’ food, so the dinosaurs died out. To her credit, Mrs. McGonagle knew this theory was fraught with difficulties (lame). She showed us pictures in a book, shrugged her shoulders and pressed on. It seemed clear to everyone in the room that somebody like a titanosaurus would have little difficulty with mice or rabbits, except that they wouldn’t make much of a hors d’oeuvre, let alone a snack or light meal. Such a dinosaur would crush such a mammal like a penny on the railroad track (paper thin— I’ve tried it).

So, in my lifetime a much more plausible theory came to be, when geologists looking for oil around the Gulf of Mexico with magnetometers discovered an enormous sub-ocean ring of shocked rock— a crater long about 1983. Scientists soon inferred that the ring is an impact crater. It’s off the coast near Chixalub, Mexico. Looking further and farther, geologists like Walter Alvarez realized that there is a layer of the unusual element iridium buried at the same geologic depth all over the world. Iridium is atomic number 77. It’s heavy; its atomic mass is 192. So when the Earth was formed from molten rock, the iridium sank to the middle. To get iridium in a nice layer near the top of the Earth’s crust took an impactor— a hurtling asteroid with primordial iridium got its guts blasted worldwide. The ejecta were spread in a circle wider than the Earth’s diameter. Phew…

Asteroid 2012 DA14 is not nearly as big— not even close. But there’s a lesson for all of us. It’s about the same size as the impactor that smacked into the atmosphere above Tunguska, Siberia in June 1908. In other words, if an asteroid the size of 2012 DA14 (about 45 meters across) were to hit the atmosphere over Paris, that would be the end of Paris as we know it.

A feature of these impacts that I still find remarkable is that at the speeds these things are moving relative to the Earth, the atmosphere acts virtually like a solid. It’s akin to the stories I heard often as a kid. If you jump off a high bridge into water, you won’t fare very well, because at that speed, water acts like concrete.  Yikes. The same was apparently true for the Tunguska object and our air. The same will be true for the next one— unless we do something about it.

The key to doing something is to find them. The Planetary Society funded some very skilled diligent astronomers in La Sagra, Spain, who used the money we supplied them to acquire a very sophisticated high-speed camera for their telescopes. They found this object. It’s through the support of our 30,000+ members around the world that these researchers came across a hurtling bit of primordial rock that could cause us tremendous harm. It’s frightening, but it’s also wonderfully exciting. We are the first generations of humans who can do something about an asteroid or comet impact. We have learned enough about the cosmos and our place in space that we can understand the danger and make a plan.

Among our projects at The Planetary Society is a scheme to use a network or squadron of laser-bearing spacecraft to ablate or cook the surface of an asteroid so that we change its velocity just a little, a few millimeters per second. That way, it would cross the Earth’s orbit when we’re not there. Other ideas include a massive spacecraft with enough gravity to gently tug an asteroid off its course. Or, we could just smash into an object with a smasher rocket (a kinetic transfer vehicle). It’s the stuff of science fiction, but it’s real.

The Chelyablinsk along with Asteroid 2012 AD14, should serve as a warning. The small one wrought small havoc. The big one is going to miss— this time. But, there are about 100,000 more out there crossing the Earth’s orbit, and we don’t know where they are. Some day in the not too distant future we humans are going to have to do something about one of these things. At end of the original movie “The Thing,” the journalist warns us: “Keep watching the skies…” It’s good advice, because our Solar System is a cosmic shooting gallery. Sooner or later, we’ll be a sitting duck.

Chelyablinsk, ice hole      Chelyablinsk, two streaks

 

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