Thursday, May 19, 2011

The Spacerock Saga

Imagine you are hurtling through space at 26,000 miles per hour. You're zipping along, but to you all seems still and peaceful. The stars are so far away they appear stationary and you have no sense that you are crossing the distance of Manhattan every two seconds. Everything around you is black. Darkness cloaks you and it's colder than the arctic on the worst of days.

Ahead, there is a small blue sphere. It glows brightly, silhouetted by the dark background of space. Each day, it grows a little larger and soon you realize you're on a collision course. It is called Earth, and you're headed for a land that will one day be known as Arizona.

[The Meteor Crater, as seen from about 35,000 feet.]

You are a meteor, made of nickel and iron. Once you were a part of the asteroid belt between Mars and Jupiter, but a collision half a billion years ago set you free, ejecting you into the solar system where you've been going it alone ever since.

Eventually, Earth looms before you and you anticipate your impact on the rocky surface below. There is no escape.

Almost as soon as you see it, you are in the planet's wispy atmosphere, slipping through it in seconds. It burns you, stripping you of some rock - solid nickel and iron turned at once into vapor by the heat.

Moments later: Impact. You crash into the Earth's surface with the force of 20 million tons of detonated TNT. Instantly, more of you is vaporized, but the majority of your 150-foot-wide bulk is melted by the force of the collision. The remainder of you that wasn't melted or vaporized is fragmented and mixed in with the surrounding Arizona rock.

Sandstone and limestone are ejected over a mile away. Your impact has left a hole in the Earth 700 feet deep and nearly a mile wide. Giant limestone rocks are piled onto the hole's rim, now 150 feet higher than the surrounding terrain - a new ridge in the Earth where seconds before the land was level.

The intense pressure turns tiny pieces of graphite into diamonds and particles of rock rain down around the crater for minutes. The divot you've created is large enough to house 20 football fields. The residents of Philadelphia could stand on its slopes with room to spare.

Fifty thousand years pass. The crater's walls still loom above the landscape. Arizona is populated and villages and towns, roads and trails settle into place around the crater. No one is really sure why there is a large hole in the ground in an otherwise level part of Arizona. 'Perhaps an ancient volcano?' some wonder.

Daniel Moreau Barringer, a mining engineer from Philadelphia, scouts the site around the turn of the century, pondering its potential as an iron mine. He is one of the first to consider it as the landing side of a meteorite. In 1903, Barringer buys the land surrounding the crater and spends twenty-six years studying it, looking for remnants of a meteor. He dies in 1929, just as his theory to the hole's origin begins to be accepted.

Today, the crater is known simply as "Meteor Crater," and sometimes as "Barringer Crater." When viewed from above at jet-cruising altitude, it's a clear fingerprint of the cosmic pebble that collided with the Earth many thousands of years ago. From above, it's a singular reminder that though the Earth is unique in our solar system, we are just one among many billions of cosmic wanderers zipping through the universe.

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[Can you spot the meteor crater from above using Google Earth? Hint: The crater looks round from above.]

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