Deception Point Page 20

This first try on here, bad said, pointing to a shiny, ebony tree st wholeness, is an iron-core shooting starite. Very heavy. This little guy landed in Antarctica a a few(prenominal) days back.Rachel studied the meteorite. It most certainly looked otherworldly-a blob of heavy grey-headed iron whose outer crust was burned and blackened.That charred outer layer is called a fusion crust, bad said. Its the result of extreme heating as the meteor falls through our atmosphere. All meteorites exhibit that charring. bad moved readily to the next sample. This next one is what we call a jolty-iron meteorite.Rachel studied the sample, noting that it as well as was charred on the outside. This sample, however, had a light- verdancyish tint, and the cross section looked deal a collage of colorful angular fragments resembling a kaleidoscopic puzzle.Pretty, Rachel said.Are you kidding, its gorgeous bad talked for a minute about the high olivine content causing the green luster, and the n he reached dramatically for the third and final sample, handing it to Rachel.Rachel held the final meteorite in her palm. This one was grayish brown in color, resembling granite. It felt heavier than a global stone, but not substantially. The only indication suggesting it was anything other than a linguistic rule rock was its fusion crust-the scorched outer surface.This, bad said with finality, is called a stony meteorite. Its the most common class of meteorite. More than ninety part of meteorites found on earth be of this category.Rachel was surprised. She had always pictured meteorites to a greater extent ilk the first sample-metallic, alien-looking blobs. The meteorite in her hand looked anything but extraterrestrial. Aside from the charred exterior, it looked similar something she might step over on the beach. bads eyes were bulging at once with excitement. The meteorite buried in the ice here at Milne is a stony meteorite-a lot comparable the one in your hand. Stony m eteorites appear roughly identical to our terrestrial igneous rocks, which makes them tough to spot. Usually a amalgamate of lightweight silicates-feldspar, olivine, pyroxene. Nothing too exciting.Ill say, Rachel thought, handing the sample back to him. This one looks like a rock someone left in a hearth and burned.Corky burst out laughing. One hell of a fireplace The meanest blast furnace ever built doesnt come tightlipped to reproducing the heat a meteoroid feels when it hits our atmosphere. They get ravagedTolland gave Rachel an empathetic smile. This is the good part.Picture this, Corky said, taking the meteorite sample from Rachel. Lets imagine this little fella is the size of a house. He held the sample high over his head. Okay its in post floating across our solar system cold-soaked from the temperature of space to minus one hundred degrees Celsius.Tolland was chuckling to himself, app atomic number 18ntly already having seen Corkys reenactment of the meteorites arriva l on Ellesmere Island.Corky began sound the sample. Our meteorite is moving toward earth and as its getting very close, our gravity locks on accelerating accelerating Rachel watched as Corky sped up the samples trajectory, mimicking the acceleration of gravity.Now its moving fast, Corky exclaimed. Over ten miles per second-thirty-six thousand miles per hour At 135 kilometers to a higher place the earths surface, the meteorite begins to encounter friction with the atmosphere. Corky shook the sample violently as he lowered it toward the ice. Falling below one hundred kilometers, its scratch line to glow Now the atmospheric density is increasing, and the friction is incredible The bearing around the meteoroid is becoming incandescent as the surface strong melts from the heat. Corky started making burning and sizzling sound effects. Now its fall past the eighty-kilometer mark, and the exterior becomes heated to over eighteen hundred degrees CelsiusRachel watched in disbelief as th e presidential award-winning astrophysicist shook the meteorite more(prenominal) fiercely, spatter out juvenile sound effects.Sixty kilometers Corky was shouting now. Our meteoroid encounters the atmospheric wall. The air is too dense It violently decelerates at more than three hundred times the force of gravity Corky do a screeching braking sound and slowed his descent dramatically. Instantly, the meteorite cools and stops glowing. Weve hit blasphemous flight The meteoroids surface hardens from its molten stage to a charred fusion crust.Rachel comprehend Tolland groan as Corky knelt on the ice to perform the coup de grace-earth impact.Now, Corky said, our huge meteorite is skipping across our lower atmosphere On his knees, he arched the meteorite toward the ground on a shallow slant. Its headed toward the Arctic oceanic on an oblique angle falling looking almost like it will skip off the ocean falling and He stirred the sample to the ice. BAMRachel jumped.The impact is ca taclysmic The meteorite explodes. Fragments fly off, skipping and spinning across the ocean. Corky went into slow motion now, rolling and tumbling the sample across the unseeyn ocean toward Rachels feet. One piece keeps skimming, tumbling toward Ellesmere Island He brought it right up to her toe. It skips off the ocean, bouncing up onto land He moved it up and over the tongue of her shoe and rolled it to a stop on top of her foot near her ankle. And finally comes to rest high on the Milne Glacier, where snow and ice quickly cover it, protecting it from atmospheric erosion. Corky stood up with a smile.Rachels mouth fell slack. She gave an impressed laugh. Well, Dr. Marlinson, that explanation was exceptionally Lucid? Corky offered.Rachel smiled. In a word.Corky handed the sample back to her. Look at the cross section.Rachel studied the rocks interior a moment, seeing nothing.Tilt it into the light, Tolland prompted, his voice warm and kind. And look closely.Rachel brought the rock close to her eyes and tilted it against the dazzling halogens reflecting overhead. Now she saw it-tiny metallic globules gleaming in the stone. Dozens of them were peppered throughout the cross section like trivial droplets of mercury, each only about a millimeter across.Those little bubbles are called chondrules, Corky said. And they occur only in meteorites.Rachel squinted at the droplets. Granted, Ive never seen anything like this in an earth rock.Nor will you Corky declared. Chondrules are one geologic structure we simply do not rent on earth. most chondrules are exceptionally old-perhaps madeup of the earliest materials in the universe. Other chondrules are frequently younger, like the ones in your hand. The chondrules in that meteorite date only about xcl million years old.One hundred ninety million years is young?Heck, yes In cosmological terms, thats yesterday. The point here, though, is that this sample contains chondrules-conclusive meteoric evidence.Okay, Rachel sai d. Chondrules are conclusive. Got it.And finally, Corky said, heaving a sigh, if the fusion crust and chondrules dont convince you, we astronomers have a foolproof method to confirm meteoric origin.Being?Corky gave a casual shrug. We simply use a petrographic polarizing microscope, an x-ray fluorescence spectrometer, a neutron activation analyzer, or an induction-coupled plasma spectrometer to measure ferromagnetic ratios.