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The Fireball That Killed the Dinosaurs Could Help Us Find Life on Other Planets

When David Kring of the University of Arizona gave a presentation at the Lunar and Planetary Science Conference in 1991, he didn’t expect a packed crowd for his talk on the petrology of the Chicxulub Structure in the Yucatan, Mexico. Normally, Kring knew, impact-cratering sessions were presented in the smallest room—the miserable Room D, a shoebox on the second floor. But the magnitude of his announcement attracted scientists across fields and disciplines, so he was bumped up to the main room.

Kring had been investigating a place called the Yucatán-6 borehole, and he and his team had discovered shock quartz and impact melt fragments in two thumb-sized bits of rock that were over half a mile beneath the surface of the Earth. This was evidence that the hole, thought for a very long time to be a volcanic center, was actually an impact structure. And not just any “impact structure,” and not just any crater―but the crater of all craters on Earth. The one behind the death of the dinosaurs 66 million years ago.

Last year, Kring was part of an expedition in which scientists drilled into Chicxulub to investigate how the disastrous collision of fireball and Earth that killed the dinosaurs also created the conditions for life to begin anew. Last month, Kring and his colleagues returned to the Lunar and Planetary Science Conference to present their findings from the new core samples they took on that expedition. The results provide new clues about how life may have begun on Earth about 4 billion years ago—and point us towards how and where we can look for life across the universe.

THE SMOKING CANNON

Back in the early 1990s, Kring knew what he was looking for—a crater of the size and magnitude that would provide evidence of catastrophic extinction—but he didn’t know where to look. “It was a race to find the impact site,” Kring tells mental_floss, “and we had made a discovery of this very thick impact ejecta deposit in Haiti, which pointed us to [the Yucatan].”

Impact ejecta is what’s blasted from the Earth or other body when a meteor crashes into it. In this case, a giant chunk of the Earth was blown a thousand miles away. Until the Haiti discovery, people were looking all over the planet for the crater. But now they had a target region. Meanwhile, Petroleos Mexicanos, an oil company, had drilled down into what they thought was a “geophysical anomaly” in the Yucatan―a salt dome, maybe, where there might be oil. That’s when Kring and his colleagues re-examined samples collected from the site and realized there were features consistent with an impact.

That the Yucatan site was still intact to be found wasn’t a given. In the last 65 million years, half of the seafloor has been subducted, where one tectonic plate slides beneath another—which would have prevented scientists from discovering samples. When Kring and his team looked at the samples they were able to take, there was shock quartz in one of the layers. “The minute you see shock quartz, that is absolutely, categorically diagnostic of impact,” says Kring. “You know that’s not a buried volcano. It’s an impact crater, and that’s your eureka moment.”

When Kring found the Chicxulub Crater, it finally provided scientific evidence for the Impact Mass Extinction Hypothesis. Developed by physicist Luis Alvarez, the theory proposes that the extinction of the dinosaurs was caused by a catastrophic asteroid impact with the Earth. The theory made a lot of sense. An impact of such magnitude would certainly leave a mark, after all. The dominant alternative hypothesis was that overdrive volcanic activity caused catastrophic climate change, leaving the dinosaurs in a bad spot. Finding an impact crater of this magnitude, scientist Gene Shoemaker would later tell Time magazine, was “the smoking cannon.”

The discovery that impact cratering is not only a geological process but a biological one caused a major shift in scientific thinking during the 20th century. The idea that you could have catastrophic events completely change the evolutionary path of the planet was staggering in its implication. Impact Mass Extinction Hypothesis, and the subsequent discovery of Chicxulub Crater, were argued by some as fundamentally more important, and bigger shifts in the tenets of geology, than learning about continental drift.

THE ORIGIN OF LIFE ON EARTH

When a fireball hit the Earth 66 million years ago, the Mesozoic Era (the Age of Reptiles) ended and the Cenozoic―the Age of Mammals―began. One second before the strike, in the part of the sea that must have had a dark shadow pooling rapidly outward as the asteroid approached, 50-foot sea monsters called mosasaurs swarmed and devoured fish and mollusks. One second after the asteroid hit, those mosasaurs were gone, and chunks of the planet were blown thousands of miles in every direction. Every continent on Earth was devastated in the blink of a geologic eye. A 300-foot tsunami washed across North and South America. The Sun was blotted out. Plants relying on photosynthesis declined or went extinct. If you were a dinosaur who couldn’t fly, you were done for. Seventy-five percent of all species of life were obliterated.

But bad as that sounds, approximately 4 billion years ago, an impact likely larger even than Chicxulub would have vaporized the sea and created a rock vapor atmosphere for thousands of years. The impacts would have produced vast subsurface hydrothermal (hot water) systems that were perfect crucibles for prebiotic chemistry. The new core samples taken from deep in Chicxulub provide physical evidence of this theory. The samples are fractured and permeable—perfect for the circulation of hot fluid. Moreover, they also have signatures of hot fluids and altered rock and hydrothermal minerals.

The hydrothermal systems caused by an asteroid collision may have lasted for as long as 2.3 million years. This is critical, because life needs time to establish itself and evolve. Those systems would have evolved into perfect habitats for the evolution of life.

Kring's Chicxulub research suggests that these are the types of places life evolved in early Earth history. Further research will look at the analysis of rock samples for radiometric signatures, to try to determine how long that system persisted. It's also given rise to a new theory: the Impact Origin of Life Hypothesis.

This impact origin of life theory is not necessarily limited to Earth, as research from Susanne Schwenzer, Oleg Abramov, and others suggest. “It is generically translatable,” says Kring. “Impact cratering, as it turns out, is an important heat engine for planetary bodies. Impact events on icy satellites can melt icy shells and produce seeds. You need liquid water for life. That may have had a role of life in our outer system.” This also applies to extrasolar planetary systems.

Whether life originated anywhere beyond Earth is still to be determined, but this is a big step toward understanding what conditions to look for. You can be sure when it’s announced, that scientist will certainly play to a standing-room-only crowd yet again.

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Big Questions
Can You Really Go Blind Staring at a Solar Eclipse?
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A total solar eclipse will cut a path of totality across the United States on August 21, and eclipse mania is gripping the country. Should the wide-eyed and unprotected hazard a peek at this rare phenomenon?

NASA doesn't advise it. The truth is, a quick glance at a solar eclipse won't leave you blind. But you're not doing your peepers any favors. As NASA explains, even when 99 percent of the sun's surface is covered, the 1 percent that sneaks out around the edges is enough to damage the rod and cone cells in your retinas. As this light and radiation flood into the eye, the retina becomes trapped in a sort of solar cooker that scorches its tissue. And because your retinas don't have any pain receptors, your eyes have no way of warning you to stop.

The good news for astronomy enthusiasts is that there are ways to safely view a solar eclipse. A pair of NASA-approved eclipse glasses will block the retina-frying rays, but sunglasses or any other kind of smoked lenses cannot. (The editors at MrEclipse.com, an eclipse watchers' fan site, put shades in the "eye suicide" category.) NASA also suggests watching the eclipse indirectly through a pinhole projector, or through binoculars or a telescope fitted with special solar filters.

While it's safe to take a quick, unfiltered peek at the sun in the brief totality of a total solar eclipse, doing so during the partial phases—when the Moon is not completely covering the Sun—is much riskier.

WOULDN'T IT BE EASIER TO JUST TELL YOUR KIDS THEY WILL GO BLIND?

NASA's website tackled this question. Their short answer: that could ruin their lives.

"A student who heeds warnings from teachers and other authorities not to view the eclipse because of the danger to vision, and learns later that other students did see it safely, may feel cheated out of the experience. Having now learned that the authority figure was wrong on one occasion, how is this student going to react when other health-related advice about drugs, alcohol, AIDS, or smoking is given[?]"

This story was originally published in 2012.

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4 Expert Tips on How to Get the Most Out of August's Total Solar Eclipse
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Richard Bouhet // Getty

As you might have heard, there’s a total solar eclipse crossing the U.S. on August 21. It’s the first total solar eclipse in the country since 1979, and the first coast-to-coast event since June 8, 1918, when eclipse coverage pushed World War I off the front page of national newspapers. Americans are just as excited today: Thousands are hitting the road to stake out prime spots for watching the last cross-country total solar eclipse until 2045. We’ve asked experts for tips on getting the most out of this celestial spectacle.

1. DON’T FRY YOUR EYES—OR BREAK THE BANK

To see the partial phases of the eclipse, you will need eclipse glasses because—surprise!—staring directly at the sun for even a minute or two will permanently damage your retinas. Make sure the glasses you buy meet the ISO 12312-2 safety standards. As eclipse frenzy nears its peak, shady retailers are selling knock-off glasses that will not adequately protect your eyes. The American Astronomical Society keeps a list of reputable vendors, but as a rule, if you can see anything other than the sun through your glasses, they might be bogus. There’s no need to splurge, however: You can order safe paper specs in bulk for as little as 90 cents each. In a pinch, you and your friends can take turns watching the partial phases through a shared pair of glasses. As eclipse chaser and author Kate Russo points out, “you only need to view occasionally—no need to sit and stare with them on the whole time.”

2. DON’T DIY YOUR EYE PROTECTION

There are plenty of urban legends about “alternative” ways to protect your eyes while watching a solar eclipse: smoked glass, CDs, several pairs of sunglasses stacked on top of each other. None works. If you’re feeling crafty, or don’t have a pair of safe eclipse glasses, you can use a pinhole projector to indirectly watch the eclipse. NASA produced a how-to video to walk you through it.

3. GET TO THE PATH OF TOTALITY

Bryan Brewer, who published a guidebook for solar eclipses, tells Mental Floss the difference between seeing a partial solar eclipse and a total solar eclipse is “like the difference between standing right outside the arena and being inside watching the game.”

During totality, observers can take off their glasses and look up at the blocked-out sun—and around at their eerily twilit surroundings. Kate Russo’s advice: Don’t just stare at the sun. “You need to make sure you look above you, and around you as well so you can notice the changes that are happening,” she says. For a brief moment, stars will appear next to the sun and animals will begin their nighttime routines. Once you’ve taken in the scenery, you can use a telescope or a pair of binoculars to get a close look at the tendrils of flame that make up the sun’s corona.

Only a 70-mile-wide band of the country stretching from Oregon to South Carolina will experience the total eclipse. Rooms in the path of totality are reportedly going for as much as $1000 a night, and news outlets across the country have raised the specter of traffic armageddon. But if you can find a ride and a room, you'll be in good shape for witnessing the spectacle.

4. PRESERVE YOUR NIGHT VISION

Your eyes need half an hour to fully adjust to darkness, but the total eclipse will last less than three minutes. If you’ve just been staring at the sun through the partial phases of the eclipse, your view of the corona during totality will be obscured by lousy night vision and annoying green afterimages. Eclipse chaser James McClean—who has trekked from Svalbard to Java to watch the moon blot out the sun—made this rookie mistake during one of his early eclipse sightings in Egypt in 2006. After watching the partial phases, with stray beams of sunlight reflecting into his eyes from the glittering sand and sea, McClean was snowblind throughout the totality.

Now he swears by a new method: blindfolding himself throughout the first phases of the eclipse to maximize his experience of the totality. He says he doesn’t mind “skipping the previews if it means getting a better view of the film.” Afterward, he pops on some eye protection to see the partial phases of the eclipse as the moon pulls away from the sun. If you do blindfold yourself, just remember to set an alarm for the time when the total eclipse begins so you don’t miss its cross-country journey. You'll have to wait 28 years for your next chance.

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