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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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Scott Butner, Flickr // CC BY-NC-ND 2.0
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Space
Look Up! The Lyrid Meteor Shower Arrives Saturday Night
Scott Butner, Flickr // CC BY-NC-ND 2.0
Scott Butner, Flickr // CC BY-NC-ND 2.0

There is a thin line between Saturday night and Sunday morning, but this weekend, look up and you might see several of them. Between 11:59 p.m. on April 21 and dawn on Sunday, April 22, the Lyrid meteor shower will peak over the Northern Hemisphere. Make some time for the celestial show and you'll see a shooting star streaking across the night sky every few minutes. Here is everything you need to know.

WHAT IS THE LYRID METEOR SHOWER?

Every 415.5 years, the comet Thatcher circles the Sun in a highly eccentric orbit shaped almost like a cat's eye. At its farthest from the Sun, it's billions of miles from Pluto; at its nearest, it swings between the Earth and Mars. (The last time it was near the Earth was in 1861, and it won't be that close again until 2280.) That's quite a journey, and more pressingly, quite a variation in temperature. The closer it gets to the Sun, the more debris it sheds. That debris is what you're seeing when you see a meteor shower: dust-sized particles slamming into the Earth's atmosphere at tens of thousands of miles per hour. In a competition between the two, the Earth is going to win, and "shooting stars" are the result of energy released as the particles are vaporized.

The comet was spotted on April 4, 1861 by A.E. Thatcher, an amateur skywatcher in New York City, earning him kudos from the noted astronomer Sir John Herschel. Clues to the comet's discovery are in its astronomical designation, C/1861 G1. The "C" means it's a long-period comet with an orbit of more than 200 years; "G" stands for the first half of April, and the "1" indicates it was the first comet discovered in that timeframe.

Sightings of the Lyrid meteor shower—named after Lyra, the constellation it appears to originate from—are much older; the first record dates to 7th-century BCE China.

HOW CAN I SEE IT?

Saturday night marks a first quarter Moon (visually half the Moon), which by midnight will have set below the horizon, so it won't wash out the night sky. That's great news—you can expect to see 20 meteors per hour. You're going to need to get away from local light pollution and find truly dark skies, and to completely avoid smartphones, flashlights, car headlights, or dome lights. The goal is to let your eyes adjust totally to the darkness: Find your viewing area, lay out your blanket, lay down, look up, and wait. In an hour, you'll be able to see the night sky with great—and if you've never done this before, surprising—clarity. Don't touch the smartphone or you'll undo all your hard ocular work.

Where is the nearest dark sky to where you live? You can find out on the Dark Site Finder map. And because the shower peaks on a Saturday night, your local astronomy club is very likely going to have an event to celebrate the Lyrids. Looking for a local club? Sky & Telescope has you covered.

WHAT ELSE IS GOING ON UP THERE?

You don't need a telescope to see a meteor shower, but if you bring one, aim it south to find Jupiter. It's the bright, unblinking spot in the sky. With a telescope, you should be able to make out its stripes. Those five stars surrounding it are the constellation Libra. You'll notice also four tiny points of light nearby. Those are the Galilean moons: Io, Europa, Ganymede, and Callisto. When Galileo discovered those moons in 1610, he was able to prove the Copernican model of heliocentricity: that the Earth goes around the Sun.

THERE'S BAD WEATHER HERE! WHAT DO I DO?

First: Don't panic. The shower peaks on the early morning of the 22nd. But it doesn't end that day. You can try again on the 23rd and 24th, though the numbers of meteors will likely diminish. The Lyrids will be back next year, and the year after, and so on. But if you are eager for another show, on May 6, the Eta Aquariids will be at their strongest. The night sky always delivers.

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Space
New NASA Satellite Called TESS Could Discover Thousands of New Planets

Since NASA’s Kepler spacecraft launched in 2009, the space agency has found and confirmed a whopping 2343 new planets. Of those, 30 are considered to be situated in a “habitable zone,” an area in which a planet’s surface could theoretically contain water.

A new satellite, set to launch today, is expected to find thousands more planets outside of our solar system, known as exoplanets. TESS, short for the Transiting Exoplanet Survey Satellite, is NASA’s latest effort to plumb the depths and darkness of outer space in search of other Earth-like planets—including those that could potentially support life.

TESS is slated to complete a two-year survey of the “solar neighborhood,” a general region which comprises more than 200,000 of the brightest nearby stars. To find these outlier planets, NASA scientists will be keeping an eye out for temporary changes in brightness, which indicate that a planet is blocking its host star.

According to Martin Still, the program scientist working on the TESS mission, the launch comes “with certainty” that TESS will find many nearby exoplanets. "We expect to find a whole range of planet sizes, between planets the size of Mercury or even the Moon—our Moon—to planets the same size as Jupiter and everything in between,” Still said in a NASA interview.

While the Kepler mission was considered a major success, NASA noted that most of the planets it recorded are those that orbit faint, faraway stars, making it difficult to conduct follow-up observations. The stars that TESS plans to survey will be 30 to 100 times brighter than those observed by its predecessor. This allows for newly detected planets and their atmospheres to be characterized more easily.

“Before Kepler launched, we didn't know for sure if Earth-sized planets existed,” Elisa V. Quintana, a NASA astrophysicist, told Reddit. “Kepler was a statistical survey that looked at a small patch of sky for four years and taught us that Earths are everywhere. TESS is building on Kepler in the sense that TESS wants to find more small planets but ones that orbit nearby, bright stars. These types of planets that are close to us are much more easy to study, and we can measure their masses from telescopes here on Earth.”

The most common categories of exoplanets are Earth- and Super Earth–sized masses—the latter of which are larger than Earth but smaller than Uranus and Neptune.

TESS is scheduled to launch from the Cape Canaveral Air Force Station in Florida on a SpaceX Falcon 9 rocket at 6:32pm EDT today.

For more information about TESS, check out this video from NASA.

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