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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15 Podcasts That Will Make You Feel Smarter
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iStock

It's easy to feel overwhelmed by all the podcast options out there, but narrowing down your choices to the titles that will teach you something while you listen is a good place to start. If you're interested in learning more about philosophy, science, linguistics, or history, here are podcasts to add to your queue.

1. THE HABITAT

The Habitat is the closest you can get to listening to a podcast recorded on Mars. At the start of the series, five strangers enter a dome in a remote part of Hawaii meant to simulate a future Mars habitat. Every part of their lives over the next year, from the food they eat to the spacesuits they wear when they step outside, is designed to mimic the conditions astronauts will face if they ever reach the red planet. The experiment was a way for NASA to test plans for a manned mission to Mars without leaving Earth. The podcast, which is produced by Gimlet media and hosted by science writer Lynn Levy, ends up unfolding like a season of the Real World with a science fiction twist.

2. STUFF YOU SHOULD KNOW

Can’t pick a topic to educate yourself on? Stuff You Should Know from How Stuff Works is the podcast for you. In past episodes, hosts Chuck Bryant and Josh Clark (both writers at How Stuff Works) have discussed narwhals, Frida Kahlo, LSD, Pompeii, hoarding, and Ponzi schemes. And with three episodes released a week, you won’t go long without learning about a new subject.

3. THE ALLUSIONIST

Language nerds will find a kindred spirit in Helen Zaltzman. In each episode of her Radiotopia podcast The Allusionist, the former student of Latin, French, and Old English guides listeners through the exciting world of linguistics. Past topics include swearing, small talk, and the differences between British and American English.

4. PHILOSOPHIZE THIS!

Listening to all of Philosophize This! is cheaper than taking a philosophy class—and likely more entertaining. In each episode, host Stephen West covers different thinkers and ideas from philosophy history in an approachable and informative way. The show proceeds in chronological order, starting with the pre-Socratic era and leading up most recently to Jacques Derrida.

5. MORE PERFECT

In 2016, Radiolab, one of the most popular and well-established educational podcasts out there, launched a show called More Perfect. Led by Radiolab host Jad Abumrad, each episode visits a different Supreme Court case or event that helped shape the highest court in the land. Because of that, the podcast ends up being about a lot more than just the Supreme Court, exploring topics like police brutality, gender equality, and free speech online.

6. SLOW BURN

The Watergate scandal was such a important chapter in American history that it has its own suffix—but when asked to summarize the events, many people may draw a blank. Slow Burn, a podcast from Slate, gives listeners a refresher. In eight episodes, host Leon Neyfakh tells the story of the Nixon’s demise as it unfolded, all while asking whether or not citizens would be able to recognize a Watergate-sized scandal if it happened today.

7. LETTERS FROM WAR

Instead of using a broad scope to examine World War II, the Washington Post podcast Letters From War focuses on hundreds of letters exchanged by four brothers fighting in the Pacific during the period. Living U.S. military veterans tell the sibling's story while reflecting on their own experiences with war.

8. LEVAR BURTON READS

Just because you’re a grown-up doesn’t mean you have to miss out on the soothing sound of LeVar Burton’s voice reading to you. The former host of Reading Rainbow now hosts LeVar Burton Reads, a podcast from Stitcher aimed at adults. In each episode, he picks a different piece of short fiction to narrate: Just settle into a comfortable spot and listen to him tell stories by authors like Haruki Murakami, Octavia Butler, and Ursula K. Le Guin.

9. BRAINS ON!

Brains On! is an educational podcast for young audiences, but adults have something to gain from listening as well. Every week, host Molly Bloom is joined by a new kid co-host who helps her explore a different topic. Tune in for answers to questions like "What makes paint stick?" and "How do animals breathe underwater?"

10. SCIENCE VS

There’s a lot of misinformation out there—if you’re determined to sort out fact from fiction, it can be hard to know where to start. The team of “friendly fact checkers” at the Science Vs podcast from Gimlet is here to help. GMOs, meditation, birth control, Bigfoot—these are just a few of the topics that are touched upon in the weekly show. The goal of each episode is to replace any preconceived notions you have with hard science.

11. FLASH FORWARD

No one knows for sure what the future holds, but Flash Forward lays out the more interesting possibilities. Some of the potential futures that host and producer Rose Eveleth explores are more probable than others (a future where no one knows which news sources to trust isn’t hard to imagine; one where space pirates drag a second moon into orbit perhaps is), but each one is built on real science.

12. HIDDEN BRAIN

What motivates the everyday choices we make? That’s the question Shankar Vedantam tries to answer on the NPR podcast Hidden Brain. The show looks at how various unconscious patterns shape our lives, like what we wear and who we choose to spend time with.

13. PART-TIME GENIUS

The fact that it’s hosted by Mental Floss founders Will Pearson and Mangesh Hattikudur isn’t the only reason we love Part-Time Genius. The podcast from How Stuff Works wades into topics you didn’t know you were curious about, like the origins of Nickelodeon and the hidden secrets at the Vatican. Each episode will leave you feeling educated and entertained at the same time.

14. ASTRONOMY CAST

It’s a big universe out there—if you want to learn as much about it as possible, start with Astronomy Cast. Fraser Cain, publisher of the popular site Universe Today, and Dr. Pamela L. Gay, director of the virtual research facility CosmoQuest, host the podcast. They cover a wide range of topics, from the animals we’ve sent to orbit to the color of the universe.

15. SCIENCE OF HAPPINESS

The Science of Happiness podcast from PRI is here to improve your life, one 20-minute episode at a time. Science has proven that adopting certain practices, like mindfulness and gratitude, can make us happier—as does letting go of less unhealthy patterns like grudges and stressful thinking. With award-winning professor Dacher Keltner as your host, you can learn how to incorporate these science-backed strategies for happiness into your own life.

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ESO, A. Müller et al.
Here's the First Confirmed Image of a Planet Being Born
ESO, A. Müller et al.
ESO, A. Müller et al.

One of the newest landmarks in the observable universe has finally been captured, according to the European Southern Observatory. The image, snapped at its Very Large Telescope (VLT) in Chile, marks the first time a newborn planet has been seen as it forms. 

The image was documented by SPHERE, an instrument at the VLT that's built to identify exoplanets. It shows a planet, dubbed PDS 70b, taking shape in the disc of gas and star dust surrounding the young dwarf star PDS 70. In the past, astronomers have caught glimpses of what may have been new planets forming, but until now it had been impossible to tell whether such images just showed shapes in the dust or the beginnings of true planet formation. The results of the research will be shared in the journal Astronomy & Astrophysics [PDF].

This latest cornograph (an image that blocks the light of a star to make its surroundings visible) depicts the new planet clearly as a bright blob beside the black star. The two bodies may look close in the photo, but PDS 70b is roughly 1.8 billion miles from PDS 70, or the distance of Uranus to the Sun. SPHERE also recorded the planet's brightness at different wavelengths. Based on information gathered from the instrument, a team of scientists led by Miriam Keppler of the Max Planck Institute for Astronomy says that PDS 70b is a gas giant a few times the mass of Jupiter with a surface temperature around 1830°F and a cloudy atmosphere.

Astronomers known that planets form from solar clouds which stars leave behind when they come into a being, but until now, the details surrounding the phenomena have been mysterious. “Keppler’s results give us a new window onto the complex and poorly understood early stages of planetary evolution,” astronomer André Müller said in a press release. “We needed to observe a planet in a young star’s disc to really understand the processes behind planet formation.”

This is just the latest history-making image captured by the ESO's Very Large Telescope. In the last 20 years, it has documented nebulae, light from gravitational waves, and interacting galaxies.

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