How Impact Craters Could Have Reversed Venus’s Rotation—The Surprising Science

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Anna: From the farthest reaches of the galaxy to

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the red dust of Mars. You're tuned in to

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Astronomy Daily, your daily briefing on, um,

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the universe. I'm Anna.

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Avery: And I'm Avery. Today on the show, an

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interstellar comet has just revealed it's

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older than our sun by billions of years.

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Perseverance scores its most impressive

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organic detection yet on Mars. And

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Europe's dark matter detective turns its gaze

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to the heart of our own galaxy and delivers

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the most stunning portrait ever made.

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Anna: We've also got a controversial plan to dump

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the world's largest space station into the

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Pacific Ocean, raising some very pointed

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questions. Plus, an asteroid that killed the

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dinosaurs may have kept underground life

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burning for 8 million years. And

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astronomers have just found that a, uh,

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famous nebula has a long lost twin

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sibling.

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Avery: It's Thursday, the 26th of June,

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2026, and this is Astronomy

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Daily.

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Anna: We start today with one of the most

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remarkable findings in the short but

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extraordinary history of interstellar

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astronomy. The comet known as 3i

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Atlas, which swept through our solar system

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last year and captured the imagination of

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scientists worldwide, has now revealed

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something almost impossible to wrap your head

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around. This comet is older than our Sun.

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Avery: Much older, potentially. Two new papers

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published in the journal Nature this week,

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using data from NASA's James Webb Space

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Telescope, report that 3i

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Atlas carries a chemical fingerprint unlike

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anything found in our own solar system. And

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that fingerprint points to an origin between

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10 and 12 billion years ago.

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Anna: To put that in perspective, our sun is about

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4 1/2 billion years old. So this

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comet may have been drifting through the

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galaxy for more than twice the lifetime of

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our entire Sol solar system before it

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happened to pass through our neighborhood.

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Avery: The key evidence comes from isotopes,

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specifically the ratio of two forms of carbon

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and a type of water molecule called semi

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heavy water, in which some of the hydrogen

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atoms carry an extra neutron.

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Astronomers using Webb's near infrared

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Spectroscope found that 3i Atlas

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has far less carbon 13 relative to

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carbon 12 than anything in our solar system.

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And carbon 13 builds up in the universe over

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time as successive generations of stars are

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born, live, and explode. Less carbon

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13 means an older origin, one from

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a time before many stars had even had the

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chance to die.

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Anna: The semi heavy water signature is equally

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telling. That kind of water tends to form in

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high radiation environments, cold,

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massive star forming regions that were far

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more common in the early universe. And taken

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together, the Webb team concludes this comet

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formed during what astronomers call cosmic

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noon, when star formation across the universe

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was at its absolute peak.

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Avery: Lead researcher Martin Cordiner of NASA's

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Goddard Space Flight center described it as a

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unique opportunity to study an ancient object

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from the distant galaxy, probably predating

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our sun and solar system. His words. On

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one hand, we get direct insight into that

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distant time and place, and on the other, we

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learned something about how our own solar

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system may be.

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Anna: A companion study from the European Southern

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Observatory's Very Large Telescope found

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complementary evidence in the comet's carbon

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and nitrogen isotope ratios, further

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cementing the picture of an ancient, cold,

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alien origin. 3i

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Atlas, it seems, is a genuine relic from

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another era of the universe

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Avery: entirely, and it's on its way out. The

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comet is now departing our solar system,

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never to return. But the data it's left

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behind will be studied for years, perhaps

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decades.

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Anna: We stay in the realm of ancient chemistry,

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but this time a little closer to home, just

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40 to 250 million km

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away, depending on where Mars and Earth

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happen to be in their orbits. NASA's

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Perseverance rover has just delivered what

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scientists are calling the most robust

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organic detection made in Jezero Crater.

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A new study published in Science Advances

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reports that the rover's SHERLOCK instrument,

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a laser based spectrometer on the end of the

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robotic arm, has detected complex

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macromolecular carbon in two mudstone

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rocks at a site called Bright angel in an

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ancient river valley called Neretva

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Vallis.

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Avery: The paper's own summary describes it as, and

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I'm quoting, the most robust organic

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detection in Jezero Crater. That thus far

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and the only detection of macromolecular

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carbon on a natural rock surface on Mars.

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That's macromolecular, meaning large,

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complex carbon based molecules, the kind that

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on Earth are associated with biology. But we

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need to be careful here.

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Anna: Absolutely. The researchers are very clear

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that detecting organic carbon on Mars

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does not mean life. The SHERLOCK instrument

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cannot distinguish between carbon produced by

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biology and carbon produced by geology

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or delivered by meteorites. What it can

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do is show that the chemical ingredients were

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there, and in this case, they were there in

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abundance. Hundreds of individual

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detections across just two rocks.

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Avery: What makes this particularly compelling is

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the location these mudstones are at. Bright

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angel connected to Naret Va Vallis, the

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ancient river channel that fed Jezero

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Crater's western delta billions of years ago.

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This was a water rich environment, exactly

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the kind of place where on Earth you would

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expect to find microbial sheltering in

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sediment.

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Anna: One of the two rocks examined is the now

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famous Chayava Falls, the very rock

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that caused such excitement last year with

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its distinctive leopard spot markings.

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Finding complex macromolecular carbon in

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it adds yet another Intriguing layer to the

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mystery. The other rock showed organic

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carbon associated with carbonate and sulfate

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minerals, both of which can be connected to

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biological processes.

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Avery: The researchers also note this is the first

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detection of this type of complex carbon in a

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mudstone on Mars outside of Gale Crater,

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where the Curiosity rover operates more than

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three and a half thousand kilometers away.

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That suggests the conditions that allowed

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organics to form and survive may have been

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widespread across Mars, not just in one

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localized area.

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Anna: The samples Perseverance has collected are

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still sealed in its sample tubes, waiting for

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a future Mars sample return mission to bring

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them back to Earth. When they arrive in a

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laboratory, scientists will be able to run

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tests orders of magnitude more

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sophisticated than anything a rover

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instrument can perform. That's when the real

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detective work begins.

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Avery: Microlensing works by detecting the tiny

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brightening of a background star when a

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foreground star and any orbiting planets pass

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in front of it. Acting as a gravitational

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lens. It's a powerful technique for finding

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cold, distant planets that are otherwise

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invisible. And to do it, you need an

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incredibly crowded starfield, which, as it

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turns out, is exactly what the galactic bulge

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provides.

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Anna: The Euclid Image already contains

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51 known planetary systems.

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Scientists expect it will also help confirm

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and measure the masses of around 60

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previously detected but poorly characterized

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exoplanets. And when Roman comes online

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and begins repeatedly monitoring the same

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field, the two data sets together will give

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us the most complete picture yet. Yet of how

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many planets exist throughout the galaxy.

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Avery: For Australian and Southern Hemisphere

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listeners, you're in an ideal position to see

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the galactic center in the night sky. Right

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now, it's high in the winter sky in the

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constellation Sagittarius. And under dark

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skies, away from city lights, you can see the

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glow of the bulge. With your naked eye,

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you're looking at the very region Euclid just

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photographed.

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Now, a story about endings and the

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complications that come with them. The

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International Space Station has been

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continuously inhabited for more than 24

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years. It's hosted astronauts from 22

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countries, conducted thousands of

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experiments, and served as humanity's

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permanent foothold in low Earth orbit. But

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its time is running out, and NASA's plan for

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how to retire it is now under scrutiny from

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some unexpected quarters.

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Anna: The plan, in brief, is

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starting in 2028, the ISS will

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begin a, uh, gradual orbital lowering.

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In mid-2029, NASA will launch

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a SpaceX built in deorbit

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vehicle and attach it to the station.

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That vehicle, fitted with 46

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Draco thrusters, will then push the

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entire structure out of orbit in a

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controlled re entry, targeting a

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splashdown in the remote South Pacific,

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near a location called Point Nemo.

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Avery: Point Nemo is the most isolated spot on the

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planet, more than 2,600 km

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from the nearest land. It's already known as

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a spacecraft cemetery. Russia's Mir station

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ended its days there, along with hundreds of

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other spacecraft. NASA chose it precisely

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because it minimizes the risk to any human

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population. But a leading ocean conservation

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organization says that calculation misses

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something important.

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Anna: The Ocean foundation based in Washington

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D.C. says the deorbit plan, and

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I'm quoting, raises serious concerns for

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ocean health that the space community has not

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adequately grappled with. The organization's

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president Mark Spalding, says there is a

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quote, troubling structural gap in

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international law that the ISS de orbit

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throws into sharp relief.

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Avery: The legal gap he's referring to is this.

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The 1972 Space Liability

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Convention requires that if a country's space

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debris falls on another nation's territory or

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damages another nation's property, the

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launching country must pay compensation.

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But international waters and the ocean floor

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beneath them, um, are not a nation's

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territory. There's no equivalent protection

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for the deep sea.

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Anna: And this isn't a small amount of debris.

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The ISS weighs roughly

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450,000 kilograms.

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While much of the structure will burn up

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during re entry, denser heat resistant

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components, including pressurized modules,

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structural beams and hardware are expected

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to survive and reach the seafloor. The

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exact quantity and composition of what will

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sink is, according to critics,

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insufficiently studied.

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Avery: The concerns have now drawn the attention of

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the U.S. government Accountability Office,

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which has issued a report highlighting the

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issues. The Ocean foundation is calling for

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NASA to conduct a full environmental impact

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assessment before proceeding with the re

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entry, currently planned for around 2030 to

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2031. There's still time, but not

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unlimited time to address these questions.

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Anna: It's a fascinating tension. The very

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success of the ISS program, the

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sheer scale of the structure humanity built

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up there is now what makes disposing of

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it so complicated. And this case,

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as legal experts have noted, is likely to

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set precedents for how we handle the growing

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number of much larger orbital platforms

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expected in the coming decades.

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Moving on to our next story. Today,

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66 million years ago, a 10

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kilometer wide asteroid slammed into

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what is now the Yucatan Peninsula of

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Mexico with a force equivalent to

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billions of nuclear weapons. The

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impact triggered Megatsunami, a uh,

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global firestorm and a years long

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impact winter that blotted out the sun

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and wiped out roughly three quarters of

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all species on Earth, including

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every non avian dinosaur. It

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is the most studied extinction event in

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history.

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Avery: But new research from the University of

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Glasgow has uncovered a remarkable footnote

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to that catastrophe. While the surface of the

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Earth was plunged into darkness and death

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underground in the shattered rocks beneath

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the crater, life may have found a way,

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and not just briefly. The new study suggests

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it found the way for 8 million years.

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Anna: The Chicxulub crater, the scar left by

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that asteroid is buried beneath layers of

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sediment and ocean in the Gulf of Mexico.

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But it still spans nearly 200

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km in diameter. When the asteroid

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hit, the immense heat it generated

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fractured the bedrock and superheated water

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trapped in the rock, creating a vast

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hydrothermal system beneath the crater.

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A network of hot water flowing through

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porous shattered rock.

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Avery: Hydrothermal systems like this are well known

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on Earth at, uh, mid ocean ridges and

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volcanic vents. They host entire ecosystems

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of organisms that live completely

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independently of sunlight. Bacteria,

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tube worms, crabs, and more, all

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powered by chemical energy from the Earth's

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interior. The question for scientists has

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always been, how long did Chicxulub's version

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of this system survive?

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Anna: Previous estimates based on computer models

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from the early 2000s suggested about 2

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million years. The new study, led by Dr. Ann

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Marie Pickerskill of the Scottish

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University's Environmental Research center,

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used advanced argon. Argon dating of

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potassium rich feldspar crystals collected

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during a 2016 drilling expedition to the

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crater's peak ring. The result? The

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system remained active for at least 8 million

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years, four times longer than anyone had

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previously estimated, and the longest impact

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generated hydrothermal system ever

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documented.

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Avery: To be clear, this doesn't mean complex life

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was thriving underground while the dinosaurs

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went extinct. Above, we're talking about

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microbial life, bacteria and other

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microorganisms sheltering in the warm,

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chemically rich porous rock, shielded from

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the radiation and temperature extremes at the

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surface. But even that is extraordinary,

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and the

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Anna: implications extend beyond Earth.

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Mars has endured countless asteroid impacts

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over its history and may have once had liquid

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water. If the same dynamics applied there,

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and there's no reason to think they wouldn't

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then. Even as Mars became cold and dry on the

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surface, underground hydrothermal systems

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could have kept microbial life viable for

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millions of years. The Chicxulub finding

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makes that possibility more credible than

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ever.

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Avery: We close today with a story that's part

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astronomy, part cosmic detective work.

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And we'll admit it a little bit poetic.

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Somewhere between 4,000 and 5,000 light years

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away, in the constellation Gemini, there's a

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supernova remnant called

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IC443.

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Astronomers gave it a more evocative nickname

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long ago, the Jellyfish Nebula, for its

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billowing tentacle like filaments of glowing

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gas.

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Anna: It's one of the most photographed nebulae in

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the sky, a favorite of astrophotographers the

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world over. Its soft, wispy tendrils of

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light are, uh, the expanding shockwave from a

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star that died in a spectacular explosion

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somewhere between 3,000 and 30,000 years ago.

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It's beautiful. It's well studied, and

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astronomers thought they knew it well.

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Avery: But new research has revealed that the

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Jellyfish Nebula has been hiding something.

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Lurking right there in the bright glare of

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the Jellyfish itself, Barely visible against

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it, is a second supernova remnant connected

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to IC443 by a bright

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filament of gas. Astrophysicists are

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calling this the first. First confirmed pair

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of sibling supernova remnants ever

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identified.

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Anna: Two massive stars, born from the same cloud

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of gas and dust, lived out their lives in

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relative proximity, and then both died in

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supernovae, leaving behind these two glowing,

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expanding shells of debris. The fact that

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their remnants are still connected by that

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filament of gas tells us the two explosions

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happened close enough in space and time to

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interact with one another.

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Avery: What makes the discovery particularly

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striking is not just what was found, but

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where it was hiding. The second remnant had

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been there all along, but the Jellyfish

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Nebula's own brightness had been obscuring

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it, like trying to see a faint star right

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next to the Full Moon. It took careful

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analysis to disentangle the two structures

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and recognize the second for what it was.

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Anna: It's a reminder that even some of the most

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familiar objects in the sky can still

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surprise us. That even after decades of

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observation, the universe has a habit of

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tucking secrets away in plain sight,

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waiting for us to look a little more

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carefully.

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Avery: And for observers in Australia and New

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Zealand, the Jellyfish Nebula is in Gemini,

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which sits low on the northern horizon in

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winter evenings. While the nebula itself

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requires a telescope, it's a wonderful target

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for astrophotographers. And now, when you

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photograph it, you can tell people you're

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looking at two nebulae for the price of one.

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Anna: And that's our universe for today. An

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ancient interstellar traveler, older than the

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Sun. The strongest hint yet that Mars once

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had the chemistry for life. The most detailed

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portrait ever made of our galaxy's crowded

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heart. The ISS's complicated

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farewell. A crater that kept life burning

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Underground for 8 million years, and a, uh,

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nebula that turned out to be twins.

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Avery: The universe keeps delivering. Make sure you

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subscribe so you never miss an episode.

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Anna: And subscribe.

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Avery: And if today's show sparked something for

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you, leave us a review. It genuinely helps

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the show reach more

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Anna: listeners, find us at astronomydaily

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IO Follow us Astrodaily Pod on

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00:18:06.200 --> 00:18:08.320
all your socials, and we'll see you right

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back here tomorrow.

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Avery: Until then, keep looking up.