Ancient Comet Shatters Time Records, Mars' Life Signs Intensify, and the ISS Faces Controversial Farewell

Anna: From the farthest reaches of the galaxy to

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

Astronomy Daily, your daily briefing on, um,

the universe. I'm Anna.

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

interstellar comet has just revealed it's

older than our sun by billions of years.

Perseverance scores its most impressive

organic detection yet on Mars. And

Europe's dark matter detective turns its gaze

to the heart of our own galaxy and delivers

the most stunning portrait ever made.

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

the world's largest space station into the

Pacific Ocean, raising some very pointed

questions. Plus, an asteroid that killed the

dinosaurs may have kept underground life

burning for 8 million years. And

astronomers have just found that a, uh,

famous nebula has a long lost twin

sibling.

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

2026, and this is Astronomy

Daily.

Anna: We start today with one of the most

remarkable findings in the short but

extraordinary history of interstellar

astronomy. The comet known as 3i

Atlas, which swept through our solar system

last year and captured the imagination of

scientists worldwide, has now revealed

something almost impossible to wrap your head

around. This comet is older than our Sun.

Avery: Much older, potentially. Two new papers

published in the journal Nature this week,

using data from NASA's James Webb Space

Telescope, report that 3i

Atlas carries a chemical fingerprint unlike

anything found in our own solar system. And

that fingerprint points to an origin between

10 and 12 billion years ago.

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

4 1/2 billion years old. So this

comet may have been drifting through the

galaxy for more than twice the lifetime of

our entire Sol solar system before it

happened to pass through our neighborhood.

Avery: The key evidence comes from isotopes,

specifically the ratio of two forms of carbon

and a type of water molecule called semi

heavy water, in which some of the hydrogen

atoms carry an extra neutron.

Astronomers using Webb's near infrared

Spectroscope found that 3i Atlas

has far less carbon 13 relative to

carbon 12 than anything in our solar system.

And carbon 13 builds up in the universe over

time as successive generations of stars are

born, live, and explode. Less carbon

13 means an older origin, one from

a time before many stars had even had the

chance to die.

Anna: The semi heavy water signature is equally

telling. That kind of water tends to form in

high radiation environments, cold,

massive star forming regions that were far

more common in the early universe. And taken

together, the Webb team concludes this comet

formed during what astronomers call cosmic

noon, when star formation across the universe

was at its absolute peak.

Avery: Lead researcher Martin Cordiner of NASA's

Goddard Space Flight center described it as a

unique opportunity to study an ancient object

from the distant galaxy, probably predating

our sun and solar system. His words. On

one hand, we get direct insight into that

distant time and place, and on the other, we

learned something about how our own solar

system may be.

Anna: A companion study from the European Southern

Observatory's Very Large Telescope found

complementary evidence in the comet's carbon

and nitrogen isotope ratios, further

cementing the picture of an ancient, cold,

alien origin. 3i

Atlas, it seems, is a genuine relic from

another era of the universe

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

comet is now departing our solar system,

never to return. But the data it's left

behind will be studied for years, perhaps

decades.

Anna: We stay in the realm of ancient chemistry,

but this time a little closer to home, just

40 to 250 million km

away, depending on where Mars and Earth

happen to be in their orbits. NASA's

Perseverance rover has just delivered what

scientists are calling the most robust

organic detection made in Jezero Crater.

A new study published in Science Advances

reports that the rover's SHERLOCK instrument,

a laser based spectrometer on the end of the

robotic arm, has detected complex

macromolecular carbon in two mudstone

rocks at a site called Bright angel in an

ancient river valley called Neretva

Vallis.

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

I'm quoting, the most robust organic

detection in Jezero Crater. That thus far

and the only detection of macromolecular

carbon on a natural rock surface on Mars.

That's macromolecular, meaning large,

complex carbon based molecules, the kind that

on Earth are associated with biology. But we

need to be careful here.

Anna: Absolutely. The researchers are very clear

that detecting organic carbon on Mars

does not mean life. The SHERLOCK instrument

cannot distinguish between carbon produced by

biology and carbon produced by geology

or delivered by meteorites. What it can

do is show that the chemical ingredients were

there, and in this case, they were there in

abundance. Hundreds of individual

detections across just two rocks.

Avery: What makes this particularly compelling is

the location these mudstones are at. Bright

angel connected to Naret Va Vallis, the

ancient river channel that fed Jezero

Crater's western delta billions of years ago.

This was a water rich environment, exactly

the kind of place where on Earth you would

expect to find microbial sheltering in

sediment.

Anna: One of the two rocks examined is the now

famous Chayava Falls, the very rock

that caused such excitement last year with

its distinctive leopard spot markings.

Finding complex macromolecular carbon in

it adds yet another Intriguing layer to the

mystery. The other rock showed organic

carbon associated with carbonate and sulfate

minerals, both of which can be connected to

biological processes.

Avery: The researchers also note this is the first

detection of this type of complex carbon in a

mudstone on Mars outside of Gale Crater,

where the Curiosity rover operates more than

three and a half thousand kilometers away.

That suggests the conditions that allowed

organics to form and survive may have been

widespread across Mars, not just in one

localized area.

Anna: The samples Perseverance has collected are

still sealed in its sample tubes, waiting for

a future Mars sample return mission to bring

them back to Earth. When they arrive in a

laboratory, scientists will be able to run

tests orders of magnitude more

sophisticated than anything a rover

instrument can perform. That's when the real

detective work begins.

Avery: Microlensing works by detecting the tiny

brightening of a background star when a

foreground star and any orbiting planets pass

in front of it. Acting as a gravitational

lens. It's a powerful technique for finding

cold, distant planets that are otherwise

invisible. And to do it, you need an

incredibly crowded starfield, which, as it

turns out, is exactly what the galactic bulge

provides.

Anna: The Euclid Image already contains

51 known planetary systems.

Scientists expect it will also help confirm

and measure the masses of around 60

previously detected but poorly characterized

exoplanets. And when Roman comes online

and begins repeatedly monitoring the same

field, the two data sets together will give

us the most complete picture yet. Yet of how

many planets exist throughout the galaxy.

Avery: For Australian and Southern Hemisphere

listeners, you're in an ideal position to see

the galactic center in the night sky. Right

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

constellation Sagittarius. And under dark

skies, away from city lights, you can see the

glow of the bulge. With your naked eye,

you're looking at the very region Euclid just

photographed.

Now, a story about endings and the

complications that come with them. The

International Space Station has been

continuously inhabited for more than 24

years. It's hosted astronauts from 22

countries, conducted thousands of

experiments, and served as humanity's

permanent foothold in low Earth orbit. But

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

how to retire it is now under scrutiny from

some unexpected quarters.

Anna: The plan, in brief, is

starting in 2028, the ISS will

begin a, uh, gradual orbital lowering.

In mid-2029, NASA will launch

a SpaceX built in deorbit

vehicle and attach it to the station.

That vehicle, fitted with 46

Draco thrusters, will then push the

entire structure out of orbit in a

controlled re entry, targeting a

splashdown in the remote South Pacific,

near a location called Point Nemo.

Avery: Point Nemo is the most isolated spot on the

planet, more than 2,600 km

from the nearest land. It's already known as

a spacecraft cemetery. Russia's Mir station

ended its days there, along with hundreds of

other spacecraft. NASA chose it precisely

because it minimizes the risk to any human

population. But a leading ocean conservation

organization says that calculation misses

something important.

Anna: The Ocean foundation based in Washington

D.C. says the deorbit plan, and

I'm quoting, raises serious concerns for

ocean health that the space community has not

adequately grappled with. The organization's

president Mark Spalding, says there is a

quote, troubling structural gap in

international law that the ISS de orbit

throws into sharp relief.

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

The 1972 Space Liability

Convention requires that if a country's space

debris falls on another nation's territory or

damages another nation's property, the

launching country must pay compensation.

But international waters and the ocean floor

beneath them, um, are not a nation's

territory. There's no equivalent protection

for the deep sea.

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

The ISS weighs roughly

450,000 kilograms.

While much of the structure will burn up

during re entry, denser heat resistant

components, including pressurized modules,

structural beams and hardware are expected

to survive and reach the seafloor. The

exact quantity and composition of what will

sink is, according to critics,

insufficiently studied.

Avery: The concerns have now drawn the attention of

the U.S. government Accountability Office,

which has issued a report highlighting the

issues. The Ocean foundation is calling for

NASA to conduct a full environmental impact

assessment before proceeding with the re

entry, currently planned for around 2030 to

2031. There's still time, but not

unlimited time to address these questions.

Anna: It's a fascinating tension. The very

success of the ISS program, the

sheer scale of the structure humanity built

up there is now what makes disposing of

it so complicated. And this case,

as legal experts have noted, is likely to

set precedents for how we handle the growing

number of much larger orbital platforms

expected in the coming decades.

Moving on to our next story. Today,

66 million years ago, a 10

kilometer wide asteroid slammed into

what is now the Yucatan Peninsula of

Mexico with a force equivalent to

billions of nuclear weapons. The

impact triggered Megatsunami, a uh,

global firestorm and a years long

impact winter that blotted out the sun

and wiped out roughly three quarters of

all species on Earth, including

every non avian dinosaur. It

is the most studied extinction event in

history.

Avery: But new research from the University of

Glasgow has uncovered a remarkable footnote

to that catastrophe. While the surface of the

Earth was plunged into darkness and death

underground in the shattered rocks beneath

the crater, life may have found a way,

and not just briefly. The new study suggests

it found the way for 8 million years.

Anna: The Chicxulub crater, the scar left by

that asteroid is buried beneath layers of

sediment and ocean in the Gulf of Mexico.

But it still spans nearly 200

km in diameter. When the asteroid

hit, the immense heat it generated

fractured the bedrock and superheated water

trapped in the rock, creating a vast

hydrothermal system beneath the crater.

A network of hot water flowing through

porous shattered rock.

Avery: Hydrothermal systems like this are well known

on Earth at, uh, mid ocean ridges and

volcanic vents. They host entire ecosystems

of organisms that live completely

independently of sunlight. Bacteria,

tube worms, crabs, and more, all

interior. The question for scientists has

always been, how long did Chicxulub's version

of this system survive?

Anna: Previous estimates based on computer models

from the early 2000s suggested about 2

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

Marie Pickerskill of the Scottish

University's Environmental Research center,

used advanced argon. Argon dating of

potassium rich feldspar crystals collected

during a 2016 drilling expedition to the

crater's peak ring. The result? The

system remained active for at least 8 million

years, four times longer than anyone had

previously estimated, and the longest impact

generated hydrothermal system ever

documented.

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

was thriving underground while the dinosaurs

went extinct. Above, we're talking about

microbial life, bacteria and other

microorganisms sheltering in the warm,

chemically rich porous rock, shielded from

the radiation and temperature extremes at the

surface. But even that is extraordinary,

and the

Anna: implications extend beyond Earth.

Mars has endured countless asteroid impacts

over its history and may have once had liquid

water. If the same dynamics applied there,

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

then. Even as Mars became cold and dry on the

surface, underground hydrothermal systems

could have kept microbial life viable for

millions of years. The Chicxulub finding

makes that possibility more credible than

ever.

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

astronomy, part cosmic detective work.

And we'll admit it a little bit poetic.

Somewhere between 4,000 and 5,000 light years

away, in the constellation Gemini, there's a

supernova remnant called

IC443.

Astronomers gave it a more evocative nickname

long ago, the Jellyfish Nebula, for its

billowing tentacle like filaments of glowing

gas.

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

the sky, a favorite of astrophotographers the

world over. Its soft, wispy tendrils of

light are, uh, the expanding shockwave from a

star that died in a spectacular explosion

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

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

astronomers thought they knew it well.

Avery: But new research has revealed that the

Jellyfish Nebula has been hiding something.

Lurking right there in the bright glare of

the Jellyfish itself, Barely visible against

it, is a second supernova remnant connected

to IC443 by a bright

filament of gas. Astrophysicists are

calling this the first. First confirmed pair

of sibling supernova remnants ever

identified.

Anna: Two massive stars, born from the same cloud

of gas and dust, lived out their lives in

relative proximity, and then both died in

supernovae, leaving behind these two glowing,

expanding shells of debris. The fact that

their remnants are still connected by that

filament of gas tells us the two explosions

happened close enough in space and time to

interact with one another.

Avery: What makes the discovery particularly

striking is not just what was found, but

where it was hiding. The second remnant had

been there all along, but the Jellyfish

Nebula's own brightness had been obscuring

it, like trying to see a faint star right

next to the Full Moon. It took careful

analysis to disentangle the two structures

and recognize the second for what it was.

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

familiar objects in the sky can still

surprise us. That even after decades of

observation, the universe has a habit of

tucking secrets away in plain sight,

waiting for us to look a little more

carefully.

Avery: And for observers in Australia and New

Zealand, the Jellyfish Nebula is in Gemini,

which sits low on the northern horizon in

winter evenings. While the nebula itself

requires a telescope, it's a wonderful target

for astrophotographers. And now, when you

photograph it, you can tell people you're

looking at two nebulae for the price of one.

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

ancient interstellar traveler, older than the

Sun. The strongest hint yet that Mars once

had the chemistry for life. The most detailed

portrait ever made of our galaxy's crowded

heart. The ISS's complicated

farewell. A crater that kept life burning

Underground for 8 million years, and a, uh,

nebula that turned out to be twins.

Avery: The universe keeps delivering. Make sure you

subscribe so you never miss an episode.

Anna: And subscribe.

Avery: And if today's show sparked something for

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Avery: Until then, keep looking up.

In this episode