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
powered by chemical energy from the Earth's
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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back here tomorrow.
Avery: Until then, keep looking up.