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October 15, 2025 23 mins
In this episode of SpaceTime, we explore groundbreaking discoveries that reshape our understanding of Mars, the Moon, and the Milky Way Galaxy.
Ancient Oceans on Mars: Geological Evidence Revealed
A new study published in the journal Geophysical Research Letters presents compelling geological evidence that Mars' Northern Hemisphere was once home to a vast ocean. Lead author Chris from the University of Arkansas discusses how comparisons between river rocks on Earth and Martian sediment reveal ancient river deltas and backwater zones, suggesting that liquid water flowed on the Red Planet, increasing the possibility of past life. This episode delves into the processes of sedimentation and erosion that shaped Mars' landscape, providing insights into its watery past.
The Moon's South Pole-Aitken Basin: Unveiling Impact Mysteries
A fresh analysis of the Moon's largest impact crater, the South Pole-Aitken Basin, sheds light on its formation and the Moon's geological history. Researchers have discovered that this massive crater's shape indicates an impact from the north, challenging previous assumptions. As the Artemis missions prepare to land near this basin, they will have the opportunity to study material excavated from the lunar interior, potentially unlocking secrets about the Moon's evolution and the asymmetries in its crust.
Nancy Chris Roman Space Telescope: Mapping the Milky Way
NASA's upcoming Nancy Chris Roman Space Telescope is set to revolutionise our understanding of the Milky Way's interstellar medium. This mission will map around 20 billion stars, using infrared light to penetrate the dust clouds obscuring our view. Chief investigator Catherine Zucker explains how this data will refine our models of star formation and the galaxy's structure, while also addressing the ongoing mysteries of galactic spiral patterns and their role in star birth.
www.spacetimewithstuartgary.com
✍️ Episode References
Geophysical Research Letters
https://agupubs.onlinelibrary.wiley.com/journal/19448007
Nature
https://www.nature.com/nature
NASA Nancy Chris Roman Space Telescope
https://roman.gsfc.nasa.gov/
Become a supporter of this podcast: https://www.spreaker.com/podcast/spacetime-your-guide-to-space-astronomy--2458531/support.
Ancient Oceans on Mars: Geological Evidence Revealed
The Moon's South Pole-Aitken Basin: Unveiling Impact Mysteries
Nancy Chris Roman Space Telescope: Mapping the Milky Way
(00:00) Evidence of ancient oceans on Mars
(10:15) New insights into the Moon's largest impact crater
(19:30) The upcoming Nancy Chris Roman Space Telescope mission
(27:00) Science Robert: Heatwaves and their impact on global mortality
Mark as Played
Transcript

Episode Transcript

Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:00):
This is Spacetime Series twenty eight, Episode one hundred and
twenty four, for broadcast on the fifteenth of October twenty
twenty five. Coming up on space Time, high seas on
the Red planet Mars, a new analysis of the largest
impact crater on the Moon, and a new mission by
NASA to study the Milky Way Galaxy's interstellar medium. All

(00:21):
that and more coming up on space Time.

Speaker 2 (00:25):
Welcome to space Time with Stuart Gary.

Speaker 1 (00:45):
A new study has provided fresh geological evidence that the
Martian northern hemisphere was once home to a vast ocean.
Billions of years ago water flowed across the Martian surface.
There's plenty of evidence a bouth observation and geological that
the Red planet once had rivers feeding into lakes and
larger bodies of water, But did those rivers ever flow

(01:07):
into an actual ocean From aorbit, There's clear evidence of
what appeared to be seashores, beaches, and river deltas flowing
to what once was a huge northern hemisphere ocean. And
now a new study reported in the journal Geophysical Research Letters,
has found more strong evidence in Martian geology that an
ocean once existed in the planet's northern Hemisphere. The stadi's

(01:30):
lead author, Corey Hughes from the University of Arkansas, says,
there are no known life forms that can survive without
liquid water, so finding evidence that liquid water once existed
on the Red planet increases the possibility that life might
also once have existed there. To better understand the geology
of ancient rivers, using colleagues compared river rocks on Earth

(01:51):
to rocks on Mars, including sandstone created by a river
that once flowed across northwestern Arkansas some three hundred million
years ago. Hugh says, you need to imagine a river
with no human built levees or dams to constrain its course.
That river would shift constantly like a ribbon snaking across
the landscape.

Speaker 3 (02:11):
You see.

Speaker 1 (02:11):
Rivers carry sediments like silk, clay, and rocks. These sediments
eat away at one side, causing the river to curve
in that direction, while at the same time depositing sand
and fine dirt on the opposite side. The region that
defines how far a river shifts from side to side
over time is called a channel belt. Also, a river
slows down as it approaches an ocean, which is a massive,

(02:34):
comparatively still body of water. As a river's flow velocity decreases,
it carries less sediment, so the solid matter starts to
fall out a suspension, creating a river delta and with
less sediment to erode its banks. A river's movement from
side to site also decreases. In other words, the channel
belt narrows as the river approaches an ocean. This section

(02:57):
where the river belt narrows and the river bed d
below sea level is called the backwater zone. The backwater
zone of a river flowing into an ocean is long.
In the case of the Mighty Mississippi River, for example,
the backwater zone begins to Ea Baton Rouge that's some
three hundred and seventy kilometers from the Gulf coast. Looking
at Mass from orbit, Hughes found geological evidence of ancient

(03:19):
river backwater zones on the Red planet. Is described that
as a large scale process, which is why he was
able to see it so clearly from space. The presence
of river deltas with long backwater zones provide strong evidence
that large rivers once float on Mars, and they emptied
it into an ocean before the surface of the Red
planet dried up. Bedans of years ago. Hugh says these

(03:41):
were very mature deltas a strong point in favor of
an ancient ocean or at least a very large sea. Now,
as rivers flow, gravity pulls the coarsest grains to the
bottom of the river bed. If the river eventually dries
up that course, sediment's buried, and over time, due to
heat and pressure, that sediment of eventually becomes sandstone. On Earth,

(04:03):
shifting tectonic plots will push that rock to the surface,
and then wind and rain will erode everything but the
coarse channel bed itself, leaving behind a sort of ridge
where the channel used to be. This process is known
as topographic inversion. When a ridgetop is composed of sandstone
that used to be at the bottom of a river,
it's called an inverted channel belt or an inverted ridge. Now,

(04:26):
Mars doesn't have tectonic plates like the Earth, so its
inverted ridges were likely formed when finer deposits around the
sandstone were eroded, and it's those inverted ridges on Mars
which provide strong evidence of long vanished rivers. It's part
of their research using colleagues studded the Weddington Sandstone, a
rock formation found across much of northwestern Arkansas. They realize

(04:50):
that stone cliffs are all part of a branching network
of inverted ridges formed by a three hundred million year
old river that once ran from modern day Indiana through
to the sea that central Arkansas. Scientists have learn about
the process of topographic inversion for thirty to forty years now,
but in northwestern Arkansas, the authors discovered the only known
example of an inverted river delta on planet Earth, and

(05:13):
that discovery has helped them identify oceans on Mars. This
is space time Still to come, a new analysis of
the largest impact crater on the Moon, and a new
mission to study the Milky Way galaxies interstellar medium. All
that and more still to come on space time. A

(05:48):
new analysis of the largest impact crater on the Moon
may help astronomers solve some of the biggest long standing
mysteries of how Earth's only natural satellite came to be.
The findings mean that when the Artamus cruise land at
the Moon's south pole in two years time, they're likely
find themselves with a treasure trove of clues that could
help scientists better understand how Earth's only natural satellite evolved.

(06:12):
The Earth's Moon was created some four and a half
billion years ago when a Mars sized planet slammed into
the early proto Earth, melting both bodies into a mag morosi,
which eventually differentiated and solidified to form the Earth as
we know it today. Meanwhile, malton ejected debris from that
impact was thrown high into orbit, gradually accreting to form

(06:33):
the Moon now. A report in the journal Nature is
providing a snapshot of the Moon's tumultuous past, one which
could help explain long standing puzzles, such as why the
Moon's crater riddle far side is so dramatically different from
its smooth knee side, which provided the backdrop for the
Apollo moon landings in the nineteen sixties and seventies. Roughly

(06:54):
four point three billion years ago, when the Solar System
was still in its infancy, a giant asteroid so It's
slammed into the fart side of the Moon, blasting at
an enormous crater known today as the South Pole at
con Basin. This massive impact feature is the largest crater
on the Moon, spanning almost two thousand kilometres north to south,
over sixteen hundred kilometa is east to west. It's thought

(07:17):
the oblong shape of the basin is the result of
a glancing blow rather than a head on impact. By
comparing the shape of the South Pole Acin Basin to
other giant impact basins across the Solar System, the authors
found that these features tend to get narrow and the
downrange direction forming a shape resembling a tear drop. Up
Ending conventional wisdom that the South Pole Acin basin was

(07:39):
formed by an asteroid coming in from a southerly direction,
the new analysis reveals that it shape narrows towards the south,
indicating an impact coming in from the north. The stadi's
lead author, Jeffrey Andrews Hannah from the University of Arizona,
says the downrange and of the basin should be covered
by a thick layer of material excavated from the lunar
interior by the impact, while the up range end should not.

(08:03):
He says it means that the Artemis missions will be
landing on the downrange rim of the basin, the best
place to study the largest and oldest impact basin on
the Moon, where most of the ejector material from deep
within the lunar interior should be piled up. It means
the location will provide new clues about the interior structure
of the Moon and its evolution through time. It had

(08:24):
long been thought that the early Moon was melted by
an energy released through its formation, creating a magma ocean
covering the entire body. As the magmaotion, crystallized, heavy minerals
sun to make the lunar mantle, while lighter materials floated
up to make its crust. However, some elements were excluded
from the solid mantel and crust and instead became concentrated

(08:46):
in the final liquids of the magma ocean. Andrews Hannah
says these leftover materials included potassium, rare earth elements, and phosphorus,
collectively referred to its creep, the achronism's first letter being K,
referreding potassium symbol in the periodic table of elements. These
elements are especially abundant on the lunary side. Andrews Hannah says,

(09:08):
if you've ever left the cannis soda in the freezer,
you may even noticed that the water becomes solid first.
The high fructose corncipt resists freezing until the very end
and instead becomes concentrated in the last bits of liquid.
He says something similar must have happened on the Moon
with creep As it cooled over many millions of years,
the magma osian gradually solidified into the crust and mantle,

(09:32):
and eventually you get to a point where you just
have a tiny bit of liquid left sandwiched between the
matal and the crust, which is the creep rich material
or the creep rich material and heat producing elements somehow
became concentrated on the lunarar side, causing it to heat
up and leading to the intense volcanism that formed the
dark volcanic planes that make up that familiar sight of

(09:53):
the so called face of the Man on the Moon. However,
the reason why the creep rich material ended up only
on the knee side and how that material evolved over
time has long been a mystery. Also a mystery is
why the Moon's crust is so much thicker on its
far side than its near side facing the Earth. It's
an asymmetry known as lunar dichotomy, which is still posing

(10:16):
a puzzle for scientists today, and this dichotomy affected all
aspects of the Moon's evolution, including the later stages of
the magma ocean. ANDREWS. Hannering colleagues think that as the
crust thickened on the lunar far side, the magma ocean
below it was squeezed out on the sides, sort of
like toothpaste being squeezed out of a tube, until most

(10:36):
of it ended up on the knee side. The new
study revealed a striking unexpected asymmetry around the basin, which
supports this hypothesis. Interestingly, the ejective blanket on the western
side is rich in radioactive thorium, but not on its
eastern flank, and this suggests that the gash left by
the impact created a window through the Moon's skin right

(10:58):
at the boundary separating the crust under lane by the
last remnants of the creep enriched magma ocean from the
regular crast. So the last dregs of the lunar magma
ocean ended up on the knees side, where one sees
the highest concentrations of radioactive elements. But at some earlier
time a thin patulayer of magma ocean would have existed

(11:18):
blow parts of the farst side of the Moon, explaining
the radioactive ejector on only one side of the South
Pole a can impact basin this space time Still to
come a new mission to study the Milky Way Galaxies
interstellar medium, and later in the Science report, a new
study claims the unprecdered heat waves of twenty twenty three

(11:39):
contributed to over one hundred and seventy eight thousand excess deaths.
All that and more still to come on space time.

(12:02):
NASA says its new Nancy Grace Roman Space Telescope we
at astronomers better understand the Milky Way Galaxies interstellar medium,
that is, the dust and gas between stars, known as
the Galactic Plane's Survey. The project will peeer through our
galaxy to its most distant edge, mapping roughly twenty billion stars,
about four times more than have currently been mapped. Astronomers

(12:25):
will use data from these stars to study and map
the dust their light travels through, contributing to the most
complete picture yet of the Milky Way structure, star formation,
and the origins of our solar system. One of the
mission's chief investigators, Katine Zuka, from the Harvard and Smithsonian
Center for Astrophysics, says that with Roman, astronomers will be

(12:46):
able to turn existing artist's conceptions of the Milky Way
into more data driven models using new constraints the three
dimensional distribution of interstellar dust. Scientists know what our galaxy
looks like by comparing observations of the Milky Way with
that of other spiral galaxies. The problem is clouds of
dust and gas make it hard to work out details

(13:08):
on the opposite side of our galaxy. It's a bit
like trying to map your neighborhood while looking through the
windows of a house surrounded by dense fog. Roman will
see through the fog of dust and gas using a
specialized camera that filled us observed infrared light. Light with
longer wavelengths than what our eyes can detect. Infra red
lights more likely to pass through dust clouds without scattering.

(13:30):
You see light with shorter wavelengths, including blue light produced
by stars, is more easily scattered. That means that stars
shining through dust appear dimmer and redder than what they
actually are. By comparing the observations with information on the
sauce stars characteristics, astronomers can disentangle a star's distance from
how much its colours have been reddened, and stating these

(13:52):
effects also reveals clues about the dust's properties. Scientists will
also learn about the dust composition and probe clouds to
investigate the physical processes behind changing dust properties. Clues in
dust influenced starlight hint at the amount of dust between
us and a star, and piecing together results from many
stars will allow astronomers to construct a detailed three dimensional

(14:15):
dust map. This would enable scientists like Zuka to create
a model of the Milky Way, which will show us
how it looks from the outside. Then scientists can better
compare the Milky Way with other galaxies that we only
observe from the outside, slotting it into a cosmological perspective
of galaxy evolution. Zucker says Roman will add a whole
new dimension to our understanding of galaxies because we'll see

(14:39):
billions and billions more stars. The thing is, the interstellar
medium does more than just mill around the Milky Way.
It fuels star and planet formation. Dense blobs of the
interstellar medium form the molecular gas and dust clouds, which
can then gravitational collapse, triggering new star formation. At the
same time, young stars hot winds that can cause surrounding

(15:02):
dust to clump together, forming planetary building blocks. The Roman
Space Telescope will identify young clusters of stars in new
distance star forming regions, as well as contribute data on
stellar nurseries previously identified by missions like NASA's now retired
Spits of Space Telescope. Zuker says, if you want to
understand star formation in different environments, you need to have

(15:24):
understood the interstellar medium that seeds it. Roman will allow
astronomers to link the three dimensional structure of the interstellar
medium with the three dimensional distribution of young stars right
across the galaxy's disc. The dust maps will refine sciences
understanding of the Milky Way spiral structure. The pin will,
like patent with stars, gas and dust tend to bunch

(15:46):
up like galactic traffic jams. By combining velocity data to
dust maps, scientists will compare observations with predictions from models
to help identify the causes of the spiral structure is
currently unclear. In fact, the very role that spiral patterns
play in star formation also remains uncertain. Some theories suggest

(16:06):
that galactic congestion triggers star formation, while others contend that
these traffic jams gather material but don't stimulate starbirth. The
Roman Space Telescope will help solve mysteries like these by
providing more data on dusty regions right across the Milky
Way galaxy. That'll enable scientists to compare numerous galactic environments
and steady starbirth in specific locations like the galaxies winding

(16:30):
spiral arms or at central Stellar bar. ROMAN is stated
to launch no later than May twenty twenty seven, with
a team working towards the potential earlier launch date, possibly
as soon as the middle of next year. Needless to say,
we'll keep you informed this report from Nasser TV.

Speaker 4 (16:51):
Astronomers around the world are working together to plan observations
for NASA's upcoming Nancy Griefs Roman space Telescope. The Galactic Play,
roman's first general astrophysics program proposed by the community, promises
to reveal the Milky Way in unprecedented detail. The Milky
Way is our home in the universe, and there's still

(17:12):
so much to explore. Roman pairs the high resolution capabilities
of the Hubble Space Telescope with the field of view
two hundred times larger, and it is able to efficiently
survey the sky a thousand times faster. The survey will
capture our Milky Way galaxy across the span of its
plane and also go deeper to map the far side

(17:34):
of the galaxy, which is largely unknown territory. ROMAN will
help astronomers fill in missing puzzle pieces in our picture
of the Milky Way, and its huge archive of data
will be immediately available for any researcher to access, allowing
for transformative new research for decades to come. With ROMAN,
astronomers will get a much better census of stars for

(17:56):
reconstructing the history of our galaxy how did we get here?
Future ROMAN surveys that will be developed by the astronomy
community will explore additional ways to push roman's unique capabilities
to explore our biggest questions, including those we haven't yet
thought to ask.

Speaker 1 (18:15):
This is space, time and time that would take another
brief look at some of the other stories making us

(18:35):
in science this week with a science report, A new
study claims the unprecedented heat waves that hit the world
in twenty twenty three contributed to some one hundred and
seventy eight thousand, four hundred and eighty six excess deaths,
more than half of which can be directly attributed to
man made climate change. The study reported in the journal
Innovation Use climate mortality data from around the world to

(18:58):
estimate how many people globally been historically dying each year
as a result of heat waves and how many deaths
in twenty twenty three were heatwave related. They found that
fifty four point two nine percent of all twenty twenty
three heat related deaths were attributable to man made climate change,
with southern, Eastern and Western Europe seeing the highest mortality

(19:20):
rates that year. Predatory fish that evolved in the first
terrestrial animals on Earth are still now revealing insights into
the origins of mammals, including new research into the eating
habits of lobe finfish, which inhabited an ancient reef in
what is now northern Australia. The new research, reported in

(19:41):
the journal Eye Science, provides fresh insights into the lives
of three hundred and eighty million year old lungfish. The
research by Flinders University involved a high tech examination of
remarkably well preserved jaw bones which were found in the
remote Gogo fossil field of northern western Australia. Scientists have

(20:01):
developed a new laser based dating technique for measuring the
age of dinosaur eggs. The findings reported in the journal
Frontiers in Earth use carbonate uranium lead dating to find
that eggs from Central China were laid in the Late
Cretaceous period around eighty five million years ago. Until now,
dating dinosaur eggs has always been difficult. Available methods are limited,

(20:24):
prone to errors because of measurement proxies such as volcanic
rocks or crystals, which may have changed between egg laying
and dating attempts. The authors say using the new method,
which involves firing lasers at eggshells, could all researchers learn
more about dinosaur populations and the climate millions of years ago.
In case you haven't noticed it yet, the EESIM is

(20:46):
the latest technological innovation. Aesims are digital built in sim
cards that eliminate the need for a physical plastic card,
allowing you to activate a sulfur or tablet plant simply
by downloading it onto a small chipm better in your
device YEA he stands for embedded any. Sims offer flexibility
in security, enabling you to easily switch between carriers, add

(21:09):
modible phone numbers to a single device, and activate plants
remotely simply by scanning a QR code with the details
which you want by Technology to Alex Haharovrot from take advice,
do lie.

Speaker 3 (21:20):
And this is where you can get a SIM that's electronic,
it's not physical, and you can now buy these. You
can buy them with twenty gig of data, you can
buy them with five or ten. You can buy them
with seven days, two weeks a month, ninety days, three
hundred and sixty five days of validity. They work depending
on how much data you have and how much have used.
And if you get them with phone calls and you
get them for a year's access for example, well you'll

(21:42):
pay a lot for that. But you can have a
SIM that just sits in your phone without interfering with
your physical SIM slot. And I've been using an e
sym that gave me global access. I got it for
a year with twenty gigabytes to cost me about eighty
seven dollars Australian and I've used about fourteen to fifteen
gigabytes and i still have plenty for the trip. But
this has become a very easy way of being connected
and not having to worry about getting somewhere using the

(22:04):
physical SIM, handing over your passport and filling with little
SIM card dejector tools it's eSIM is the in thing,
and I'm using an iPhone Air as you speak right now.
It doesn't even have a physical SIM slot, so I
have to use an eesim. I've got one from my
provider at home, but I've gotten one for global travels
and it's fantastic. You'll probably use one on your next
overseas trip.

Speaker 1 (22:24):
That's Alex aharav Rout from Tech Advice to out Live
and that's the show for now. Space Time is available

(22:46):
every Monday, Wednesday and Friday through Apple Podcasts, iTunes, Stitcher,
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Time's also broadcast through the National Science Foundation, on Science

(23:08):
Own Radio and on both iHeartRadio and tune in Radio.
And you can help to support our show by visiting
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(23:32):
Just go to space Time with Stewart Gary dot com
for full details.

Speaker 2 (23:37):
You've been listening to space Time with Stuart Gary. This
has been another quality podcast production from bytes dot com
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