When a private eye in a rain hammered
city wants to unravel a web of crime and
corruption, they often have one mantra.
Follow the money. In a trail of dollar
signs, ones, and zeros, provided they
are dogged enough, they usually find the
perpetrator.
When it comes to the planet Mars,
scientists have a different mantra.
Follow the water. The case they're
trying to crack is one of the coldest
cases on the books. One that has baffled
investigators for hundreds, if not
thousands of years. Did life ever arise
on Mars? And like all good
investigations, it's all about
collecting the right evidence. If water
did once flow on Mars, signatures of
life could be found in its sediments.
find the water, potentially find signs
of life. It's a good thing then that
science has set to work detective with
steel in their hearts who rarely sleep
and whose memories are literally
photographic
rovers. And today we're going to look at
the times they blew this water case wide
open.
I'm Alex Mccoan and you're watching
Astramm. Join me in this gritty supercut
because Mars is covered in a lot of
grit. For the moments, Mars rovers have
proven once and for all that water used
to flow on the Martian surface. It's
quite the story. Just don't expect a fem
fatal.
There have been six successful rover
missions on Mars, but of those, we're
going to focus on three. NASA's
Opportunity and Perseverance Rovers and
China's Zurong. So, let's take a closer
look at the first of our three rovers
going back to about halfway through its
mission. The date is the 15th of
December, 2010, 2,449
souls into Opportunity's mission to find
evidence of past oceans on Mars.
Up until this point, Opportunity had
traveled over 25 km, investigating
rocks, craters, and bedrock while
traversing sandjunes and plains. The
areas it had explored so far contained
clues that suggested that these areas
were regularly flooded by water.
Although it fell short of confirming
that a constant body of water was
present there, like an ocean,
Opportunity was now looking for
something more definitive.
Mars' harsh environment had also started
to take a toll on Opportunity with some
onboard motors failing, meaning it
couldn't stow its robotic arm away
anymore. Our persevering champion had
just arrived at Santa Maria Crater. But
for scientists, the most exciting
prospect for the mission was finally on
the horizon, a big 22 km crater where
clays had been detected by the Mars
Reconnaissance Orbiter.
Clays are significant because they are
hydrated minerals, meaning surface water
was likely to have pulled there for
lengthy periods of time. After spending
three fairly uneventful months at the
Santa Maria crater, Opportunity headed
towards the closest hill on the crater
rim known as Cape York. Along the way,
it came across a few small craters, some
of which were very young with ejector
from the impact strewn across the place.
But Opportunity didn't stay for long.
Approaching Endeavor, that's the name of
the crater, Opportunity was finally able
to see some variation in the landscape
after years of simply crossing flat
plains of sandjunes. Peaks and capes
started to rise up on the horizon as
Opportunity approached the crater rim.
On Saul 2709, Opportunity finally
arrived at Cape York and specifically a
place known as Spirit Point, named after
Opportunity sister rover that had come
to the end of its mission on the other
side of the planet only a few months
previously.
Opportunity had traveled over 30 km up
until this point, 50 times further than
the original planned mission distance.
Mission planners decided not to go into
the crater as points of interest were
again found around the rim of the
crater. Bedrock is exposed to the
surface there which allowed opportunity
to study the oldest rocks it had seen so
far on this journey.
It was also around these peaks and capes
along the rim where the hydrated
minerals or clays were detected by the
MRO.
Perched on top of Spirit Point,
Opportunity looked over Endeavor,
providing a perspective about just how
big this crater is.
From the onset, Opportunity began
discovering phenomena never before seen
on Mars. The soil found around the
area's Opportunity had thus far explored
contained countless smooth, tiny round
rocks, nicknamed blueberries. Strange
geological formations that have thus far
defied scientific explanation, though we
think they may hint at a watery past.
However, around Endeavor, no blueberries
were to be found. Instead, the soil
looks much coarser, the rock sharper,
and not as rounded. Mission controllers
were so impressed by the variation of
this area compared to the initial
landing site that they said that this
section of the mission provided the
equivalent of a second landing site for
the price of one.
The first point of interest Opportunity
examined was a large ejector rock called
Tisdale 2. It was unlike any other rock
so far examined on Mars. It had volcanic
characteristics but contained more zinc
and bromine than previously seen. It was
determined to be a type of breer, old
rock fragments having been fused
together. This was further evidence for
water. The impact that threw this bit of
ejector likely released hot underground
water that deposited zinc in the rock.
Just a short distance from Tisdale 2,
Opportunity discovered perhaps the most
conclusive evidence that water existed
on Mars thus far. Can you guess what it
is from this picture?
Look closely at the bottom of this image
and you'll see a thin white line exposed
in this outcrop. A close-up examination
of the vein revealed it to be gypsum,
the alpha particle X-ray spectrometer on
the rover's arm, detecting the minerals
calcium and sulfur, together making
calcium sulfate. They named this vein
the Homestake Deposit, and it likely
formed from water dissolving calcium out
of volcanic rocks, which combined with
sulfur and was then deposited as calcium
sulfate into an underground fracture
that later became exposed at the
surface. The impact that threw Tisdale 2
likely had something to do with this
vein as well. If this is the case, it
shows that water once flowed through
underground fractures on Mars. Later
analysis of the data Opportunity
collected showed that not only was this
likely to be gypsum, but also that the
water here would have been much less
acidic than it would have been around
other locations on the planet, meaning
it could have been more conducive to
life.
Martian winter was soon setting in,
meaning shorter days and a lower sun in
the sky. For a solar powered rover that
can't adjust the angle of its solar
panels, this is not the ideal situation.
But for the first time since the mission
began, Opportunity had the opportunity
to spend the winter on a slope aimed
towards the sun. Meaning that for this
winter, it would be confined to an area
named Gley Haven.
This area was not only aimed towards the
sun, but it was also rocky, meaning
Opportunity had a lot it could examine
during these few months. This 360°
panorama shows the tracks of opportunity
as it carefully navigated its way to its
winter lodgings.
Months had passed and winter was turning
again to summer.
On soul 2947,
Opportunity moved again for the first
time since it set up camp in Gley Haven.
Luckily, everything that was functioning
from before seemed to still be
functioning, and Opportunity headed out
to the next point of interest.
M data suggested clays were present in
this area and the mission team were
determined to find it. A beckoning
outcrop was spotted around Soul 3057 and
the microscopic camera revealed
something about it that no one was
expecting. Much like Opportunity's
landing site, these smooth polished
blueberry rocks were observed. However,
this time they were very much a part of
the rock.
They were also smaller than what
Opportunity had seen before, only a few
millimeters in diameter and not rich in
iron like the landing site blueberries.
A few of the exposed blueberries
observed had been eroded away, revealing
their internal structure.
Scientists described these blueberries
as crunchy on the outside and softer in
the middle. They are different in
concentration. They are different in
structure. They are different in
composition. They are different in
distribution. It was quite the mystery.
Opportunity had just one more place to
visit on its trip around Cape York, and
that was the clay patch dubbed White
Water Lake. On its way there, the Earth
and Mars were just going through a phase
called Solar Conjunction, where Mars is
behind the Sun, which blocks
communications between mission
controllers and the rover. This has
happened a few times during the course
of the mission already, but this time
Opportunity gave mission controllers a
bit of a scare as during the
communications blackout, Opportunity's
onboard computer reset into standby
mode. Thankfully, communications were
restored. Opportunity booted back up
properly and it carried on to Whitewater
Lake. And it was there Opportunity
discovered Espirinance, the pale rock in
the upper center of this image, which is
about the size of a human forearm. This
was it, the treasure scientists had been
looking for.
Espirinanc's composition was found to be
higher in aluminium and silica and lower
in calcium and iron, more so than any
other rock Opportunity had examined in
more than 9 years on Mars. Testing found
that this rock had a clay mineral
content due to intense alteration by
water. Opportunity spent weeks here
making sure the measurements were
correct, getting everything it could get
done before Martian winter came around
again. Opportunity left Cape York on
soul 3344.
Having spent nine Earth years or five
Martian years on Mars's surface, they
found the best evidence out of any Mars
mission that neutral pH water once
existed on Mars. But scientists were not
content to let the mystery end there. To
get a clear idea of where water and thus
potential life had once resided on Mars,
other locations on the dusty surface
needed to be explored. As such, in 2021,
our next robo was sent to locations
within a crater known as Yzero,
thousands of kilometers away.
In Yzero Crater, there is a June field
known as Saitar. In amongst these dunes,
there is a series of outcroppings that
were of particular interest to
Perseverance's mission due to the many
different layers of exposed rock they
gave access to. These different layers
likely represented different geological
eras, which would give scientists the
clearest picture of the history of
Yzero, as well as giving them an
opportunity to find life itself.
Outcroppings are of particular interest
because Perseverance's drilling
equipment only allows it to dig several
centime.
If it wasn't for outcroppings, where
erosion had exposed these layers to the
Martian atmosphere, Perseverance would
not have access to them.
However, sandjunes are of particular
danger to a rover like Perseverance.
With help an entire solar system away,
if Perseverance was to start wheel
spinning in a section of particularly
loose June, it would likely spell the
end of its mission, much like it did for
the Spirit Rover in 2009.
As such, Perseverance's trusty sidekick,
Ingenuity, a small helicopter, the first
of its kind on the Martian surface that
had traveled to Mars along with
Perseverance, was sent in to conduct
some preliminary reconnaissance.
If it could find a route through the
sandunes that look safe, Perseverance
could get its sample tubes to the vital
outcroppings of Saitar.
Ingenuity began its scouting before the
Solar Conjunction and flew for several
flights from September through to
December 2021. Flying at a height of 10
meters, these reconnaissance expeditions
allowed scientists to pick out the
perfect route. Perseverance set off in
early November 2021, beginning its
exploration of the dunes. It picked its
way carefully, being sure not to travel
too fast in case it fell into any
unforeseen sand trap. It moved between
dunes that were a meter high, finding
the flattest path. But thankfully,
Ingenuity had led it through.
Perseverance was able to make it to the
protruding rock known as Brack. By now,
Perseverance had had time to practice
drilling into Martian rock with its cing
drill. Some of this successful and some
not so. But either way, now that it had
its technique down, Perseverance quickly
was able to obtain new samples. deciding
to call the first empty sample container
at Brack an atmosphere sample. These
next two samples were officially
Perseverance's fifth and sixth sample
tubes and their third and fourth rock
samples. From these accumulated samples,
scientists were able to make an
unexpected discovery. These were not
sedimentary rocks as had first been
anticipated. Instead, Perseverance had
discovered the ignous rock, Olivine.
Olivine is a type of rock that can
actually be found here on Earth. For
instance, in parts of Australia. Unlike
sedimentary rocks which are made by
particles of sand and other detritus
slowly accumulating on top of each other
over time, an ignous rock like olivine
is formed by the cooling of magma. As
such, it seems that at one time or
another, Yzero crater must have been
witnessed to some volcanic activity.
While this might initially seem to be
bad news, you might correctly conclude
that not much life could be found in
magma, scientists could discern signs of
water erosion on the rocks. The ridges
at the ends of the crater showed signs
of water motion. Whatever volcanic
activity had happened here, the water
that created Yzero's delta must have
come after it had already cooled. As
such, the presence of ignous rocks was
actually good news. Ignous rock is
usually very high in minerals. This is
why the areas around volcanoes are so
fertile.
The presence of water and high mineral
count rocks could have been the perfect
conditions for life.
In the future, scientists will be able
to send missions to locations like the
Yzero Crater Delta as they make future
attempts to locate alien life. Indeed,
once humans land on Mars, as is planned
for the 2030s, it's not unimaginable
that archaeological dig sites will be
one day set up in locations like this,
with humans in space suits gently
brushing away the fine oxidized iron and
bassalt rock to see if signs of life can
be found underneath. But still,
scientists yearned for clearer pictures
of Mars's ancient watercapes than this.
And it was now likely that water had
pulled in craters and flowed in rivers.
But what about the step beyond that?
Could ancient Mars have once housed
oceans? If true, this would be exciting
for those searching for signs of ancient
alien life. A shoreline could have
supported an abundance of life, possibly
entire diverse ecosystems.
and they might have left behind bio
signatures like scavenger hunt clues we
can use to paint a picture of Mars's
ancient coastal habitats.
Shore environments offer key advantages
to budding life. They concentrate
organic molecules through evaporation,
promote the formation of complex
molecules like RNA and protein and
provide mineralrich surfaces and energy
sources like UV radiation, heat and
chemical gradients, all of which can
drive the chemistry needed for life to
arise. In contrast, rivers are too
dynamic and dilute to support the
delicate chemical conditions needed for
life to arise. They constantly flush
materials downstream, making it
difficult for molecules to accumulate
and react the way they need to to form
life. So, if researchers could find
evidence of a standing body of water on
Mars, like a lake or an ocean, they'd be
in a much better spot to search for
remnants of microbial life. The Chinese
Tanwen 1 mission might have captured the
most compelling evidence yet for ancient
oceans on Mars.
It's the first on the ground data ever
collected of a suspected ocean zone and
it makes a strong case that our
shoreline theory is on the right track.
On the 23rd of July 2020, the Tanwen 1
spacecraft began its 202day journey to
Mars. Aboard it carried an orbiter,
lander, and the Tsurang rover. The aim
of the mission was to investigate Mars'
geology, climate, and habitability
through three key activities. By
studying the surface and subsurface of
the Utopia Plenicia, a region scientists
think could be an ancient ocean basin
based on mapping from satellite data. by
performing climate and weather
monitoring including magnetic field
variations and dust activities effect on
solar panels and climate
and by searching for signs of water and
habitability. Investigating whether the
region harbored conditions suitable for
life in the past. On the 10th of
February 2021, Tanwin 1 entered into
orbit around Mars. Controllers spent
three months testing the probe systems,
shifting its orbital path from
equatorial to polar and preparing it for
its main science mission. Finally, on
the 14th of May, the lander touched down
on the red planet. And a week later, the
Tsurang rover was successfully deployed,
making China only the second nation in
history to successfully deploy a rover
on Mars, behind the USA.
For China, this mission represented more
than just scientific discovery. It
showcased their spaceflight capabilities
and autonomy and demonstrated they can
launch and operate missions without
relying on foreign navigation or
communication systems. The Tanwen
mission, meaning questions to heaven,
laid the foundation for future Chinese
missions like a Mars sample return and a
possible crude mission to Mars by 2033.
The 240 kg rover was deployed in a
region of Mars known as Utopia Penicia,
the largest known impact basin in the
whole solar system. It's the same region
where the NASA Viking missions landed
almost 50 years ago. But recently,
interest in this area was revived due to
a 2016 NASA discovery. Turns out it is
home to a massive amount of underground
ice. About as much water as you'd find
in Lake Superior, about 12,100
km cubed or 1 * 10 ^ 16 L.
So to study this promising region, the
Tsurong rover came equipped with 13
different scientific payloads which can
be thought of as four categories. Radars
to detect subsurface structures up to
100 meters underground, including the
ground penetrating roper radar,
spectrometers to analyze soil and rock
compositions, including a laser induced
breakdown and infrared spectrometer,
optical cameras that will image the
planet from both the orbiter and the
rover, as well as provide topography and
navigation capabilities, and monitors
for atmosphere and space environments
that will detect the magnetic field,
space radiation, and the climate of
Mars, including a surface magnetometer
and the Mars Climate Station designed to
monitor local temperature, wind,
pressure, and even record sound. The
rover also carried a deployable wireless
selfie camera that produced some of the
mission's most iconic images, like
these.
So, loaded up with all these scientific
payloads, what exactly did Zurang
discover about the Martian coastline
that past missions had missed?
To fully understand this, we need a
quick geography lesson. On Earth,
sediment particles are transported by
wind, water, and ice, carried through
rivers, or moved downhill by glaciers.
The sediment is eventually deposited in
low energy environments like river
deltas, lake and ocean floors, flood
planes, and the base of hills or
mountains. But it can also happen along
coastlines, more specifically along the
part of the beach known as the
foresshore. This is a dynamic part of
the shoreline between the high tide and
low tide lines. Here, sediment can be
added or removed depending on things
like wind, tides, weather events, and
the type and size of sediment particles.
On Earth, the foreshore zone tends to
slope gently towards the sea. The
gradient of the slope depends on the
type of sediment. For example, beaches
made of smaller, finer particles result
in low gradient beaches, while beaches
with cobbles may be stacked as steep as
20°. These sloping layers record the
long-term balance between sediment
supply, wave energy, and water level and
can be preserved in the geological
record for millions of years.
Back on Mars, the Sirong rover was hard
at work studying the planet's subsurface
topography. It did this by sending radio
waves into the ground using its rover
radar. When the radio wave hits a
boundary between two different
materials, for example, when the
composition shifts from fine grained
sediment to coarser sand, the signal
bounces back. This creates a reflector
in the radar image. What grabbed the
Tsurang's team's attention was not just
that signals were bouncing back, but the
angle they were bouncing back at. All 76
of the geological reflectors they
encountered sloped in the same direction
at an angle between 6 and 20°.
Putting the pieces together, the team
realized that 10 to 35 m below the
planet's surface lies a 1.3 km stretch
of terrain sloping towards the lowlands.
It seemed like more than coincidence.
Could this be proof of what they were
looking for? The indisputable evidence
for an ancient shoreline on Mars? The
team hurried to compare this Martian
picture to the buried beaches found on
Earth and found the Bay of Bengal to be
such a strikingly similar Earth analog
they even featured this finding in their
paper. One of the co-authors of the
original research paper that published
the findings said, "It's a simple
structure, but it tells you there had to
be waves. There had to be a nearby river
supplying sediment, and all these things
had to be active for some extended
period of time. We also know that the
sun and Mars's bigger moon, Phobos, do
affect the planet's surface gravity,
which could have caused tides on the
ancient ocean."
The team briefly considered but
ultimately ruled out other possible
explanations for the sloping structures.
They argued both sandjunes and lava
flows would lead to slopes pointing in
multiple directions. Yet in the Tsurang
data, all the reflectors point the same
way. They concluded that these slopes
were more consistent with a coastal
forshore environment, strengthening the
case that Mars once had dynamic
shorelines that experienced tides, wind,
and waves, just like Earth does today.
For decades, scientists have been locked
in heated debate over the question of
Mars's oceans. The evidence seemed
frustratingly unclear. Prominent
researchers dismissed shoreline evidence
as artifacts or poor image resolution,
and climate modelers struggle to explain
how liquid water could exist on an early
Mars with a fainter sun. You see, 3.5
billion years ago, our sun was about 25%
dimmer than it is now. Too faint to keep
Mars above freezing. And yet our climate
models predict that at the time Mars
would have been covered in rivers,
lakes, and even oceans.
This leads to what is known as the faint
young sun paradox. If the heat for
liquid water didn't come from the sun,
it must have come from Mars's
atmosphere.
This has led to three theories trying to
solve the faint young sun paradox. The
first says Mars was warm and wet. The
idea is that Mars's atmosphere was
loaded with greenhouse gases, mainly
carbon dioxide and water vapor, which
made it so dense it could trap enough
heat to allow liquid water to persist
for millions of years. This would
explain the evidence pointing to
rainfall, lakes, and oceans. But the
problem is according to our models,
carbon dioxide and water vapor alone
can't produce the warming needed for
this scenario. Other gases like methane,
ammonia, or hydrogen would be needed,
but they are unstable and hard to
maintain long term. The second
possibility is that Mars was only warm
and wet some of the time, mainly in
response to major events like massive
volcanic eruptions or asteroid impacts.
These could release huge amounts of heat
or greenhouse gases, creating long-lived
warm spells where ice melted, rivers
flowed, and erosion occurred. But we
can't know for sure if the intensity and
frequency of these spells would have
been enough to carve all the valleys and
fill the lakes we see evidence for
today.
And finally, some think Mars spent most
of its history as a frozen ball.
Landscapes were dominated by snow and
ice, but under certain conditions, like
changes in Mars's orbit or sudden
heating events, the ice melted. This
explains why Mars shows signs of both
glacia activity and flowing water. But
what could have melted all that ice
often enough for the erosion we see to
occur?
None of these three scenarios perfectly
explain Mars's past climate.
Frustratingly, despite the strong
evidence for shorelines, we still don't
know how to reframe our models of Mars's
early climate to allow for water to
persist there. Although a paper released
in the journal, Communications, Earth,
and Environment in December 2025 found
evidence in Perseverance's data that
suggested clays it saw had been sculpted
by consistent heavy rain, lending weight
to one of the rainfall options. Still,
solving the faint young sun paradox may
be the key to understanding whether Mars
was ever truly habitable.
So, it's too soon to get carried away
imagining some billionaire digging up
Martian beaches and turning them into
resorts. The truth is, we still need
more data to put the full puzzle
together. Tragically, even in the best
investigation cases, evidence can go
missing. Perseverance spent much of its
time on Mars collecting samples for a
future retrieval mission in 2027 or 2028
with a return scheduled for the late
2030s. This would have given us more
clarity into the planet's complex and
ancient geology and perhaps closed the
debate for good. But then NASA was
threatened with massive budget cuts in
2025. And while Congress passed a bill
in early 2026 that secured NASA's
funding, Perseverance's sample return
mission was the one exception. Those
clues to water conditions on ancient
Mars and one sample that NASA described
as the clearest sign of life ever found
on the red planet will remain trapped on
a world tens of millions of kilometers
away from our own. It may be up to
humans who might one day live on Mars to
walk over there and pick them up if we
are to find out the secrets those
samples contain.
Even though Sirong was only designed to
last 93 Earth days, it persisted well
beyond this timeline, collecting data
for an impressive 358 days until it went
dormant on the 20th of May 2022. With
appropriate temperature and sunlight
conditions, Surirang was expected to
wake up in December 2022, but never did
due to excess dust accumulation.
As we look to the future, more questions
remain to be answered. If Mars had
stable oceans for millions of years,
what happened to all that water? How did
the planet transition from a potentially
habitable world to the frozen desert we
see today? Could a similar fate await
Earth? And if life did emerge in these
ancient coastal environments, could
traces of it still exist, buried beneath
the surface? Our metal detectives might
have enabled scientists to follow the
water, but the suspected existence of
fossilized life itself on Mars is a case
to solve for another day.