Imagine you're standing on Mars, like, billions of years ago,
but not the Mars we see in pictures today.
This Mars is, well, it's totally different.
It has rivers and lakes and maybe even a whole ocean up
north.
Crazy, right?
How did Mars go from that to a dry, dusty desert?
It is a pretty crazy transformation
when you think about it.
Yeah.
So in this deep dive, we're going to travel back in time
and explore this ancient Mars, this planet that
was once full of water, welcome to cosmos in a pod space
and astronomy series.
To understand the mystery, you've
got to look at the atmosphere.
See, billions of years ago, Mars had this thick atmosphere
packed with carbon dioxide.
And that acted like a giant blanket, trapping heat
and letting liquid water flow.
So like, how do we know all this?
Is there like evidence of this watery past still on Mars today?
Oh, absolutely.
Martian surface, it's basically a history book, right?
Full of clues.
And one of the biggest clues is this massive canyon system
called Valles Marineris.
It's huge, way bigger than the Grand Canyon here on Earth.
Like, it stretches over 4,500 kilometers.
4,500 kilometers?
Yeah.
Wow, that's like the width of the US.
Yeah.
So how does a canyon tell us about water?
Well, think about it.
Something had to carve out something that massive
and the most likely culprit.
A ton of water flowing for millions and millions of years.
OK, so a giant canyon hints at water.
But are there any other features that back that up?
There's this really cool spot inside Valles Marineris
called Noctus labyrinthus, which means labyrinth of night.
It's this maze of canyons and plateaus.
And they also show signs of water erosion.
It's almost like Mars is trying to tell us its story,
you know, through these canyons and stuff.
So if Mars had all this water, how did it all vanish?
What happened to its atmosphere?
Well, the main theory is that Mars' magnetic field,
it's kind of weak.
And that's a problem.
See, unlike Earth, Mars doesn't have the strong magnetic shield
to protect it from the solar wind.
And the solar wind, well, it's this constant stream
of charged particles from the sun
that basically chipped away at Mars' atmosphere
over like billions of years.
And eventually, well, most of the atmosphere was gone.
Wow, so the sun basically blew away Mars' atmosphere.
That's kind of sad.
Did the water disappear with the atmosphere too?
A lot of it did.
As the atmosphere thinned, the water on the surface,
well, it started to evaporate.
And some of it broke down.
The hydrogen escaped into space.
But the oxygen, the oxygen reacted with iron in the soil.
And that's how you get iron oxide.
Or rust, that's what gives Mars its red color.
So Mars is literally rusty.
That's a fun fact.
Is any of that ancient water still around today?
Actually, yeah.
Funny enough, Noctus labyrinthus,
that place with the canyons, is one of the most humid places
on Mars.
At night, fog forms there because water vapor
evaporates from the soil and freezes.
Pretty cool, huh?
It's like a little ghost of Mars' watery past.
Let's talk about some specific places on Mars
to give us even more clues about its watery history.
Let's start with Copritis Chasma, this deep canyon that's
tucked inside Valle Es Marineris.
What's so special about it?
Copritis Chasma, well, there's evidence
there of a huge ancient lake.
Some scientists think it might have been as big as the Black
Sea.
A lake the size of the Black Sea on Mars.
Wow.
That makes you wonder if anything lived in it.
Do scientists think we might find signs of life
in Copritis Chasma?
It's definitely a good spot to look.
I mean, the conditions back then
might have been perfect for, say, microbial life to pop up.
Mind blowing.
Are there any other places on Mars
that might hold clues about ancient Martian life?
Oh, yeah, tons.
Gale Crater, for example.
That's where the Curiosity Rover landed.
And it's this huge impact crater with this mountain
of layered sediments right in the middle called Mount Sharp.
And scientists think Gale Crater used to be a giant lake.
And that Mount Sharp formed from all the sediment
that settled at the bottom over millions of years.
So Curiosity landed in an ancient lake bed.
Talk about being in the right place.
What has Curiosity found in Gale Crater so far?
Well, it's found a bunch of cool stuff.
Clear signs of water erosion, mineral-rich soil
that could have supported life, and even organic molecules,
which are like the building blocks of life.
It's like Curiosity is telling us
a story bit by bit about what Mars used to be like.
So we've got canyons and craters that were once lakes.
Any other cool features from Mars's water world?
Well, there's Hellas Planitia.
That's a massive impact crater, one
of the biggest in the whole solar system.
It's massive, like 2,300 kilometers across.
It probably formed when a giant asteroid hit Mars billions
of years ago.
The impact was so powerful that it created this huge basin.
And a lot of scientists think that basin filled with water
and became a giant lake.
A lake that big must have been an amazing sight.
What does Hellas Planitia look like today?
Today, it's known for its weird weather.
Sometimes it gets really hazy.
And in the Martian winter, it gets covered in frost.
You can actually see it from Earth,
this big white spot on Mars.
It's pretty cool.
From canyons to lakes to a giant frost covered basin,
Mars really was a different world.
Let's talk about another crater, Jezero Crater.
That's where the Perseverance Rover is now.
What's so special about Jezero Crater?
Oh, Jezero Crater has evidence of an ancient river delta.
Imagine a river flowing into a lake and dropping off sediment.
Over time, that sediment builds up and creates
this fan-shaped delta.
And that's what we see at Jezero Crater.
It's like a snapshot of the past.
So Perseverance landed right in this ancient river delta.
That sounds like the perfect spot
to hunt for signs of past life.
It really is.
Perseverance has sent back some incredible images
of sediment layers and rocks that were definitely
shaped by water billions of years ago.
Perseverance is doing more than just taking pictures, right?
I mean, it's got all this high-tech gear,
and it's doing experiments that could pave the way for humans
to go to Mars someday.
Exactly.
One of the coolest things it's done
is generate oxygen from the Martian atmosphere.
That technology could be a game changer
for future human missions.
We could make breathable air and even rocket fuel
right there on Mars.
Talk about making Mars feel a bit more like home.
Speaking of breakthroughs, let's talk
about the robots that have made all these discoveries possible.
These rovers are amazing.
They really are.
We wouldn't know nearly as much about Mars without them.
Curiosity, for example, has been roaming around Mars
for over a decade.
How far has it traveled?
Almost 30 kilometers.
That's pretty impressive for a robot on another planet.
It's amazing what humans can build, isn't it?
What are some of the most important things curiosity
has taught us about Mars?
Oh, so much.
It's found evidence of ancient streams, lakes, even groundwater.
It's confirmed that there were organic molecules on Mars,
meaning the ingredients for life were there.
And it's also helped us understand how Mars' climate
changed over time, how it went from being potentially
habitable to the dry planet we see now.
Wow, that's incredible.
What about perseverance and ingenuity, the helicopter?
What makes them different from the other rovers?
Perseverance is collecting rock and soil samples
that will eventually be brought back to Earth.
Wow, that would be amazing.
Imagine holding a piece of Mars in your hand.
What else is perseverance doing?
Well, besides making oxygen, it's
testing out how to navigate autonomously,
which is important for future human explorers.
It even has radar that can look for underground water ice.
It sounds like perseverance is really paving the way
for humans to go to Mars.
And ingenuity, the helicopter, it's
crazy that we can fly something on another planet.
I know, right?
Ingenuity proved that powered flight is possible on Mars,
even with that thin atmosphere.
That opens up so many possibilities
for future missions.
Imagine drones scouting ahead of rovers
or carrying stuff around.
That would be incredible.
OK, we've talked about Mars' past,
but there's one more thing we need to discuss.
Mars' two tiny moons, Phocos and Deimos.
What can you tell us about them?
Phocos and Deimos are a bit of a mystery.
They're both pretty small compared to our moon,
and they're kind of lumpy and potato shaped.
That makes scientists think they might be captured asteroids.
Captured asteroids.
So like they were just floating around,
and Mars grabbing grabbed them.
Yep, pretty much.
And now they're stuck orbiting Mars,
but their stories don't end there.
Oh, what do you mean?
So their destinies are kind of tied to Mars,
but in different ways.
Phobos, the bigger one, it's actually
spiraling in towards Mars.
Mars' gravity is pulling it closer.
So it's going to crash into Mars.
Not quite crash, no, but it's going
to meet a pretty spectacular end.
As Phobos gets closer, it'll cross this line
called the Roche limit.
The Roche limit.
What's that?
It's the point where basically Mars' gravity gets
so strong that it overpowers the gravity holding Phobos
together.
Oh, so Phobos is going to get ripped apart.
Exactly.
And when that happens, it'll create this ring of debris
around Mars, like a cosmic dust cloud.
Whoa, a ring around Mars.
That's pretty wild.
What about Deimos?
What happens to it?
Deimos is actually moving away from Mars very slowly,
but it's drifting further out.
It might even escape Mars' gravity completely one day.
So one moon gets shredded, and the other flies off into space.
The Martian system is a pretty wild place.
OK, we spent a lot of time talking
about water on ancient Mars, but the big question
is, was there ever life?
Could those lakes and rivers have actually
had living things in them?
Well, we know Mars had water, organic molecules,
and energy from the sun.
Yeah.
And those are basically the ingredients you
need for life as we know it.
So the potential was there, but have we
found any actual proof of life on Mars?
Not yet, but there have been some pretty interesting clues.
For example, Curiosity found methane in the Martian
atmosphere.
Methane, like the stuff we use for stoves and stuff?
Yeah, that's the one.
Now, methane can come from geological stuff,
but it can also be made by living things,
specifically microbes.
So the methane Curiosity found could
be a sign of tiny Martian bugs.
That's pretty exciting, but I guess
it's hard to know for sure where the methane came from.
It is, and that's one of the things Perseverance
is trying to figure out.
It's got instruments that can look
for signs of past life in that old lake bed in Jezero Crater.
Fingers crossed it finds something.
It sounds like the search for life on Mars
is a really slow and careful process.
It is, but each new discovery gets us closer to figuring out
if we're alone in the universe or not.
Speaking of pushing boundaries, let's talk about the future
of Mars exploration.
Do you think humans will ever actually go to Mars?
I think it's just a matter of time.
We're already sending robots that can drive around,
collect samples, even make oxygen.
Sending humans is the next step.
It would be amazing, but I bet it would be super challenging.
What are some of the biggest hurdles to getting humans
to Mars?
Well, first, there's the trip itself.
It takes like six to eight months to get to Mars,
and that's just one way.
Astronauts would have to deal with radiation, zero gravity,
and being stuck in a small spacecraft for a long time.
That sounds rough.
And what about once they get to Mars?
What kind of dangers would they face there?
Mars is pretty harsh.
The atmosphere is super thin, so you'd need a spacesuit
to go outside.
The temperature swings wildly, too, like 70 degrees Fahrenheit
during the day and then negative 200 at night.
Bruh, that's cold.
I can only imagine what you'd need
to pack for a trip like that.
And there's no air to breathe on Mars, right?
And the radiation is a problem, too, I guess.
Yeah, and there's also the dust.
It's really fine and gets everywhere.
It could mess with equipment and even be bad for your health.
So getting humans to Mars is a huge challenge,
but it sounds like it would be worth it.
Why are we so obsessed with going to this planet?
For one thing, Mars can teach us about the early solar system.
Studying it might help us understand how planets form,
how they change, maybe even how life started.
It's like a window into the past.
So learning about our own origins
is one reason to go to Mars.
What else?
Humans are explorers.
It's in our nature.
Mars is like the next big frontier, a challenge that
makes us want to push our limits.
Yeah, I get that.
There's something really exciting about exploring
the unknown, but are there any practical reasons
to go to Mars?
Could it benefit humanity in a real way?
Maybe.
Some people think Mars could be a backup plan for humanity,
if something really bad happened to Earth.
That's a scary thought.
And some people even talk about terraforming Mars,
making it more like Earth so we could live there.
Yeah, terraforming.
That would mean changing Mars' atmosphere, warming it up,
getting water flowing again.
It sounds like science fiction, but is it really possible?
It would be incredibly hard, but some scientists
think it could be done eventually.
Imagine a green Mars, a second home for humans.
That would be amazing.
But right now, Mars is still pre-dry and dusty.
It is, but it wasn't always that way.
And who knows what other secrets we'll discover
as we keep exploring?
Well, this deep dive has definitely made me even more
curious about Mars.
We've learned about its watery past, the possibility of life,
the robots exploring it, and even the idea of humans
going there someday.
We've only just scratched the surface.
There's so much more to learn.
Absolutely.
I bet there are tons of surprises waiting for us
on Mars.
But for now, let's take a break and think
about everything we've learned about Mars' ancient past.
We'll be back in a bit to wrap things up
and talk about what the future holds for Mars exploration.
OK, so we've covered a lot about ancient Mars,
its watery past, the hints of life,
the rovers exploring it now, and the idea of humans
going there one day.
But we haven't talked about Mars' moons yet,
Phobos and Dimos.
Oh, yeah, those two.
They're pretty interesting in their own way.
They're not like our moon, are they?
I mean, they're much smaller, and they kind of
look like potatoes just tumbling around Mars.
Yeah, their shape is a big clue about where they came from.
Scientists think they're captured asteroids,
not moons that formed along with Mars, like our moon did.
Captured asteroids.
So Mars just like snagged them with its gravity.
Yep, basically.
It's like a cosmic game of catch, and Mars won.
But their story isn't over yet.
Oh, what do you mean?
Their fates are kind of tied to Mars, but in different ways.
Phobos, the bigger one, is actually
spiraling in towards Mars.
It's getting closer and closer because of Mars' gravity.
Wait, so it's going to crash into Mars?
Not exactly crash, no.
But it's going to get ripped apart.
As it gets closer to Mars, it's going to cross this line
called the Roche limit.
Roche limit?
What's that?
It's the point where Mars' gravity gets so strong
that it overpowers the gravity holding Phobos together.
Oh, so Phobos is going to like explode.
Kind of.
It'll get torn to shreds by Mars' gravity
and create this ring of debris around the planet,
like Saturn's rings, but made of Phobos bits.
Wow, a ring around Mars.
That's a crazy thought.
So what about Deimos?
Does it get shredded too?
Nope.
Deimos is actually moving away from Mars slowly,
but it's getting further away.
It might even escape Mars' gravity entirely one day
and just like float off into space.
So one moon gets ripped apart and the other one escapes.
The Martian system is a pretty wild place.
Well, I think we've covered pretty much everything
there is to know about ancient Mars.
It's watery past, the hints of life,
the rovers exploring it now, and the possibility
of humans going there someday.
It's been an incredible journey.
It has been fascinating, hasn't it?
And it's only the beginning.
There's so much more to discover on Mars.
Yeah, who knows what other secrets are
waiting to be uncovered?
Maybe we'll find proof that life existed there
or even that it still exists today.
That would be incredible.
It's a big question, isn't it?
Are we alone in the universe?
It's a question that will keep driving us to explore Mars
and the rest of the cosmos.
Well, thanks for joining us on this deep dive.
It's been a pleasure talking about Mars with you.
The pleasure was all mine.
And for all you space fans out there,
don't forget to follow and subscribe to Cosmos
in a Pod and our YouTube channel for more explorations
of the universe.
Keep looking up and keep wondering.