If you were to drill straight down into Mars,
what would you find?
This is the Jezero Crater on Mars.
And three and a half billion years ago,
it looked very different.
It used to be an ancient river delta
that carried clay minerals into the crater lake.
It might have even hosted Martian life.
Fast forward to now,
and the Jezero Crater has become a perfect landing site
for NASA's shiny new rover.
Meet Perseverance.
If I were to search for past lifeforms on Mars,
this is the place I'd start looking, too.
Only instead of collecting rock samples,
I'd send a rover to drill through the surface.
What's the worst that could happen?
Did you know Mars has marsquakes?
They're like earthquakes but on Mars.
NASA's Martian lander called InSight
detected 480 of these marsquakes in 2020 alone.
Luckily, there isn't much out there to damage.
For us, these marsquakes are a good thing.
They create seismic waves that our scientists can study.
And based on these studies,
they can theorize about the Martian interior.
But you and I would be doing this the hard way.
We would drill through Mars
to see what secrets it holds inside.
If you started drilling through the reddish,
iron oxide-abundant surface layer of Mars,
the first thing you'd discover
is that the interior is not so red.
But don't be surprised.
In 2012, NASA sent the Curiosity rover to Mars.
It landed about 3,700 km (2,300 mi) from the Jezero Crater.
Curiosity discovered that the layer beneath the surface of Mars
is slate-blue.
That's because it contains high levels of silicon.
And as you drill, you should continue to expect the unexpected.
The next discovery you'd make is that
the crust layer on Mars is thinner than the one on Earth.
Remember InSight?
This little lander indicated that the Martian crust
is only around 20 or 37 km (12-23 mi) thick,
compare that to the Earth's crust which is
approximately 40-50 km (25-31 mi) thick under the continents.
If water still exists in liquid form on Mars,
it could be several kilometers inside this crust.
And there are radioactive elements in the liquid mantle below the crust.
These elements release geothermal heat through their decay.
And it should be enough heat to melt thick sheets of subsurface ice.
This geothermal heat
could be why there was liquid water on Mars
four billion years ago,
even though the surface temperatures were below freezing.
But enough theory, let's keep drilling.
Boring through Mars would be even harder than drilling through Earth.
The deepest we've ever drilled on Earth
was 12.2 km (7.6 mi) into its crust.
And that came with high budget costs,
technical difficulties and plenty of bad luck.
But on Mars, this would be an unimaginably tricky endeavor.
The InSight lander tried drilling,
but it encountered unexpected soil properties.
The drill probe was trying to go 5 m (16 ft) deep
but could only go a fraction of the distance before popping out.
Then there was Curiosity.
It experienced a mechanical error.
The drill feed mechanism that was supposed to move the drill bit forward
wasn't moving when commanded.
Luckily, scientists designed a new,
more human form of Martian drilling.
Now, the rover uses the force of its robotic arm
to push the drill bit into the surface as it spins.
But don't get your hopes high about
reaching the mantle of Mars too soon.
It took Curiosity the entire day to drill a mere 5 cm (2 in) hole.
Based on that,
going 5 km (3 mi) down would take up to 300 years.
And you'd need a bigger drill.
There's still so much we have to learn about Mars.
But maybe drilling isn't the most effective way to do it.
Especially since we haven’t gotten very far into the crust of our own planet.
But we'll leave digging into that story for another WHAT IF.