(wind rustling) (birds chirping) - [Narrator] The wild borderlands of Northern California might seem like a strange place to find an international group of scientists.

- Okay, BRAILLE team head out.

- [Narrator] But it turns out this lava encrusted landscape is helping answer one of humanity's oldest questions.

Are we alone?

(bird chirping) - [Jen] This place has a lot of caves and we think they're a good analog for Mars.

So to get ready for a future mission to Mars, we're practicing here.

- [Narrator] Jen Blank is lead researcher on a project that would be looking for life on Mars.

It's known as BRAILLE, which stands for Biologic and Resource Analog Investigations in Lowlight Environments.

- [NASA Operator] About 20 meters off the surface of Mars.

- [Narrator] NASA has already been looking for signs of life just below the planet's surface, but they think they're more likely to find those signs a bit deeper.

- [Jen] You guys got your knee pads?

(strap zips) - [Narrator] And in this case, that means caves.

- We think lava tube caves are on every rocky planet in our solar system.

Caves offer protection from the really crazy, harsh temperatures and from the solar radiation that is hitting the surface of Mars.

- [Ben] Up, two, three.

- [Narrator] So if there is or was life on Mars, it will likely be found underground.

But to find that life, the scientists will need the help of some dogs.

(legs stamping) Affectionately known as Spots, four-legged robots like these might someday be Mars' first spelunkers.

- These are our two robots.

We call them very originally, Spot 1 and Spot 4, surprisingly.

(fans whir) These are legged robot platforms.

Standing up Spot 4.

So you can see they're very agile.

This allows them to go through really rough terrain, such as you see around me in lava tubes.

- [Narrator] Before the Spots are ready for Mars, they'll have to go through a long period of training.

One of the first things they'll have to learn is how to detect features that might be life.

- What we see are these features that are growing up from the floor and then we call them polyps.

We also see that there's really white sort of bleachy colors on the cave wall.

So what we're really interested in is getting Spot enough training so that when it goes autonomously exploring a cave, it can identify these features without having a human present.

- [Narrator] You may be wondering what might life on Mars look like?

- Life, if it lived on Mars, and there's a good chance it did I think, given what we're learning about the history of Mars, probably would either be extinct or frozen as ice.

So, it's more likely we're going to find evidence of life at the microbial level.

But key question, will that be preserved and for how long?

When it gets entombed in rock, in the dark, in a stable temperature and humidity regime, you can detect remnants of life millions of years later.

Shall we colloroid sample?

- [Narrator] Diana Northup is an expert on the kinds of life that inhabit caves.

- [Diana] Look at this.

- [Team Member] Oh wow.

- [Diane] It's almost like it's broken.

- [Team Member] Yeah.

- And then formed that interesting rim structure.

- [Narrator] But unlike earth, most lifeforms on Mars probably won't be carbon based.

- [Diana] We know that there is some organic carbon, but not tons of it.

And so, we think that they will be rock eaters.

- [Narrator] Rock eaters or chemolithorophs are organisms that get energy from the minerals around them rather than say sunlight.

- Some of the organisms that you see on the wall around you are basically rock eaters.

So these are organisms that are more likely to have a role on a place like Mars.

(legs stamping) - [Narrator] Recognizing life forms is just one part of the Spot's training.

Another major one is getting the robots to work autonomously.

- So you can see on top of them, they're carrying what we call our autonomy backpack.

So that's computers and sensors for the robot to see what's around it and do what we can mostly do all right, which is work out where we are, how to walk without falling over, and how to go and explore this wonderful cave system.

- [Narrator] That autonomy is essential because it can take several minutes for a signal from earth to travel the approximately 140 million miles to Mars.

- It takes some time.

Like I don't want to send a command here and wait eight minutes to send the next one.

So we are just trying to make the robots explore and decide, "What should I do?"

- [Narrator] Autonomy researcher, Maira Saboia, will be assessing whether the Spots can make the complex decisions necessary to be truly autonomous.

(legs stamping) In this case, the robots must find a fire extinguisher and a backpack hidden in the cave without help from a human.

- [Team Member] Okay.

(legs stamping) - So we place them in locations that are hard to find and we hope the robot's going to be able to find them.

And after it finds the objects, so it's going to change the mode to go closer to get higher resolution image for longer time.

- One minute.

- [Narrator] Each test run is timed to measure how quickly and accurately the robots perform.

- [Jen] We look at how fast they can see the artifacts and whether they see them all correctly, whether they have high confidence in their detection and test how well the robots make their own decisions.

- [Narrator] The first Spot must detect the target, then communicate that to the second Spot, who will then go in for a closeup.

- [Ben] Spot 1 is currently moving.

Spot 4 is parked.

Trying to get a better image of the backpack.

- [Narrator] Even as the Spots move autonomously through the cave, they're still pups and they need to be on a leash.

- [Jen] Each robot dog has a human shepherd who's walking along with a little controller and they can take over manually or press that stop button, mainly for the safety of the robot 'cause they're kind of expensive.

And also, we don't want to crash into the cave too much.

- [Narrator] And to accomplish everything the scientists are looking for, the robots will need to do more than just communicate with each other.

As the Spots move through the cave, they're sending mapping data back to the team at the cave's entrance.

In a real world scenario, data collected at locations like this can then be transmitted back to scientists on Earth.

- 30 seconds.

(legs stamping) - [Narrator] Naturally, things don't always go as planned.

- [Ben] There's something wrong.

Spot is now not responding.

- Five seconds.

Three, two, one, stop.

(timer rings) - [Narrator] But that's okay, because at this point it's all about the training.

- [Ben] Spot 4 is moving again.

- Ultimately, this is a feasibility study.

You know, we're far from a real mission to another planet, but we've been getting better and better.

(legs stamping) - [Narrator] So these pups aren't quite ready for space yet, but when they get there, it'll be because of the lessons they learned in these local caves.

- [Ben] Good dog.

(legs stamping) (no audio) - Great people just doing their thing in their own northwesty way.

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