NARRATOR: Mars has had two of the ingredients for life: the energy of the sun and liquid water.

Now Curiosity stands poised to discover the third ingredient: organic molecules, but only if the rover manages to sample Martian rocks and soil. And that depends on the strength and precision of Curiosity's robotic arm.

BRANDON METZ: The robotic arm is extremely complex, because we have five joints. We have what we call the azimuth joint, which is really just kind of…you can think of your shoulder moving back and forth. Then we have elevation, which, again, is like your shoulder moving up and down. And then we have the elbow, which actually works like the elbow; it usually moves like that. And then we have wrist, which is just, kind of, like the wrist: it moves it about here. And then we have turret, which allows us to, like, rotate 360, you know, in either direction. So, so the robotic arm it is really an engineering masterpiece.

NARRATOR: The arm supports a turret of instruments that collect, process and deliver samples to the rover's onboard laboratories. Curiosity will not be the first spacecraft to scoop up Martian soil, but drilling on Mars will be historic.

DANIEL LIMONADI (Surface Sampling Lead, Mars Science Laboratory): We haven't drilled on another planetary body since Apollo.

APOLLO ASTRONAUT: Okay, Bob. I've got my tools of the trade, right here.

DANIEL LIMONADI: Their drills were more challenging in that they needed to get, like, one-meter to two-meter cores, but they had astronauts that could react to the situation. Once you penetrate the surface of another planet, now you have to deal with all kinds of unknowns…

MICHAEL WATKINS: …how to keep the drill perfectly clean; how to isolate it from the mechanical workings of the motors; how to not drill into a rock that will end up clogging the system, so that we can't use it anymore. These are really the big challenges.

NARRATOR: Engineers tested several drill designs before settling on an exceptionally sturdy model.

DANIEL LIMONADI: It's a rotary percussive drill. And that's typically what you would buy to go, to like drill through concrete in your yard or whatever. The main difference is the average person, in their yard, doesn't want to collect the powder. So we have a powder collection system, effectively, around the drill bit.

NARRATOR: The drill's rotation carries the powdered rock up inside the turret, where it's passed through a sieve to filter out larger particles. To keep the sample flowing through the system requires a whole lot of shaking.

DANIEL LIMONADI: Most spacecraft, you try to keep pristinely clean, and then you try not to bang them up more than they have to. We, on purpose, shake the turret really hard, and we know we're going to get dirt everywhere. We have to get used to more violent hardware. It's more like a mining operation a fine precision operation.

MICHAEL WATKINS: Actually, to understand how to build that drill system that doesn't shake the arm apart or shake the rover computer too much was a big challenge.

NARRATOR: But the scariest thing about drilling on Mars is not the vibration or the dust. Curiosity is likely to drill on uneven or steep terrain. If the rover slips, it could yank on the arm and damage it. If the drill gets stuck in the rock, it could anchor the rover in place. But there's a backup plan.

DANIEL LIMONADI: If, heaven forbid, the bit would get stuck, we actually have two spare drill bits. We would un-chuck the bit, leave it there, and then we would grab another one to live another day.

ENGINEER: Three, two, one, go.

NARRATOR: After years of piecemeal testing, a milestone draws a crowd: the first end-to-end sampling test, from drilling to sifting powdered rock to delivering a sample, the equivalent of dropping an aspirin in a thimble.

DANIEL LIMONADI: One of the kind of comedies of scale of this rover, is we have, you know, a 900 kilo rover with a100 kilo arm, and we drop off a little, tiny, you know, sample to each instrument. And that's enough for them to do their science.

NARRATOR: A pinch of powdered rock may tell us whether Mars ever harbored the building blocks of life.