Equipped with a marshmallow-shaped lump of plutonium for energy and rock-vaporizing lasers for eyes, NASA's Curiosity rover is en route to an ancient crater on the red planet.
I want to tell you about a special place on the surface of Mars. Back in the solar system's early days, a large object slammed into the red planet, leaving behind a hundred-mile crater -- a dent large enough to withstand three billion years of erosion. The Gale Crater, as the site is known, is almost as wide as Earth's Chicxulub crater, the impact zone of the asteroid that is thought to have killed the dinosaurs. Because Mars orbits close to the solar system's main asteroid belt, it's not unusual to find impact craters there; just recently, a group of geophysicists counted more than 600,000.
But Gale is no ordinary crater. Over eons, thin layers of sediment have accumulated at its center, forming a lumpy, striated mountain that towers three miles high, so high that its peak crests above the lip of the crater. The mountain's rocky layers make up a geologic time capsule, a fine-grained record of Martian history that stretches back more than a billion years. If we could examine those layers up close, we could look deep into the Martian past, perhaps deep enough to see what the planet was like when it had an atmosphere and liquid water.
And we recently sent a super-futuristic robot there to do just that.
On its way to the Gale Crater, right now, is NASA's Curiosity rover, the most sophisticated robot in the history of space science: a dune buggy equipped with a set of tools and instruments to shame Inspector Gadget. Curiosity can vaporize rock, analyze soil samples, gauge the weather, and film in HD. It's due to touch down in the Gale Crater on August 5, completing an eight-month journey through the local solar system. Once it lands, the rover will begin a slow ascent up Aeolis Mons, the mountain in the crater's center, probing its layers for signs that Mars once supported life. It will also collect new data about the surface of Mars, which NASA will use to determine the feasibility of future manned missions there.
A few weeks ago I visited NASA's Jet Propulsion Laboratory in Pasadena, California, to talk with Michael Mischna, a planetary scientist who works on the Curiosity team. What follows is our conversation about Curiosity's mind-blowing technologies and what those technologies might tell us about the history of Mars.
This mission features a lot of next-level engineering, but its landing technology might be its most impressive feature. Can you describe how Curiosity will land on the Martian surface?
Mischna: Curiosity, like most of the spacecraft that have gone to Mars, will arrive in a capsule; as it approaches the surface, the friction of Mars' atmosphere will slow the spacecraft and trigger a special steering system onboard. That's one of the unique things about this mission -- the capsule isn't just a ballistic object plummeting through space. It actually moves in response to precise conditions in the atmosphere. After the capsule slows to a certain speed, a parachute will deploy to slow it down even further. The capsule's heat shield will drop off the bottom and expose the rover to the Martian atmosphere, after which the rover will detach from the parachute and plummet to the ground on this cool thing we call a sky crane. A sky crane is a rocket system in the underbelly of the spacecraft; its rockets fire towards the ground, allowing the spacecraft to slow and then hover 30 to 50 meters from the surface. Then cables come down and Curiosity, the rover, is lowered to the ground. When the rover senses touchdown on the surface, the cables detach and the sky-crane system launches off into the distance.
Another thing to note -- there are going to be orbiters passing overhead at the time of entry. When the Phoenix Lander landed on Mars back in 2008, we were able to capture remarkable images of it rocketing through the atmosphere, with its parachutes deployed. We're going to try to do the same thing with this one, but it's a hit or miss thing because it requires a high level of precision to pull that kind of thing off.
You say the sky crane launches off in the distance; is that because you want to avoid damaging the rover?
Mischna: Exactly. You want to make sure that it lands sufficiently far away so that nothing happens to the rover. The gravity on Mars is about one-third of the gravity we have here on Earth, which means you don't need as much rocket power to make the spacecraft hover -- but it's still a lot of power. To get something of this size to the Martian surface, you have to come up with a whole new landing system because the air bags, which we used on previous rovers, just aren't going to work. It would be like dropping a piano wrapped in bubble wrap and expecting it to land without damage. We had to completely rethink our approach to landing, but that's a good thing, because we hope this will be the first of many projects like it, eventually leading to human exploration on Mars. And if you're going to send humans to Mars, you're going to need to bring a lot of heavy equipment -- places to live, food, water, etc.
Curiosity is about 10-15 feet long, roughly the size of a Mini Cooper, and yet it has a wide range of scientific instruments onboard. In fact, the official name of this rover is the Mars Science Laboratory. What are its most impressive instruments?
Mischna: The remote sensing mask is really extraordinary. It has two rectangular eyes -- a primary imaging camera with a bunch of different filters and focal lengths, and another large, circular camera that can fire a laser that turns rock into vapor, which is picked up by another camera that interprets its composition. So, yeah, this rover can go around firing laser beams at rocks and other materials to find out what they're made of; I'd say that's one of its most impressive instruments.
It also has a meteorology station that will measure the temperature, pressure, wind and relative humidity of the Martian surface. It has a 7-foot robotic arm with a number of different components at the end of it, including scoops and percussion drills that allow it to chip off and pick up rock samples. It also has an alpha proton x-ray spectrometer, which can identify minerals in surface rocks by firing x-rays into them. It has a microscopic camera called MAHLI, the Mars Hand Lens Imager, that images microscopic features in the soil, which can tell you how it evolved over time. There is another instrument called DAN that fires neutrons into the surface, in order to detect water underneath it. Last but not least, there's SAM, which is an acronym for Sample Analysis from Mars. This is the rover's real workhorse; it takes soil samples, drops them into an oven where they are baked to over 1000º Celsius and then senses the gases that leach off, which can tell you the composition of the rock.