For the first time since launching the Curiosity rover in 2011, NASA is sending a spacecraft to the surface of Mars. Exciting! Surface missions are sexy missions: Everyone loves roving robots and panoramic imagery of other worlds. But the agency's latest interplanetary emissary won't be doing any traveling (it's a lander, not a rover). And while it might snap some pictures of dreamy Martian vistas, it's not the surface that it's targeting.
InSight—short for Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport—will be the first mission to peer deep into Mars' interior, a sweeping geophysical investigation that will help scientists answer questions about the formation, evolution, and composition of the red planet and other rocky bodies in our solar system.
The mission is scheduled to launch some time this month, with a window opening May 5. When the lander arrives at Mars on November 26 of this year, it will land a few degrees north of the equator in a broad, low-lying plain dubbed Elysium Planitia. The locale will afford InSight—a solar-powered, burrowing spacecraft—two major perks: maximum sun exposure and smooth, penetrable terrain. It is here that InSight will unfan its twin solar arrays, deploy its hardware, and settle in for two years of work.
Using a five-fingered grapple at the end of a 2.4-meter robotic arm, the lander will grab its research instruments from its deck (a horizontal surface affixed to the spacecraft itself), lift them into the air, and carefully place them onto the planet's surface. A camera attached to the arm and a second one closer to the ground will help InSight engineers scope out the lander's immediate surroundings and plan how to deploy its equipment.
"Have you ever played the claw game at arcades?” asks payload systems engineer Farah Alibay. “That's essentially what we're doing, millions of miles away." The process will require weeks to prepare, plan, and execute, and involve JPL's In-Situ Instrument Lab—a simulation facility in Pasadena, California where mission planners can practice maneuvering the lander before beaming instructions to Mars. But if the InSight team can pull it off, it will be the first time a robotic arm has been used to set down hardware on another planet.
InSight has two main instruments, the first of which is the Seismic Experiment for Interior Structure, or SEIS. An exquisitely sensitive suite of seismometers, SEIS is designed to detect the size, speed, and frequency of seismic waves produced by the shifting and cracking of the Red Planet's interior. You know: Marsquakes.
"It's as good as any of the Earth-based seismometers that we have," says InSight project manager Tom Hoffman; it can measure ground movements smaller than the width of a hydrogen atom. "If there happened to be a butterfly on Mars, and it landed very lightly on this seismometer, we'd actually be able to detect that," Hoffman says. Other things it could detect, besides Marsquakes, include liquid water, meteorite impacts, and plumes from active volcanoes.
For as sensitive as it is, SEIS is damn hardy. "Seismometer designs on Earth are meant to be delicately handled, placed down, and never touched again," says lead payload systems engineer Johnathan Grinblat. SEIS's journey to Mars will be a little more exciting, what with the rocket launch, atmospheric entry, descent, and landing. "It's going to vibrate and experience lots of shocks, so it has to be robust to that," Grinblat says.
It'll also need to withstand dramatics swings in temperature; temperatures at Mars' equatorial regions can reach 70° Fahrenheit on a sunny summer day, and plummet as low as -100° Fahrenheit at night. To see that it does, InSight engineers matrioshka-d its instruments inside multiple layers of protection. The first is a vacuum-sealed titanium sphere, the second an insulating honeycomb structure. The third is a domed wind and thermal shield that will cover the sensors like a high-tech barbecue lid.
Those systems in place, InSight will reach for its second instrument, the Heat Flow and Physical Properties Probe. Also known as HP3, the 18-inch probe is effectively a giant, self-driving nail. It will jackhammer itself some 16 feet into Mars' soil—deep enough to be unaffected by temperature fluctuations on the planet's surface. "When scientists study temperature flow on Earth, they have to burrow even deeper," says Suzanne Smrekar, InSight's deputy principal investigator, because the moist soil conducts heat deep underground. “So Mars is actually pretty easy, relatively speaking.”
Tell that to the probe. Its descent through the Martian terrain will take weeks. As it burrows, it will pause periodically to measure how effectively the surrounding soil conducts heat. Temperature sensors will trail the probe on a tether, like thermometric beads on a string. Together, the temperature readings and conductivity measurements will tell InSight's scientists how much heat is emanating from the planet's insides—and that heat, or lack of it, will help tell researchers what the planet is made of, and how its composition compares to Earth's.
But before InSight takes Mars' temperature and senses for quakes, it'll have to launch, brave the desolate wilds of interplanetary space, and land. Exciting? Unquestionably. But also: "Everything about going to Mars is terrifying," Alibay says. "We're launching on a rocket that is a barely controlled bomb. We're going through six months of vacuum, being bombarded by solar electric energetic particles. We're going to a planet that we have to target, because if we miss it, we can't just turn around. And we have to land. And once we're on the surface, doing the deployments, any number of things could go wrong."
Alibay's not a pessimist. She's an engineer; anticipating misfires and miscalculations, she says, is part of the job description. Plus, she knows her history: Fewer than 50 percent of Mars missions succeed. "Not because we don't know what we're doing," she says, "but because it's really hard."
Not that that should ever prevent NASA from trying. After all: We do not go to space because it is easy.
Check out the clean room where NASA prepared InSight for launch.
Researchers recently discovered clean water ice just below Mars' surface. InSight could detect even more.
Go behind the scenes as NASA tests the most powerful rocket ever, part of the agency's a decades-spanning effort to send astronauts to explore asteroids, Mars, and beyond.
