The Martian surfaceNASA / JPL / Cornell

In 2012, it took the Curiosity rover seven minutes to descend from the top of the Martian atmosphere down to the surface, slowing from a speed of 13,000 miles per hour to zero. It took double that for signals from the spacecraft to reach Earth. NASA scientists and engineers held their breath as these minutes passed, waiting to learn the fate of their spacecraft. (Curiosity turned out fine.)

This year, NASA will again experience these “seven minutes of terror” when its newest Mars mission arrives at the planet in November. Unlike the Curiosity rover, the InSight lander—the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport—will spend its lifetime in one spot on the Martian surface, burrowing beneath the soil to study the properties of planet’s interior.

The mission launches early Saturday from California, weather permitting. (Right now, meteorologists with the U.S. Air Force wing that oversees launch operations at Vandenberg Air Force Base predict just a 20 percent chance of good weather for liftoff. InSight has until June 8 to launch, when Earth and Mars begin to shift out of the alignment that makes for a quick, direct trip.)

But before enduring another terrifying descent, NASA has to get through six months of waiting.

During the long cruise, InSight’s team of scientists, engineers, and other staff will practice operations, test out command sequences, and exercise a whole lot of patience.

The journey begins with a collective sigh of relief from the people InSight leaves behind on Earth. By the time a spacecraft reaches the launchpad, virtually every piece of it has been vigorously tested—dunked into cryogenic chambers, shaken violently from side to side, blasted with loud noises. It’s held together with heavy metal, but also some blood, sweat, and tears. When the spacecraft finally launches into space, a weight is lifted in more ways than one.

“You’re relieved. It’s done,” says Florence Tan, the deputy chief technologist at NASA’s Science Mission Directorate. Tan was the electrical lead engineer for Curiosity’s sample-analysis unit. She also worked on the Cassini mission that plunged into Saturn last year, and which took seven years to reach its destination. “You can’t do anything about it. You can’t bring something back.”

The flutes and bubbly will come out, but the celebration will be short. Within days of launch, the InSight team must conduct a check of the spacecraft’s hardware to make sure it survived the stresses of launch. They’ll make more checks like that, monitoring the health of the instruments and various systems.

Most of the cruise is one giant dress rehearsal. Staff undergo a barrage of operations-readiness tests. They practice the operations, data collection, and analysis that their spacecraft will experience once it’s on Mars. They simulate everything from the deployment of instruments to planning meetings. They test how and when to send commands, making sure a set from one team doesn’t interfere with another’s.

During Curiosity’s nine-month cruise, NASA plopped a replica rover in the New Mexico desert and had scientists and engineers back at the lab pretend it was the real thing. They’d study grainy photos of the landscape and plan where to take the rover, where to drill for soil samples.

“When we finally arrive, we’re not like deer caught in headlights,” Tan said.

NASA doesn’t make it easy, either. “The people who created the tests would throw a few glitches in to see how we would react if there was a problem,” said Paul Mahaffy, the principal investigator of Curiosity’s sample-analysis unit that Tan helped build.

And, all the while, they’re periodically checking in with the spacecraft to assess the health of instruments and various systems. It’s rare, but disaster can strike during the cruise phase. In 2002, a spacecraft dispatched to study two comets in the inner solar system broke apart just six weeks after launch. CONTOUR—COmet Nucleus TOUR—fired its engines to push itself out of Earth’s orbit and bring it closer to its targets, but ended up overheating and split into pieces. Tan, who helped build CONTOUR, says its untimely demise was a shock.

InSight will make similar course corrections on its way to Mars. The lander, with its spindly legs and round solar panels on either side, looks kind of like a mosquito. It will delve deeper than previous missions, which were concerned mostly with the Martian surface, like canyons, rocks, and soil, and investigate the planet’s interior, its crust, mantle, and core.

After landing, the lander’s 7-foot-long arm will extract two instruments and place them on the surface in front of it. A seismometer will track quakes, which on Mars are called, appropriately, Marsquakes. Scientists believe quakes could be produced by meteorites hitting the surface or tectonic activity beneath the surface.  A “heat probe” will measure the planet’s interior temperature. Back on the spacecraft, two radio antennas will track how the interior affects the planet’s motion around the sun.

And there will be a camera, ready to capture the lander’s little workspace millions of miles away from Earth.

Scientists hope the InSight mission will help them learn more about the formation of the solar system’s rocky planets, including Earth. Of course, InSight has to survive the journey and then stick the landing before any of that happens. And sending a spacecraft to Mars is easier than gently setting it down on the surface.

Only one country, the United States, has successfully landed something on Mars (though there have been failures, and as recently as 1999). Several landers launched by the Soviet Union in the 1970s all failed, either during descent or minutes after landing. The last attempt to put a lander on Mars was in 2016 by the Europeans. The spacecraft, named Schiaparelli after a 19th-century astronomer, crashed. In images taken by Mars orbiters afterward, Schiaparelli appears as a charcoal-colored splat against the rusty-red terrain.

When the time for landing comes for InSight, Matt Golombek will get brought in. Golombek is “the landing site guy” at NASA’s Jet Propulsion Laboratory in California; he’s spent 20 years picking out and evaluating potential sites for Mars missions, including the first successful rover, Sojourner, which reached the planet in 1997. The landing site for every Mars mission is always “a smooth, flat, boring place,” Golombek said. Rocky terrain, sharp outcrops, and sloped areas could all damage or tip over spacecraft. And since InSight doesn’t have roaming powers, the team has little room for error. The landing procedures are automated, so there’s not much they can do as the spacecraft makes it descent.

“It’s sort of like launch,” Golombek said. “You’re sitting there, the rocket’s all preprogrammed, and all you can do is pray that it does its job.”

I asked him if he ever gets impatient during the months-long wait until this nail-biting moment.

“No, I think I’ve done this enough times to know that it doesn’t matter,” he said. “You’re just gonna have to wait.”

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