Early next week, NASA will attempt the grueling feat of landing a spacecraft on Mars, hoping to add to its growing collection of tech on the Red Planet’s surface. This time, NASA hopes to place a robotic lander, called InSight, on a flat, boring part of the Martian terrain in order to study the planet’s interior. And to do that, the car-sized robot must perform a perfectly synchronized landing routine — one that will slow the vehicle down from more than 12,000 miles per hour to zero in just six-and-a-half minutes.

Launched on May 5th from California, InSight has been traveling through space for the last six months and is scheduled to enter Mars’ atmosphere on Monday, November 26th. During its descent to the surface, the lander will be subject to extremely high temperatures, speeds, and forces. To survive, InSight will autonomously go through dozens of programmed steps, such as deploying a supersonic parachute and igniting onboard thrusters. Each of the steps must happen at precisely the right time to help the lander touch down safely. “[We have] to take out all this energy we have when we arrive at Mars so we have a soft landing when we get to the surface,” Rob Grover, the systems lead on the landing for InSight at NASA’s Jet Propulsion Laboratory, tells The Verge.

landing on Mars is no trivial task

Such a complex procedure is needed because landing on Mars is no trivial task. The biggest obstacle that InSight’s engineers had to contend with is the planet’s atmosphere. Even though Mars’ atmosphere is quite thin — less than one-hundredth the density of Earth’s atmosphere — it’s thick enough to cause incoming vehicles to heat up on the way down to the ground. That means Martian spacecraft need proper shielding if they hope to reach the surface without melting. But because the atmosphere is thinner than ours, it also means that parachutes on Mars aren’t as effective at slowing down spacecraft as they are on Earth. Engineers had to add thrusters to ensure that the lander would touch down gently.

InSight is equipped for all of this. But it’s possible the lander may encounter a particularly uninviting environment when it arrives, as the vehicle will be landing in the middle of Mars’ dust storm season. So far, the weather seems calm, but it’s possible a storm may develop before InSight’s landing. If so, the mission team would have to do some last-minute reworking of the flight plan — though they’re confident InSight can handle it. “We’ve designed the system to be able to handle that range of environments,” says Grover. “It’s currently looking like we’re not going to have a dust storm, but we still have [some time] to go, and a dust storm can blow up in a matter of days.”

For space enthusiasts, InSight’s landing may conjure up memories of NASA’s last mission to Mars — when the space agency landed the Curiosity rover on the Red Planet’s surface. For that trip, the landing was dubbed the “Seven Minutes of Terror.” The label referred to the fact that Curiosity also had to perform a synchronized routine in a short period of time to get down in one piece. While it used parachutes and thrusters, Curiosity even had to be lowered down with a specialized tether known as a sky crane at the end of the fall, so that it could land safely.

At 789 pounds, InSight is not as heavy as the nearly 2,000-pound Curiosity, so its landing does not need to be as complicated (i.e. no sky crane necessary). However, it is similar in size and weight to another recent Martian lander that didn’t fare so well. In 2016, Roscosmos and the European Space Agency attempted to land a joint spacecraft called Schiaparelli on Mars, in order to test out landing techniques for a future rover. But during its descent, the lander’s onboard computer received bad data from the spacecraft’s instruments, which caused the vehicle to release its parachute earlier than planned. As a result, Schiaparelli slammed into the Martian ground, creating a new crater on the surface.

every piece of the landing puzzle must be executed as planned — without any help from those on Earth

Since 1999, when the agency lost the Mars Polar Lander, NASA has landed its vehicles safely on the Red Planet, so hopefully things go a bit better for InSight. But the more recent Schiaparelli incident does highlight how every piece of the landing puzzle must be executed as planned — without any help from those on Earth. At the time of InSight’s landing, one light signal from our planet will take about eight minutes to reach Mars. “By the time we’re understanding what’s happening with the landing, there’s a large enough delay that we can’t actually control the vehicle from Earth,” says Grover. “Everything has to be completely autonomous and automated.”

Once InSight hits the atmosphere, that’s when the automated routine kicks in. At that time, InSight will be moving at about 12,300 miles per hour. The lander descends, equipped with a heat shield that’s pointed downward. That’s to protect the spacecraft’s sensitive instruments from temperatures reaching a peak 2,700 degrees Fahrenheit. The atmosphere slows the lander to less than 1,000 miles per hour.

When the vehicle reaches about seven miles above the surface, the lander deploys a supersonic parachute to slow even further. The heat shield eventually drops away and when the lander reaches a mile high, it drops away from the back shell with the parachute and ignites its onboard thrusters. These engines maneuver the lander to a safe spot and lower the spacecraft gently down to the ground.

During the last year, the mission team conducted multiple dress rehearsals for the landing, which last for days at a time. During these events, the InSight team mimicked what they’ll be doing during the time leading up to the landing, using a test spacecraft located at the Denver headquarters of Lockheed Martin — the primary contractor of InSight. Prior to the fateful fall, engineers will constantly assess what the weather is like on Mars and what the spacecraft’s trajectory looks like. They’ll then make tweaks to the planned landing sequence, depending on the most up-to-date information they have. For instance, if a dust storm does happen to develop before the landing, they’ll change the timing of when the parachute deploys to best fit the atmosphere.

the mission team conducted multiple dress rehearsals for the landing, which last for days at a time

They even did one dress rehearsal where everything went off the rails. “We have a team of gremlins working behind the scenes that throw all kinds of problems and issues at us for us to work through in the rehearsal,” says Grover. “That one in particular is a lot of fun and really stresses the team and gets us ready for whatever might come our way during the landing.”

The team conducted their final dress rehearsal in October, so now it’s time for the real thing. InSight is scheduled to land on Mars at around 3PM ET on November 26th. Once on the ground, the lander will send out a beacon about 10 seconds after touchdown to alert engineers on Earth that the spacecraft is alive and firmly in place. There’s also the possibility of getting an outside perspective of how the landing went. Two experimental probes, known as the MarCO satellites, are riding to the RedPlanet with the lander, and they’ll try to provide information about the landing from space.

“Since they’re experimental, we’re not completely sure they’re going to work on landing day,” says Grover. “But if we have that data, we’ll have a lot of information about the lander, and we’ll know with real clarity that we’re successfully on the surface.”

If all goes well with landing (which will prompt a small celebration), engineers will then spend the next two to three months deploying InSight’s instruments. The lander has two main tools to study the Martian interior: a seismometer to listen for Mars quakes and a self-hammering nail that will dive 16 feet underground to take the planet’s temperature. InSight is equipped with a robotic arm that will gingerly place the two instruments away from the lander. And once deployed, the data collected from these instruments will help scientists better understand the types of rocks in Mars’ mantle and core.

These instruments are very sensitive, though, and the seismometer must remain very still to get the best data. If the seismometer is deployed too close to InSight, even tiny vibrations on the lander, perhaps caused by wind, could muck up the data. That’s why scientists will spend a few weeks to find the best spots to deploy these instruments, using InSight’s cameras. “If you ever play those claw games at carnivals, you want to make sure you’re perfectly lined up with the prize you want before you push the button to go try and grab it,” Elizabeth Barrett, a science system engineer at NASA JPL, tells The Verge.

“After spending so many years working on it, when the data arrives, it’s a little surreal.”

NASA scientists have specifically picked the flattest, most boring place on Mars to help the instruments do their best jobs. However, Barrett says the instruments can still work if InSight happens to land on a slope of some kind. “We have a little bit of tilt that we can still accept and meet our mission goals,” says Barrett. “We can work around putting the instruments in locations that may not be perfect for them, but they still can actually get good science data.”

Scientists will know for sure what InSight’s terrain looks like when it lands. But for now, the focus is on making sure the landing goes according to plan. For many on the team, touching down on the surface of Mars will represent years of hard work and preparation culminating in a single event. “We’re excited,” says Grover, anticipating the moment when he’s in the control room for the landing. “After spending so many years working on it, when the data arrives, it’s a little surreal.”