Editor’s Note: NASA's Perseverance rover successfully landed on Mars on February 18 just before 4 p.m. eastern time. Read more about the mission here.
After a seven-month, nearly 300-million-mile journey to Mars, NASA’s Perseverance rover is poised to undertake one of the most challenging engineering feats in human history: touchdown on the red planet.
At 3:55 p.m. eastern time today, the 2,260-pound rover—the heaviest object ever sent to the surface of another planet—should set its wheels in the ruddy dirt of Jezero Crater to begin its search for signs of past life. But to get to the ground, the rover must endure what NASA calls the seven minutes of terror. The spacecraft carrying the rover has been hurtling from Earth to Mars and will slam into the atmosphere at high speed. So in the span of about seven minutes, the spacecraft must slow its descent and settle gently on the surface.
“Landing on Mars is really all about finding a way to stop,” says Allen Chen, the lead engineer for Perseverance’s entry, descent, and landing (EDL) system. “Perseverance will hit the atmosphere going over 12,000 miles per hour, but it needs to touch down at about two miles per hour.”
To land, Perseverance will use a sky crane, a system devised by NASA and used in 2012 to successfully deposit the Curiosity rover in Mars’s Gale Crater. And, for the first time, video cameras and microphones will capture the full descent of a spacecraft as it lands on Mars. “We really want to take people along for the ride this time and see what it’s like to land on another planet,” Chen says.
You can watch live coverage of the landing on NASA TV starting at 2:15 p.m. eastern time, as the mission control team at the Jet Propulsion Laboratory in California track the spacecraft’s descent. But the video and audio of Perseverance’s landing will take more time to transmit to Earth. Due to the current distance between the two planets, sending even a basic radio signal to Earth will take about 11 and a half minutes. And before it can transmit audio or video, the rover must first indicate that it is safe. It will then have several other tasks to perform during its first days on Mars, such as starting up its surface operations software and deploying a mast with its primary science cameras.
If everything goes according to plan, the rover will send back an image tomorrow that will show the view looking down on Perseverance from above. By Monday, the team hopes to release video from the same view. The data for high-quality footage will take longer to transmit and process, so NASA should release high-resolution footage of the entire landing sequence in the coming weeks.
But first, the spacecraft has to make it safely to the surface.
Entry, descent, and landing
Tucked behind a heat shield, the rover will begin to slow when it hits the atmosphere, “like a meteor going across the sky,” Chen says. Thrusters will direct the spacecraft toward its landing site as its body produces lift, “kind of like an airplane in some ways.”
Once it slows to about twice the speed of sound, Perseverance will deploy a 70-foot-wide parachute. “You fire this parachute pack out of the back of the vehicle with basically a cannon,” Chen says. A new technology called the range trigger will fire the parachute according to how close the spacecraft is to the landing site, allowing Perseverance to target a smaller landing zone than Curiosity, which deployed its parachute once it hit a certain velocity. The spacecraft will then jettison its heat shield and get its first look at the ground using radar and another new system called terrain-relative navigation.
“Terrain-relative navigation gives the system eyes, almost literally,” Chen says. By snapping photos of the surface and comparing them to onboard maps, which were created from photos taken by spacecraft orbiting Mars, Perseverance can land with enough precision to touch down in an area scattered with boulders and sloped inclines.
“The Jezero landing site that we’re going to was actually rejected as a landing site for Curiosity because it was too unsafe,” Chen says. But with terrain-relative navigation and the range trigger system, Perseverance can go where no Mars rover could go before.
Even after the chute has slowed the rover, it will still be hurtling toward the ground at about 160 miles an hour. “That’s about as fast as a skydiver would be going, diving straight at the ground without a parachute, here on Earth,” Chen says. In the wispy Martian atmosphere, where the air is less than one percent as thick as Earth’s, a parachute cannot slow the craft any further.
About 1.3 miles above the surface, the spacecraft will release from the parachute and then fire up rocket engines on its descent stage, slowing to about 1.7 miles an hour. At 70 feet above the ground, the descent stage will perform the sky crane maneuver: the landing system will lower the rover to the surface on tethers, then cut the cords and fly off to crash away from the rover.
“Perseverance will lower itself from that rocket-powered jetpack that’s called the descent stage, deploy its wheels—that’s our landing gear—and touch down, you know, slower than I can walk,” Chen says.
Eyes and ears on another planet
As part of the mission, NASA is planning to capture a Mars landing like never before. A camera on the Curiosity rover filmed some of the mission’s landing in 2012, but the Perseverance landing will be recorded from all angles. At various stages, and sometimes simultaneously, multiple cameras will be looking up from the descent stage at the parachute, looking down from the descent stage at the rover, looking up from the rover at the sky crane, and looking down from the rover at the ground.
“It’s the kind of stuff I’ve always been trying to imagine,” Chen says. The first video, showing the rover touch down as seen from above, could be released as early as Monday, and high-resolution video from all of the cameras will be released in the following weeks.
Perseverance will also record audio of the descent using one of two microphones. Attached to the left side of the vehicle above the middle wheel, one mic is expected to capture sounds of the engines firing, pyrotechnic devices on the EDL system blowing bolts and severing cables, the rush of the wind, and hopefully “those wheels actually crunching down onto the surface of Mars,” says David Gruel, the assembly, test, and launch operations manager for Perseverance.
And then, for the first time in history, people will be able to listen to what it sounds like on another planet. “The microphone will be sitting there on the surface of Mars, attached to the rover, listening to the ambient noises,” Gruel says. It will remain on for about a minute after landing, and it could be switched on again for brief recording sessions as long as its temperature-sensitive parts survive the frigid Martian nights.
A second microphone is attached to the rover’s SuperCam, an instrument equipped with a laser to vaporize rocks and determine their composition. That mic will listen to rocks being zapped and maybe even the wheels of Perseverance crunching against the desiccated dirt as it rolls across an alien world.
“We use a lot of imagery, but we’ve never used sound to take part or participate as if you’re on another planet,” Gruel says. “Who knows what exciting discoveries we might have with it.”