- NASA’s Perseverance rover is set to land on Mars on Thursday, February 18.
- Entry, descent, and landing are the trickiest parts of a Mars mission, often called the “seven minutes of terror.”
- To land in the Jezero Crater, Perseverance will use a jetpack and advanced navigation system.
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NASA is about to accomplish an unprecedented feat: The agency’s Perseverance Mars rover is set to film its own high-stakes landing.
The vehicle has almost reached its destination. On February 18, after nearly seven months and 300 million miles of space travel, the robot is slated to to plummet through the thin Martian atmosphere, deploy a parachute and a jetpack, then gently land in an ancient lake bed.
Once set up there, it will search for mineral deposits from an old lake, which could contain signs of ancient microbial life. The rover is programmed to cache samples of Martian rock and soil so that a future mission can carry them back to Earth for scientists to study.
But first, the rover must land successfully.
“I don’t think I’m exaggerating when I say that entry, descent, and landing is the most critical and most dangerous part of a mission,” Allen Chen, who leads that process for Perseverance at NASA’s Jet Propulsion Laboratory, said in a press briefing. “Success is never assured and that’s especially true when we’re trying to land the biggest, heaviest, and most complicated rover we’ve ever built to the most dangerous site we’ve ever attempted to land at.”
A series of precise, automated maneuvers must go exactly right to safely deliver Perseverance to its destination. There’s no room for error.
That’s why aerospace engineers have a special nickname for this phase of a Mars mission: “seven minutes of terror.”
For Perseverance, this process will be all the more terrifying because of its landing site. Mars’ Jezero Crater is a dried-up lake bed rich with exposed layers of ancient rock, which could hold remnants of past microbial life. Steep cliffs run through the middle of the landing site, along with sand dunes and boulders.
“Jezero Crater is a great place, magnificent place for science,” Chen said. “But when I look at it from a landing perspective, I see danger.”
If Perseverance arrives safely, however, it will then beam back the first video footage of a landing on another planet. High-definition cameras and microphones on the rover should record the whole thing, and NASA has said it will make the footage available later.
“We’re really looking forward to bringing everyone for the ride,” Chen said.
A parachute and a jetpack will slow Perseverance’s plummet
A NASA animation shows what the Perseverance landing should look like if all goes well:
The illustration below breaks down each step of that process.
“We’ve got literally seven minutes to get from the top of the atmosphere to the surface of Mars, going from 13,000 mph to zero in perfect sequence, perfect choreography, perfect timing,” Adam Steltzner, chief engineer of the Perseverance mission, said in a 2012 NASA-JPL video about the Curiosity rover (which is still going strong on Mars). “The computer has to do it all by itself with no help from the ground. If any one thing doesn’t work just right, it’s game over.”
The first step in Perseverance’s landing process is for the spacecraft that’s carried it 300 million miles to drop its cargo: a top-shaped capsule with the rover inside. This entry capsule will succumb to Mars’ gravity and plummet towards the planet, protecting Perseverance with a heat shield.
The capsule will plow through the Martian atmosphere at over 12,000 mph, and its shield should deflect material that’s been super-heated by that extreme speed. The outside of the heat shield will get as hot as 2,370 degrees Fahrenheit. This will cause it to streak across the Martian sky like a bright meteor.
Mars’ atmosphere is about 1% as thick as ours on Earth, but it should still slow the capsule down.
The capsule must use its thrusters to steer itself toward the landing target, since pockets of air with varying density can tilt it off-course.
Once it’s slowed to twice the speed of sound, Perseverance will deploy a 70-foot-wide parachute. Then the capsule will jettison its heat shield, clearing the way for the rover’s radar system to survey the land below. An autopilot-like navigation system should kick in to reconfigure the vehicle’s trajectory toward the landing site.
That system, called “terrain-relative navigation,” compares what the rover’s cameras see to an onboard map of the Martian surface, built from satellite imagery. It should recognize and avoid the cliffs, sand dunes, and boulder fields that litter Jezero Crater.
Perseverance’s supersonic parachute can only slow its descent to about 150 mph – as fast as a skydiver plummeting to Earth with no parachute. That’s why NASA engineers also equipped the rover with a jetpack.
About a mile above the Martian surface, the jetpack will ignite its engines, with the rover attached to its underside.
The jetpack will separate from the remaining parts of the entry capsule and fly Perseverance to a safe spot identified by the terrain-relative navigation. By the time the rover reaches its landing place, its speed should have slowed to about 1.5 mph.
Very slowly, the jetpack will unspool 25-foot-long nylon cords that will lower Perseverance until its wheels touch the ground.
A few minutes later, mission controllers should get the signal that the rover touched down.
After that, assuming everything has gone right, the rover will spend a few months checking and calibrating its scientific instruments. Then it will release a helicopter from its belly and turn its cameras to the drone as it lifts off for the first-ever controlled flight on another planet.
Then the rover will continue on its core mission: searching for ancient rocks that could hold hints of microbial alien life.