NASA’s Mars rover aims for dicey landing to search for ancient life
They call it the “seven minutes of terror,” which doesn’t do justice to the weeks of anxiety, troubleshooting, second-guessing, sleepless nights — the mental cataloguing of all that could go wrong and all that must go exactly right. One cataloger is Matt Wallace, deputy project manager for NASA’s Perseverance rover mission. He has a simple way of describing what the space agency expects him and his fellow engineers to do: “Land a car on Mars.”
This is one of the hardest technological feats human beings have ever attempted. The spacecraft carrying Perseverance, which launched from Earth at the end of July, is expected to arrive on Thursday at Mars at 12,000 miles per hour — six times faster than a bullet shot from an M16 — in what amounts to a controlled collision. Somehow, that velocity has to reach zero, with the rover deposited lovingly on the surface inside a crater named Jezero.
Hitting the 4.8-milewide landing site targeted by NASA after a journey of 300 million miles is akin to throwing a dart from the White House and scoring a bull’s eye in Dallas.
This is one of NASA’s most important endeavors, the first multibillion-dollar Mars mission in nine years and the initial phase of a three-mission campaign to return samples of Martian soil to Earth. The rover is poised to land just days after two other robotic spacecraft, launched by China and the United Arab Emirates, reached Mars and went into orbit.
Perseverance will do more than probe the surface: It will also test technologies that someday could be used on Mars by astronauts, including a system for converting atmospheric carbon dioxide to oxygen. NASA’s human spaceflight program aims for a return mission to the moon in coming years, but Mars remains the horizon goal.
NASA describes this as an astrobiology mission. Perseverance has instruments that might detect structures consistent with ancient life on the Red Planet. Or those instruments might detect nothing remotely suggestive of life. Either way, NASA wants the soil samples back for study in laboratories, hoping to answer fundamental questions about life in the solar system and beyond. Finding a second data point for life would be one of the greatest discoveries in the history of science.
But first the engineers have to pull off the EDL — the entry, descent and landing. It is the hardest part of the mission, fraught with opportunities for what aerospace engineers call “a bad day.” The EDL requires a heat shield, a parachute, rocket thrusters and a sky crane that finally lowers the rover to the surface. All these things have to work with exquisite precision and entirely autonomously.
“We’re basically watching the spacecraft disassemble itself as it’s hurtling toward the ground,” Wallace said. “Success depends on everything going right, down to fractions of a second. There’s no go-back, no retry.” Humans have been exploring Mars robotically for more
than half a century, and roughly half the missions (including those operated by other countries) have failed. Spacecraft have simply vanished. Still, NASA has been on a roll with its rovers in recent years — first with Spirit and Opportunity, which landed in 2004, and then with the heftier Curiosity, which is still chugging along. When Curiosity touched down softly in 2012, the video of the “seven minutes of terror” and the wild high-fiving celebration at the Jet Propulsion Laboratory earned viral traffic on the Internet.
Past success does not guarantee future success. This time, the rover landing will be different in two key respects. First, there are more cameras involved, and it will be visually more appealing. Engineers will have multiple angles (with some time delay because of the 11 minutes it takes for a signal to reach Earth at the speed of light) on what the rover is experiencing as it lands on Mars.
Second, this is a much harder target. Curiosity in 2012 landed on flat terrain, the equivalent of a massive empty parking lot. Perseverance will attempt to touch down inside Jezero Crater, a 30-mile-wide basin crammed with boulders, gullies, cliffs and, most enticingly, the remnants of an ancient river delta with sediments that scientists hope will contain evidence of past life on Mars.
From a science perspective, that’s a great target. Engineers view it differently.
“When I look at it from a landing perspective, I see danger,” Allen Chen, the 41-year-old leader of the EDL team, said.
The spacecraft will have to use a new system, packed with artificial intelligence, to scan the terrain and match it with maps of Mars to try to pick out a landing spot. If all goes well, the autonomous decision-making of the spacecraft will ensure it is not stuck in deep sand, or dangling over a cliff, or perched on top of a boulder. Or upside down. “Landing upside-down is a bad day,” Chen said.
NASA engineer Swati Mohan and her colleagues developed the terrain relative navigation system after asking themselves: How do you give a robot a brain like the one in the skull of Apollo 11 astronaut Neil Armstrong? When Armstrong descended to the moon in the lunar module, the Eagle, he peered out the window to steer his spacecraft by the landmarks spotted below, dodging boulders and craters that could have spelled disaster.