After a seven-month journey through the vacant reaches of interplanetary space, NASA’s Perseverance rover is on the cusp of reaching its destination and beginning the most ambitious quest to date for signs of past life on Mars.
The U.S. spacecraft is not alone. In addition to several probes that have been operating on Mars for years, two new arrivals showed up last week, including an orbiter dispatched by the United Arab Emirates and China’s first Mars mission, which consists of an orbiter and a lander that will attempt to set down later this spring.
But for the hundreds of scientists and engineers connected with Perseverance, including many in Canada, the drama and anticipation will peak shortly before 4 p.m. ET on Thursday, when the US$2.2-billion spacecraft will have to go from a cruising speed of just under 20,000 kilometres an hour as it hits the Martian atmosphere to sitting safely at rest on the planet’s surface less than seven minutes later.
“It’s different every time, thrilling every time … and terrifying every time,” said Jim Bell, a planetary scientist at Arizona State University. He has been through the experience on four previous occasions as part of the science team on every Mars rover mission since the concept was first tested in 1997.
One obvious difference is that Dr. Bell will be at his home base in Tempe rather than at mission control at the Jet Propulsion Laboratory in Pasadena, Calif. Because of restrictions related to the COVID-19 pandemic, most of the science team and journalists covering the mission will experience the landing remotely.
Of course, the entire mission is remote in the sense that no human has ever set foot on Mars, but over the years, increasingly sophisticated rovers have created a vivid impression of what it might be like to walk around on the planet’s dusty, boulder-strewn surface.
The rover’s immediate predecessor, dubbed Curiosity, set down in the summer of 2012 in Gale crater and it has been busy ever since, meticulously gathering data on what that location was like more than 3.1 billion years ago at a time when it’s thought that water covered the crater floor.
Perseverance has a more demanding task and an even more intriguing landing site to go with it. Its goal is to look for places where Martian microbes may have flourished and left traces of their existence at an even earlier time, more than 3.7 billion years ago, and then collect rock samples that can be picked up and returned to Earth by a future mission.
The place chosen for the rock hunt is Jezero crater, named by the International Astronomical Union after a village in Bosnia and Herzegovina that sits beside a mountain lake. Like its namesake today, Jezero crater was once a lake environment. Its key feature is a dried out river delta where swift-moving water that once flowed in through a gap in the crater rim dumped mud and debris in a large fan-shaped structure.
On Thursday, the rover will attempt to touch down near or possibly on top of the feature to probe its multilayered history. Planetary scientists have had their eyes on the steep-sided delta for years. Only with Perseverance, which will attempt to guide itself down to the surface using a technology called “terrain-relative navigation,” has there been the capability to land a rover so close to a feature that is so interesting but with so many potential hazards.
“This site is all about the delta. … It has the promise of being scientifically rewarding and also visually stunning‚” said Dr. Bell, who led the development of Mastcam-Z, the camera that will serve as the rover’s keenest eyes on Mars.
About two days after the rover lands, the camera is scheduled to rise up on its mast and begin scanning its surroundings, offering panoramic views that include colours beyond the reach of the human eye.
“That’s crucial. … It links what we can see from orbit with what we might find at a cliff face,” said Chris Herd, a planetary geologist at the University of Alberta who is part of the team of scientists that will use the camera data to help determine where the rover should search for samples that may reveal if Mars once hosted life.
None of that will happen right away. Even if Perseverance has a flawless landing, the rover will spend its first several weeks checking out its many instruments and systems. It will also deploy a small helicopter that will attempt the first powered flight on another world.
But if all goes well, the delta awaits, said Mariek Schmidt, a geologist at Brock University in St. Catharines, Ont., who worked on previous rover missions and recently joined the Perseverance science team.
Those earlier rovers paved the way by showing that Mars was once a habitable world, at least for microbial life, Dr. Schmidt said. Now, with Perseverance, it may be possible to determine if something actually lived there.
“We’re asking some really big-picture questions that we haven’t been able to ask before,” she said. “In order do that, we’re going to have to bring samples home.”
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