It's been one year since a nuclear-powered, one-armed, six-wheeled robot punched through the Martian atmosphere at a blazing 12,000 miles per hour, and a supersonic parachute slowed it way down until a rocket-powered "jetpack" could fire its engines and then gently lower it onto the surface.
NASA's Perseverance rover was too far away for engineers on Earth to control it in real time – which meant that the spacecraft had to execute that daredevil maneuver all by itself. All that the robot's handlers on Earth could do was wait for confirmation that it had touched down safely.
"It is a nail-biting experience," Rick Welch, Perseverance's deputy project manager. "There's no doubt about it."
Dramatic as the Feb. 18, 2021 touchdown was, the milestones that the car-sized rover has hit in the year since then could one day prove far more momentous.
Perseverance is hunting for evidence of microbes that may have once lived on the red planet – a first for a NASA robot. It begins a new chapter of Martian exploration: one that not only searches for ancient signs of microbial Martians, but that lays the groundwork to send samples of Mars rocks and dirt back to Earth.
One of the mission's main objectives is to collect samples of rocks and dirt and stash them on the surface of Mars so that a future mission could pick them up and bring them back to Earth to study. The $2.7-billion rover is equipped with a suite of scientific instruments including a rock-blasting laser, cameras and spectrometers.
But a robot geologist – even one as advanced as Perseverance – can only do so much. Scientists really hope to get pieces of the planet back to their labs.
"That's really the major reason for wanting to collect and return samples," says Welch. "We could really understand Mars much better by getting those samples here on Earth."
A history of searching for life on Mars
Perseverance is the first NASA rover sent to search for signs of ancient life. Nearly a half-century ago, NASA sent a pair of landers to Mars, marking the first U.S. mission to successfully touch down on the planet. The Viking mission, launched in 1975, aimed to look for current life on Mars – and came up empty.
"The results from the Viking Landers were ambiguous and taught us that we needed to better understand the surface of Mars and potential habitats on Mars," says Mary Voytek, NASA's senior scientist for astrobiology.
Follow-up missions of orbiters, landers and rovers looked to see if Mars was even habitable to begin with. They focused on searching first for signs of ancient water — a key to life as we know it here on Earth. Rovers like Spirit and Opportunity, launched in 2003, and Curiosity, launched in 2011, provided the groundwork for Perseverance to begin searching for ancient microbes in the rocks and dirt on Mars.
Perseverance is searching an area on Mars known as Jezero crater. Scientists think this might have been an ancient lake fed by a flow of Martian rivers. Over the next few months, the rover is making a beeline towards a river delta at the edge of the crater.
"Life as we know it requires habitable environments," says Amy Williams, an astrobiologist at the University of Florida and scientist on the mission. The assumption is that life on Mars would need water as a universal solvent, much like life here on Earth. "Finding environments where we know water flowed is one of the big boxes we can check off to say this is a really great location for us to perform this investigation."
Much like river deltas here on Earth, scientists expect to find layers and layers of rich, geological history trapped in the sediment — a prime spot for drilling samples which might have trapped evidence of past Martian life.
Confirming ancient life on another planet would be an extraordinary finding, experts say one that will require extraordinary evidence.
"Having samples returned is the only way that I, and I'm sure many other astrobiologists, would be truly convinced that we had found evidence for life on Mars," says Williams.
The rover is equipped with drills and sample tubes and has already begun collecting bits of Martian rock. In its first year, it has collected and stashed 6 samples, with the opportunity to collect up to 40.
NASA and the European Space Agency are working together to develop a mission to collect those samples, launch them off the surface of Mars and safely return them to Earth.
"It is an incredibly complex mission," says Lori Glaze, NASA's planetary science division director, of the technical and funding challenges ahead.
The agency awarded Lockheed Martin a contract to develop the Mars ascent vehicle, which will be the first rocket to launch a payload off of another planet. But other pieces of the mission's architecture are still in the works.
"We're still pretty early on in the development but we are working to get those samples back here as soon as we can," says Glaze.
If all goes well, scientists could have their hands on Martian rocks in 2031.
The little chopper that could
While scientists wait for Perseverance to collect Martian samples, the mission is breaking ground in other ways. A tiny helicopter stowed away on the belly of the rover has completed 19 successful flights on the surface of Mars. What started as a proof of concept — that engineers could even design an aircraft that could fly in Mars' thin atmosphere — is now helping the rover spot new places to explore.
"It really is game changing," says Glaze. "The helicopter is able to fly over areas that are too rugged for the rover to traverse. We're able to see these high-resolution images in areas the rover can't actually reach and thinking forward to maybe future exploration."
Ingenuity is helping navigate Perseverance to that key target: a geologically-rich river delta where scientists hope to peel back layers of Martian history written in the rocks by ancient water. Over the next several months, Perseverance will make its way there — with Ingenuity hopping along ahead to scope out the path.
But all good things must come to an end. While it hasn't shown any signs of slowing yet, the parts on the tiny aircraft will eventually give out. "I think [the team] will miss it when it's gone," says Glaze.
The path ahead
The rover is also helping plan for future human missions to Mars, like taking fabric samples that could one day be used for Mars-bound astronaut suits and exposing them to the planet's harsh atmosphere. Another experiment called MOXIE is working to convert that atmosphere into oxygen that could potentially be used for fuel or for life support, pure enough to breathe.
As it makes its way towards the sediment-rich river delta of Jezero crater, Perseverance is sending back stunning images of its new home on Mars.
"We started getting back some early images, just from where we are right now, of the valley," says Briony Horgan, a planetary scientist at Purdue University and scientists on the mission. "It really is like Monument Valley on Mars. It's fantastic."
Perseverance is putting a lot of ground under its six wheels thanks to rugged new tires and a self-driving computer. The rover pretty much drives itself at blazing speeds — at least for a robot.
"We can drive on the order of up to about 200 meters a day," or about 650 feet, says Horgan. "It's a pretty good speed, especially if you consider it is a robot driving itself 150 million miles away."
But the state-of-the-art rover, which has traveled more than two miles already, will have plenty more exploring to do to catch up with its predecessors. Curiosity has covered nearly 17 miles on the Martian surface, while Opportunity covered more than 28 miles before reaching its final resting place: Perseverance Valley.
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