The spacecraft was sent to space Thursday in a launch that had no technical problems – even despite an earthquake that struck just before liftoff, and a preparation period that came during the coronavirus outbreak. Shortly after it was launched, Nasa announced that it had received its first signal from the spacecraft.
But soon after it was in space and headed towards Mars, it became apparent that something had gone wrong with the craft. After that initial signal, mission controllers received more detailed telemetry or spacecraft data that showed there had been a problem.
The signal, which arrived on Thursday afternoon, showed that the spacecraft had entered a state known as "safe mode". That shuts down all but its essential systems, until it receives new messages from ission control.
The hibernation state is intended to allow the spacecraft to protect itself in the case of unexpected conditions, and will be triggered when the onboard computer receives data that shows something is not as expected.
Nasa's engineers think that the state was triggered because part of the spacecraft was colder than expected while it was still in Earth's shadow. The spacecraft has now left that shadow and temperatures are now normal, Nasa said in an update.
Mission controllers will now conduct a "full health assessment", the space agency said, and are "working to return the spacecraft to a nominal configuration for its journey to Mars".
The mission's deputy project manager, Matt Wallace, later announced that Nasa will probably switch the craft back to its normal cruise state after a day or so. "Everything is pointing toward a healthy spacecraft ready to go to Mars and do its mission," he said.
The craft had also had some trouble getting a proper connection to the deep-space tracking stations that will communicate with the spacecraft as it flies through space, Mr Wallace said. But that problem appears to have been overcome and a good communication link has been established, he said.
The US, the only country to safely put a spacecraft on Mars, is seeking its ninth successful landing on the planet, which has proved to be the Bermuda Triangle of space exploration, with more than half of the world's missions there burning up, crashing or otherwise ending in failure.
China is sending both a rover an orbiter. The UAE, a newcomer to outer space, has an orbiter en route.
It's the biggest stampede to Mars in spacefaring history. The opportunity to fly between Earth and Mars comes around only once every 26 months when the planets are on the same side of the sun and about as close as they can get.
The launch went off on time at 7:50 a.m. despite a 4.2-magnitude earthquake 20 minutes before liftoff that shook NASA's Jet Propulsion Laboratory in Southern California, which is overseeing the rover.
Launch controllers at Cape Canaveral wore masks and sat spaced apart because of the coronavirus outbreak, which kept hundreds of scientists and other team members away from Perseverance's liftoff.
"That was overwhelming. Overall, just wow!" said Alex Mather, the 13-year-old Virginia schoolboy who proposed the name Perseverance in a NASA competition and watched the launch in person with his parents.
About an hour into the flight, controllers applauded, pumped their fists, exchanged air hugs and pantomimed high-fives when the rocket left Earth's orbit and began hurtling toward Mars.
"We have left the building. We are on our way to Mars," Perseverance's chief engineer, Adam Steltzner, said from JPL.
If all goes well, the rover will descend to the Martian surface on Feb. 18, 2021, in what NASA calls seven minutes of terror, during which the craft will go from 12,000 mph (19,300 kph) to a complete stop. It is carrying 25 cameras and a pair of microphones that will enable Earthlings to vicariously tag along.
Perseverance will aim for Jezero Crater, a treacherous, unexplored expanse of boulders, cliffs, dunes and possibly rocks bearing the chemical signature of microbes from what was a lake more than 3 billion years ago. The rover will store half-ounce (15-gram) rock samples in dozens of super-sterilized titanium tubes.
It also will release a mini helicopter that will attempt the first powered flight on another planet, and test out other technology to prepare the way for future astronauts. That includes equipment for extracting oxygen from Mars' thin carbon-dioxide atmosphere.
The plan is for NASA and the European Space Agency to launch a dune buggy in 2026 to fetch the rock samples, plus a rocket ship that will put the specimens into orbit around Mars. Then another spacecraft will capture the orbiting samples and bring them home.
Samples taken straight from Mars, not drawn from meteorites discovered on Earth, have long been considered "the Holy Grail of Mars science," according to NASA's now-retired Mars czar, Scott Hubbard.
To definitively answer the life-beyond-Earth question, the samples must be analyzed by the best electron microscopes and other instruments, far too big to fit on a spacecraft, he said.
"I've wanted to know if there was life elsewhere in the universe since I was 9 years old. That was more than 60 years ago," Hubbard said from his Northern California cabin. "But just maybe, I'll live to see the fingerprints of life come back from Mars in one of those rock samples."
Additional reporting by agencies