NASA's latest Mars rover Perseverance launched on Thursday on an astrobiology mission to look for signs of ancient microbial life on the Red Planet－and to fly a helicopter-drone on another world for the first time.
Previous trips to Mars have discovered it was far warmer and wetter 3 billion years ago than it is today, creating the conditions necessary for carbon-based life.
Perseverance's goal is to go a step further, and discover whether "habitable" translated to "habited".
"There would be no bigger discovery in the history of humanity than finding life that is not on our own world," NASA administrator Jim Bridenstine said.
"If we were to make a discovery that it in fact was, everything from that point forward is going to be 'Okay, what other life is out there? How do we get to it? How do we study it'?"
An Atlas V rocket carrying Perseverance's spaceship took off on schedule at 7:50 am from Cape Canaveral, Florida, and its stages separated according to plan.
But as the spacecraft passed through the Earth's shadow, the temperature of a heating system dropped, triggering a "safe mode" that switched off all but essential systems. NASA said it hadn't encountered this problem before because previous spaceships followed a different flight path, but added the issue was not serious and the vessel would soon be back in normal mode.
If all goes to plan, Perseverance will reach Mars on Feb 18, becoming the fifth rover to complete the voyage since 1997.
Last week, China launched Tianwen-1, its first Mars rover, which should arrive by May.
By next year, Mars could have three active rovers, including NASA's Curiosity, which landed in 2012.
Faster and smarter
Perseverance is an improved version of Curiosity－faster, smarter, and capable of autonomously navigating 200 meters per day.
About the size of a small SUV, it weighs a metric ton, has 19 cameras and two microphones－which scientists hope will be the first to record sound on Mars.
It has a 2-meter-long robotic arm, and is powered by a small nuclear battery.
Once on the surface, NASA will deploy the Ingenuity Mars Helicopter－a 1.8-kilogram aircraft that will attempt to fly in an atmosphere that is only 1 percent the density of Earth's.
The idea is to lay down a proof of concept that could one day revolutionize planetary exploration, since rovers can only cover a few dozen kilometers in their whole life-spans and are vulnerable to sand dunes and other obstacles.
Another goal is to help pave the way for future human missions－and a major obstacle is the planet's atmosphere of 96 percent carbon dioxide.
Liquid oxygen can be brought from Earth, or oxygen can be mined from ice underneath the Martian surface.
But Perseverance's primary mission is to scour the planet for evidence of ancient life-forms.
The rover's drill will collect around 30 intact rock cores and place them in test tubes, to be collected by a future joint US-European mission.
It will be the job of Earth Return Orbiter, an Airbus satellite, to grab the packaged samples and then ship them back to Earth, with the hope that they will arrive by 2031.
Indisputable proof of past life on Mars will most likely not be confirmed, if it exists, until these samples are analyzed, which is unlikely to happen before the 2030s.
Agencies and Jonathan Powell in London contributed to this story.