Tianwen-1 was launched on a Long March-5 carrier rocket from Hainan Island, a resort province off the south coast of the mainland, state media said.
Livestreams showed a successful liftoff, with rockets blazing orange and the spacecraft heading upward across clear blue skies.
Hundreds of space enthusiasts cried out excitedly on a beach across the bay from the launch site.
Launch commander Zhang Xueyu announced to cheers in the control room that the rocket was flying normally about 45 minutes later.
“The Mars rover has accurately entered the scheduled orbit,” he said in brief remarks shown live on state broadcaster CCTV.
China’s space agency said that the rocket carried the probe for 36 minutes before successfully placing it on the looping path that will take it beyond Earth’s orbit and eventually into Mars’ more distant orbit around the sun.
It marked the second flight to Mars this week, after a United Arab Emirates orbiter blasted off on a rocket from Japan on Monday.
And the US is aiming to launch Perseverance, its most sophisticated Mars rover ever, from Cape Canaveral, Florida, next week.
China’s tandem spacecraft – with both an orbiter and a rover – will take seven months to reach Mars, like the others.
If all goes well, Tianwen-1, or “quest for heavenly truth”, will look for underground water, if it is present, as well as evidence of possible ancient life.
This is not China’s first attempt at Mars.
In 2011, a Chinese orbiter accompanying a Russian mission was lost when the spacecraft failed to get out of Earth’s orbit after launching from Kazakhstan, eventually burning up in the atmosphere.
This time, China is going at it alone.
It is also fast-tracking, launching an orbiter and rover on the same mission instead of stringing them out.
China’s secretive space programme has developed rapidly in recent decades.
Yang Liwei became the first Chinese astronaut in 2003, and last year Chang’e-4 became the first spacecraft from any country to land on the far side of the moon.
Conquering Mars would put China in an elite club.
“There is a whole lot of prestige riding on this,” said Dean Cheng, an expert on Chinese aerospace programmes at the Heritage Foundation in Washington.
Landing on Mars is notoriously difficult.
Only the US has successfully landed a spacecraft on Martian soil, doing it eight times since 1976.
Nasa’s InSight and Curiosity rovers still operate today.
Six other spacecraft are exploring Mars from orbit: three American, two European and one from India.
Unlike the two other Mars missions launching this month, China has tightly controlled information about the programme – even withholding any name for its rover.
National security concerns led the US to curb co-operation between Nasa and China’s space programme.
In an article published earlier this month in Nature Astronomy, mission chief engineer Wan Weixing said Tianwen-1 would slip into orbit around Mars in February and look for a landing site on Utopia Planitia – a plain where Nasa has detected possible evidence of underground ice.
Wan died in May from cancer.
The landing would then be attempted in April or May, according to the article.
If all goes well, the 240kg golf cart-sized, solar-powered rover is expected to operate for about three months, and the orbiter for two years.
Though small compared with America’s hulking, car-sized 1,025kg Perseverance, it is almost twice as big as the two rovers China sent to the moon in 2013 and 2019.
Perseverance is expected to operate for at least two years.
This Mars-launching season – which occurs every 26 months when Earth and Mars are at their closest – is especially busy.
At no other time in our history have we seen anything like what is unfolding with these three unique missions to Mars
The UAE spacecraft Amal, or Hope, which will orbit Mars but not land, is the Arab world’s first interplanetary mission.
Nasa’s Perseverance rover is up next.
“At no other time in our history have we seen anything like what is unfolding with these three unique missions to Mars. Each of them is a science and engineering marvel,” the Space Foundation’s chief executive officer Thomas Zelibor said in an online panel discussion earlier this week.
China’s road to Mars has hit a few bumps: a Long March-5 rocket, nicknamed Fat 5 because of its bulky shape, failed to launch earlier this year.
The coronavirus pandemic forced scientists to work from home.
In March, when instruments needed to be transported from Beijing to Shanghai, three team members drove 12 hours to deliver them.
While China is joining the US, Russia and Europe in creating a satellite-based global navigation system, experts say it is not trying to overtake the US lead in space exploration.
Instead, Mr Cheng said China is in a “slow race” with Japan and India to establish itself as Asia’s space power.
