As it happened: Nasa rover performs 'flawless' landing on Mars

"This was the best so far," says Matt Wallace, who has previously worked on five other missions to Mars.

Covid threatened the entire mission, Nasa officials are saying.

Whether it was the people who clean the equipment or those that supply the nitrogen, everything was interrupted by the pandemic.

Scientists had to travel from California to Florida for the launch, another difficulty as many people are trying to remain home to limit the spread of the deadly virus.

"The team, like all of you out there, are worried," says Mike Wallace.

"They're worried for their parents and grandparents, and kids out of school."

Perseverance is carrying onboard a metal plaque, symbolising the pandemic and the impact that it has had on planet Earth.

Jennifer Trosper adds: "I've worked from my laundry room for the last several months."

"Sometimes," she adds, "people cant hear me because the washer's going."

"This is not typically how we would design a Mars mission," she continues.

It will be around 10 sols - or Martian days which are about 40 minutes longer than Earth days - before Nasa plans to deploy its onboard helicopter.

It will be the first remote flight on another planet, and is one of the most exciting elements of the Perseverance project.

Scientists say about five flights are planned for the helicopter, dubbed Ingenuity, over the next 30 days.

Mars is now our laboratory, scientist at today's press conference are proudly saying.

Perseverance will study "how planets form and how they evolve, and Mars is a great place to answer those questions," says Jennifer Trosper.

"For the first time, we're going to see ourselves in high definition video landing on another planet," says Matt Wallace.

"We think we've captured, hopefully, some pretty spectacular video. And they come with a microphone as well," he says.

One still image from the descent stage, looking down at the rover, may be available as soon as tomorrow.

But the first video probably won't be out until Monday, he says.

The rover landed near a sand dune field, scientists say, and may need to find a way around it in order to access the delta that Nasa hopes to study.

It remains to be seen what course the rover will take, as scientists are still trying to determine the exact location of Perseverance.

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"Those seven minutes are still pretty raw for me right now," says Allen Chen, engineer in the Entry, Descent, and Landing Systems programme.

"The vehicle is going for a roller coaster ride, and you are too," he continues.

"You're second guessing yourself as you go. And these things have already happened. It's crazy," he says.

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"Wow, we have a science mission. It has been a long road to get here," begins project scientist Ken Farley.

He describes the mission as a "decades-long relay race" through space.

Farley goes on the thank all the thousands of scientists that have participated in the Mars mission through the years, including those that are no longer working with the programme now but played pivotal roles over the past decade.

"We're really excited to get going on this," he says.

The first two photos from Perseverance show rocks, he says, that appear to be about 10cm, and will probably be some of the first rocks inspected by Perseverance.

The photos also appear to show the ancient delta, which Perseverance will explore in the coming months.

"Looks like Mars," he jokes.

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"When all good things happen it feels like your dreaming," says deputy project manager Jennifer Trosper.

"And I feel like I'm dreaming today."

She adds that "if everything goes well" an over-flight mission will soon allow scientists to access more photos - and even video - from Perseverance.

"We think we're facing southeast, based on the shadows," she says adding that the batteries on the rover are currently charged at 95%.

"Everything looks great," she says.

The entire Perseverance team, many of whom are not able to be present at the Jet Propulsion Lab due to Covid restrictions, were just honoured on screen.

The scientists took bows and waved as they were recognised.

"They look good. They look good on TV," said their boss, Matt Wallace.

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"You just got a chance to watch this team do the hardest thing we do in this business," says Matt Wallace, Perseverance deputy project manager.

Landing on the surface of Mars, he continues.

The "system performed flawlessly," he says.

"A couple million lines of flight software code were running," he says, calling it "just a difficult thing to do".

"It's very gratifying and quite a relief, to be through it," he adds.

"The good news is the spacecraft, I think, is in great shape."

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"I can't wait to get all the instruments turned on," says Lori Glaze, Nasa's planetary science division director.

She says it won't be long until we have all the data, including audio recordings, of the moment that the lander passed through the Martian atmosphere.

"We're going to get to see it and live it and participate - every one of us - on its way down."

Mike Watkins, director of Nasa Jet Propulsion Laboratory (JPL) - which is the HQ for US Mars missions - is now speaking.

He begins by praising the scientists who were forced to work remotely due to the coronavirus pandemic.

"We had to change the tyres while going down the highway starting last year," he says.

"We have just landed a representative of the planet Earth on Mars," he says, noting that the region has never been visited by humankind before.

"I believe that that magical sense that we bring is the main reason that Nasa exists and JPL exists."

"I had to get up the in the night twice to replace a sweated through wet t-shirt with a new one," says Nasa associate administrator Thomas Zurbuchen.

"This night, I"m sure I'll just need one of them."

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Nasa associate administrator Thomas Zurbuchen begins by saying that the team had a backup contingency plan, as every Nasa mission does.

He then dramatically ripped up the contingency plan, now that it is no longer needed.

He goes on to praise Nasa scientists for wearing two masks each during the landing, in order to prevent the spread of Covid-19.

"What an amazing moment," he says, as a video is shown of the moment that masked scientists began fist bumping each other in celebration as the rover landed.

"This is the first time for months that we're all in the same room," he continues.

Joe Biden has tweeted his appreciation for everyone at Nasa involved with Perseverance's successful touchdown.

An attached picture shows the president monitoring the spacecraft's progress from the White House.

The Nasa press conference in California is just beginning now.

It starts with an acknowledgement of "what a thrilling day today's has been".

"We now have the most advanced rover yet on the surface of Mars."

Nasa acting administrator Steve Jurczyk begins by saying that he spoke to US President Joe Biden after the successful landing.

"His first words were 'congratulations man', and I knew it was him," says Jurczyk.

"He talked about how proud he was of what we accomplished. And he wanted me to send my regards to Percy," he said, using a nickname for Perseverance.

Biden, he says, plans to soon congratulate the Perseverance team in person.

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French President Emmanuel Macron has tweeted his congratulations to the scientists that worked on the Martian lander.

"Such pride!" he said, pointing out that one of the cameras was designed in a French labratory.

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Before the era of robotic spacecraft, scientists and authors alike speculated that Mars might be home to intelligent life with advanced civilisations.

But when the American Mariner 4 spacecraft flew by Mars in 1965, it returned pictures of a dry, cratered, seemingly barren world.

It was becoming clear that any life on the Red Planet must be a godawful small affair, as David Bowie once sang.

Thus, when Nasa launched its two Viking landers to Mars in 1975, the spacecraft carried experiments designed to detect signs of microbes in the Martian soil. The results from one of these tests, known as the labelled release (LR) experiment, remains a source of controversy to this day.

A sample of Martian soil was picked up and placed in a small tube to which a squirt of radioactive carbon was added. Were any Martian micro-organisms present, the hope was that they would recognise the nutrient, "eat" it and give off radioactive gas.

"No-one, including me, was very hopeful this would work on Mars," the experiment's chief scientist Gil Levin said in a 2014 interview with SPIE TV.

"Surprisingly, as soon as the first squirt of radioactive nutrient hit that Martian soil, we got a big bulge of gas coming out. And it came out for the entire seven days, or Martian sols, of the experiment. That was astounding."

Levin and colleagues also ran a "control", to exclude the possibility that chemicals in the Martian soil could react to produce the gas. The results again pointed to microbial production, according to Levin.

But another experiment on Viking had found no native organic matter in the Martian soil.

How could life exist without organic matter? This discrepancy led to the labelled release experiment being judged inconclusive. But a few advocates, such as Dr Levin, continue to believe in the results.