Jonathan Amos
Science correspondent, BBC News

Image source, Airbus

Airbus-France will build the huge satellite that brings the first Martian rock samples back to Earth.

This material will be drilled on the Red Planet by the US space agency's next rover, Perseverance, before being blasted into orbit by a rocket.

It'll be the Airbus satellite's job to grab the packaged samples and then ship them home.

The joint American-European project is expected to cost billions and take just over a decade to implement.

But scientists say it's probably the best way to confirm whether life has ever existed on the Red Planet.

Any evidence is likely to be controversial and will need the powerful analytical tools only found in Earth laboratories to convince the doubters, the researchers argue.

"This is not just twice as difficult as any typical Mars mission; it's twice squared - when you think about the complexity involved," said Dr David Parker, the director of human and robotic exploration at the European Space Agency (Esa).

"And this satellite that Airbus will build - I like to call it 'the first interplanetary cargo ship', because that's what it will be doing. It's designed to carry cargo between Mars and Earth," he told BBC News.

Read the full story here.

Image source, NASA / JPL-CALTECH

We've answered some of the common questions around Perseverance - like how it will get to Mars, what its mission is while there, how scientists on Earth will receive samples picked up by the rover - and more.

Check out our guide here.

Paul Rincon
Science editor, BBC News website

Image source, NASA

After the controversy over the labelled release experiment aboard Nasa's Viking landers in the 70s, another important episode in the search for Martian life occurred in the latter half of the 1990s.

On 6 August 1996, a team including the late David S McKay, and his Nasa Johnson Space Center colleagues Everett Gibson and Kathie Thomas-Keprta, sent shock waves around the world when they published a paper in the prestigious journal Science detailing possible evidence of extra-terrestrial life preserved in a Martian meteorite.

The rock, named Allan Hills 84001, or ALH84001, had been found in Antarctica in 1984 and seemed to contain tiny structures resembling fossilised bacteria when viewed under a high-powered scanning electron microscope.

But the structures were smaller than any microbial life known at the time.

They also found crystals of the mineral magnetite with features that made them indistinguishable from those produced by microbes on Earth. ALH84001 also contained complex organic molecules that appeared to be "indigenous" to the meteorite.

Then-US President Bill Clinton subsequently made a special address about the discovery, external, where he said: "Rock 84001 speaks to us across all those billions of years and millions of miles. It speaks of the possibility of life. If this discovery is confirmed, it will surely be one of the most stunning insights into our Universe that science has ever uncovered."

However, it didn't take long for sceptical scientists to pick apart the evidence.

Some researchers suggested the bacteria-like structures could be uneven patches in the coating used to prepare samples for the electron microscope.

Sceptics also claimed that magnetite like that found in the meteorite could have formed when Martian carbonate minerals were heated to sufficiently high temperatures.

Many scientists disagree with the evidence. But the surviving team members stand by the findings and have even published similar results from other Martian meteorites.

Image source, NASA

Jonathan Amos
Science correspondent, BBC News

The US space agency's Perseverance robot has left Earth on a mission to try to detect life on Mars.

The one-tonne, six-wheeled rover was launched out of Florida by an Atlas rocket on a path to intercept the Red Planet in February next year.

When it lands, the Nasa robot will also gather rock and soil samples to be sent home later this decade.

Perseverance is the third mission despatched to Mars inside 11 days, after launches by the UAE and China.

Perseverance is being targeted at a more-than 40km-wide, near-equatorial bowl called Jezero Crater. Satellite images suggest this held a lake billions of years ago.

Scientists say the rocks that formed in this environment stand a good chance of retaining evidence of past microbial activity - if ever that existed on the planet.

Perseverance will spend at least one Martian year (equivalent to roughly two Earth years) investigating the possibility.

Unlike the previous four rovers Nasa has sent to Mars, its new machine is equipped to directly detect life - either current or in fossilised form.

Read the full story here.

Joining Perseverance on its mission to Mars is the helicopter Ingenuity, which scientists hope will send them the first aerial photos of the Martian landscape.

Ingenuity project manager MiMi Aung earlier described what needs to happen from now until the helicopter's first flight.

"The very first [milestone] is when we turn on the helicopter to check the health. The next major milestone will be when perseverance rover deploys the Ingenuity helicopter to the surface."

Once that happens, the 4lb (1.8kg) Ingenuity will start to work on its own and will never again return to the rover.

"The first major milestone then will be the helicopter surviving the first cold martian night, about -90C (-130F) and we've designed the helicopter to keep itself warm."

Aung says there are five planned flights for the helicopter over a 30 day period once the craft reaches Mars.

US Vice-President Mike Pence, who leads the Trump administration's space efforts and chairs the National Space Council, has offered his congratulations on the successful launch.

The vice-president called it a "great day for American leadership in space".

Image source, NASA

Perseverance is carrying the first spacesuit material samples ever sent to Mars.

Nasa advanced spacesuit designer Amy Ross is working on developing new suits for manned missions to the Moon and Mars - and the Perseverance mission will help determine suitable materials.

As the rover explores its landing site, Jezero Crater, it will also collect data on five small pieces of material embedded on the rover.

Ross said, external the materials are meant to be on the outermost layer of the spacesuit - which will be exposed to the most radiation.

"There's ortho-fabric, something we have a lot of experience using on the outside of spacesuits. That's three materials in one: It includes Nomex, a flame-resistant material found in firefighter outfits; Gore-Tex, which is waterproof but breathable; and Kevlar, which has been used in bulletproof vests."

They are also testing Vectran - a cut-resistant fabric currently used on spacesuit gloves - Teflon and polycarbonate.

As these materials are exposed to radiation on Mars they will weaken. Scientists want to know how long they last under such conditions.

Nasa's Associate Administrator Thomas Zurbuchen has a chat with the two young Americans who named the rover and helicopter.

"I'm over the moon, that was probably the coolest, most exciting thing I've seen ever," says Vanessa Rupani, the high school student who is behind the helicopter's name, Ingenuity. "I can't wait for it to land in February."

Alex Mather, the 13-year-old who came up with the name Perseverance, described the moment of launch.

"It zooms into space, it's bright as the Sun, birds and the bugs are all going crazy and all of the car alarms within probably a whole mile radius are turned on and - it was just so overwhelming on a sensory level."

Paul Rincon
Science editor, BBC News website

The Perseverance rover is carrying an advanced suite of scientific instruments that will be used as an "integrated system" to search for the signatures of life in Jezero Crater.

Deputy project scientist Ken Williford told me: "We're looking around with our robotic eyes, Mastcam-Z - the two zoom cameras up on the mast - looking at the colours and textures and structures that we see around us."

The team also uses a Norwegian-built ground-penetrating radar on the back of the rover called Rimfax to determine whether rock structures extend below the surface of Mars. The radar helps the scientists understand the "stratigraphy" of the environment - how the rocks are layered and organised together.

An instrument on the rover's mast called Supercam contains a camera, lasers and spectrometers.

Dr Williford, who is based at Nasa's Jet Propulsion Laboratory in Pasadena, said: "We fire a laser at a distance of some metres away from a target, and we use LIBS - laser-induced breakdown spectroscopy - to measure the elemental composition of the rock and Raman and infrared spectroscopy to measure the mineralogy - and potentially even detect organic matter if it's there at high enough concentrations."

"We do that to allow us to select specific parking places where we can deploy the robotic arm."

At the end of the 2.1 metre (6 ft 11 in) -long robotic arm is a structure called the turret which houses an instrument called Sherloc and another called Pixl, with a coring drill in between.

When the rover is parked near a rock of interest, an abrading bit is placed in the drill and it is used to wear down and flatten a 4.5cm circular patch of the rock. The turret is then turned around and the Sherloc instrument is placed against the patch.

Sherloc has a sub-system consisting of a camera with a magnifying lens - called Watson - that's used capture the rock's texture. "We're looking for interesting shapes and colours," says Dr Williford.

Sherloc's spectroscopy system is then used to make a map of the minerals in an area about the size of a postage stamp. To do this, a deep ultraviolet laser that's about the diameter of a human hair is swept over the square centimetre-scale area.

This could detect any organic matter - the carbon-bearing building blocks of life.

The turret is then turned around and the Pixl instrument is used to map the same area. This is an X-ray fluorescence instrument then maps the same area of rock as Sherloc was used on to give its elemental composition.

"All of those things together, we use to construct a multi-faceted set of data, within which we look for concentrations of biologically-important elements, minerals and molecules, including organic matter. And in particular, [it's] when those things are concentrate in shapes that are suggestive of biology," says Dr Williford.

You can read more here.

The Perseverance Twitter account confirms the communication.

The signal from Perseverance has been acquired, prompting applause from the scientists on the ground.

Adam Steltzner, chief engineer at JPL, says the launch process is now complete and the cruise phase is next.

"We are on our way to Mars, we're no longer in orbit around Earth and what will happen next is we'll start our cruise phase. It'll be about seven months before we make it to the Red Planet."

During that time, there are a number of planned trajectory change manoeuvres that must be done.

"In fact we're targeting to miss Mars right now," he says, noting the initial rocket burns sent the craft in the general direction of Mars so the trajectory could be adjusted properly later on.

Steltzner says for the coming months, scientists will monitor the craft, "make sure it's healthy and happy and tweak its trajectory to be right on target".

Re-live the moment. Heading off Earth to go to the Red Planet.

Perseverance is powered by 10.6 lbs (4.8kg) of plutonium-based fuel. Its power system - called a Multi-Mission Radioisotope Thermoelectric Generator - produces electricity by using the heat emitted from the radioactive element as it decays.

The system will charge the rover's two primary batteries, as well as helping to keep the tools and other parts of the rover at proper operating temperatures in the harsh Mars environment.

Rita Baranwal, Assistant Secretary of Energy for Nuclear Energy, says it's similar to what was used in the two Viking missions that landed on Mars in the 70s.

This generator system will be able to power the rover for 14 years, according to Nasa. It also gives scientists the ability to operate the rover at any time, day or night.

Astronaut Zena Cardman, a microbiologist who has studied life in Earth's extreme environments, says there are places on Earth that resemble some of the environments on Mars.

"If you take a look at Mars today it's very cold and very dry, and we have some places on earth that are actually a lot like that, places like Antarctica, or deserts."

But looking for ancient life - from a time when, perhaps, Mars looked a lot like Earth today - will be a bit different.

Cardman says scientists have to look at rocks for their chemical signatures since early life forms wouldn't leave behind fossils or footprints.

Nasa says the spacecraft with the 2020 rover has successfully separated from the rocket, and Perseverance is now "flying free".

The craft is currently over the Indian Ocean - less than an hour after liftoff in Florida.

We're looking for spacecraft separation in the next few minutes.

During Nasa's live coverage of the launch, scientists at the JPL in California experienced an earthquake.

The United States Geological Survey says it was a 4.2 magnitude quake.

The scientists at JPL said they felt the shakes - as did many on social media - but reported no damages.

A cracking shot of the United Launch Alliance vehicle clearing the pad.

Image source, EPA

Mike Watkins, JPL director, says one of the difficulties with rover missions is that scientists can't use their "human response" to address challenges.

He compares it to driving a car - if you see something on the road, you can shift your course. But scientists can't "drive" the rover the same way.

"We've had to prepare the rover to do a lot of that stuff on its own," he says, calling Perserverence a machine that can function more or less without us.

"We've got to give it intention, but it's going to have to do it all by itself."

The second burn is now underway, and the main engine has started.

This is the burn that gets the rocket moving quickly in the direction it needs to go to eventually head off to Mars.

Firing so far is going well, Nasa says.