'Never say never,' Prof Caroline Smith of the Natural History Museum in London tells BBC Breakfast.

Image source, NASA

Although the search for life is Perseverance's main focus, the mission will also aim to perform the first powered flight on another planet.

Ingenuity is a 1.8kg (4lb) drone-like helicopter that will ride to Mars attached to the belly of the rover.

But that's not straightforward when the Martian atmosphere is 100 times thinner than Earth's.

Laura Foster explains in this video.

Image source, Nasa

It's often said that about half of all missions to Mars have failed.

But getting a more precise figure for successful and unsuccessful Mars shots is more complicated than it sounds.

It's not a simple calculation - as it should be - because there's often disagreement on how to define success and failure.

A few years ago we learned that the British-built Beagle 2 probe - which failed to phone home after plunging through the Martian atmosphere on 25 December 2003 - had actually reached the surface intact.

Given the historical difficulties of getting down in one piece, should Beagle 2 be considered a partial success?

Or there's the Soviet Union's Mars-3 lander. On 2 December 1971, it became the first spacecraft to land softly on Mars. The plucky probe was in the middle of transmitting an image when its systems went dead. Does that make it a success or failure?

Read the feature.

Image source, SPL

The launch of Perseverance is simply the first step in a bigger plan to deliver rocks and soil from Mars to Earth.

This plan, called Mars Sample Return, will see Nasa collaborate with the European Space Agency. Perseverance will seal samples of Martian rock in containers and leave them on the surface for another rover, launched later in the 2020s, to pick them up.

See how the plan will work with our animated guide.

Perseverance is going up on a United Launch Alliance Atlas rocket. The top man at ULA has stuck his head outdoors and said, "let's do this".

Weather forecasts for lift-off sound promising. There's currently a 20% chance of weather scuppering the launch.

It's a case of watching the clouds - big puffy white clouds are a particular concern for rocket launches.

Image source, Reuters

Welcome to our live coverage of the launch of Nasa's next Mars rover, Perseverance. Between 12:50 and 14:50 BST (07:50 and 09:50 EDT) on Thursday, the robot rover should lift off from Cape Canaveral Air Force Station in Florida atop an Atlas 5 rocket.

The Nasa mission is the first to hunt directly for the signatures of life since the Viking landers in the 1970s. During its first billion years, Mars' surface had liquid water - an essential requirement for life on Earth.

If biology once existed on Mars, signs may be preserved in the rocks of Jezero Crater, which was a lake 3.5 billion years ago or more.

But Perseverance will also aim to produce oxygen from carbon dioxide in the Martian atmosphere - a test that could pave the way for human missions to the planet.

And a drone-like helicopter will hitch a ride to Mars on the rover's belly. Scientists want to perform the first powered flight on the surface of the Red Planet.

So get ready for an exciting event in the space calendar, as BBC News brings you full coverage of the launch.

Image source, Reuters