Scientists are to select the pieces of Mars that will one day be brought back to Earth.
Researchers hope that studying the samples of rock and soil from its surface could help them look for life on the red planet.
Nasa's Mars misssion is scheduled to launch on Thursday, carrying a rover that will explore the surface. It is just one of three crafts to set off in the "Summer of Mars", as missions from the US, China and the UAE all take advantage of the helpful alignment of the planets to set out to study our neighbour.
Scientists at Imperial College London and the Natural History Museum will help the Nasa Perseverance rover select the Martian samples to be brought back to Earth, as part of its mission to find ancient microbial life
Jezero crater, the 28-mile (45km) wide destination of Perseverance, contains sediments of an ancient river delta, a location where evidence of past life could be preserved if it ever existed on the planet.
Professor Sanjeev Gupta, from Imperial, will help Nasa oversee mission operations from a science and engineering point of view.
He said: "This is crucial to understand what the Martian climate was like early in Mars' history and whether it was habitable for life.
"This information will be used to help us define the best spots to collect rock samples for future return to Earth.
"Laboratory analyses of such samples on Earth will enable us search for morphological and chemical signatures of ancient life on Mars and also answer key questions about Mars' geological evolution."
Professor Mark Sephton, also from Imperial, will help identify samples of Mars that could contain evidence of past life.
He said: "I hope that the samples we select and return will help current and future generations of scientists answer the question of whether there was ever life on the Red Planet.
"With one carefully chosen sample from Mars, we could discover that the history of life on the Earth is not unique in the Universe."
Professor Caroline Smith, from the Natural History Museum, will study the mineralogy and geochemistry of the different rocks found in the crater.
Dr Keyron Hickman-Lewis, who is preparing to join the museum, will study the palaeoenvironments of sedimentary horizons exposed in Jezero crater and the potential for signatures of ancient microbial life preserved within.
Dr Hickman-Lewis said: "Mars probably presents our best chance of finding life elsewhere in the Solar System, and the fact that Mars 2020 plans to prepare samples for eventual return to Earth gives us a unique opportunity to discover traces of that life. "
Nasa's Perseverance rover and the recently launched UAE Hope mission will blaze a trail ahead of the launch of the UK-built Rosalind Franklin rover, due to blast into space in 2022.
The Rosalind Franklin rover, which was built by Airbus in Stevenage, Hertfordshire, will be able to drill 6.5ft (2m) below the surface, gathering samples from regions not affected by radiation.
Perseverance will carry instruments geared to search for the carbon building blocks of life and other microbes and to reconstruct the geological history of the Red Planet.
The instruments will analyse samples from the surface, with selected samples collected by drilling down to 2.8in (7cm) and then sealed in special tubes and stored on the rover.
When the rover reaches a suitable location, it will drop the tubes on the surface of Mars to be collected by a future retrieval mission, which is currently being developed.
The Sample Fetch rover, being developed by Airbus, will collect the samples and take them to the Nasa Mars Ascent vehicle.
Nasa and European Space Agency (ESA) scientists are planning how the samples will be curated on their return.
The rover also carries the Ingenuity Mars helicopter, which will fly short distances and marks the first attempt at powered, controlled flight on another planet.
If the test of the helicopter is successful, it could lead to more flying probes on other planets.
Perseverance will also trial technologies to help astronauts make future expeditions to Mars.
This includes testing a method for producing oxygen from the Martian atmosphere, and identifying other resources such as subsurface water.
Sue Horne, head of space exploration at the UK Space Agency, said: "It is amazing that we are undertaking the first step of a sequence of missions to collect samples from Mars and return them to Earth."
Additional reporting by agencies
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