The Mars Perseverance rover, which landed on the planet in 2021, has already been tasked with collecting samples of rock, regolith and atmosphere that will ultimately be sent back with Nasa’s sample retrieval lander (SRL).

Expected to launch in 2028, the plan is to land the SRL on Mars where it will remain in place to receive the collection of samples collected by Perseverance. The lander would be the first to bring along a rocket and two helicopters that will be designed to send the samples into Mars’ orbit to meet the earth return orbiter, which would then take the samples the rest of the way home.

But the review board identified a number of issues with the current plan that could hamper efforts to retrieve the samples unless a thorough revamp of the project is carried out.

It said the plan had “unrealistic budget and schedule expectations” from the beginning and there were still major uncertainties about the performance of the launch vehicles.

It also...