NASA has planned to bring back to earth the samples the perseverance rover has been collecting. Perseverance was sent by NASA to discover in behalf of humans whether Mars can support life of not. It has also been collecting rock samples in Jezero crater since it landed on Mars by drilling rocks.
The two helicopters are based at Ingenuity and are for back up. Instead of NASA sending a sample fetch rover to Mars, they will make us of the two helicopters. NASA have been working closely with ESA on the sample return program.
ESA had already built the sample collecting rover before NASA changed their plan. The rocket became too big such that the return rocket and the rover could not fit in one lander. The had to use one lander for each.
On the other hand, the Curiosity rover has been at work for eleven years now since it landed on the red planet.
The two helicopters will have small wheels at the bottom that will enable them to drive towards the location of samples that will be deposited by the rover.
The Earth Return Orbiter and Sample Retrieval Lander are expected to land on Earth in 2033. This will be after the completion of the Sample Retrieving Mission and they will be carrying samples of rocks from Mars.
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