WASHINGTON D.C.: As part of its efforts to return Martian rocks and soil samples to Earth, NASA is sending two additional mini-helicopters for use on Mars.

Arizona State University's Meenakshi Wadhwa, chief scientist for the retrieval mission, said the Perseverance rover has already gathered 11 rock and soil samples, with more rock drilling planned. The most recent sample, a sedimentary rock, holds the greatest promise of containing possible evidence of ancient Martian life.

"There's a diversity of materials already in the bag, so to speak, and really excited about the potential for bringing these back," she said, as quoted by the Associated Press.

If Perseverance breaks down, the two helicopters being built and launched later this decade would load the samples onto the return rocket, instead.

The helicopters, weighing just just 4 pounds, will be modeled after NASA's successful Ingenuity helicopter, which has made 29 flights since arriving with Perseverance on Mars in early 2022.

Perseverance's impressive performance on Mars prompted space officials to cancel plans to launch a separate rover, according to NASA officials.

"We have confidence that we can count on Perseverance to bring the samples back, and we have added the helicopters as a backup means," noted Jeff Gramling, director of NASA's Mars sample return program, according to the Associated Press.

NASA is collaborating with the European Space Agency on the retrieval mission.