An image from NASA's Perseverance Mars rover shows where the rover drilled into a rock called Rochette and collected two samples. Credit: NASA/JPL-Caltech

WASHINGTON — NASA’s Perseverance Mars rover has collected and stored the first samples of Martian rock for later return to Earth, but exactly when those samples will arrive on Earth remains uncertain.

At a Sept. 10 news briefing, NASA officials and project scientists hailed the collection of two samples from a rock dubbed “Rochette” as a major step forward in the long-term Mars sample return effort that will conclude no earlier than a decade from now with those samples returned to Earth.

“These now represent the beginning of Mars sample return,” said Meenakshi Wadhwa, an Arizona State University planetary scientist who serves as Mars sample return principal scientist for NASA.

The successful collections of the first two samples came a month after the rover tried and failed to collect a sample from another rock, called Roubion. Scientists concluded that the problem was not with the sampling system but instead with the rock itself: it was weaker than expected and crumbled during the sampling process.

The two volcanic rocks are similar, but likely were exposed to different amounts of water, said Yulia Goreva, Perseverance return sample investigation scientist at JPL. Roubion experienced much more alteration in the form of salts created by the exposure to water.

“If these rocks experienced water for long periods of time, there may be habitable niches in these rocks that could have supported ancient microbial life,” said Katie Stack Morgan, Perseverance deputy project scientist at JPL. The project thus decided to collect two samples of Rochette, with plans to later store them in separate sample caches to increase the likelihood at least one makes it back to Earth.

Perseverance will collect about three dozen samples during its mission. Scientists said at the briefing they were planning their next sample collection efforts and left open the possibility of making another attempt to collect samples from Roubion.

Two future missions will retrieve those samples and bring them back to Earth. A lander mission, led by NASA and including a European Space Agency rover, will pick up the samples, load them into a container and launch them into orbit around Mars. An ESA-led orbiter, with a NASA-provided collection system, will grab the samples and return them to Earth.

Those later missions will launch no earlier than 2026, although they are still in what NASA calls Phase A, focused on initial studies. “As part of Phase A, we are exploring a bunch of different trades and trying to best understand how we can execute this mission,” said Lori Glaze, director of NASA’s planetary science division. “We’re where we should be right now.”

She didn’t elaborate on what trades were being studied or when that would be complete. An independent review last year recommended NASA consider several changes, ranging from pushing the launch of the missions to 2028 to considering splitting the sample return lander into two spacecraft and using nuclear, rather than solar, power for it. There’s growing skepticism in the planetary science community that the two Mars sample return missions could be ready to launch in 2026.

Funding, she added, is not an issue. “We are extremely pleased with the budget request that the president put forward for fiscal year 2022 and beyond, and I think we are in a really good place right at this moment with the funding that we have,” she said. That budget proposal included $653 million for Mars sample return in 2022 and projected spending $3.5 billion from 2022 through 2026.

In the meantime, Perseverance will continue to collect samples for eventual return to Earth. “In our science community, we’ve talked about Mars sample return for decades,” said Wadhwa. “Now it’s actually starting to feel real.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...