NASA needs help fetching rocks from Mars, and on Tuesday, agency officials announced that they have not yet quite decided how to do that. Instead, they are leaving a final decision to the incoming administration of President-elect Donald J. Trump.
But the officials said they had figured out how to potentially launch the mission and bring those red planet rocks back to Earth sooner by reducing the size and weight of the mission, known as Mars Sample Return. Cost estimates last year had risen to as much as $11 billion. With the revisions, Mars Sample Return is still expensive, but would be less than $8 billion.
“That’s a far cry from $11 billion,” Bill Nelson, the NASA administrator, said during a telephone news conference on Tuesday.
Bringing Martian rock and soil samples to Earth is among the top priorities of planetary scientists. While spacecraft in orbit and rovers on the surface of Mars have discovered plenty, their capabilities are limited. By studying fresh rocks up close with the latest, most powerful instruments in their laboratories, scientists could unravel mysteries of the red planet’s past, including possibly whether life ever arose there.
The first phase of Mars Sample Return is already underway. NASA’s Perseverance rover, which landed on Mars in 2021, has been drilling and collecting cylindrical samples of rock and soil in Jezero Crater, which contains an ancient river delta.
The rest of the plan, devised by NASA’s Jet Propulsion Laboratory in California, requires a complex choreography. First, a new robotic spacecraft would land near the Perseverance rover, which would then hand over about 30 of its rock samples to launch into orbit around Mars. Yet another spacecraft, from the European Space Agency, would retrieve those samples, take them back to Earth and drop them off within a small disk-shaped vehicle that would land in a Utah desert.
That plan remains essentially the same, but the key to the change was realizing that the rocket to launch the samples from the surface of Mars into orbit around the planet did not need to be as big and heavy as the initial design.
With a smaller rocket, NASA no longer had to build a lander that was larger than any it had ever made before.
Instead, the mission could again use the sky crane system, which had successfully deployed the Curiosity and Perseverance robotic rovers that are currently exploring Mars. The sky crane lowers the lander with the rocket by cable from a hovering rocket stage.
NASA officials also left open the possibility that instead of the sky crane, the agency might buy a lander from a commercial company.
Mr. Nelson, who will step down as NASA administrator with the change of presidents later this month, said NASA officials under Mr. Trump’s administration would most likely be able to make a decision sometime next year.
“What we wanted to do was to give them the best possible options so that they can go from here,” Mr. Nelson said.
However, he also said that to keep the program from being further delayed, it would need Congress to provide at least $300 million this year.
Like many of NASA’s most ambitious projects, Mars Sample Return aims to do something that has never been done before, and that makes it hard to predict how difficult and expensive it will be.
Originally, the two spacecraft needed for the mission — the lander built by NASA and an orbiter built by the European Space Agency to bring the rocks back — were to launch in 2026, and NASA’s share of the cost would be $3 billion.
An independent review in 2020 concluded that a 2028 launch date was more realistic and the cost would be between $3.8 billion and $4.4 billion. A second review in 2023 found those predictions to have been too optimistic. NASA’s share of the mission would instead be $8 billion to $11 billion, the panel said. And the agency’s officials concluded the rocks would not be delivered to Earth before 2040.
“We pulled the plug on it,” Mr. Nelson said.
NASA then sought alternative ideas from aerospace companies as well as from experts within the space agency, starting from scratch on a brand-new mission or suggesting better ways to accomplish a specific part of the current plan.
A team within NASA evaluated the options and came up with changes that are more so revisions than a complete overhaul.
“We’re really excited about this,” said Nicola Fox, the associate administrator for NASA’s science mission directorate. “As always, my priority is to find a path forward for our sample return within a balanced overall science program so that NASA’s science continues to deliver.”
One spacecraft could launch in 2030 at the earliest, the other in 2031, Dr. Fox said.
Other changes include switching from solar panels to a radioactive heat source to provide power, and simplifying the system for moving the rock samples from Perseverance to the rocket that would launch them to space.
After NASA announced that it was looking for new ideas, the Jet Propulsion Laboratory slowed its work on Mars Sample Return and in February last year laid off more than 500 employees, or about 8 percent of its work force.
NASA officials did not discuss details of any of the commercial options. From the initial proposals, NASA had commissioned studies from eight companies, which included aerospace giants like Lockheed Martin as well as two newer rocket companies led by billionaires — Elon Musk’s SpaceX and Jeff Bezos’ Blue Origin.
Mr. Musk has prioritized reaching Mars with Starship, his next-generation vehicle, pledging to launch versions of that rocket without any people aboard toward that destination as soon as 2026. However, Starship remains under development and has not yet orbited Earth.
