At the western end of Mars’ Jezero Crater, a river channel and pile of sediments resembling river deltas on Earth hold clues about how Mars evolved from a more Earth-like world to the barren, inhospitable surface seen today.

Since 2021, NASA’s Perseverance rover has collected more than 20 samples of rocks and sediments from the crater floor, delta fan and hills above it – resources that could answer crucial questions about what happened to the red planet’s climate and geology and improve understanding of our own.

But those samples could be stranded on Mars if Congress fails to provide adequate funding for the space agency to design and build the Mars Sample Return mission, Jonathan Lunine, the David C. Duncan Professor in the Physical Sciences and chair of the Department of Astronomy in the College of Arts and Sciences, testified March 21 before a congressional subcommittee reviewing NASA’s science programs.

“The benefit of succeeding in bringing back rock and soil from an ancient riverbed on a planet 140 million miles away is that it will tell the world that this nation has the imagination, will and courage to accomplish just about anything,” Lunine said in written testimony. “And that message is priceless. To not complete Mars Sample Return – to leave the samples stranded on Mars – would be … a national disgrace.”

Lunine was one of four experts invited to testify at the U.S. House Subcommittee on Space and Aeronautics hearing titled, “Advancing Scientific Discovery: Assessing the Status of NASA’s Science Mission Directorate.” Watch a replay here.

Earlier this year, budget uncertainty led NASA to plan for the lower of two proposed funding levels for the mission and to lay off staff at its Jet Propulsion Lab in California. Current appropriations bills defer a decision on funding, which could range from $300 million to nearly $1 billion, while the agency reassesses the mission’s architecture.

Nicola Fox, associate administrator of NASA’s Science Mission Directorate, said that after an independent review board’s “sobering analysis” of the mission’s costs and challenges last fall, the agency would complete its internal reassessment this spring.

“It’s our willingness to acknowledge these challenges and overcome them, to conduct science in ways that have barely been imagined, that makes us NASA,” Fox testified.

Lunine called Mars Sample Return the most ambitious robotic program the United States has ever attempted, requiring challenging new technology and involving multiple NASA centers and the European Space Agency.

But having served as a member of an independent review board that examined the mission last year, Lunine said he’s “supremely confident” that it can and will be done despite budget pressures requiring difficult choices.

“It can be done because American engineering prowess is up to the task,” he told lawmakers. “It will be done because as a nation we surely will not simply walk away from a daring, highly visible and scientifically important challenge.”

Successive National Academies of Sciences decadal surveys have identified the mission as the top priority in planetary science, Lunine said, to help answer the questions: Did life begin on Mars? How did Mars dry up? Exactly when did it dry up?

Only instruments in laboratories on Earth, instruments far more precise and powerful than those carried by the Mars rovers, can precisely analyze the collected rock and soil samples to determine their composition and age, Lunine said. In the same way, the samples Apollo astronauts returned from the moon established a definitive chronology for the earliest history of the Earth-moon system – the program’s most profound scientific achievement, Lunine said. More than a half-century later, moon samples continue to be studied by increasingly capable instruments.

“The samples returned from Mars in the coming decade will be analyzed not only by scientists active today, but by scientists who are not yet born, using laboratory techniques not yet invented,” Lunine said. “These precious records of early Mars will be a lasting scientific treasure and a legacy of American technological prowess.”