WASHINGTON — A Senate hearing Aug. 1 intended to discuss NASA’s search for life beyond Earth turned into a discussion about the long-standing process the scientific community uses to prioritize missions.

The hearing by the Senate’s space subcommittee on “The Search for Life: Utilizing Science to Explore our Solar System and Make New Discoveries” featured witnesses from within and outside the agency to discuss astrobiology research regarding other worlds in the solar system and on distant exoplanets.

The hearing was the second in a series planned by the committee to examine issues to go into a future NASA authorization bill. “What do you see as the science-related priorities that are most important to be reflected in that bill?” asked subcommittee chairman Sen. Ted Cruz (R-Texas) during the hearing.

One of the witnesses, David Spergel, a professor of astronomy at Princeton University and former chair of the Space Studies Board, mentioned the decadal survey process used in astrophysics and other disciplines, where scientists identify the top research priorities in their field and potential missions, from small to large, that should be flown in support of those priorities.

He noted that the astrophysics community was preparing to start work on its next decadal survey, due to be completed in late 2020. “We’ll begin by thinking about what are the key driving questions. The search for life will almost certainly be one,” he said. “Others will include understanding the processes of galaxy formation, star formation and the emergence of structure.”

Sen. Ed Markey (D-Mass.), ranking member of the subcommittee, raised the question of prioritizing missions again later in the hearing. Another witness, Sara Seager, a professor of physics and planetary science at the Massachusetts Institute of Technology, suggested it was worth reconsidering how the decadal process works.

“It’s kind of the structure that we’re, let’s say, forced to abide by,” she said. “Any institution, any kind of structure, that’s been around for more than half a century should be reviewed to see if it’s still effective.”

She said she thought there were “many areas for room for improvement” in the decadal process. Asked for specifics, she argued that the current process leads to mission concepts that are “very complicated” and thus expensive, like the James Webb Space Telescope. There may be a case, she said, for more focused missions that, while still large, do not attempt to be all things for all astronomers. “We can’t really do that in the current formulation of the survey,” she said.

How the decadal survey is organized makes it difficult for younger scientists to make their voices heard, she added. “Sometimes the younger people know more.”

Spergel and other witnesses, though, defended the decadal survey process while agreeing it can be improved. “The decadal process has been an effective way for prioritization,” he said. “It’s a process that can be and is being improved.” One such improvement, he said, is doing a better job of defining proposed missions and estimating their cost before recommending them, citing the experience with JWST.

“I think it’s an important and strong process that needs to be adhered to, because it really allows the best science to come forward,” said Ellen Stofan, former NASA chief scientist and current director of the National Air and Space Museum. “It’s not the person who shouts the loudest or has the most connections. It really is the best science.”

Thomas Zurbuchen, NASA associate administrator for science, said he welcomed the guidance provided by the decadal surveys. “For me, the decadal has been a very successful activity, but like every human endeavor, it should always be questioned and should be improved as we go forward,” he said. Seager’s concerns on issues like diversity of inputs during the decadal process “resonated” with him, he said.

That discussion of the decadal process was one of several topics touched upon during the 80-minute hearing officially about the search for life beyond Earth. Senators asked questions on other topics, ranging from planetary defense against near Earth asteroids to space weather to the importance of NASA continuing to perform Earth science research.

The hearing also briefly discussed the latest cost and schedule overruns with JWST. Unlike the House Science Committee, which spent several hours on the topic in a two-part hearing July 25 and 26, the Senate space subcommittee spent only a few minutes about it, with Cruz asking the witnesses to explain “that incredible increase” in its costs.

“That’s the question I’m asking myself and my team on a regular basis,” Zurbuchen responded. He blamed the increase on several issues, including “excessive optimism,” and development of multiple new technologies, and additional time needed to complete integration and testing work for the spacecraft.

Asked by Cruz if JWST’s delays would lead to a reassessment of the use of cost-plus versus fixed-price contracting, Zurbuchen argued complex missions like JWST would not fit well in a fixed-price approach. “For new, innovative projects of the type that nobody has ever done, it will be very hard to get a fixed-price contract from a company,” he said.

Spergel, in his opening statement, asked Congress to spread out the additional cost incurred by JWST’s delays across the agency, versus simply the astrophysics program. “JWST’s delays are frustrating for all of us,” he said, but said the mission will ultimately be “a flagship of all of NASA” with its scientific discoveries.

“Since JWST is an agency-wide priority, new costs should be spread across the agency,” he said. “If they’re borne entirely by the astrophysics directorate, they’ll have a devastating effect on future missions and the scientific program.”

Spergel and others said that JWST and NASA’s next large astrophysics mission, the Wide-Field Infrared Survey Telescope, offered national leadership at a time when Europe and especially China are developing new capabilities that could soon rival the U.S.

“I think we are leading the world,” he said. “I have been very impressed by the investments the Chinese are making in space science. They were really not even significant players 10 years ago. Looking to where they might be a decade from now, if we stop investing, they will be the leaders.”