WASHINGTON — Members of the Senate Commerce space subcommittee used a March 12 hearing on the NASA budget to debate with each other, and the head of the agency, about what the agency’s priorities should be.

Sen. Ted Cruz (R-Texas), chairman of the subcommittee, expressed concern that NASA was spending too much money on Earth science and not enough on exploration programs.

“Since the end of the last administration, we have seen a disproportionate increase in the amount of federal funds that have been allocated to the Earth science program, at the expense of, and in comparison to, exploration and space operations, planetary science, heliophysics, and astrophysics,” he said in his opening remarks.

To illustrate his point, Cruz displayed a chart showing that NASA’s request for Earth science funding had increased 41 percent between the 2009 and the 2016 budget proposals, while other NASA programs saw either decreases or far smaller increases. “In my judgment, this does not represent a fair or appropriate allocation of resources,” he said. “It is shifting resources away from the core functions of NASA.”

Bolden, asked by Cruz to define the “core mission” of NASA, defended the agency’s work by citing language in the National Aeronautics and Space Act that created the space agency. “Essentially, our core mission from the very beginning has been to investigate and explore space and the Earth environment, and to help us make this place a better place,” he said.

Cruz disagreed. “I would suggest that almost any American would agree that the core function of NASA is to explore space,” he said. “It’s what sets NASA apart from any other agency.”

Another Republican on the subcommittee, Sen. Cory Gardner (R-Colo.), also said NASA was investing too much in Earth science over exploration. “It seems to me that NASA has perhaps drifted away from its core mission, and I’m concerned about that,” he said.

Democratic members, however, defended the agency’s work in Earth science as part of its overall scope of missions. Gary Peters (D-Mich.), who was named the ranking member of the space subcommittee March 3, argued that an increase in Earth science funding was a recovery from past cuts.

“We must avoid false choices between robotic exploration, human exploration, the study of the universe, or the study of our own planet,” he said in his opening statement. “We must avoid the temptation to view NASA’s mission as a set of competing priorities.”

“In some quarters, it seems to be fashionable to say that Earth science is not part of the exploration program,” said Sen. Bill Nelson (D-Fla.), ranking member of the full committee. Work on Earth science, he said, was linked to all of the agency’s initiatives.

Bolden made a similar argument, arguing that NASA’s exploration program was dependent on a variety of other NASA programs, including Earth science. “We can’t go anywhere if the Kennedy Space Center goes underwater and we don’t know it,” he said.

Cruz indicated at the end of the hearing that he planned to revisit the issue in a future authorization bill. “It is my hope that this committee will work in a bipartisan manner to help refocus those priorities where they should be: to get back to the hard sciences, to get back to space, to focus on what makes NASA special,” he said.

Beyond the discussion about NASA’s roles, Bolden used the hearing to quietly promote the nomination of Dava Newman as the agency’s deputy administrator. Newman, present at the hearing, was nominated by the White House for the position in October 2014, but has yet to be confirmed by the Senate.

“One of these days you all, hopefully, if this committee seeks to support her, will have someone who can come before this committee and speak very authoritatively,” he said in response to a question on aeronautics research. Newman is a professor of aeronautics and astronautics at the Massachusetts Institute of Technology.

Nelson indicated he supported the nomination, noting Bolden has been making progress at NASA despite not having a deputy for a year and a half. “He’s got everybody pulling in the right direction, which is a significant accomplishment for the administrator,” he said of Bolden.