There can be little question that new NASA Administrator Jim Bridenstine wants humans to return to the Moon and to open Earth's celestial neighbor to commercial activity. Just check the lunar background of his new Twitter account or some of his writings on the subject. Soon, however, his commitment to the Moon will be tested.

On Thursday—just his third full day on the job—a group of lunar scientists, engineers, and mission planners sent Bridenstine a letter to complain about the cancellation of the Resource Prospector program. This mission would send a rover to the polar region of the Moon to look for, and study, ice deposits that scientists hypothesize are there. Advocates of lunar exploration say this source of water could provide propellant for exploration missions deeper into the Solar System.

In recent years, the existence of this water has become a key reason that NASA (and other national space agencies) have begun to formulate plans for the development of lunar resources. Indeed, when President Trump signed Space Policy Directive 1 last December, he redirected NASA back toward the Moon, including for the purposes of "long-term exploration and utilization" of that sphere.

But before humans go to the very cold polar regions, it would be best to know what exactly they might find there. This was the purpose of the Resource Prospector mission, to better characterize water ice deposits at the polar regions and to assess the ease (or difficulty) with which they might be obtained.

However, on April 23, the day Bridenstine was sworn into office, the Resource Prospector mission was formally canceled by NASA. (It does not appear as though Bridenstine was behind the change). This prompted an outcry from lunar scientists with the Lunar Exploration Analysis Group who have cheered on the Trump administration's proposed return to the Moon.

Incredulity and dismay

"This action is viewed with both incredulity and dismay by our community, especially as the President's Space Policy Directive 1 directs NASA to go to the lunar surface," the group wrote to Bridenstine, in a letter dated April 26. "RP was the only polar lander-rover mission under development by NASA."

The group noted that the Resource Prospector was recently moved from NASA's human exploration budget into its science budget but said this was misguided for two reasons. First, in design work over the last five years, the prospector has not been optimized for science—but rather as a precursor for human exploration. Second, NASA's lunar science program is designed for small robotic landers, not the 300kg prospector rover.

We feel that time is of the essence," Neal said.

In an interview with a co-signer of the letter, the lunar exploration group's emeritus chair, Clive Neal, told Ars that they recognized that they were hitting Bridenstine with this issue even as he had only begun his job. However, Neal said, the mission is due to be closed down in May. "

Two other lunar scientists, who did not want to be quoted for this article, suggested the move to kill the Resource Prospector could be an effort to subvert the nascent return to the Moon program. The prospector was to land on the Moon in 2022 and could inform human exploration plans going forward. Absent a commitment to the lander, these scientists suggested, it will be much easier for the next presidential administration to cancel the Moon landings and put NASA back on a "Journey to Mars."

Thus the prospector might be viewed as an early test of Bridenstine's—and the Trump White House's—true affinity for lunar landings.