Scientists helping NASA put a rover on the moon are concerned about why the mission was canceled and why they were told to end operations within the next month.

The mission would have involved sending a robot to the moon’s polar region in 2022 to probe for things like underground water and hydrogen.

According to the Lunar Exploration Analysis Group (LEAG), the mission had been halted on April 23, and were told to wrap up by the end of May.

In a letter sent to NASA Administrator James Bridenstine on Thursday, LEAG asked NASA to re-instate the Resource Prospector mission, which was still in its early stages of preparation. The mission’s end comes after President Donald Trump signed a directive in December that called on NASA, along with private companies, to work towards returning humans to the moon.

“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 LEAG said in its letter (emphasis theirs). “RP was the only polar lander-rover mission under development by NASA (in fact, by any nation, as all of the international missions to the lunar poles are static landers) and would have been ready for preliminary design review at the beginning of 2019.”

Phil Metzger, a planetary physicist at University of Central Florida stated, “There are no other [NASA] missions being planned to go to the surface of the Moon.”

Budget problems may be at the heart of the issue. The LEAG letter mentions that RP was initially funded through the Human Exploration and Operations Mission Directorate, but then transferred to the Science Mission Directorate (SMD) budget.

Dana Hurley, a planetary scientist, who works at the Applied Physics Lab in Maryland and who is on the LEAG executive committee.

“If we want to go back to the moon and really work on the moon and make it a place that we can set up research stations and study processes that are occurring on the moon … all these things are really enabled by being able to use resources on the moon for making fuel, propellant, life support, that sort of thing,” Hurley told the Washington Post. “This mission is a first step in trying to understand how we’re going to exploit those resources.”

An update appeared on NASA’s RP website has indicated that NASA still plans to explore the moon.

“NASA is developing an exploration strategy to meet the agency’s expanded lunar exploration goals. Consistent with this strategy, NASA is planning a series of progressive robotic missions to the lunar surface. In addition, NASA has released a request for information on approaches to evolve progressively larger landers leading to an eventual human lander capability. As part of this expanded campaign, selected instruments from Resource Prospector will be landed and flown on the Moon. This exploration campaign reinforces Space Policy Directive 1, which calls for an innovative and sustainable program of exploration with commercial and international partners to enable human expansion across the solar system, including returning humans to the Moon for long-term exploration.”