NASA has canceled a mission to assay the resources that may be available to humans on the moon, even though President Donald Trump's administration made it a priority to send humans back there, according to media reports. 

The Resource Prospector mission would have sent a rover to the moon's polar regions to learn about water and other deposits on and just beneath the lunar surface. Scientists have sent an open letter to new NASA Administrator Jim Bridenstine, urging him not to shut down the agency's only current moon mission, which has already been in development for four years, according to a report by The Verge.

The Resource Prospector mission consisted of a lander and a solar-powered rover equipped with a drill. The rover would have scouted the lunar surface, digging up soil for analysis. Scientists know that water ice exists on the moon, but the Resource Prospector would have provided scientists with a more complete understanding of these deposits. 

Such knowledge is crucial to expanding a human presence on the moon. Lunar ice can potentially be melted and split into oxygen and hydrogen, providing a local source of water, oxygen and rocket propellant, The Verge reported. This would not only help make human activities more self-sustaining but also dramatically reduce launch costs, because many of these vital resources could be produced on-site. 

"If we can demonstrate that we can access the water on the moon, then we can start to design the equipment that will mine it and deliver it to the outpost," Phil Metzger, a planetary physicist at the University of Central Florida who is part of the science team for Resource Prospector, told The Verge.

NASA’s Resource Prospector rover would have scouted the lunar surface for subsurface water, hydrogen and other volatiles. A drill would have allowed the rover to sample the lunar soil down to a depth of 1 meter.
NASA’s Resource Prospector rover would have scouted the lunar surface for subsurface water, hydrogen and other volatiles. A drill would have allowed the rover to sample the lunar soil down to a depth of 1 meter.
Credit: NASA

Although it was not yet fully funded, the Resource Prospector mission had gotten well past the drawing board. Engineers had been working on the project for four years, and prototypes were tested on Earth in 2015 and 2016, according to The Verge. Plans had the mission launching in 2022. "It's far enough along that it's a real mission," Clive Neal, an engineering professor at the University of Notre Dame and Lunar Exploration Analysis Group (LEAG) emeritus chair, told The Verge.

Issues likely started when the mission was transferred from one directorate within NASA to another, according to Metzger. Originally, it was funded with money allocated for human exploration, The Verge reported. However, it was moved to the section that funds scientific missions. Although Resource Prospector was a robotic mission, it didn't fit as well within the Science Mission Directorate's priorities or budget, which is likely why it was canceled, The Verge said.

As for why the mission was moved, "I don't really know what the motive was, but I'm guessing it was probably budget-related," Metzger told The Verge. NASA's human exploration program is currently working on the massive Space Launch System rocket, which accounts for a sizable portion of the program's budget. Given the recent growth of private launch companies, a number of people have criticized NASA's decision to continue developing this costly rocket.

Several scientists at LEAG, which advises NASA on lunar exploration, wrote a letter to Bridenstine, urging him to re-evaluate the decision to cancel the mission. In their letter, they explained the mission's importance in current plans to return humans to the moon and expand the nation's lunar presence overall.

The decision to cancel the Resource Prospector mission is peculiar given the current administration's plans for NASA. Trump has repeatedly called for NASA to return humans to the moon and even signed Space Policy Directive 1, ordering NASA to return astronauts to the moon ahead of crewed missions to Mars and beyond. As of now, "there are no other [NASA] missions being planned to go to the surface of the moon," Metzger told The Verge.

The Resource Prospector also fit in nicely with the Trump administration's desire to foster NASA's partnerships with the commercial space industry, as there's been increased interest in lunar exploration from private companies. Several businesses have plans to send their own spacecraft to the moon, and some would like to set up commercial operations there. The moon could even serve as a space port for longer-distance missions, like those to Mars, The Verge said. 

"Of course, it could turn out that the water [on the moon] isn't easily accessible at all, and that could change a lot of plans within the industry," The Verge wrote. The Resource Prospector mission was critical to answering this question.

You can read The Verge's story here: https://www.theverge.com/2018/4/27/17287154/nasa-lunar-surface-robotic-mission-resource-prospector-moon.

Follow Harrison Tasoff @harrisontasoff. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.