NEW ORLEANS —Despite President Trump's declared intention to send human explorers to the moon before Mars, astronomers and planetary scientists remained wary. While some expressed their enthusiasm for the plan, others questioned whether it would ever become a reality.

"It's all hot air until someone actually does something," exoplanet scientist Stephen Kane of the University of California, Riverside, told Space.com.

On Dec. 11, Trump signed Space Policy Directive 1, a document that shifts U.S. policy, directing NASA to land astronauts on the moon before sending them on to the Red Planet. The document made no mention of funding or deadlines. [From Ike to Trump: Presidential Visions for Space Exploration]

"This time, we will not only plant our flag and leave our footprint, we will establish a foundation for an eventual mission to Mars," Trump said at the event.

President Donald Trump holds up his Space Policy Directive 1, which directs NASA to return astronauts to the moon, after signing it in the Roosevelt Room of the White House on Dec. 11, 2017. (Image credit: Aubrey Gemignani/NASA)

"The proof is in the pudding"

Space.com caught up with several space scientists at the American Geophysical Union meeting in New Orleans, Louisiana, to ask their opinions about the president's new policy. While several declined to comment due to their role as civil servants, others were more than happy to share their feelings.

"I'm very excited about it," said Alan Stern, the principal investigator for NASA's New Horizons mission to Pluto. "This administration really understands the value of space for American leadership in the world."

Stern, Stern, board chair of the Commercial Spaceflight Federation based in DC and vice president of the Southwest Research Institute based out of San Antonio, Texas, has had his own aerospace consulting practice since 2008. He compared America's economic connection to space exploration with 16th-century Europe's economic connection to North and South America.

"The proof's in the pudding," Stern said. "It's going to be up to NASA to come through, with the commercial sector, to find a sustainable and affordable way to begin with the moon and then send humans throughout the solar system." [In Photos: President Trump's Administration and NASA]

Kane also tied space exploration to colonization, pointing out that successful missions would require constant support that might not show immediate benefits to the taxpayers footing the bill. Rather than the Americas, he pointed to his native country of Australia.

"Australia is only slightly more hostile than Mars," Kane said, somewhat tongue in cheek. Colonists relied on replenishment from Britain for years before they were able to survive on their own, much as the first explorers on the moon and Mars will need to do.

John Burgener, a geophysicist and owner of the private corporation Telegistics, thinks that the moon will provide a better jumping-off point for preventing incoming impactors from wiping out human civilization. By placing astronauts and bases on the lunar soil, he said scientists will be able to both monitor and divert potentially hazardous comets and asteroids.

"Mars doesn't offer any advantage in terms of protecting Earth, although it's an interesting adventure," Burgener said. "Mars may push humanity to do great and wonderous things, like Columbus coming to North America pushed the Europeans to do great and wonderous things, but in terms of protecting Earth, offering us the ability to observe more of the solar system and the universe, the moon is a much better goal."

The moon as destination and resource

Others view the moon as a fantastic resource.

"I view the moon as scientifically fascinating," said William McKinnon, a New Horizons researcher at Washington University in Missouri.

McKinnon pointed out that the moon was also a good plan because "we know how to do it and do it well," while "going to Mars is still a very complicated problem."

Paul Estrada, a solar system scientist at the SETI Institute in California, was concerned about how the plan to hit the moon would actually play out. While he said that he was not against going to the moon in principle, he was concerned that pushing exploration would cause research science to suffer.

"He's not going to take the money out of other programs, he's just going to shift money within NASA — at least, that's what I think," Estrada said. "So, unless NASA's budget gets significantly increased, someone is going to suffer."

"Just shifting money around, where they should be putting more money in rather than reallocating money, is just going to affect the budgets of research," he said.

Follow Nola Taylor Redd on Twitter @NolaTRedd or Google+. Follow us at @Spacedotcom, Facebook or Google+. Originally published on Space.com.