CHICAGO — Momentum is growing behind a bold vision of building a settlement on Mars, allowing humans to tap into its resources and make it our second home. But a prominent astronomer from Chicago is raising red flags about the idea of colonizing the red planet.

Mars has always had the ability to capture the collective imagination. Presidents have been talking about going there for years. Former President Barack Obama said he thought we’d make it there and back by the “mid-2030s.” President Donald Trump also said he plans to establish a foundation for an eventual mission to Mars.

When it comes to American ingenuity, the sky’s the limit. Buzz Aldrin can prove it — his footprints are on the moon. Almost 50 years after the moon landing, Aldrin said it’s time for another great American exploration and national undertaking: the colonization of Mars.

“I’m a firm believer that the resources, the effort to get people there, should result in the building up of a settlement, a colony,” Aldrin said.

The possibility has enticed philosophers and physicists, environmentalists and entrepreneurs. Among them is Elon Musk, who said his space transport company SpaceX could help humanity become a “multi-planet” species while harvesting resources from the red planet.

Even renowned physicist Stephen Hawking said such a colony, “will completely change the future of the human race.”

But in a recent TED Talk, Adler Planetarium astronomer Lucianne Walkowicz warned that it’s dangerous to think of Mars as a “back-up planet.”

“I worry this excitement of colonizing Mars and other planets carries with it a long dark shadow: the belief by some that Mars will be there to save us from the self-inflicted destruction of the only planet we know of: the Earth,” Walkowicz said.

For Walkowicz, the idea that we can mine Mars for resources is dangerous because it gives humanity permission to waste the resources we already have.

“For anyone to tell you that Mars will be there to back up humanity is like the captain of the Titanic telling you that the real party is happening later in the life boats,” Walkowicz said.

Walkowicz spent the last year in Washington D.C. as the chair of astrobiology at the Library of Congress, breaking the mold and bringing a colorful perspective to the buttoned-down beltway. That includes studying the question of Mars exploration and its ethical implications for humanity.

“This was very much at the crossroads of social concerns and space travel,” Walkowicz said. “When people go to any place, whether it’s on Earth or out in space, they bring a variety of motivations with them.”

She worries that in the effort to colonize, we may be gaining the stars but losing our home, as warnings about climate change become more dire.

“When we’re faced with challenges like climate change, where we can lower the amount of carbon outputs that we’re doing, but we’re still going to have an important role for technology in mitigating those effects for people, we can use travel in space and maintaining life in space as a way of testing those methods,” Walkowicz said.

As for Aldrin, he sees the colonization of Mars as the next big national project — one that could boost morale just like the moon mission. Even if he doesn’t think he’ll see it in his lifetime.

“We have a chance again to excel, and Americans need to excel, particularly in these times,” Aldrin said.

And as we the ponder our place in the cosmos and whether there really any limits, Walkowiczv said it’s important to remember at least one.

“Human beings are human beings everywhere they go, whether it’s just across this globe or to a whole other one,” Walkowicz said.