Early Mars was probably kinda warm and kinda wet, but solar winds have beaten it down over time into the windy, freezing Mars we aspire to escape to today.

What’s more, new data from the Mars Atmosphere and Volatile Evolution (MAVEN) mission shows that the planet’s atmosphere has been severely depleted of CO2 and other vital gases. A paper detailing the research was published Thursday in the journal Science.

This might be an insurmountable obstacle in our quest to terraform Mars’s atmosphere into something livable, at least with the technologies we can envision realizing in the next few hundred years.

Here’s how a research team measured the presence of the gas argon in the atmosphere, looking at lighter and heavier isotopes: At higher altitudes, the team learned that the lighter argon isotope is more prevalent, which means more vulnerable to being sucked out by solar winds. They concluded that two-thirds of Mars’s argon supply has been depleted over the course of the planet’s lifetime. By extrapolating the process and associated results for other gases, they were able to conclude that Mars probably once did have a carbon-rich atmosphere much like Earth’s — but no longer.

Mars wasn't always like this, not that that helps us much now.

In the short-term, this information doesn’t have much effect on our plans for Mars, which are increasingly competitive and grand. Even if NASA and the private contenders like SpaceX are able to stick to their proposed timelines completely, we’re looking at several decades before humans are staying on the surface for extended periods of time. But the longer game has always been to colonize Mars extensively, and we cannot colonize Mars extensively without terraforming.

To successfully transform Mars’s atmosphere from hostile to at least marginally less hostile, we’re going to need to warm it, and this is where the planet’s lack of CO2 becomes a massive problem. If the gas was sequestered as ice in the polar regions, we would have eventually been able to mobilize it as a heat source and distribute it back over the planet. But once it’s been lost to space, we cannot put it back.

“I don’t think this is something that’s going to be easy to get around,” co-author Bruce Jakosky tells Inverse. “I think this really kills the idea of terraforming, unless maybe we can import some gas [from Earth].”

This is possible in theory, but it’s a daunting prospect when you consider the quantities involved; Jakosky likened it to importing the gas of 1,000 comets. This leaves us with wilder ideas like manufacturing chlorofluorocarbons — greenhouses gases — but again, the scale of such an undertaking would be “humongous,” says Jakosky. “It’s centuries downstream at best … you’d need a million times more [gas] than we have here on Earth.”

Without terraforming, our future on Mars will be restricted to domes, or some other protective environments that are similar. The lifestyle would be more closely analogous to how we’d live on the moon than how we live here on Earth.

“I think we have the capability and technology to do a human mission to Mars, to have people orbiting in 15 years, in a way that’s safe and credible,” Jakosky says. “That’s where we are [for] now.”

Photos via Jakosky et al., p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 10.0px Arial; -webkit-text-stroke: #000000} span.s1 {font-kerning: none} NASA’s Goddard Space Flight Center