Making Mars more Earth-like would be a gargantuan task. From giant mirrors to tiny microbes, here's the thinking behind making Mars habitable for humans.
At the end of 1990's sci-fi adventure Total Recall, all it takes is the push of a button. In a matter of minutes, Mars' sky transforms from a hellish red to an Earth-like blue. After nearly suffocating on the Martian surface just moments before, Arnold Schwarzenegger takes in lungfuls and lungfuls of that sweet, sweet breathable Martian air.
This is terraforming, the concept of making a planet more hospitable to humans, and it's been cropping up in pop culture since the early 1900s, everywhere from books to movies to video games. Once upon a time, the idea of turning Mars into Earth 2.0 might have been merely a fanciful notion, as theoretical as actually going to the planet at all.
But in 2020, Mars is very much on the agenda. NASA, SpaceX, Virgin Galactic -- they all want to put space boots on the ground, and in some cases as soon as the 2030s. But as scientists work toward blastoff, the concept of terraforming will most likely be a case of "failure to launch."
You might say Mars is a rough neighborhood.
The planet, about 70% the size of Earth, has an atmosphere of mostly carbon dioxide and boasts an average temperature of -81 degrees Fahrenheit (-62 degrees Celsius). Because the atmosphere is so thin (Earth's is more than 100 times denser) there's not much shielding from radiation.
These conditions pose more than a few problems if humans are planning an extended stay. Terraforming, broadly speaking, would address the creation of a thicker atmosphere and an increase in atmospheric pressure. Getting even more ambitious, it would allow for breathable air. Maybe one day, Martian farmers could work in their shirt sleeves tending to whatever vegetation they've planted in a soil rich with microbes. Mars could be self-reliant for essentials like food and water. Who doesn't love some economic growth?
"If we're really serious about long-term occupation of people on Mars, I do have a hard time seeing that as just a trailer park on Mars," said Caleb Scharf, director of astrobiology at Columbia University.
There's a solid pile of ideas around terraforming Mars, and they all sound pretty wild. Mostly, they have to do with getting a lot of greenhouse gas into the atmosphere, releasing it from the planet's ice and soil.
In 1993, researchers Robert Zubrin and Chris McKay wrote a paper analyzing theories for terraforming the red planet. One involved building giant orbital mirrors to reflect sunlight to raise the temperature of Mars, melt the frozen water on the planet and thereby release carbon dioxide into the atmosphere. In another scenario, settlers could build factories whose express purpose is to pump out artificial greenhouse gases like fluorocarbon gases. Humans could maybe harness ammonia-rich asteroids, aligning them to hit Mars.
Then there's the idea from SpaceX founder Elon Musk: Nuke Mars. You can literally squeeze it onto a T-shirt and buy it from SpaceX's online merch shop. Musk maintains that lobbing nuclear bombs at the ice caps could melt the ice and put sufficient carbon dioxide into the air.
If space weren't a vacuum devoid of sound, though, you might hear screeching brakes in the background right now. It turns out humans can't really do any of this.
"Terraforming, if you really did it, is on this crazy scale which is way beyond the scale of any engineering we've ever attempted as humans," Scharf said, "It's going to be a long, rough ride." And, most certainly, one that would take generations upon generations to play out.
In July 2018, researchers Bruce Jakosky and Christopher Edwards released a study making it clear that for all the ideas that have been bandied about for decades, humans just don't have the technology right now to terraform Mars.
"Theoretically, it's possible to terraform Mars, but the ways you could do it just aren't at all practical today," said Jakosky over the phone.
There's a laundry list of questions to answer: How exactly do you build a giant mirror in space? How do you get access to and redirect the thousands of asteroids needed to sling at Mars? Would it be safe to have anyone on the surface while you do this? How do you build a factory when you don't even have a tent pitched? What happens when you nuke the ice caps, and the gases just refreeze?
Furthermore, the study found that even if humans could tap every available source of carbon dioxide on Mars, from the ice caps to mineral deposits, Mars' pressure would only bump up to about 7% of Earth's.
Having sufficiently popped the terraforming bubble, it's unsurprising NASA is focusing its efforts elsewhere.
"NASA is not currently planning any activities around terraforming Mars," said spokeswoman Kathryn Hambleton by email.
But just because you can't flip a climate change switch on a planet doesn't mean there aren't other ways to alter it, perhaps on a much smaller scope.
One idea researchers are looking into is using aerogel to maybe one day build structures like greenhouses. Aerogel is a super low-density solid that's 99% air. It's a good insulator, and NASA's already using it on its Mars rovers. In a study published in July, Harvard University associate professor Robin Wordsworth did an experiment. He shined a lamp set to simulate Martian sunlight on 2 to 3 centimeters of silica aerogel and was able to heat the surface below by as much as 150 degrees F. That would be enough to melt ice on Mars.
"You could just do a small amount of [building aerogel structures] in a certain area and then build on that as time goes by," said Laura Kerber, a NASA Jet Propulsion Lab research scientist who worked on the study.
Now, aerogel isn't perfect — it's brittle and has to be produced somewhere. But Kerber is cautiously optimistic, and the team want, to do further experiments with aerogel in places like Antarctica.
Taking a more controlled approach could help address some of the ethical considerations around terraforming, like whether humans have the right to alter and — let's be real — potentially screw up an entire planet. And as Scharf, Zubrin and Kerber all pointed out, planetwide terraforming would likely wipe out whatever evidence of life we haven't found, or even just the geologic record of the solar system we no longer have on Earth.
"There's so much more we have to learn about, like pristine Mars as it is, before we are going to change it," Kerber said.
Though a terraformed Mars isn't something anyone alive today will live to see, Zubrin thinks it could still happen. He equates it to Jules Verne's books From Earth to the Moon (1865) and Around the Moon (1870), which described a launch to the moon, eerily similar to the one that would take place 100 years later. In the story, a three-astronaut crew blasts into space from Florida and splashes down in the Pacific Ocean, to be picked up by a US military ship. A notable difference: They were basically fired out of a giant cannon.
"He got a lot right, but it's quaint because this is a 19th century mind grappling with a 20th century problem," Zubrin said. In that way, Zubrin thinks the fact anyone can conceptualize even theoretical ways to terraform Mars means it'll be plausible in the future. In fact, he believes that in 100 years, humans might just be techie enough. He imagines leaps in biotechnology, nanorobotics — maybe there will be bioengineered plants that could put out far more oxygen than the ones on Earth.
Zubrin's relying on the technological sophistication of future humans, he said: "They're going to do it."