Ever since learning the surface of the planet Mars is cold and dead, scientists have wondered if there was a way to make it friendlier to life.

In a groundbreaking study published Aug. 7 in Science Advances, researchers from Northwestern University, University of Chicago, and University of Central Florida have proposed a revolutionary approach toward terraforming Mars. This new method, using engineered dust particles released into the atmosphere, could potentially warm the Red Planet by more than 50 degrees Fahrenheit, to temperatures suitable for microbial life — a crucial first step toward making Mars habitable. 

The proposed method is more than 5,000 times more efficient than previous schemes to globally warm the planet, representing a significant leap forward in our ability to modify the Martian environment, according to lead author and Northwestern electrical and computer engineering graduate student Samaneh Ansari, who works in the lab of Northwestern professor Hooman Mohseni.

What sets this approach apart is its use of resources readily available on Mars, making it far more feasible than earlier proposals that relied on importing materials from Earth or mining rare Martian resources.

This strategy would take decades. But it appears logistically easier than other plans proposed so far, the researchers said.

“This suggests that the barrier to warming Mars to allow liquid water is not as high as previously thought,” said Edwin Kite, an associate professor of geophysical sciences at the University of Chicago and corresponding author on the study.

Making the planet suitable for humans to walk on the surface unaided requires much more work — astronauts still won’t be able to breathe Mars' thin air. But perhaps groundwork could be laid by making the planet habitable for microbes and food crops that could gradually add oxygen to the atmosphere, much as they have done for Earth during its geologic history.

A new approach to an age-old dream

There is a rich history of proposals to make Mars habitable — Carl Sagan himself came up with one back in 1971. These have ranged from outright daydreams, such as science fiction writers depicting turning one of Mars’ moons into a sun, to more recent and scientifically plausible ideas, such as engineering transparent gel tiles to trap heat.

Any plan to make Mars habitable must address several hurdles, including deadly UV rays and salty soil. But the biggest is the planet’s temperature — the surface of Mars averages about -80 degrees Fahrenheit.

One strategy to warm the planet could be the same method that humans are unintentionally using here on Earth: releasing material into the atmosphere, which would enhance Mars' natural greenhouse effect, trapping solar heat at the surface.

The trouble is that tons of these materials would be needed — literally. Previous schemes depended on bringing gases from Earth to Mars, or attempting to mine Mars for a large mass of ingredients that aren’t very common there are both costly and difficult propositions. But the team wondered whether it could be done by processing materials that already exist abundantly on Mars.

Changing the shape of the planet’s dust

Scientists have learned from rovers like Curiosity that dust on Mars is rich in iron and aluminum. By themselves, those dust particles aren’t suitable to warm the planet; their size and composition mean they tend to cool the surface slightly rather than warm it. But if dust particles could be engineered to have different shapes or compositions, the researchers hypothesized, perhaps they could trap heat more efficiently.

The researchers designed particles shaped like short rods, similar in size to commercially available glitter. These particles are designed to trap escaping heat and scatter sunlight towards the surface, enhancing Mars' natural greenhouse effect.

“How light interacts with sub-wavelength objects is fascinating,” Ansari said. “Importantly, engineering nanoparticles can lead to optical effects that far exceed what is conventionally expected from such small particles.”

A step toward feasibility

Mohseni, a study co-author and the AT&T Professor of Information Technology at the McCormick School of Engineering, as well as a professor of physics and astronomy in the Weinberg College of Arts and Sciences, believes that they have just scratched the surface.

“We believe it is possible to design nanoparticles with higher efficiency, and even those that can dynamically change their optical properties,” he said.

“You'd still need millions of tons to warm the planet, but that’s five thousand times less than you would need with previous proposals to globally warm Mars,” Kite said. “This significantly increases the feasibility of the project.”

Calculations indicate that if the particles were released into Mars’ atmosphere continuously at 30 liters per second, the planet would warm by more than 50 degrees Fahrenheit. The effect could be noticeable within as soon as months. Similarly, the warming would be reversible, stopping within a few years if release was switched off.

The authors used the Quest high-performance computing facility at Northwestern and the University of Chicago Research Computing Center.

Potential impact and future research

Much work remains to be done, the scientists said. They don’t know exactly how fast the engineered dust would cycle out of Mars’ atmosphere, for example. Mars does have water and clouds, and, as the planet warms, it’s possible that water would increasingly start to condense around the particles and fall back to the surface as rain.

"Climate feedbacks are really difficult to model accurately," Kite cautioned. "To implement something like this, we would need more data from both Mars and Earth, and we'd need to proceed slowly and reversibly to ensure the effects work as intended."

While this method represents a significant leap forward in terraforming research, the researchers emphasize that the study focuses on warming Mars to temperatures suitable for microbial life and possibly growing food crops — not on creating a breathable atmosphere for humans.

“This research opens new avenues for exploration and potentially brings us one step closer to the long-held dream of establishing a sustainable human presence on Mars,” Kite said.