The harsh and frigid atmosphere of Mars, which is 95 percent carbon dioxide, is thin. With temperatures averaging around 81°F below zero, the planet is unfriendly to life as we know it, from dust storms to cosmic radiation.
It does, however, share many similarities with Earth, as we know it was originally a blue planet with a thicker atmosphere and oceans on its surface billions of years ago.
Jim Green, the outgoing director of NASA's planetary science division, told The New York Times earlier this week that it would be possible to warm and thicken the Martian atmosphere by erecting a gigantic magnetic barrier between it and the Sun.
The goal would be to prevent solar wind from bombarding Mars with radiation, allowing particles to escape the planet's already thin atmosphere.
"It's doable," Green told the publication. "Stop the stripping, and the pressure is going to increase. Mars is going to start terraforming itself."
Green isn't the only one who is intrigued by the idea. Astrophysicist and former NASA scientist Hakeem Oluseyi appeared on CNN for an interview this week to expand Green's concept.
"It's like an umbrella for a planet," Oluseyi told CNN.
Increased air pressure and temperature would allow humans to "begin the process of growing plants in the soils," according to Green, who emphasized that being able to walk on the planet's surface without a spacesuit would provide humanity "flexibility and mobility."
He pointed, though, stated that the "first level of terraforming", which he set at 60 millibars - "the Armstrong limit, where your blood doesn't boil if you went out on the surface" - is still "a factor of 10 from where we are now."
Using a "physical shield that reflects light," the retiring scientist also suggested that another planet in our solar system, Venus, could be terraformed, lowering the second planet's extremely high atmospheric temperature.
There's also the Confidence of Life Detection (CoLD) scale, which is one of Green's most recent notable recommendations. The scale is divided into seven levels, each of which serves as a benchmark that must be met before proceeding to the next level.
Level one would be the discovery of life signatures such as biological molecules. The second stage would be to rule out the notion that the evidence is the result of Earth contamination. Finally, scientists would declare that they have discovered proof of extraterrestrial life.
Green has served as NASA's chief scientist for the past three years, as well as serving as the director of the agency's planetary science division for 12 years. At the beginning of this year, he announced his retirement.
