When Mars’ magnetosphere died about 4.2 billion years ago, it took the greater part of the Red Planet’s habitability with it. Most of the atmosphere blew away, open bodies of liquid water either evaporated or froze into the soil, and any life that might have once existed on Mars must have mostly died if it even existed in the first place.
Now NASA engineers believe that they can create an artificial magnetosphere by placing a magnetic shield at Mars’ L1 LeGrange point. The shield could deflect the solar wind and radiation to protect Mars’ atmosphere and possibly provide a starting point in the path to making Mars habitable again. The atmosphere could even begin to recover enough for frozen carbon dioxide at the poles to begin the sublimation process. As the atmosphere thickens, the extra carbon dioxide could produce enough of a greenhouse effect for water ice in the soil to melt and form liquid bodies of water. Naturally, these bodies of water would be smaller than what Mars once had, but it could be enough to restore Mars’ ability to naturally sustain life.
If the magnetic shield is successfully deployed, it could make human exploration and eventual colonization of Mars easier by reducing the risks associated with radiation exposure and an atmosphere that engineers at JPL have described as “thick enough to be annoying, but too thin to be very helpful.” Astronauts could worry less about getting a puncture in their EVA suit because the thicker atmosphere made possible by the shield gives them more time to notice the leak and apply a patch to that puncture. They could also worry less about cancer risks and other health hazards caused by increased radiation exposure. That basically means they can spend more time exploring Mars with the peace of mind that comes with having basically killed two cosmic dragons with one stone.
Don’t expect the effects of having the magnetic shield in position to take place quickly, though. Any reasonable plan to terraform Mars is likely to take decades to show any noticeable effects once it begins. The good news is that some research has already been done into inflatable structures that could serve as the replacement for Mars’ magnetosphere. Such a thing would also reduce the amount of effort it would otherwise take to terraform Mars. Those interested in doing exactly that wouldn’t have to jump-start the dynamo effect that would be needed to get Mars’ natural magnetosphere going again, for instance.