Mars may have been habitable more recently than thought

Mars may have hosted life billions of years ago, a possibility that has long intrigued scientists. Now, new evidence suggests the planet was habitable for even longer than previously thought, due to the presence of a global magnetic field. These findings change what was once believed about the history of Mars and could help uncover more about the planet and our solar system at large.

Disappearing dynamo

Like the Earth, Mars had a magnetic field surrounding it — the "dynamo." Mars' dynamo was "driven by convection within the planet's iron core much like Earth's," and "could shield the surface from harmful cosmic rays, crucial for maintaining a habitable environment," said Earth.com. While the Mars of today is dry and barren, it may have once been full of life before the dynamo vanished. A recent study published in the journal Nature Communications suggests that Mars' magnetic field may have been around longer than scientists were aware of, only disappearing approximately 3.9 billion years ago, compared to the previous estimates of 4.1 billion years.

Researchers formerly suspected that the dynamo was gone 4.1 billion years ago because "huge impact basins that were formed during a period of bombardment between 4.1 and 3.7 billion years ago do not retain any record of strong magnetism in their rock," said Space.com. They concluded that the craters only formed when there were no other strong magnetic fields present. However, the new study argues that those craters "formed while the dynamo of Mars was experiencing a polarity reversal — north and south poles switching places — which, through computer simulation, can explain why these large impact basins only have weak magnetic signals today," said The Harvard Gazette.

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The search for the Martian

These findings are significant because 200 million years is a lot of time for life to potentially develop. The dynamo's extended timeline "overlaps into the era when the surface of the Red Planet became covered in water, evidence for which has been discovered by NASA Mars rovers," said Space.com. "With the magnetic field still in place to shield the surface, life may have had a chance to get started in a watery environment without being killed off by radiation from space."

Scientists have been actively looking into finding evidence of life on Mars. For example, a Caltech study found a potential habitable zone for underground microbes on Mars. The area would be "beneath a certain amount of ice," said New Atlas: "Too shallow and the strong ultraviolet radiation will cook them, but too deep and there won't be enough visible light filtering down for them to feed on." Bringing in this new data on the dynamo could provide insight into habitable zones as well.

"We are trying to answer primary, important questions about how everything got to be like it is, even why the entire solar system is the way that it is," said Sarah Steele, a student at the Harvard Kenneth C. Griffin Graduate School of Arts and Sciences and a lead author of the study, in a statement. "Planetary magnetic fields are our best probe to answer a lot of those questions, and one of the only ways we have to learn about the deep interiors and early histories of planets."