Life may have flourished on Mars till a few billion years ago

The search for life on Mars has brought scientists face to face with a new piece of information, that the red planet was likely habitable until quite recently. A new paper presents evidence that Mars was likely teeming with life billions of years ago. Scientists have been trying to find signs of life on the neighbouring planet, and if it did exist, when did it vanish?

Researchers in Harvard's Paleomagnetics Lab in the Department of Earth and Planetary Sciences worked to understand the "when" part. In their paper published in Nature Communications, they say that Mars' life-enabling magnetic field could have survived until about 3.9 billion years ago. This is hundreds of millions of years more recent as compared with previous estimates of 4.1 billion years.

Griffin Graduate School of Arts and Sciences student Sarah Steele led the study and used simulation and computer modelling to estimate the age of the Martian "dynamo", or the global magnetic field produced by convection in the planet's iron core.

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Senior author Roger Fu, the John L. Loeb Associate Professor of the Natural Sciences and his team say that the magnetic field capable of deflecting harmful cosmic rays was around for much more time than current estimates claim.

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The team simulated the cooling and magnetisation cycles of Martian craters which are only weakly magnetic. Scientists believe they formed after the dynamo shut down. They say that these basins initially formed amid hot rock when no other strong magnetic fields were present.

Magnetic poles flipped and craters were formed

However, Steele and the team say this early shutdown of the magnetic field isn't necessary for the craters to form. Instead, they say that the craters were formed when the north and south poles switched places in the dynamo of Mars. This is why, they say, these large impact basins only have weak magnetic signals today.

Earth's magnetic poles also flip every few hundred thousand years. "We are basically showing that there may not have ever been a good reason to assume Mars's dynamo shut down early," Steele said.

"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," Steele said.

"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."