Now cold, dry, and stripped of what was once a potentially protective magnetic field, the red planet is a kind of forensic scene for scientists investigating whether Mars was indeed once habitable, and if so, when.
This timeline was hypothesized using basic principles of paleomagnetics, or the study of a planet’s prehistoric magnetic field.
Scientists know ferromagnetic minerals in rock align themselves with surrounding magnetic fields when the rock is hot, but these small fields become “locked in” once the rock has cooled.
This effectively turns the minerals into fossilized magnetic fields, which can be studied billions of years later.
“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.”
There is evidence that suggests life may have flourished on Mars billions of years ago. The red planet is now dry, cold, and devoid of its once-protective magnetic field. For scientists examining whether Mars was habitable in the past and, if so, when, it serves as a sort of forensic scene.
Researchers at Harvard’s Paleomagnetics Lab in the Department of Earth and Planetary Sciences have been motivated by the “when” question in particular. The most convincing argument to date, according to a recent paper in Nature Communications, is that Mars’ life-supporting magnetic field may have persisted until roughly 3 to 9 billion years ago, as opposed to earlier estimates of 4 to 1 billion years ago, or hundreds of millions of years more recently.
The study’s lead researcher, Sarah Steele, a student at the Griffin Graduate School of Arts and Sciences, has estimated the age of the Martian “dynamo,” or global magnetic field, created by convection in the planet’s iron core, similar to that on Earth, using computer modeling and simulation. Alongside senior author Roger Fu, the John L. The group has strengthened their argument that the Martian dynamo, which could deflect dangerous cosmic rays, existed for a longer period of time than is generally believed, according to Loeb, Associate Professor of the Natural Sciences.
Their reasoning developed from experiments that simulated the cooling and magnetization cycles of massive craters on the surface of the red planet. Researchers believe these well-studied impact basins formed after the dynamo shut down because they are known to be only weakly magnetic.
Using fundamental ideas from paleomagnetics—the study of a planet’s ancient magnetic field—this timeline was conjectured. We know that when the rock is hot, ferromagnetic minerals in it align themselves with the surrounding magnetic fields; however, when the rock cools, these tiny fields become “locked in.”. In effect, the minerals become fossilized magnetic fields that can be examined after billions of years.
By examining weak magnetic field basins on Mars, scientists hypothesized that these basins formed in the midst of hot rock when there were no other strong magnetic fields present, or after the planet’s dynamo had dissipated.
However, the Harvard team claims that those largely de-magnetized craters can be explained without this early shutdown, Steele said. Instead, they contend that the craters were created during a polarity reversal in Mars’ dynamo, in which the north and south poles switched positions. This, they claim, can account for why these massive impact basins only have weak magnetic signals today through computer simulation. Every few hundred thousand years, the Earth’s magnetic poles flip as well.
“Essentially, we are demonstrating that there might not have been a valid reason to believe that Mars’ dynamo shut down early,” Steele stated.
Their findings expand upon earlier research that initially challenged accepted timelines for Martian habitability. Through the analysis of various magnetic populations in thin slices of the rock, they were able to infer a longer-lasting magnetic field until 3point 9 billion years ago using a powerful quantum diamond microscope in Fu’s lab and the well-known Martian meteorite Allan Hills 84001.
Although it can be a little intimidating to challenge a long-held belief, Steele claims that they have been “spoiled rotten” by a community of planetary researchers who are receptive to fresh perspectives and possibilities.
“Our goal is to provide answers to fundamental, significant questions about how everything came to be as it is, including why the solar system as a whole is the way it is,” Steele stated. One of the only ways we can discover the deep interiors and early histories of planets is through their magnetic fields, which are also our best probe for many of those questions. “.
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