Mars' magnetic field emerged earlier and lasted longer than previously thought


May 1 (UPI) -- Mars' ancient magnetic field emerged earlier and persisted for longer than scientists previously thought, according to a new study.

On Earth, the churn of molten metal deep in its core fuel's a powerful magnetic field. The phenomenon is what's known as dynamo. The Red Planet's dynamo has long been extinct, but new analysis -- published this week in the journal Science Advances -- suggests it was active for longer than researchers thought.

"We find that the Martian dynamo operated at 4.5 billion and 3.7 billion years ago," first study author Anna Mittelholz, postdoctoral fellow in the University of British Columbia's department of earth, ocean and atmospheric sciences, said in a news release. "Dynamo timing is a big part of a planet's evolution, and what we find is very different from what we have thought so far."

"The dynamo tells us something about the planet's thermal history, its evolution, and how it got to where it is today, and it is unique for each of the terrestrial planets -- Earth, Mars, Venus and Mercury," Mittelholz said.

As new volcanic rocks cool and crystallized, minerals align themselves in the direction of the global magnetic field. Scientists previously detected the signature of magnetism in Martian rocks dated between 4.2 and 4.3 billion years old. Planetary scientists also observed the absence of magnetic patterns in volcanic basins dated to 3.9 billion years old.

But a recent survey of Martian rocks using new satellite data revealed the signatures of an ancient magnetic field in the Red Planet's Lucus Planum lava flow that formed some 3.7 billion years ago.

Researchers also found evidence of magnetism inside Borealis Basin, located in the Red Planet's northern hemisphere. The massive basin was formed 4.5 billion years ago by a large impact that melted a large potion of the crust and mantle.

"We have these two observations that point to a dynamo at the earliest known time in Mars' history, and a dynamo that was present half a billion years after many people thought it had already switched off," said study co-author Catherine Johnson, senior scientist at the Planetary Science Institute in Arizona.

So why do some 3.9 billion-year-old rocks on Mars lack evidence of magnetism. According to the study's authors, it is possible Mars' dynamo briefly paused and then restarted by the time the Lucus Planum formed. It's also possible ancient impacts excised the types of rocks featuring minerals strongly influenced by magnetism.

The new research was made possible by MAVEN, the Mars Atmosphere and Volatile Evolution satellite, which flies closer to the Red Planet's surface, allowing it to pick more subtle magnetic signals. The satellite's more precise data can help scientists differentiate between magnetism produced by rocks closer to the surface and older rocks buried deeper in the planet's crust.

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