Earth and Environmental Studies Professor Stefanie Brachfeld, along with researchers at Harvard and the Universities of Hawaii and Minnesota, is studying the life and death of Mars’ magnetic field with the assistance of a grant from NASA.
The team is creating synthetic rocks, magnetizing them and then subjecting them to high pressure to simulate meteorite impact events to see how impacts affect magnetization. “My colleagues and I use spacecraft data and rover data to determine the chemical recipe for the rocks,” Brachfeld explains. “We are searching for an explanation for why the Mars magnetized regions are so much stronger than their counterparts on Earth, and what that means in terms of the intensity of the ancient field.”
The Mars Global Surveyor (MGS) mission found that, similar to Earth’s crust, much of the southern hemisphere of Mars, a region called the Southern Cratered Highlands, has regions that are magnetized.
The presence of magnetized regions of crust on Mars surprised scientists, Brachfeld says, because the planet no longer has a magnetic field. “Some of the magnetization directions on Mars point upwards and some point downwards,” says Brachfeld. “These results indicate that Mars’ former magnetic field reversed just as Earth's field does, but the Martian magnetic field has since shut off.”
Earth’s magnetic field originates inside its core and extends up to the surface and out beyond its atmosphere, providing a shield from solar wind and radiation. Without the magnetic field, Earth’s atmosphere could be eroded away by these particles, much like Mars.
The researchers are asking the following questions: How strong was Mars’ magnetic field? What was its shape? When and why did the field shut off and will Earth's field eventually shut off as well? “The satellite data is fascinating,” she says. “The MGS data indicate that the magnetic signal in the Mars Southern Cratered Highlands dwarfs magnetized regions on Earth.”
“It is possible that Mars’ magnetized crust had an even stronger signal in the past, prior to being slammed by thousands of meteorites, and what MGS observed is just a remnant of the former signal,” Brachfeld says.