Could Mars have been habitable longer? Magnetic field study says yes

A new study strengthens the theory that Mars’ magnetic field, which once supported a life-enabling atmosphere, may have lasted longer than previously believed. While the Red Planet is now cold, dry, and without a protective magnetic shield, evidence suggests it may have once been habitable billions of years ago.

Research from Harvard’s Paleomagnetics Lab provides the most compelling support yet that Mars’ magnetic field could have persisted until about 3.9 billion years ago, rather than the previously estimated 4.1 billion years. This conclusion, detailed in a Nature Communications paper, was led by graduate student Sarah Steele and senior author Roger Fu, who applied simulations and modeling to estimate the life span of Mars' “dynamo”—the magnetic field generated by the planet’s iron core.

The researchers focused on weakly magnetic impact basins on Mars, hypothesizing that these craters formed during periods of magnetic polarity reversals, where the north and south poles switch. This insight challenges the long-held view that Mars’ magnetic field shut down early. The team argues that polarity reversals, rather than an early shutdown, could explain the weak magnetic signals observed in Martian craters. These pole reversals are also known to occur on Earth.

Earlier work by Fu’s lab involved studying the Allan Hills 84001 Martian meteorite using a quantum diamond microscope. This analysis suggested that Mars’ magnetic field may have persisted until 3.9 billion years ago, supporting the current findings.