Martian impact basins, as assume to be demagnetise due to an inactive planetary dynamo, may instead reflect the impact of a reversing magnetic field, a new study suggests. Led by Dr Silpaja Chandrasekar, PhD, indicates that Mars’s fluctuating dynamo may have active longer than anticipate, with implications for understanding planetary evolution.
In a paper publish in the journal Nature Communications, researchers explore how the magnetic fields of large Martian impact basins, which appear weak, can be influence by prolong cooling and reversing dynamo activity rather than an early cessation of the dynamo.
They model cooling patterns in these basins and find that frequent polarity reversals, switching the magnetic field’s direction, significantly reduce the intensity of magnetism within these regions, creating a “demagnetised” appearance.
In History, studies on Mars’s dynamo, a mechanism that generates planetary magnetism, have center on determining its operational timeline and role in planetary climate and structure.
Evidence from young volcanic formations and meteorites, such as Allan Hills 84001, implies that Mars’s dynamo might have persist until 3.7 billion years ago, challenging assumptions of its early shutdown.
Researchers theorise that during cooling periods, oppositely magnetise layers form within Martian basins due to magnetic field reversals, leading to weak magnetic signals.
This study quantified this by evaluating factors like reversal rate, Curie depth, and thermal cooling timescale.
Using finite element analysis and thermal simulations, the team analyse cooling behaviours in various Martian basins, assessing how different reversal frequencies affect field strength.
For higher reversal rates (above 1.5 reversals per million years), significant reductions in magnetic field strength were observed, particularly at higher altitudes above 200 kilometres.
Basin size influence the magnetic patterns detect, smaller basins display dipolar fields, while larger ones exhibit complex magnetic structures, with field strength peaks along their rims.
A gradual decline in peak field strength align with theoretical predictions for materials undergoing slow magnetisation changes in response to continuous reversals.
This study proposes that frequent dynamo reversals, rather than an early dynamo shutdown, explain weak magnetic fields in Martian basins.
Larger basins exceeding 800 kilometres display weakened magnetism with higher reversal rates.
Smaller basins can appear demagnetise even at moderate reversal frequencies, adding complexity to Martian magnetic analysis.
The study gives new insights into Mars’s core convection and atmospheric dynamics, reinforcing the possibility of a reversing Martian dynamo persisting up to 3.7 billion years ago, shaping the planet’s early magnetic landscape.
