Comet's punch jumbled up Mars' magnetism

Washington D.C : When Mars had a near-miss encounter with comet C/2013 A1, aka Siding Spring in 2014, its magnetic field was momentarily thrown into chaos, according to data collected by the Mars Atmosphere and Volatile Evolution (MAVEN) probe's magnetometer.

Jared Espley, a MAVEN science team member at NASA's Goddard Space Flight Center in Greenbelt, Maryland, said that Comet Siding Spring plunged the magnetic field around Mars into chaos, adding "We think the encounter blew away part of Mars' upper atmosphere, much like a strong solar storm would."

Unlike Earth, which a boasts an magnetic field generated from within, Mars' magnetic field is created by the interaction between its plasma-rich upper atmosphere and solar winds. It is considerably weaker than Earth's magnetic field.

Most comets boast a magnetic field similar to Mars, generated by the interaction between charged plasma particles in their coma and solar winds.

In 2014, when comet Siding Spring passed within 87,000 miles of Mars, its coma nearly touched the Martian surface. The comet's magnetic field merged with and overwhelmed Mars' much weaker magnetosphere.

Espley explained that the main action took place during the comet's closest approach, but the planet's magnetosphere began to feel some effects as soon as it entered the outer edge of the comet's coma.

The first effects were minor ripples and waves pulsing across the Martian magnetosphere. As the comet's coma penetrated the atmosphere, however, Mars' magnetic field was plunged into chaos.

Researchers hope studying the interactions between the two magnetic fields will aid their understanding of how solar winds and solar storms interact with the magnetospheres of both Mars and Earth.

This research is published in Geophysical Research Letters.