When comet C/2013 A1, also referred to as Siding Spring, had a close encounter with Mars back in 2014, nobody thought about the effects that it might have had on the planet. Now, new data from the MAVEN probe's magnetometer suggests that this flyby actually threw Mars' magnetosphere into chaos for a brief period of time.
"We think the encounter blew away part of Mars' upper atmosphere, much like a strong solar storm would," said Jared Espley, a MAVEN science team member at NASA's Goddard Space Flight Center.
How is this possible? Mars' magnetic field stems from the relationship between its plasma-rich upper atmosphere and solar winds, rendering it much weaker than the Earth's magnetic field, which is generated from the inside of its structure.
Comets possess magnetic fields on par with Mars' as they are also generated by the same interaction of charged plasma particles in the clouds around their nucleus and solar winds.
When Siding Spring came within 87,000 miles of Mars back in 2014, these clouds, also referred to as a comet's coma, came very close to coming into contact with the surface of Mars. This led to the merging of the comet's magnetic field with Mars' magnetosphere, which is much weaker and thus became overwhelmed.
"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," Espley said.
The first noticeable effects were just small ripples and waves that make their way across the planet's magnetosphere, but as the coma made its way into the atmosphere, the magnetic field was thrown into a state of chaos.
Espley and his team believe that by studying the interactions between these two magnetic fields, we can gain a better understanding of the effects of solar winds and solar storms on the magnetospheres of planets such as Mars and Earth.
"With MAVEN, we're trying to understand how the sun and solar wind interact with Mars," said Bruce Jakosky, MAVEN's principal investigator. "By looking at how the magnetospheres of the comet and of Mars interact with each other, we're getting a better understanding of the detailed processes that control each one."
