In October 2014 comet C/2013 A1 also called Siding Spring came up close and personal as it crossed the planet Mars. NASA’s Mars Atmosphere and Volatile Evolution spacecraft (MAVEN) also entered orbit around the planet a few weeks before this fly past. While most instruments on the MAVEN were switched off during the event so as to protect the sensitive equipment, the magnetometer was left running.

Afterwards it was observed that the comet’s powerful magnetic field temporarily merged with, and overwhelmed, the planet’s weak field. Simply speaking the charged particles from the comet’s tail entered the atmosphere of Mars and charged it giving rise to storms. This is incredible given the fact that the two bodies were separated by 140,000 kilometers even at the closest point of the flypast.

Jared Espley, a MAVEN science team member at NASA’s Goddard Space Flight Center in Greenbelt, Maryland said 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.

Think of this science project as studying a curtain which gets ruffled when a speeding wind flows past the door. This state of affairs lasted for a while before Mars was gradually saw its atmosphere come back to normal.