Researchers observe comet flyby effects on Martian atmosphere

A "once-in-a-lifetime" chance to watch a comet flying close to Mars gave a unique insight into the effect of such a near miss on a planet's atmosphere, according to a University of Leeds academic. Professor John Plane, a member of the Atmospheric and Planetary Chemistry group in the University's Faculty of Mathematics and Physical Sciences , collaborated in the analysis and interpretation of observations made with NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft of Comet C/2013 A1 Siding Spring’s flyby on October 19. The comet travelled within about 87,000 miles of Mars, less than half the distance between Earth and the Moon and more than ten times closer than any comet is known to have come to our planet. Professor Plane said: “The chance to see a comet from the Oort Cloud, the most distant region of our Solar System, brush past a planet in the inner Solar System is incredibly small, so this was a once-in-a-lifetime opportunity. What’s more, NASA’s MAVEN spacecraft happened by coincidence to arrive at Mars a month before the comet. It was amazingly good luck. Data from observations carried out by the MAVEN, NASA’s Mars Reconnaissance Orbiter (MRO), and a radar instrument on the European Space Agency's (ESA’s) Mars Express spacecraft revealed that debris from the comet added a temporary and very strong layer of ions to the ionosphere, the electrically charged layer high above Mars.