Comet Siding Spring peppered Mars' atmosphere with meteors

WASHINGTON, Nov. 7 (UPI) -- When Comet Siding Spring passed worryingly close to Mars, NASA and other space agencies were forced to hide their orbital probes on the opposite side of the Red Planet -- safe from the space debris barreling through the thin Martian atmosphere.

But as the probes and rovers sheltered in place, they were able to make a number of scientific observations and measurements, as well as collect samples -- studying and documenting, for the first time, the collision between a passing comet's rocky dust tail and a planet's atmosphere in real time.

"This historic event allowed us to observe the details of this fast-moving Oort Cloud comet in a way never before possible using our existing Mars missions," Jim Green, director of NASA's Planetary Science Division, said in a statement released by the space agency.

"Observing the effects on Mars of the comet's dust slamming into the upper atmosphere makes me very happy that we decided to put our spacecraft on the other side of Mars at the peak of the dust tail passage and out of harm's way," Green added.

Instruments on both NASA's Mars Reconnaissance Orbiter and the European Space Agency's Mars Express spacecraft a strong ionization of Mars upper atmosphere as ice, dust and rocks from Siding Spring's tail hit the Martian air. The same debris that ionized the atmosphere likely created one heck of a meteor shower, but neither of the Mars rovers on the planet's surface were able to capture images of streaking meteors.

NASA's MAVEN probe was even able to collect samples of the comet's debris -- the first time any spacecraft has captured Oort Cloud comet dust. Scientists hope these samples, combined with the array of other readings captured by Mars' probes and rovers, will help them better understand how such a close comet flyby will affect the Martian atmosphere over time.