Spacecraft Report First Data From Mars Comet Flyby

Chuck Bednar for redOrbit.com – Your Universe Online
The debris from Comet C/2013 A1 Siding Spring during its recent flyby of Mars added a temporary and exceptionally strong layer of ions to the electrically charged layer of the planet’s atmosphere, according to data collected by the NASA and ESA spacecraft responsible for obtaining the first up-close observations of such an event.
Those observations, which were made by NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) mission, the US space agency’s Mars Reconnaissance Orbiter (MRO), and a radar instrument on the ESA’s Mars Express spacecraft as Siding Spring flew past Mars at a distance of approximately 87,000 miles on October 19, revealed new information about the comet’s impact on the ionosphere and the basic properties of its nucleus.
Based on these observations, scientists were able to make a direct connection from the input of debris from a specific meteor shower to the formation of this type of transient layer in response. This marks the first time something like this has ever happened on any planet, including the Earth, NASA officials explained in a statement Friday.
[ Watch the Video: Mars Orbiter Observes Comet Siding Spring ]
Comet C/2013 A1 began its journey in the furthest region of the solar system, an area known as the Oort Cloud. At the time of its closest approach to Mars, it was less than half the distance from the Red Planet than the moon is from the Earth and less than one-tenth the distance of any comet that has ever passed by our planet.
During the flyby, dust from Siding Spring impacted Mars and was vaporized high within the planet’s atmosphere, producing what NASA scientists believe would have been an impressive meteor shower. The resulting debris may have caused significant temporary changes to the upper atmosphere, and could have also resulted in longer-term perturbations, based on observations by probes orbiting the planet and both Earth-based and space telescopes.
“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,” explained Jim Green, director of NASA’s Planetary Science Division at the agency’s Washington headquarters. “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.”
“MAVEN is well suited for studying the effects of the dust from the comet in the Martian atmosphere, because it makes measurements at the altitudes where the dust was expected to have an effect,” added Bruce Jakosky from the University of Colorado-Boulder’s (CU-Boulder) Laboratory for Atmospheric and Space Physics (LASP), a principal investigator on the MAVEN mission. “We also should be able to see if there are long-term effects from the comet dust in that same region of the atmosphere.”
MAVEN, which had only recently reached Mars at the time of Siding Spring’s flyby, detected the comet in two different ways: observing intense ultraviolet emissions from magnesium and iron ions high in the atmosphere following the meteor shower using its remote-sensing Imaging Ultraviolet Spectrograph (IUVS), and directly sampling and determining the composition of some of the comet’s dust using the Neutral Gas and Ion Mass Spectrometer.
The former instrument detected emissions that were far more intense than even the strongest meteor showers experienced on Earth, while the latter detected eight different types of metal ions – including sodium, magnesium and iron, NASA said. The spectrometer also collected the first-ever direct measurements of the composition of dust from a comet originating from the Oort Cloud, an icy region located far beyond our solar system’s outermost planets.
“They call this comet encounter a once-in-a-lifetime event, but it’s more like once-in-a-million years,” noted CU-Boulder associate professor Nick Schneider, a LASP research associate and lead IUVS scientist for the mission. “MAVEN got there just in time, and we were ready. The numbers suggest a Martian would have seen many thousands of shooting stars per hour – possibly enough to be called a meteor storm – so it must have been a spectacular event that night on Mars.”
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