NASA’s robotic Mars explorers, including three orbiters and the two rovers, Curiosity and Opportunity, are getting ready to observe Comet Siding Spring make its first known appearance in the inner solar system when it passes within 82,000 miles (132,000 kilometers) of Mars on October 19.
Hurtling through space at about 35 miles (56 kilometers) per second, the approaching Oort-cloud comet was discovered in 2013 by Robert H. McNaught at Siding Spring Observatory. Mars’ orbiting spacecraft will try to observe the comet, then hide behind the planet to avoid being hit by some of the comet’s potentially dangerous debris.
Although the comet will fly very close to Mars, it is not expected to made a direct collision. However, the comet’s trail of debris, or coma, of dust and gas may well engulf the Red Planet, according to a report by EarthSky.org. Such an event could cause “significant damage” to orbiting spacecraft, NASA says.
Currently, NASA has three spacecraft circling Mars. Its Mars Reconnaissance Orbiter (MRO) and Mars Odyssey spacecraft have been orbiting the planet for quite awhile, while the Mars Atmosphere and Volatile EvolutioN mission (MAVEN) only arrived at the Red Planet a couple of months ago, as did India’s Mars Orbiter Mission (MOM).
According to NASA, three teams of experts have provided forecasts for the comet’s flyby of Mars. They say the danger to spacecraft is not from the comet’s nucleus, but from its trail of debris. And the greatest risk will not be when the comet is closest to Mars, but about an hour-and-a-half later when the dust trail arrives.
Comet Siding Spring has traveled billions and billions of miles from the Oort Cloud, which is composed of material left over from the formation of the solar system. This is probably the first time it has come this close to the sun, NASA says.
“The close fly-by of Mars by Comet Siding Spring is unique, unexpected, and lucky for us,” said space instrument scientist David Humm, in a statement, adding that the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) has a “significant advantage” because of its proximity to the comet at its nearest approach to Mars.
“CRISM is both a spectrometer and a camera,” explains Humm. “It can identify molecules by the light they emit and characterize mineral by the light they reflect. We can then make an image of any material we identify, and see its distribution. If we’re fortunate, CRISM will be able to detect some features in the comet gas and dust, and we can make images of the distribution of different gases detected and learn something about the nature of the dust.”
“We’re getting ready for a spectacular set of observations,” said Jim Green, head of NASA’s planetary science division, in a report by CBS News.
By learning more about the comet’s structure and composition, scientists hope to shed more light on how the planets formed, according to Carey Lisse, senior astrophysicist at Johns Hopkins University’s applied physics laboratory.
“Think about a comet that started its travel probably at the dawn of man and it’s just coming in close now,” said Lisse, as reported by CBS News. “And the reason we can actually observe it is because we have built satellites and rovers. We’ve now got outposts around Mars.”