Comet Closing In On Mars Will Avoid Collision, But NASA Still Worries About Its Satellites [VIDEO]
NASA continues to monitor a comet on a near-collision course with Mars later this year, this week releasing new pictures of its 12,000-mile-wide tail of vapor and dust. Astronomers are eager for more information about the speed and direction of the tail because, while the core of the comet will widely miss, the fan of debris will likely pelt the planet at near lightning speed.
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The pictures of the comet, called Siding Spring, show an original and a processed version of the same Hubble Space Telescope shot. They detail the nucleus, hazy coma, and massive tail shooting off behind two jets spraying in opposite directions from the comet nucleus. "This is critical information that we need to determine whether, and to what degree, dust grains in the coma of the comet will impact Mars and spacecraft in the vicinity of Mars," said Jian-Yang Li of the Planetary Science Institute in a statement.
Comets are among the more mysterious members of the solar system. Often many miles across, they are thought to come from the deepest fringe of the sun's influence, a region called the Oort Cloud where they spend hundreds or thousands of years at the long end of their orbits. As they approach, the sun melts the ice, and the comet sheds a tail of vapor and dust.
Some comets make it around the sun and return in a regular orbit, like the one on which the European Space Agency plans to land a spacecraft. Others, like the ill-fated ISON comet, burn up near perihelion. Siding Spring's orbit, shown in detail in the video below, will take it within 86,000 miles of Mars on Oct. 19. The radius of the coma, its vapory shroud, is predicted to completely envelop the planet.
The comet poses no threat to humans, but it does threaten the three manmade satellites that orbit Mars. (The planet's atmosphere will protect the two Mars rovers crawling across its surface.) NASA estimates that the speed at which the comet's particles could hit the orbiters, relative to their own speed, is 35 miles per second — or 126,000 mph.
"Our plans for using spacecraft at Mars to observe comet Siding Spring will be coordinated with plans for how the orbiters will duck and cover, if we need to do that," Rich Zurek, Mars Exploration Program chief scientist at NASA's Jet Propulsion Laboratory, said in a statement earlier this year. A colleague noted that the most important months for observation will be April and May but that preparations for a worst-case scenario must be made well in advance.
According to NASA, Siding Spring follows an orbit around the sun that lasts 1 million years. Its perihelion, the moment it comes closest to the sun, will take place Oct. 25 when the comet is 130 million miles from the sun, between the orbits of Earth and Mars. When Hubble took the newly released picture on March 11, Siding Spring was within Jupiter's orbit some 353 million miles from Earth.
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