An odd, tailless comet that made a fleeting pass into the inner solar system in 2014 before heading back out to the distant Oort cloud actually may have been visiting close to its birthplace.
The comet, called C/2014 S3, is physically more like an inner belt, rocky asteroid than an icy comet forged in the solar system's deep freeze, a new study shows.
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The discovery has scientists thinking C/2014 S3 is a sample of the rocky material that served as building blocks for Earth and the terrestrial planets.
Figuring out how the body ended up in the solar system's nether regions -- and determining how many other similar objects may exist -- could be a Rosetta stone for understanding how the solar system ended up in its present configuration.
"It's the first time that a rocky, inner solar system object has ever been seen coming from the Oort cloud," University of Hawaii astronomer Karen Meech told Discovery News.
The Oort cloud, located beyond Pluto and the Kuiper Belt, extends about 2,000 to as much as 200,000 times farther away from the sun than Earth.
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C/2014 S3, which scientists are calling a "Manx" comet after the tailless Manx cat, also is the first rocky inner solar system body that is active like a comet, though at a vastly reduced rate.
Computer modeling indicates the Manx has 100,000- to 1 million times less water than what typically is found on comets, which explains C/2014 S3's tailless appearance. As approaching comets are warmed by the sun, water ice vaporizes off their bodies and forms distinctive, bright tails.
By the time the dark, tailless C/2014 S3 was spotted by the Panoramic Survey Telescope and Rapid Response System, or Pan-STARRS, in 2014, it already was nearing its closest approach to the sun, which was roughly twice as far as Earth. Scientists estimate C/2014 S3 completes an orbit in 860 years.
Analysis of the Pan-STARRS imagery shows materials in C/2014 S3 have undergone little processing, indicating the comet has been in deep freeze for a very long time. Scientists theorize it is made of inner solar system materials that have been stored in the Oort cloud.
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If scientists can find another 50 to 100 Manx objects, they could resolve long-standing debates about the origin and evolution of the solar system.
"Depending how many we find, we will know whether the giant planets danced across the solar system when they were young, or if they grew up quietly without moving much," European Southern Observatory astronomer Olivier Hainaut said in a statement.
"For the first time, we'll have the ability to make predictions that we can test with observations," Meech added.