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Comet 67P/Churyumov–Gerasimenko, the hurtling hunk of dust and ice that's being tailed by an Earth-made space probe as it hurtles toward the sun,

We're learning more about the comet that a European Space Agency paired up with its Rosetta probe, thanks to a special issue of the journal Science that collects much of the information scientists have been able to glean from about the comet.

The probe met up with the 2.5-mile-wide comet last August; it sent a lander to the rocky surface in November. And now the probe is hitching a ride back toward Earth, observing the comet as it gets closer to the sun.

The ESA predicts, "the Rosetta mission should become the key to unlocking the history and evolution of our Solar System."

Here's a roundup of the new research about Comet 67P/Churyumov–Gerasimenko:

  • It has "goosebumps" – textures on steep cliff faces – whose origin isn't yet known.
  • The comet is 70-80 percent porous, the ESA says, "with the interior structure likely comprising weakly bonded ice-dust clumps with small void spaces between them."
  • Along with water, it releases gases such as carbon monoxide and carbon dioxide, at levels that vary daily and perhaps seasonally.
  • The comet "was releasing the earthly equivalent of 40 ounces (1.2 liters) of water into space every second at the end of August 2014," says NASA, which is assisting the ESA.
  • A "remarkable array of surface features" are on the comet, in five main categories: "dust-covered; brittle materials with pits and circular structures; large-scale depressions; smooth terrains; and exposed more consolidated ('rock-like') surfaces."
  • Its surface composition is "very homogenous," scientists say, "dominated by dust and carbon-rich molecules, but largely devoid of ice."
  • Scientists don't know why the comet has a double-lobed shape that resembles a barbell. One theory is that it began as a single body and eroded in the middle. But it's also possible that "two separate comets formed in the same part of the Solar System and then merged together at a later date," the ESA says.

Researchers are hoping to learn new things about Comet 67P as it nears the sun. The comet will make its closest approach on Aug. 13, between the orbits of Earth and Mars.
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