Scientists using Europe's comet-orbiting Rosetta spacecraft have discovered that the complicated ancient body is coated with surprisingly simple organic molecules and surrounded by a changing cloud of gases, according to new research released on Thursday.
After a 10-year journey, Rosetta reached Comet 67P/Churyumov-Gerasimenko in August and put itself into orbit for an unprecedented long-term study. In November it released a piggyback-riding spacecraft, which descended to the comet's surface for a series of independent studies.
Comets are believed to be frozen leftovers from the formation of the planets some 4.6 billion years ago. The Rosetta mission is intended to shed light on the solar system's early days by studying one of its pristine comet remnants.
The teams found the comet's body, which is about 100 million times more massive than the International Space Station, is covered in dunes and ripples, with little detectable water ice on its surface and generous quantities of hydrocarbons.
Scientists must first figure out how the comet has changed over time, details of which will emerge as 67P travels toward the sun and heats up, developing a coma, or a visible atmosphere, and a tail.
Over time, seasonal effects also may be discovered, said Rosetta scientist Myrtha Hassig, with the Southwest Research Institute in San Antonio, Texas.
"We're taught that comets are made mostly of water ice. For this comet, the coma sometimes contains much more carbon dioxide than water vapor," said Rosetta scientist Stephen Fuselier, also with Southwest Research Institute.
Rosetta will continue to fly around the comet as it moves toward and then away from the sun. The closest approach, about 116 million miles (186 million km) away from the sun, will be on August 13.
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