Comet's age revealed by the type of ice it carries

Rosetta helped settle a long-running debate among astronomers by measuring the levels of molecular nitrogen, carbon monoxide and argon in comet 67P's ice.
By Brooks Hays  |  March 9, 2016 at 10:43 AM
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PARIS, March 9 (UPI) -- New research suggests 67P/Churyumov-Gerasimenko is roughly the same age as the solar system, which is approximately 4.568 billion years old.

According to scientists with the French National Centre for Scientific Research, or CNRS, the giveaway was the comet's ice. Because it's mostly crystalline, astronomers believe the comet originated in the protosolar nebula.

The new findings, detailed in the Astrophysical Journal, suggest the structure and makeup of a comet's ice can be used to determine its age.

Previously, researchers have squabbled over the nature of comet ice. One camp believed comets host crystalline ice and normally arranged water molecules. The other argued comet ice is amorphous and its water molecules disordered.

The European Space Agency's Rosetta probe and its Rosina instrument, a spectrometer, have helped settle the debate by measuring the levels of molecular nitrogen, carbon monoxide and argon in comet 67P's ice.

Researchers compared the measured gas levels to those predicted by lab experiments and computer models designed to mimic different types of comet ice. The results suggested only crystalline ice could host the levels of N2, CO and Ar measured by Rosina.

The cooling of the protosolar nebula that formed the solar system allowed for the formation of crystalline ice and a unique signature of absorbed gases.

"If comets are made of crystalline ice, this means that they must have formed at the same time as the solar system, rather than earlier in the interstellar medium," researchers at CNRS wrote in a news release.

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