Clathrate ices discovered in Comet 67P/Churyumov-Gerasimenko could answer questions astronomers have about the formation of the solar system.
Comets are made of ice, dust and other materials, but astronomers have long questioned whether this ice is in the form of a highly ordered crystal or a random amorphous structure. One form of crystalline ices, known as clathrates, were the target of a successful search of the coma (or atmosphere) of Comet 67P.
This form of ice contains gas trapped within its structure, leading to a high degree of order within the structure. Molecules of the gases are released at specific temperatures, a phenomenon recorded by astronomers studying the coma of the body, popularly known as Rosetta's comet.
The discovery of clathrate ices in the coma of the comet suggests the frigid body likely formed significantly closer to the sun than previously believed.
"The structure and phase of the ice is important because it tells us a lot about how and where the comet may have formed. If the building blocks of 67P were predominantly crystalline ices and clathrates, then 67P likely agglomerated from chunks of ice closer to the sun. The protosolar nebula closer to the sun experienced higher temperatures and more turbulence where crystalline ices could form as the nebula cooled," said Adrienn Luspay-Kuti of the Southwest Research Institute (SwRI).
Comets with irregular amorphous ices likely formed further away from the sun, where temperatures are lower, and turbulence is reduced.
Astronomers believe that the material within comets may, in many ways, be similar to the substances that were present during the formation of the solar system. Without the ability to directly sample ice and dust within the nucleus of comets, studying the coma of the frozen bodies can provide a glimpse inside the frigid structures. By analyzing material found here, astronomers believe they can learn more about the building blocks of our local solar family.
Data from the Rosetta spacecraft, managed by the European Space Agency (ESA), was examined, revealing the clathrate ice structure.
Comet 103P/Hartley, or Hartley 2, was examined by NASA scientists during the Epoki mission in November 2010. This comet, orbiting around the sun once every 6.5 years, is thought to be similar in structure to 67P. Comparison of the two comets could confirm the presence of clathrate ices, and provide further evidence of their formation close to the sun.
Analysis of the coma surrounding Comet 67P was profiled in the journal Science Advances.
