Is Rosetta's Comet Growing an Atmosphere?

It's been five months since the European Space Agency's (ESA) Rosetta spacecraft finally caught up to its quarry, the comet 67P/ Churyumov-Gerasimenko. Now, data from the comet-chaser has been released, revealing some amazing insight about the hurtling space rock's surface.

NASA has already reported that 67P is melting much faster than it was half-a-year ago, largely because the icy comet is drawing ever-closer to the Sun in a wide-but-spiraling orbit. Soon enough, it will grow too hot even for the Rosetta spacecraft to stand, and the primary stage of this historic mission will come to an end next August.

In the meantime, however, Rosetta scientists get to investigate this small alien world as it gradually changes.

"To be up close and personal with a comet for an extended period of time has provided us with an unprecedented opportunity to see how comets transform from cold, icy bodies to active objects spewing out gas and dust as they get closer to the Sun," Sam Gulkis, the principal investigator of Rosetta's MIRO instrument, explained in a NASA statement.

Aside from meltwater and dust, experts from the ESA and other space agencies have found that comet 67P is "gassing out," releasing carbon monoxide and carbon dioxide. Interestingly, the ESA reports that Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) is finding large fluctuations in the composition of the comet's coma, representing daily and even seasonal variations in the major gases expelled.

According to measurements from MIRO, ROSINA, and GIADA (the Grain Impact Analyzer and Dust Accumulator), the majority of what 67P's surface is shedding continues to be dust and water vapor. However, as the comet warms, this may change, with more gas being released from the surface.

"As the gas-dust coma continues to grow, interactions with charged particles of the solar wind and with the Sun's ultraviolet light will lead to the development of the comet's ionosphere and, eventually, its magnetosphere," the ESA reports.

Essentially this means that the comet will have a thin, albeit temporary, atmosphere - although not one you or I could live in.

"Rosetta is essentially living with the comet as it moves towards the Sun along its orbit, learning how its behavior changes on a daily basis and, over longer timescales, how its activity increases, how its surface may evolve, and how it interacts with the solar wind," ESA Rosetta scientist Matt Taylor said in a statement.

"We have already learned a lot in the few months we have been alongside the comet," he added, "but as more and more data are collected and analyzed from this close study of the comet we hope to answer many key questions about its origin and evolution."

To find all that Rosetta has revealed so far, check out a recent special issue of the journal Science.

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