ADVERTISEMENT
2 /3 FREE ARTICLES LEFT THIS MONTH Remaining
Chemistry matters. Join us to get the news you need.

If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.

ENJOY UNLIMITED ACCES TO C&EN

Physical Chemistry

Solid CO2 spotted on a comet

Rosetta spacecraft explores 67P/Churyumov-Gerasimenko’s seasonal extremes

by Elizabeth K. Wilson
November 21, 2016 | APPEARED IN VOLUME 94, ISSUE 46

[+]Enlarge
Credit: ESA/Rosetta/NAVCAM
The comet 67P/Churyumov-Gerasimenko, as seen fromRosetta.
Credit: ESA/Rosetta/NAVCAM
The comet 67P/Churyumov-Gerasimenko, as seen fromRosetta.

Before it ended its mission in September, the European Space Agency’s Rosetta spacecraft, which began orbiting comet 67P/Churyumov-Gerasimenko in 2014, made the first observation of solid CO2 on a comet. The craft also unveiled complex sublimating and freezing patterns taking place in the comet’s water ice and dust. These phenomena result from seasonal and diurnal extremes that a comet experiences during its elliptical orbit around the sun. An international team led by Gianrico Filacchione of the Institute for Space Astrophysics & Planetology examined data from Rosetta’s infrared spectrometer and found a patch of solid CO2 that existed on the comet’s surface when it was in its deep winter. This patch of CO2 ice disappeared within three weeks after reexposure to the sun. CO2 is so volatile that its ice sublimation temperature is a very low –190 °C; therefore, scientists expected it to exist only below the comet’s surface. The Filacchione team’s findings suggest that even more volatile species, such as carbon monoxide and methane, could also exist as surface ice during the comet’s winter (Science 2016, DOI: 10.1126/science.aag3161). Another team, led by Sonia Fornasier of the Paris Observatory, found that exposed water ice survives on 67P’s surface for a short time and that it is well-mixed with dust, which may help explain why comet cores appear dark even if they are rich in water ice (Science 2016, DOI: 10.1126/science.aag2671).

X

Article:

This article has been sent to the following recipient:

Leave A Comment

*Required to comment