Comet 67P/Churyumov–Gerasimenko is shooting off brilliant jets of gas and dust as it swings past the sun. With the Rosetta spacecraft in tow, the space rock will make its closest approach to the sun on August 13. Such an intimate encounter is illuminating parts of the comet that have been shrouded in darkness for years and will allow Rosetta to collect data on the chemical composition and speed of gas and dust particles ejected from the comet’s surface.
Instruments aboard the spacecraft have already glimpsed the effects of one of these eruptions. A jet that shot from the comet on July 29 appeared to be launching particles from the space rock at a speed of at least 10 meters per second and may have actually pushed incoming particles from the solar wind away from the comet’s surface for a few minutes, Rosetta team members reported August 11. Data collected by the spacecraft also revealed higher levels of methane, carbon dioxide and hydrogen sulfide — but not water — around the time of the outburst. Studying what shoots from the comet during other outbursts may give clues to whether these eruptions are ejecting materials from the comet’s surface or freeing ones trapped well below it, the scientists say.