Comet 67P/C-G on 11 September 2015. Credit: ESA/Rosetta/NavCam – CC BY-SA 3.0
Over the past two years, Rosetta has kept a close eye on many properties of Comet 67P/Churyumov-Gerasimenko, tracking how these changed along the comet's orbit. A very crucial aspect concerns how much water vapour a comet releases into space, and how the water production rate varies at different distances from the Sun. For the first time, Rosetta enabled scientists to monitor this quantity and its evolution in situ over two years.
In a new study led by Kenneth C. Hansen of the University of Michigan, in the US, measurements of water production rate based on data from ROSINA, the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, are compared with water measurements from other Rosetta instruments.
The combination of all instruments shows an overall increase of the production of water, from a few tens of thousands of kg per day when Rosetta first reached the comet, in August 2014, to almost 100,000,000 kg per day around perihelion, the closest point to the Sun along the comet's orbit, in August 2015. In addition, ROSINA data show that the peak in water production is followed by a rather steep decrease ...