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Rosetta's comet is losing two glasses of water a second

Rosetta's comet is losing two glasses of water a second
In early June, Rosetta measured the quantity of water that its target comet Churyumov-Gerasimenko is losing in the form of steam: 300 ml of water, which is two glasses, every second. But the closer the comet gets to the Sun, the more water it will lose.

European Space Agency diagram which summarises the observation made by the MIRO instrument on 6 June while the comet was at a distance of 350,000 km from the Sun.
Credit: ESA

After travelling for 10 years, the European Space Agency’s (ESA) spacecraft is currently approaching its final target, the Churyumov-Gerasimenko comet. While Rosetta’s “pilots” in Darmstadt, Germany are programming the delicate orbital manoeuvres, scientists are already using the on board instruments. Such was the case when on 6 June, MIRO (Microwave Instrument for the Rosetta Orbiter) which is a sort of miniaturised radio telescope that works in the microwave field was used to measure the quantity of water that the comet is losing in the form of steam. The result was 300 ml of water per second. The ESA has calculated that at this rate, it would take 100 days to fill an Olympic swimming pool… But when the measurement was taken, Churyumov-Gerasimenko was 583 million kilometres from the Sun. Yet, in the weeks and months to come, the comet will get closer to our star. It will therefore heat up more and will lose more water, forming a coma (atmosphere around its nucleus) then a tail. On 6 June, Rosetta was 350,000 km from the comet, which is just less than the distance from Earth to the Moon. On 30 June, it was already just 72,000 km from its target.
Rosetta will arrive in the vicinity of Churyumov-Gerasimenko in early August, before the cometary activity is too high. This relative “calm” is all the more important as in November the spacecraft will release the Philae lander which will become the first machine to land on a comet’s nucleus. In its Extreme Exploration exhibition, the Cité de l’Espace in Toulouse presents a full-scale model of this 100 kg robot.  It also offers its visitors the chance to make a comet, the famous “dirty snowballs”, so that they can get a better idea of the nature of these wandering objects that could perhaps have carried water and the building blocks of life during the formation of our planet Earth. See the video below.

Published 1 July 2014