Rosetta's Comet 'Sweats' Two Glasses of Water a Second

©ESA

Water From A Comet

ESA's Rosetta spacecraft has found that comet 67P/Churyumov-Gerasimenko is releasing the equivalent of two small glasses of water into space every second, even at a cold 583 million kilometers from the Sun.

The first observations of water vapor streaming from the comet were made by the Microwave Instrument for Rosetta Orbiter, or MIRO, on 6 June, when the spacecraft was about 350,000 kilometers from the comet.

Since the initial detection, water vapor has been found every time MIRO has been pointed towards the comet.

"We always knew we would see water vapor outgassing from the comet, but we were surprised at how early we detected it," says Sam Gulkis, the instrument's principal investigator at NASA's Jet Propulsion Laboratory in Pasadena, California, USA.

"At this rate, the comet would fill an Olympic-size swimming pool in about 100 days. But, as it gets closer to the Sun, the gas production rate will increase significantly. With Rosetta, we have an amazing vantage point to observe these changes up close and learn more about exactly why they happen."

Water is a major volatile component of comets, along with carbon monoxide, methanol and ammonia. MIRO is designed to help determine the abundance of each of these ingredients, in order to understand the nature of the comet's nucleus, the process of outgassing and where they originate on the surface.

These gases stream away from the nucleus carrying dust, forming the comet's surrounding 'coma.' As the comet moves closer to the Sun, its coma will expand and, eventually, pressure from the solar wind will cause some of the material to stream out into a long tail.

Rosetta will be there to watch these developments up close. The comet -- and Rosetta -- will make its nearest approach to the Sun in August 2015, between the orbits of Earth and Mars.

Determining the changes in production rate of water vapor and other gases as the icy object moves around the Sun is important for comet science. But it is also vital for mission planning, because once Rosetta is closer to the comet, the outflow of gases may alter the craft's trajectory.

"Our comet is coming out of its deep-space slumber and beginning to put on a show for Rosetta's science instruments," says Matt Taylor, ESA's Rosetta project scientist.

"Rosetta's engineers will also be using MIRO's observations to help them plan for future mission events when we are operating close to the comet's nucleus."

Today, the spacecraft is within 72,000 km of its destination. Six out of a total of ten rendezvous maneuvers still need to be carried out to ensure that Rosetta arrives at a distance of just 100 km from the nucleus on 6 August.

More About Rosetta:
Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI. Rosetta will be the first mission in history to rendezvous with a comet, escort it as it orbits the Sun, and deploy a lander.

Comets are time capsules containing primitive material left over from the epoch when the Sun and its planets formed. By studying the gas, dust and structure of the nucleus and organic materials associated with the comet, via both remote and in-situ observations, the Rosetta mission should become the key to unlocking the history and evolution of our solar system, as well as answering questions regarding the origin of Earth's water and perhaps even life.

More About MIRO:
MIRO is a small and lightweight spectrometer instrument, the first of its kind launched into deep space. The MIRO science team comprises 22 scientists from the US, France, Germany and Taiwan. Resembling a miniaturized ground-based radio telescope, it was designed to study the composition, velocity and temperature of gases on or near the comet's surface and measure the temperature of the nucleus down to a depth of several centimeters. Studying the nucleus temperature and evolution of the coma and tail will provide information on how the comet evolves as it approaches and leaves the vicinity of the Sun, and more about exactly why that happens. During Rosetta's flybys of asteroids Steins and Lutetia in 2008 and 2010, respectively, the instrument measured thermal emission from these asteroids and searched for water vapor. MIRO was built at NASA's Jet Propulsion Laboratory, home of principal investigator Samuel Gulkis. Hardware subsystems were provided by the Max-Planck-Institute for solar system Research and LERMA of the Observatoire de Paris. The consortium also includes LESIA of the Observatoire de Paris.

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