[meteorite-list] Rosetta Comet 'Pouring' More Water Into Space

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=4456

Rosetta Comet 'Pouring' More Water Into Space
Jet Propulsion Laboratory
January 22, 2015

There has been a significant increase in the amount of water "pouring" 
out of comet 67P/Churyumov-Gerasimenko, the comet on which the Rosetta 
mission's Philae lander touched down in November 2014.

The 2.5-mile-wide (4-kilometer) comet was releasing the earthly equivalent 
of 40 ounces (1.2 liters) of water into space every second at the end 
of August 2014. The observations were made by NASA's Microwave Instrument 
for Rosetta Orbiter (MIRO), aboard the European Space Agency's Rosetta 
spacecraft. Science results from the MIRO team were released today as 
part of a special Rosetta-related issue of the journal Science.

"In observations over a period of three months [June through August, 2014], 
the amount of water in vapor form that the comet was dumping into space 
grew about tenfold," said Sam Gulkis, principal investigator of the MIRO 
instrument at NASA's Jet Propulsion Laboratory in Pasadena, California, 
and lead author of a paper appearing in the special issue. "To be up close 
and personal with a comet for an extended period of time has provided 
us with an unprecedented opportunity to see how comets transform from 
cold, icy bodies to active objects spewing out gas and dust as they get 
closer to the sun."

The MIRO instrument is a small and lightweight spectrometer that can map 
the abundance, temperature and velocity of cometary water vapor and other 
molecules that the nucleus releases. It can also measure the temperature 
up to about one inch (two centimeters) below the surface of the comet's 
nucleus. One reason the subsurface temperature is important is that the 
observed gases likely come from sublimating ices beneath the surface. 
By combining information on both the gas and the subsurface, MIRO will 
be able to study this process in detail.

Also in the paper released today, the MIRO team reports that 67P spews 
out more gas from certain locations and at certain times during its "day." 
The nucleus of 67P consists of two lobes of different sizes (often referred 
to as the "body" and "head" because of its duck-like shape), connected 
by a neck region. A substantial portion of the measured outgassing from 
June through September 2014 occurred from the neck region during the afternoon.

"That situation may be changing now that the comet is getting warmer," 
said Gulkis. "MIRO observations would need to be carefully analyzed to 
determine which factors in addition to the sun's warmth are responsible 
for the cometary outgassing."

Observations are continuing to search for variability in the production 
rate and changes in the parts of the nucleus that release gas as the comet's 
distance from the sun changes. This information will help scientists understand 
how comets evolve as they orbit and move toward and then away from the 
sun. The gas production rate is also important to the Rosetta navigation 
team controlling the spacecraft, as this flowing gas can alter the trajectory 
of the spacecraft.

In another 67P paper released today, it was revealed that the comet's 
atmosphere, or coma, is much less homogenous than expected and that comet 
outgassing varies significantly over time.

"If we would have just seen a steady increase of gases as we closed in 
on the comet, there would be no question about the heterogeneity of the 
nucleus," said Myrtha Hässig, a NASA-sponsored scientist from the Southwest 
Research Institute in San Antonio. "Instead we saw spikes in water readings, 
and a few hours later, a spike in carbon dioxide readings. This variation 
could be a temperature effect or a seasonal effect, or it could point 
to the possibility of comet migrations in the early solar system."

The measurements on the coma were made by the Rosetta Orbiter Spectrometer 
for Ion and Neutral Analysis Double Focusing Mass Spectrometer (ROSINA 
DFMS) instrument. Measuring the in situ coma composition at the position 
of the spacecraft, ROSINA data indicate that the water vapor signal is 
strongest overall. However, there are periods when the carbon monoxide 
and carbon dioxide abundances rival that of water.

"Taken together, the MIRO outgassing results and results about heterogeneous 
fountains from ROSINA suggest fascinating new details to be learned about 
how comets work,"said Claudia Alexander, NASA project scientist for the 
U.S. Rosetta team, from JPL. "These results are helping us move the field 
forward on how comets operate on a fundamental level."

Rosetta is currently about 107 million miles (171 million kilometers) 
from Earth and about 92 million miles (148 million kilometers) from the 
sun. 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 a 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. Rosetta is the first mission in history to 
rendezvous with a comet, escort it as it orbits the sun, and deploy a 
lander to its surface.

Rosetta is an ESA mission with contributions from its member states and 
NASA. Rosetta's Philae lander is provided by a consortium led by the German 
Aerospace Center, Cologne; Max Planck Institute for Solar System Research, 
Go?ttingen; French National Space Agency, Paris; and the Italian Space 
Agency, Rome. JPL, a Division of the California Institute of Technology, 
Pasadena, manages the U.S. contribution of the Rosetta mission for NASA's 
Science Mission Directorate in Washington. JPL also built the MIRO and 
hosts its principal investigator, Samuel Gulkis. The Southwest Research 
Institute (San Antonio and Boulder), developed the Rosetta orbiter's IES 
and Alice instruments, and hosts their principal investigators, James 
Burch (IES) and Alan Stern (Alice).

For more information on the U.S. instruments aboard Rosetta, visit:

http://rosetta.jpl.nasa.gov

More information about Rosetta is available at:

http://www.esa.int/rosetta


Media Contact

DC Agle
Jet Propulsion Laboratory, Pasadena, Califorina
818-393-9011
agle at jpl.nasa.gov 

Dwayne Brown
NASA Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov 

Markus Bauer
European Space Agency, Noordwijk, Netherlands
011-31-71-565-6799
markus.bauer at esa.int 

2015-029