[meteorite-list] Rosetta Comet 'Pouring' More Water Into Space
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 22 Jan 2015 17:09:49 -0800 (PST)
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 H?ssig, 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:
More information about Rosetta is available at:
Jet Propulsion Laboratory, Pasadena, Califorina
agle at jpl.nasa.gov
NASA Headquarters, Washington
dwayne.c.brown at nasa.gov
European Space Agency, Noordwijk, Netherlands
markus.bauer at esa.int
Received on Thu 22 Jan 2015 08:09:49 PM PST