Copyright: R. Evans, J. Trauger, H. Hammel and the HST Comet Science Team
Copyright: Water map: ESA/Herschel/T. Cavalié et al.; Jupiter image: NASA/ESA/Reta Beebe (New Mexico State University)
Herschel’s observations found that there was 2–3 times more water in the
southern hemisphere of Jupiter than in the northern hemisphere, with
most of it concentrated around the sites of the 1994 comet impact.
Additionally, it is only found at high altitudes.
“Only Herschel was able to provide the sensitive spectral imaging needed
to find the missing link between Jupiter’s water and the 1994 impact of
comet Shoemaker-Levy 9,” says Thibault Cavalié of the Laboratoire
d’Astrophysique de Bordeaux, lead author of the paper published in Astronomy and Astrophysics.
“According to our models, as much as 95% of the water in the stratosphere is due to the comet impact.”
Another possible source of water would be a steady rain of small
interplanetary dust particles onto Jupiter. But, in this case, the water
should be uniformly distributed across the whole planet and should have
filtered down to lower altitudes.
Also, one of Jupiter’s icy moons could deliver water to the planet via a giant vapour torus, as Herschel has seen
from Saturn’s moon Enceladus, but this too has been ruled out. None of
Jupiter’s large moons is in the right place to deliver water to the
locations observed.
Copyright: NASA, ESA, H. Weaver & E. Smith (STScI) and J. Trauger & R. Evans (Jet Propulsion Laboratory)
Finally, the scientists were able to rule out any significant
contributions from recent small impacts spotted by amateur astronomers
in 2009 and 2010, along with local variations in the temperature of
Jupiter’s atmosphere.
Shoemaker-Levy 9 is the only likely culprit.
“All four giant planets in the outer Solar System have water in their
atmospheres, but there may be four different scenarios for how they got
it,” says Dr Cavalié. “For Jupiter, it is clear that Shoemaker-Levy 9 is
by far the dominant source, even if other external sources may
contribute also.”
“Thanks to Herschel’s observations, we have now linked a unique comet
impact – one that was followed in real time and which captured the
public’s imagination – to Jupiter’s water, finally solving a mystery
that has been open for nearly two decades,” adds Göran Pilbratt, ESA’s
Herschel project scientist.
The observations made in this study foreshadow those planned for ESA’s future Jupiter Icy moons Explorer
mission launching towards the Jovian system in 2022, where it will map
the distribution of Jupiter’s atmospheric ingredients in even greater
detail.
Notes for Editors
“The spatial distribution of water in the stratosphere of Jupiter from
Herschel-HIFI and –PACS observations,” by T. Cavalié et al. is published
in Astronomy & Astrophysics, 553, A21, May 2013.
The observations were obtained under the Herschel Guaranteed Time Key
Programme “Water and related chemistry in the Solar System”. HIFI
observations were taken in July 2010 and PACS observations were made in
October 2009 and December 2010. The results were complemented with data
on the stratospheric temperature of Jupiter taken at NASA’s Infrared
Telescope Facility taken during the same period.
Herschel is an ESA space observatory with science instruments provided
by European-led Principal Investigator consortia and with important
participation from NASA.
For further information, please contact:
Markus Bauer
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.bauer@esa.int
Thibault Cavalié
Laboratoire d’Astrophysique de Bordeaux (joint research unit of the CNRS-INSU and University Bordeaux, France)
Tel: +33 5 57 77 61 24
Email: cavalie@obs.u-bordeaux1.fr
Göran Pilbratt
ESA Herschel Project Scientist
Tel: +31 71 565 3621
Email: gpilbratt@rssd.esa.int
