Comet Discovered to Have Its Own Northern Lights

An atmospheric light show previously relegated to planets and Jupiter moons is found on comet using data from ESA’s Rosetta spacecraft.

from NASA instruments aboard the ESA (European Space Agency) Rosetta mission have helped reveal that comet 67P/Churyumov-Gerasimenko has its own far-ultraviolet aurora. It is the first time such electromagnetic emissions in the far-ultraviolet
have been
documented on a celestial object other than a planet or moon.A paper on the findings was released
today in the journal Nature Astronomy.

On Earth, aurora
(also known as the northern or southern lights) are generated when electrically
charged particles speeding from the Sun hit the upper atmosphere to create
colorful shimmers of green, white, and red. Elsewhere in the solar system, Jupiter and some of its moons – as well as Saturn,
Uranus, Neptune, and even Mars – have all exhibited their own version of northern lights.
But the phenomena had yet to be documented in comets.

Rosetta is space
exploration’s most traveled and accomplished comet hunter. Launched in 2004, it
orbited comet 67P/Churyumov-Gerasimenko (67P/C-G) from
Aug. 2014 until its dramatic end-of-mission comet landing in Sept.
The data for this most recent study is on what mission
scientists initially interpreted as “dayglow,” a process caused by
photons of light interacting with the envelope of gas – known as the
coma – that radiates from, and surrounds, the comet’s
nucleus. But new analysis of the data paints a very different picture.

glow surrounding 67P/C-G is one of a kind,” said Marina Galand of Imperial
College London and lead author of the study. “By linking data from
numerous Rosetta instruments, we were able to get a better picture of what was going on. This enabled us to
unambiguously identify how 67P/C-G’s ultraviolet atomic emissions form.”

The data
indicate 67P/C-G’s emissions are actually auroral in nature. Electrons streaming
out in the solar wind – the stream of charged particles flowing out from the
Sun – interact with the gas in the comet’s coma, breaking apart water and other
molecules. The resulting atoms give off a distinctive far-ultraviolet light. Invisible
to the naked eye, far-ultraviolet has the shortest wavelengths of radiation in
the ultraviolet spectrum.

Exploring the
emission of 67P/C-G will enable scientists to learn how the particles in the
solar wind change over time, something that is crucial for understanding space
weather throughout the solar system. By providing better information on how the
Sun’s radiation affects the space environment they must travel through, such
information could ultimately can help protect satellites and spacecraft, as
well as astronauts traveling to the Moon and Mars.

“Rosetta is the gift that keeps on giving,”
said Paul Feldman, an
investigator on Alice at the
Johns Hopkins University in Baltimore and
a co-author of the paper. “The treasure trove of data it returned over its
two-year visit to the comet have allowed us to rewrite the book on these most
exotic inhabitants of our solar system – and by all accounts there is
much more to come.”

NASA Instruments Aboard
ESA’s Rosetta

NASA-supplied instruments contributed to this
investigation. The Ion and Electron Sensor (IES) instrument detected the amount
and energy of electrons near the spacecraft, the Alice instrument measured the
ultraviolet light emitted by the aurora, and the Microwave
Instrument for the Rosetta Orbiter (MIRO) measured the amount of water
molecules around the comet (the MIRO instrument includes contributions from
France, Germany, and Taiwan). Other instruments aboard the spacecraft used in
the research were the Italian Space Agency’s Visible and InfraRed Thermal
Imaging Spectrometer (VIRTIS), the Langmuir Probe (LAP) provided by Sweden, and
the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) provided
by Switzerland.

was an ESA mission with contributions from its member states and NASA. Rosetta’s
Philae lander, which
successfully landed on the comet in November 2014, was
provided by a consortium led by the German Aerospace Center in Cologne; Max
Planck Institute for Solar System Research in Gottingen, Germany; the French
National Space Agency in, Paris; and the Italian Space Agency in Rome. A
division of Caltech, NASA’s Jet Propulsion Laboratory in Southern California
managed 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, Mark Hofstadter. The Southwest Research Institute (San Antonio
and Boulder, Colorado), developed the Rosetta orbiter’s IES and Alice
instruments and hosts their principal investigators, James Burch (IES) and Joel Parker (Alice).

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

More information about Rosetta is available

News Media Contact

DC Agle

Jet Propulsion Laboratory, Pasadena, Calif.


Josh Handal

NASA Headquarters, Washington



Source: Jet Propulsion Laboratory

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