Cometary Impact on Neptune
Measurements performed by the space observatory Herschel point to a collision about two centuries ago
Two centuries ago a comet may have hit Neptune, the outer-most planet in our solar system.
A comet may have hit the planet Neptune about two centuries ago. This is indicated by the distribution of carbon
monoxide in the atmosphere of the gas giant that researchers - among them scientists from the French observatory
LESIA in Paris, from the Max Planck Institute for Solar System Research (MPS) in Katlenburg-Lindau (Germany) and
from the Max Planck Institute for Extraterrestrial Physics in Garching (Germany) - have now studied. The scientists
analyzed data taken by the research satellite Herschel that has been orbiting the Sun at a distance of
approximately 1.5 million kilometres since May 2009. (Astronomy & Astrophysics, published online on July 16th, 2010)
In February 2010 scientists from MPS discovered strong evidence for a cometary impact on Saturn about 230 years
ago (see Astronomy and Astrophysics, Volume 510, February 2010). New measurements performed now by the instrument
PACS (Photodetector Array Camera and Spectrometer) on board the Herschel space observatory indicate that Neptune
experienced a similar event. For the first time, PACS allows researchers to analyze the long-wave infrared
radiation of Neptune.
The atmosphere of the outer-most planet of our solar system mainly consists of hydrogen and helium with traces
of water, carbon dioxide and carbon monoxide. Now, the scientists detected an unusual distribution of carbon
monoxide: In the upper layer of the atmosphere, the so-called stratosphere, they found a higher concentration
than in the layer beneath, the troposphere. The only explanation for these results is a cometary impact. Such
a collision forces the comet to fall apart while the carbon monoxide trapped in the comet's ice is released and
over the years distributed throughout the stratosphere.
The instrument PACS was developed at the Max Planck Institute for Extraterrestrial Physics. It analyzes the
long-wave infrared radiation, also known as heat radiation that the cold bodies in space such as Neptune emit.
The research satellite Herschel carries the largest telescope ever to operate in space.
E. Lellouch et al.:
Other press releases:
First results of Herschel /PACS observations of Neptune,
Astronomy & Astrophysics, Vol. 518, L152 (2010),
on July 16th, 2010 available under
preprint in astro-ph
T. Cavaliť et. al.:
A cometary origin for CO in the stratosphere of Saturn?,
Astronomy & Astrophysics, Vol. 510, February 2010,
Link to the full Press Release by the Max Planck Institute for Solar System Research (MPS):
MPS press release