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Evidence for more dust than ice in comets
October 14, 2005Observations of Comet 9P/Tempel 1 made by ESA's Rosetta spacecraft after the Deep Impact collision suggest that comets are 'icy dirtballs', rather than 'dirty snowballs' as previously believed.
Comets spend most of their lifetime in a low-temperature environment far from the Sun. Their relatively unchanged composition carries important information about the origin of the Solar System.
On 4 July this year, the NASA Deep Impact mission sent an 'impactor' probe to hit the surface of Comet 9P/Tempel 1 to investigate the interior of a cometary nucleus.
The 370 kg copper impactor hit Comet Tempel 1 with a relative velocity of 10.2 kilometres per second. The collision was expected to generate a crater with a predicted diameter of about 100-125 metres and eject cometary material. It vaporised 4500 tonnes of water, but surprisingly released even more dust.
Tempel 1's icy nucleus, roughly the size of central Paris, is dynamic and volatile. Possibly the impact would also trigger an outburst of dust and gas, and produce a new active area on the comet's surface.
Just before impact, the Hubble Space Telescope spotted a new jet of dust streaming from the icy comet. No one knows for sure what causes these outbursts.
Rosetta, with its set of very sensitive instruments for cometary investigations, used its capabilities to observe Tempel 1 before, during and after the impact.
At a distance of about 80 million kilometres from the comet, Rosetta was in the most privileged position to observe the event.
European scientists using Rosetta's OSIRIS imaging system observed the comet's nucleus before and after the impact. OSIRIS comprises a narrow-angle camera (NAC) and a wide-angle camera (WAC). Both cameras imaged the extended dust coma from the impact in different filters.
OSIRIS measured the water vapour content and the cross-section of the dust created by the impact. The scientists could then work out the corresponding dust/ice mass ratio, which is larger than one, suggesting that comets are composed more of dust held together by ice, rather than made of ice comtaminated with dust. Hence, they are now 'icy dirtballs' rather than 'dirty snowballs' as previously believed.
The scientists did not find evidence of enhanced outburst activity of Comet 9P/Tempel 1 in the days after the impact, suggesting that, in general, impacts of meteoroids are not the cause of cometary outbursts. Scientists also hope to make a 3D reconstruction of the dust cloud around the comet by combining the OSIRIS images with those taken from ground observatories.
Michael Küppers, lead author of the results, Max-Planck Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany
E-mail: kueppers @ mps.mpg.de
Gerhard Schwehm, ESA Rosetta Project Scientist
E-mail: gerhard.schwehm @ esa.int
The paper by Küppers and colleagues entitled 'A large dust/ice ratio in the nucleus of comet 9P/Tempel 1' has been featured in the 12 October press release for Nature.
European Space Agency
Tempel 1's icy nucleus, roughly the size of central Paris, is dynamic and volatile. Possibly the impact would also trigger an outburst of dust and gas, and produce a new active area on the comet's surface.
Just before impact, the Hubble Space Telescope spotted a new jet of dust streaming from the icy comet. No one knows for sure what causes these outbursts.
Rosetta, with its set of very sensitive instruments for cometary investigations, used its capabilities to observe Tempel 1 before, during and after the impact.
At a distance of about 80 million kilometres from the comet, Rosetta was in the most privileged position to observe the event.
European scientists using Rosetta's OSIRIS imaging system observed the comet's nucleus before and after the impact. OSIRIS comprises a narrow-angle camera (NAC) and a wide-angle camera (WAC). Both cameras imaged the extended dust coma from the impact in different filters.
OSIRIS measured the water vapour content and the cross-section of the dust created by the impact. The scientists could then work out the corresponding dust/ice mass ratio, which is larger than one, suggesting that comets are composed more of dust held together by ice, rather than made of ice comtaminated with dust. Hence, they are now 'icy dirtballs' rather than 'dirty snowballs' as previously believed.
The scientists did not find evidence of enhanced outburst activity of Comet 9P/Tempel 1 in the days after the impact, suggesting that, in general, impacts of meteoroids are not the cause of cometary outbursts. Scientists also hope to make a 3D reconstruction of the dust cloud around the comet by combining the OSIRIS images with those taken from ground observatories.
Michael Küppers, lead author of the results, Max-Planck Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany
E-mail: kueppers @ mps.mpg.de
Gerhard Schwehm, ESA Rosetta Project Scientist
E-mail: gerhard.schwehm @ esa.int
The paper by Küppers and colleagues entitled 'A large dust/ice ratio in the nucleus of comet 9P/Tempel 1' has been featured in the 12 October press release for Nature.
European Space Agency
Comets News and Current Comets Events RSSCosmic connections: Imperial scientist locates the origin of cosmic dust
The research, published in the journal Geology, shows that some of the cosmic dust falling to Earth comes from an ancient asteroid belt between Jupiter and Mars. This research improves our knowledge of the solar system, and could provide a new and inexpensive method for understanding space.
Water is 'designer fluid' that helps proteins change shape, scientists say
Ubiquitous on Earth, water also has been found in comets, on Mars and in molecular clouds in interstellar space. Now, scientists say this common fluid is not as well understood as we thought.
New Findings Show Diverse, Wet Environments on Ancient Mars
Mars once hosted vast lakes, flowing rivers and a variety of other wet environments that had the potential to support life, according to two new studies based on data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and other instruments on board NASA's Mars Reconnaissance Orbiter (MRO).
SOHO discovers its 1500th comet
The ESA/NASA SOHO spacecraft has just discovered its 1500th comet, making it more successful than all other comet discoverers throughout history put together. Not bad for a spacecraft that was designed as a solar physics mission.
Laser fluorescence could find life on Mars
A team of scientists from the United States and the United Kingdom has developed a technique using ultraviolet light to identify organic matter in soils that they say could be used to document the existence of life on Mars.
Key molecule discovered in Venus's atmosphere
Venus Express has detected the molecule hydroxyl on another planet for the first time. This detection gives scientists an important new tool to unlock the workings of Venus's dense atmosphere.
LIDAR Imaging Detector Could Build 'Super Road Maps' of Planets and Moons
Technology that could someday "MapQuest" Mars and other bodies in the solar system is under development at Rochester Institute of Technology's Rochester Imaging Detector Laboratory (RIDL), in collaboration with Massachusetts Institute of Technology's Lincoln Laboratory.
Solar Games at Paranal
Cerro Paranal, home of ESO's Very Large Telescope, is certainly one of the best astronomical sites on the planet. Stunning images, obtained by ESO staff at Paranal, of the green and blue flashes, as well as of the so-called 'Gegenschein', are real cases in point.
FSU geochemist challenges key theory regarding Earth's formation
Working with colleagues from NASA, a Florida State University researcher has published a paper that calls into question three decades of conventional wisdom regarding some of the physical processes that helped shape the Earth as we know it today.
UMd-led team finds ancient asteroids formed at solar system's start
Using visible and infrared data collected from telescopes on Hawaii's Mauna Kea, a team of scientists, led by the University of Maryland's Jessica Sunshine, have identified three asteroids that appear to be among our Solar System's oldest objects.
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