From: LARRY KLAES (ljk4_at_msn.com)
Date: Mon Sep 19 2005 - 19:42:38 UTC
>From: Ed Campion <Edward.S.Campion_at_nasa.gov>
>Reply-To: Ed Campion <Edward.S.Campion_at_nasa.gov>
>To: gsfc_press_releases_at_listserv.gsfc.nasa.gov
>Subject: GSFC Release / COMET TEMPEL-1 MAY HAVE FORMED IN GIANT PLANETS
>REGION
>Date: Mon, 19 Sep 2005 15:09:23 -0400
>
>
>
>Nancy Neal-Jones / Cynthia O'Carroll
> September 19, 2005
>NASA Goddard Space Flight Center
>301 286 0039 / x-464
>
>Release 05-39
>
>COMET TEMPEL-1 MAY HAVE FORMED IN GIANT PLANETS REGION
>
>Comet Tempel-1 may have been born in the region of the solar system
>occupied by Uranus and Neptune today, according to one possibility from an
>analysis of the comet's debris blasted into space by NASA's Deep Impact
>mission. If correct, the observation supports a wild scenario for the solar
>system's youth, where the planets Uranus and Neptune may have traded places
>and scattered comets to deep space.
>
>"Our observation is a definitive investigation revealing the composition of
>comet Tempel-1," said Dr. Michael Mumma of NASA's Goddard Space Flight
>Center, Greenbelt, Md. Mumma and his team used the powerful Keck telescope
>on top of Mauna Kea, Hawaii, to analyze in great detail light emitted by
>Tempel-1 gas ejected by the impact. Because each type of atom and molecule
>emits light at unique colors (frequencies), the team was able to determine
>the comet's chemical composition by separating its light into its component
>colors with an instrument called a spectrometer. Mumma is lead author of a
>paper on this research that appeared in Science on September 15.
>
>Comets are chunks of ice and dust that zoom around the solar system in
>elongated orbits. This "dirty snowball" is the nucleus of the comet. Comet
>nuclei are thought to be cosmic leftovers, condensed remains of the gas and
>dust cloud that formed the solar system. As a comet gets close to the sun,
>solar heat liberates gas and dust from the nucleus, forming the coma, which
>is an extensive, bright cloud around the nucleus, and one or more tails.
>
>Repeated solar heating can remove materials that have low freezing
>temperatures from the surface, giving the comet a crust that's different
>chemically from its interior. This makes it hard to discover a comet's true
>composition by simply looking at gas that's evaporating from the surface.
>NASA's Deep Impact mission crashed into comet Tempel-1 July 4, 2005,
>allowing scientists to test whether material ejected from its protected
>interior was closer to pristine.
>
>By observing Tempel-1 before, during, and after impact, the team was able
>to distinguish surface gas from the impact debris, and they discovered that
>the interior does indeed have a different chemistry. "The amount of ethane
>(C2H6) in the cloud around the comet was significantly higher after impact
>than before," said Mumma.
>
>There are two possible explanations for this. In the first, the surface
>crust is different from the interior due to solar heating. The interior,
>however, is all the same. In the second, the interior is a mix of regions
>with different compositions because the nucleus is actually composed of
>smaller "mini-comets" (cometesimals), each with a different chemistry. Deep
>Impact could have just so happened to hit one of these cometesimals, while
>the gas seen before impact might have came from a different region on the
>comet with different chemistry. Multiple impacts in different regions of
>the comet are necessary to determine which scenario is correct, according
>to the team.
>
>If the first scenario is correct, the comet could have formed in the region
>now bounded by the orbits of Uranus and Neptune, based on its interior
>chemistry. Different chemicals get frozen into a comet depending on its
>location. A comet that forms farther from the sun will have greater amounts
>of ices with low freezing temperatures, like ethane, than a comet that
>forms closer to the sun. By measuring the relative amounts of each
>chemical, astronomers can estimate where a comet formed.
>
>Formation in this location supports a theory that the gas giant planets
>Uranus and Neptune formed closer to the sun than their current locations.
>The theory, proposed by Dr. Alessandro Morbidelli of the Observatoire de la
>Cote d'Azur, Nice, France, and his team, says that gravitational
>interaction between the gas giant planets and numerous small planets left
>over from the solar system's formation (planetesimals) brought the giant
>planets into an unstable orbital configuration. Neptune and Uranus were
>tossed outward and could have exchanged orbits. As they migrated outward,
>their gravity disrupted a large disk of comets that had formed in the
>region where Uranus and Neptune currently reside. Some were scattered into
>deep space, to a roughly spherical region called the "Oort cloud" that
>surrounds our solar system at about 10,000 times the earth-sun distance.
>Others were directed to the Kuiper belt, a region beyond Neptune that
>extends to several hundred times the Earth-sun distance.
>
>If some Kuiper belt comets have similar chemistry to some Oort cloud
>comets, it would support this model of the solar system's rowdy early days
>by showing that certain comets had a common origin despite very different
>final destinations. Tempel-1 shares certain orbital characteristics with
>the "ecliptic" comets, a group that likely comes from the "scattered"
>Kuiper belt. "The amount of ethane in Tempel-1, however, is similar to the
>amount in the dominant group of comets that come from the Oort cloud
>region," said Mumma. Its chemical similarity to Oort cloud comets supports
>the idea that some Kuiper belt and Oort cloud comets formed in the same
>place. This research was funded by NASA, the National Science Foundation
>and the National Research Council. For an image, please visit:
>
><http://www.nasa.gov/mission_pages/deepimpact/media/deepimpact-090905.html>http://www.nasa.gov/mission_pages/deepimpact/media/deepimpact-090905.html
>
>
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