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High organic content from Comet 9P/Tempel 1

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  • Joe (uk-ufo) McGonagle
    http://www.newscientist.com/article.ns?id=dn7961 Deep Impact collision ejected the stuff of life a.. 13:10 07 September 2005 b.. NewScientist.com news service
    Message 1 of 1 , Sep 11, 2005
      http://www.newscientist.com/article.ns?id=dn7961

      Deep Impact collision ejected the stuff of life
      a.. 13:10 07 September 2005
      b.. NewScientist.com news service
      c.. Maggie McKee

      <images removed but available at the link above>
      Millions of kilograms of fine dust particles and water and a
      "surprisingly high" amount of organic molecules sprayed into
      space when NASA crashed its Deep Impact spacecraft into Comet
      9P/Tempel 1 on 4 July 2005, reveal a trio of new studies.

      The observations bolster theories that comets may have seeded
      Earth with the raw materials for life and suggest they may be
      sponge-like - rather than hardened - at their cores.

      On 4 July, about 80 telescopes on Earth and in space trained
      their sights on Comet Tempel 1 when a 370-kilogram copper
      impactor was sent hurtling into its path. Just after the smash, a
      bright vapour plume spewed from the surface at about 5 kilometres
      per second, followed quickly by a stream of particles that spread
      into a cone.

      The cone appeared to remain attached to the comet's surface for
      about 22 hours before separating into a detached arc. Researchers
      used this gravitational attraction to estimate the mass and
      density of the comet's main body, or nucleus. They found that the
      72 trillion kilogram-nucleus was extremely porous, with as much
      as 80% of its volume taken up by empty space.

      "That tells me there is no solid layer all the way down to the
      centre," says Mike A'Hearn, the mission's principal investigator
      at the University of Maryland in College Park, US. He says he had
      expected that the ice might become denser towards the core of the
      nucleus, but that instead "probably all the way in, ice is all in
      the form of tiny grains".

      A touch crumbly
      "It's like a sponge, with a lot of cavities," agrees Horst Uwe
      Keller, an astronomer at the Max-Planck Institute for Solar
      System Research in Germany. He observed the event with Europe's
      Rosetta spacecraft and says the discovery confirms previous
      observations suggesting other comets are also porous. "When you
      touch it, it just crumbles under your hands."

      Observers estimate the impact released about 5 million kilograms
      of water from beneath the comet's surface and between two and
      five times as much dust. There was so much dust, in fact, that
      mission members have not been able to see the impact crater with
      the high-resolution camera on the mission's flyby spacecraft,
      about 500 km away.

      To add to the problem, that camera was malfunctioning but now
      image-processing techniques may have revealed a glimpse of the
      crater and team members may release the image later on Wednesday.

      Building blocks
      The team estimates the impact blasted away a crater about 100
      metres wide and up to 30 m deep. Crucially, organic molecules
      were among the material ejected. Neither the full range of
      molecules nor their abundances have been determined yet, but
      researchers say they have found a surprisingly high amount of
      methyl cyanide, a molecule seen in large quantities in another
      comet.

      This supports theories that comets may have brought water and the
      building blocks of life to Earth, and the team hopes to
      eventually "identify all the species comets brought in abundance
      to early Earth", says A'Hearn.

      The observations have also apparently ruled out another theory -
      that impacts with other objects may be responsible for the
      occasional stream of gas and dust seen coming off of comets.
      Although Tempel 1's surface is pockmarked with craters ranging
      from 40 m to 400 m across, astronomers watching the comet both
      before and after the impact noticed that it released the streams
      relatively often in spurts of activity apparently triggered by
      sunlight.

      "I don't think the hypothesis that outbursts are caused by
      impacts is really valid," says A'Hearn. "Probably comets undergo
      outbursts like this very frequently and the fact that everyone
      was looking intensively [at this comet] for an extended period
      allowed us to see phenomena that are probably common and weren't
      seen before."

      Journal reference: Science (DOI: 10.1126/science.1118923)
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