archive: SETI [ASTRO] From Near-Earth Asteroids To Water On Mars: Latest ISO

SETI [ASTRO] From Near-Earth Asteroids To Water On Mars: Latest ISO

Larry Klaes ( )
Wed, 12 May 1999 13:21:39 -0400

>X-Authentication-Warning: majordom set sender
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>Date: Wed, 12 May 1999 14:47:10 GMT
>From: Ron Baalke <>
>Subject: [ASTRO] From Near-Earth Asteroids To Water On Mars: Latest ISO
>Reply-To: Ron Baalke <>
>ESA Science News
>11 May 1999
>>From Near Earth Asteroids to water on Mars -- astronomers review
>latest ISO results
>Near-Earth Asteroids -- asteroids whose orbits bring them close
>to Earth -- very likely originate from collisions between larger
>asteroids that orbit the Sun between the planets Mars and Jupiter.
>This result, obtained by ESA's infrared space telescope, ISO, was
>presented yesterday at the workshop on ISO results on Solar System,
>held at ESA's Villafranca Satellite Tracking Station in Spain. Other
>findings related to the atmosphere of Mars and the giant planets --
>Saturn, Jupiter, Neptune and Uranus -- were also presented during
>a press conference yesterday morning.
>About 250 Near-Earth Asteroids (NEA) are known so far, with sizes
>ranging from one to 40 kilometres in diameter. But according to Alan
>Harris, of the German Aerospace Centre (Berlin), there are more
>than 2000 NEA not yet identified. Their origin is still unclear, but
>scientists are working with two main ideas: many probably originate
>from collisions among the larger bodies in the Main Belt of asteroids,
>between Mars and Jupiter, while others might be old, 'dead' comets
>that have undergone so many fly-bys of the Sun that they have lost
>all their coma -- the beautiful comet tail of dust and gas.
>The infrared observations made by Harris with ISO provide
>information about the surface and mineralogy of the NEAs, and
>confirm that many are fragments of larger asteroids. ISO sees a
>rocky surface without much residual dust; a dusty surface is what
>would be expected if the NEA were 'dead comets'. Harris, however,
>is still analyzing the data and has not yet ruled out the possibility
>of finding traces of dust in one of the asteroids observed, the orbit
>of which is very similar to that of a comet.
>As Harris points out, knowledge on the composition of these objects
>is necessary to predict the consequences of a future impact on the
>Earth. "We still know just a few of them, and although the odds that
>any one will hit the Earth in the near future are very low, there's a
>possibility. Therefore, the more we know about these objects, the
>better", he said.
>The new data about Mars refer to the water in the atmosphere: ISO
>sees that it condenses and freezes close to the planet's surface.
>This result will help to understand the behaviour of the Martian
>"We got these observations while NASA's Mars Pathfinder mission
>was also studying the planet, and the results of both missions are
>in agreement. ISO confirms the Mars Pathfinder data", said Therese
>Encrenaz, of the Observatoire de Paris-Meudon.
>Encrenaz also described the detection of new molecules in the
>atmospheres of the giant planets, mainly hydrocarbons like the
>radical CH3, never detected before, and benzene. Benzene is a
>common molecule on Earth (in petrol for instance), but is
>apparently less common on other planets. ISO's spectrometers see
>it now in Saturn.
>The discovery of water in the atmosphere of Saturn's largest moon,
>Titan, was also reviewed by Athena Coustenis of the Observatoire
>de Paris-Meudon.
>ISO Science Homepage
>ISO Data Centre
>[NOTE: Images supporting this article are available at