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The Planetary Report • September/October 1997

The Color of Europa

On the Cover: Tyre, an ancient impact basin more than 140 kilometers (90 miles) across, grabs our attention in one of the highest-resolution pictures of Europa yet obtained by Galileo. In this false-color image, the bright blue, east-west ridges crossing the region are much younger than the crater, illustrating how the moon maintains its youthful appearance. Older, darker surfaces are covered over with clean, relatively coarse-grained ice that is extruded along the fractures in Europa's frigid crust. Coarse-grained ice, which forms at warmer temperatures, may be a sign of liquid water below. Galileo images Tyre on April 4, 1997 from a distance of 703,776 kilometers (434,430 miles).


4 A Brief History of the Moon: William Hartmann draws on both his scientific and artistic backgrounds to recount the leading theory of the Moon's formation, based largely on his research with Donald R. Davis.

12 The Color of Europa: Paul Geissler compares results from Voyager and Galileo of this icy Jovian moon.

14 On to Eros! Clark Chapman gives some hints on observing this tiny nearby object, which the Near-Earth Asteroid Rendezvous (NEAR) spacecraft is heading toward.

18 Carl Sagan Memorial Station: Louis Friedman presents a special surprise to the Society bestowed by the Pathfinder team.


3 Members' Dialogue Remembering Gene Shoemaker; science and the public.

16 Basics of Spaceflight Assembly, Test, and Launch Operations (ATLO).

19 News & Reviews The importance of the improbable.

20 Factino NEAR flyby yields its first close-ups of Mathilde.

20 World Watch Houston, do we really have a problem?

23 Society News Thousands celebrate at Planetfest; Rover Roundup papers published. 

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