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The Planetary Report • March/April 1989

Comets: Mementos of Creation

On the Cover: Comets are frequent visitors to the skies of Earth. Since we reside in the inner solar system, as these small bodies of ice and dust pass us by they are heated by the Sun and pummeled by the solar wind, sometimes forming spectacular tails that can stretch out millions of miles behind them. Comets may be clumps of matter left over from the creation of the solar system, so by studying them we learn about our own origins. Seen here Is Comet Ikeya-Seki, which graced our skies in 1965.
Science Graphics

Features

4 Comets: Mementos of Creation: Carl Sagan and Ann Druyan explain how comets tell us about the history of our solar system.

10 Changing Views of Mars: Stephen Larson compares telescopic views of Mars from the last century to modern view of the Red Planet.

13 The Concept of Extraterrestrial Intelligence—An Emerging Cosmology? Steven Dick asks what place the idea of life beyond Earth holds in the history of science.

20 Lunar Polar Explorers: James D. Burke looks at the possibility of ice in permanently shadowed regions on our Moon.

Departments

3 Members' Dialogue SETI, exploring other planets, and TDRS.

18 World Watch Rethinking space policy.

22 Society Notes Mission to Planet Earth; stamp honoring the Very Large Array.

24 News & Reviews Research funding cuts.

26 Funding Planetary Science—A National Perspective Another view of the current situation. 

28 Q&A How do such large storms form in Mars' relatively thin atmosphere?

astronaut on Phobos
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