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The Planetary Report • January/February 1993

The Changing Face of Earth

On the Cover: This composite image clearly shows how our planet's surface is divided into plates that continually slide over, under, and past one another, remaking Earth's face. Here the rift zones, where new crustal material flows up from Earth's interior, are indicated in bright yellow. New crust forming along the Mid-Atlantic Ridge (right) is pushing Africa and South America apart. The volcanic Galápagos Islands are products of the East Pacific Rise (left), marked by fractures in the ocean floor.
Image courtesy of Peter W. Sloss, National Geophysical Data Center

Features

4 Snowflakes Fallen on the Hearth: The Evolution of the Earth: Carl Sagan and Ann Druyan take on the task to describing the complex geologic history of our planet.

12 Roving Through Death Valley: 1992 Test Program Wrap-Up: Alexander Kemurdjian reports on testing Mars rovers in California.

Departments

3 Members' Dialogue Responses to The Planetary Report articles.

16 Readers' Service Angle of Attack.

17 World Watch Japan's Planet-B mission, revitalizing NASA, and European Mars goals.

18 News & Reviews Killer comet, or terrifying Toutatis?

19 Society Notes MarsLink launched; Paine Memorial Fund established.

20 Q&A What was the "mystery object" in the last images from Phobos 2?

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