<DIV><B>Mission: Planet Earth</B><BR></div><DIV><DIV><b>MISSION, PLANET EARTH</b></div><DIV>When I was an astronaut, I spent hours gazing down at the Earth below. Our planet is beautiful. It's home to everything we know and hold dear.</div><DIV> <BR></div><DIV>When I looked out the window, I could see winding rivers emptying into blue oceans, mountainsides of a tropical rain forest, and muddy waters of river deltas. I could see city lights twinkle at night and contrails of airplanes crisscross the sky.</div><DIV>More than anything, though, I could see how fragile Earth is. When I looked toward the horizon, I could see a thin, fuzzy blue line outlining the planet. At first, I didn't know what I was seeing. Then I realized it was Earth's atmosphere. It looked so thin and so fragile, like a strong gust of interplanetary wind could blow it all away. And I realized that this air is our planet's spacesuit--it's all that separates every bird, fish, and person on Earth from the blackness of space.</div><DIV>In the last few decades we've started to change that atmosphere. Some of the changes, like the smog hovering over Los Angeles, are even visible to astronauts in space. Others are invisible to the eye but are now easy to measure. The most dangerous--the one that will affect everything on our planet--is the warming that we now know we humans are causing.</div><DIV>Our warming climate is not visible to astronauts, but its effects will be. The next generation of astronauts could look down and see deserts where we now have lakes, meadows where we now have glaciers, and oceans where we now have beaches. Future astronauts may even have to launch into space from a new launch pad--Cape Canaveral could be underwater. They may look down and say, "That's where Washington, D.C., used to be," or "Did you know farmers used to grow wheat in Kansas?"</div><DIV>To a person standing on the ground, our air seems to go on forever. The sky looks so big, and people haven't worried about what they put into the air. From space, though, it's obvious how little air there really is. Nothing vanishes "into thin air." The gases that we're sending into the air are piling up in our atmosphere. And that's changing Earth's life-support system in ways that could change our planet forever.</div></div><DIV>Copyright © 2009 by Sally Ride and Tam O'Shaughnessy</div> <BR><BR><i>Continues...</i> <!-- copyright notice --> <br></pre> <blockquote><hr noshade size='1'><font size='-2'> Excerpted from <b>Mission: Planet Earth</b> by <b>Sally Ride</b> Copyright © 2009 by Sally Ride. Excerpted by permission.<br> All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.<br>Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.