Biology: The Unity and Diversity of Life (14th Edition)

Published by Brooks/Cole Publishing Co.
ISBN 10: 1305073959
ISBN 13: 978-1-30507-395-1

Chapter 19 - Self-Quiz - Page 317: 14

Answer

b.

Work Step by Step

Mars is only about half the size of Earth, so it doesn't have much of a gravitational pull to be able to keep gases, including oxygen, from escaping into space; therefore, any organisms that may have lived or are living on Mars would be anaerobic. Also, Mars has no ozone layer, so if it houses any organisms, these species would most likely live underground to escape the sun's UV radiation. The discovery that Mars may contain water could support the idea that Mars may have supported or continues to support life in some form.
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