On the Cover: <i>Mars Global Surveyor</i> has finally begun its mission to map the surface of Mars in unprecedented detail. Equipment problems delayed the mapping mission for many months, as the spacecraft settled into a near-circular orbit. But by March 1999 the spacecraft was returning spectacular images. Here we see a field of dark sand dunes in the Nili Patera region of Syrtis Major, a dark triangular area that has been observed from Earth for many decades. In this image, the spacecraft has resolved details as small as 3 meters across. The shapes of the dunes indicate that dark sand has been steadily blowing from upper right to lower left by the Martian wind. The area shown is 2.1 kilometers (1.3 miles) across.
4 Beginnings of Galactic Exploration/Some Thoughts on SETI: Of all Planetary Society programs, none generates more passion than SETI, which fascinates in many ways, as you'll find in short essays by Philip Morrison and Christopher Chyba.
7 An Ocean in Callisto? After the success of Galileo's magnetometer experiment in investigating the possibility of an ocean on Europa, scientists decided to take a closer look at the data from another Jovian moon. The surprising results from Callisto, reported for us by David J. Stevenson, suggest there is a layer of liquid water trapped within this perplexing world of ice.
12 Mars Global Surveyor: A Close Eye on Mars: The journey of Mars Global Surveyor has been long and difficult, but the new images have proved well worth the wait, presented here by Jennifer Vaughn.
14 Whatever Happened to Planet X? John Anderson describes the verification that trans-Plutonian space contains many small bodies, and an unexplained mystery: The slowing of the Pioneer spacecraft.
3 Member's Dialogue Opinions on humans to Mars.
18 News & Reviews Media gatekeepers; E&O versus R&D.
19 World Watch The NASA budget and Hubble Space telescope; Mars Express nearing approval
20 Q&A When did we discover how hot Jupiter is?
22 Society News Historic projects bring students to space.