If one were to judge by recent headlines, science did not approach the end of the millennium on a stellar note. Hopes of new revelations about the Red Planet were dashed when three probes--Mars Climate Orbiter, Deep Space2 and the Mars Polar Lander mysteriously went silent. And the Hubble Space Telescope had to shutter its eye on the distant cosmos when a gyroscope failed, pending a repair mission by the Space Shuttle.

But those events, as saddening as they were, are only part of the picture. Looking back over the final year of the 20^th century, it is clear that 1999 was far from a bust. Nearly all fields had their smattering of breakthroughs, underscored by the steady accumulation of knowledge.

MARS MAPPED

Despite the setbacks, spacecraft continue to probe the solar system and plumb the cosmos. And there was no shortage of speculation on ways to go to space, from air-breathing engines and space balloons to ultralight sails. Scientists continued the debate as to whether robots or humans should explore space in the first place, and considered how humanity might make money among the stars. Here on Earth, Scientific American compiled a Web guide to exploring other worlds.

To that end, colonizing Mars remained a distant goal. The Mars Global Surveyor, launched in 1996, at last completed the first detailed maps of the Martian surface this year. They reveal an exotic and extreme landscape that makes our home planet look pretty bland by comparison. The spectacular Martian scenery includes a six-mile-deep crater that could swallow half the U.S. and a dead volcano that towers to 17 miles.

The spacecraft also sends back daily weather reports which indicate that Mars is far from being a dead world. Its camera captured huge dust devils--much like our tornadoes--and provided evidence that the sand dunes on Mars are still being shaped by winds. Pictures of the Northern polar regions revealed watery stormclouds that mark the arrival of fall. And recently, researchers analyzing the planet's topography reported convincing evidence that a flat plain does, indeed, mark the site of an ancient sea.

APOLLO REMEMBERED

After having its mission extended for two years to observe Jupiter's moons, the intrepid Galileo spacecraft successfully completed a risky flyby of Jupiter's turbulent moon, Io. Sailing just 380 miles above the surface, it returned some of the sharpest images yet of the most volcanically active body in the solar system. The new pictures, which were released by NASA on November 19, revealed a fiery landscape swept with colossal lava flows, vast lava lakes, towering and collapsing mountains and more than 100 active volcanoes.

Charting individual planets aside, other astronomers continued their efforts at mapping the entire universe, hoping to answer the question of whether space is finite.

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