2 space exploration favorites all but converge in night sky
To the lower right of Saturn glows Mars, fainter and orange-reddish. To the right of Mars are Pollux and Castor, marking the heads of the mythological Gemini twins. The two planets and two stars make a lovely, curving row.
Keep an eye on Saturn and Mars from night to night, and you'll see that they're closing in on each other. They'll appear closest together on June 16 and 17, when they'll be separated by no more than the width of a pencil held at arm's length.
Turn binoculars on Saturn this week, and just above it you'll spot a swarm of stars known as the Beehive Star Cluster.
At this moment, Saturn and Mars share an extraordinary distinction: Spacecraft are visiting them on long-term reconnaissance missions.
In 1997 NASA launched the truck-sized Cassini space probe on its way to Saturn. It got there in 2004, braked into orbit, and has been studying the giant planet, its rings, and its many moons ever since. In January 2005 it sent a lander parachuting onto the cloud-hidden mud flats of Titan, Saturn's largest moon. In some ways Titan is the most Earthlike other world in the solar system -- except that at minus 290 degrees Fahrenheit, storms and floods of liquid methane take the place of water, ice serves as bedrock, and equatorial deserts sport vast, windblown dunes of granules that apparently resemble coffee grounds.
Geysers from the south pole of Saturn's little moon Enceladus ; the mysterious wasp's nest texture of Hyperion; the sugar-and-chocolate coatings of Iapetus , with a taller-than-Everest mountain ridge ringing its equator -- all were new finds by Cassini. The craft is studying lightning in the clouds of Saturn itself a thousand times as powerful as lightning on Earth, intricate detail in the 170,000-mile-wide plain of Saturn's rings, and much more. Of the thousands of pictures Cassini has been sending back, few match anything in science fiction. You can browse them at www.nasa.gov/mission_pages/cassini/main.
Mars is a lot easier to reach; it's only about one-sixth as far from Earth as Saturn is on average. Several spacecraft are active on and around Mars right now. The twin Mars Exploration Rovers, Spirit and Opportunity, continue to creep across the rocky, sandy hills and plains 2 1/2 years after they landed, stopping frequently to analyze the geology of their surroundings. Designed to work for 90 days, they refuse to quit.
NASA's Mars Global Surveyor, which began mapping the planet from orbit in 1999, continues to add to its archive of more than 212,000 images. Its more advanced successors, Mars Odyssey and Mars Reconnaissance Orbiter, are further detailing the planet's geology, weather, and near-space environment. The European Space Agency's Mars Express craft is about to begin investigating the planet's underground composition to a depth of about a mile, courtesy of ground-penetrating radar. For more about all of these, see marsprogram.jpl.nasa.gov/missions/present/.
And yet, NASA is suddenly turning away from its spectacular record of space-science successes. It has no choice; the Bush administration has mandated that the agency work primarily toward returning astronauts to the moon by 2020. This is a heroic goal, but it's fantastically expensive and will have very little scientific payoff. The money is coming out of everything that NASA does to investigate the universe, its origins, its history, and our place within it.
Alan M. MacRobert is a senior editor of Sky & Telescope and Night Sky magazines in Cambridge (SkyandTelescope.com , NightSkyMag.com ). His column appears the first Saturday of every month. 
