Shuttle Crew Stows Its Gear for a Florida Landing Today : Space: But clouds, wind could postpone Columbia’s touchdown. Delays could make it the longest mission.

Kathryn Thornton said Saturday that she and her fellow astronauts aboard the space shuttle Columbia “have put our toys away” as they shut down experiments to get ready to end a 16-day mission.

Columbia is scheduled to land at Kennedy Space Center at 3:45 a.m. PST today if it can zoom through low-lying clouds and wind gusts following a cold front. Another landing chance occurs a couple of hours later.

“We’ll just be watching the winds tomorrow,” said Lee Briscoe, mission operations director.

As ground controllers eyed the weather, astronauts began stowing their gear and deactivated experiments.

“We have put our toys away,” Thornton told a ground controller.

Thornton is the mission’s payload commander in charge of the key experiments aboard the orbiter.

Also Saturday, astronaut Al Sacco deactivated a furnace aboard the spaceship in which more than three dozen crystals had grown.

Sacco said the samples looked good. He is principal investigator for the growth of crystals that can act as catalysts and filters in chemical processing. Purer crystals could one day lower the cost of refining gasoline, oil and other petroleum products, researchers said.

Other shuttle experiments have included studies of combustion and whether the starches some plants produce are diminished in the near-weightlessness of space.

If the shuttle cannot land in Florida today, NASA will try for a Monday landing in Florida with Edwards Air Force Base in California as an optional landing site. The shuttle will not try to land at Edwards today.

Briscoe said the spacecraft has enough food and fuel to stay in orbit through Wednesday.

But he said the flight will not be prolonged beyond Tuesday.

A delay could send Columbia into the record books as the longest mission ever, beating a record of 16 days and 15 hours set earlier this year by Endeavour.