Washington: Wide range of experiments devoted to medicine, biology, physics and earth observation on board space shuttle Columbia have run their course, as the research mission completed 12 days in space.

India-born astronaut Kalpana Chawla and first time Israeli astronaut Ilan Ramon successfully completed over 39 trials of the 'structure of flame balls' experiment using 15 different fuel mixtures.

In all, tiny fires continued to burn for over six hours with the longest flame burning for nearly 80 minutes. The experiment uses the least amount of fuel to burn fires for longer duration of time and is aimed at developing fuel-efficient car engines, National Aeronautics and Space Administration (NASA) said.

Chawla was also responsible for 'mechanics of granular materials' test that completed its 10th and final run. The test will further the understanding on how granules behave under microgravity environment and help develop new techniques to build stronger houses in areas prone to quakes and landslides.

Other experiments that concluded include the ones dealing with the growth of yeast and bacteria in zero gravity, and the study of bone cells' reaction to weightlessness.

The spacefarers aboard Columbia and the International Space Station took time out from their observations to have a chat via radio about their families and work schedules.

"We're really excited to be able to talk to you guys, one space lab to another big old space lab on that beautiful station of yours," Columbia commander Rick Husband told the Space Station crew.

"It's been great to hear all the good science you're doing," replied space station commander Kenneth Bowersox.

PTI