'I have seen some incredible sights,' said final e-mail

"This was definitely one to beat all," Laurel Clark said in an e-mail to her friends and family a day before she died in the Columbia disaster. She had travelled to the ocean depths as a submarine doctor and dived in Scotland with elite US Navy Seals. But nothing could match the glory and majesty of space.

"I have seen some incredible sights: lightning spreading over the Pacific, the Aurora Australis lighting up the entire visible horizon with the cityglow of Australia below, the crescent moon setting over the limb of the Earth, the vast plains of Africa and the dunes on Cape Horn," the e-mail said.

Then there were the "rivers breaking through tall mountain passes, the scars of humanity [and] the continuous line of life extending from North America, through Central America and into South America." Mount Fuji in Japan "looks like a small bump from up here, but it does stand out as a very distinct landmark".

Mrs Clark even managed a fleeting glimpse of her native Wisconsin: "Magically, the very first day we flew over Lake Michigan and I saw Wind Point [near the lakeside town of Racine where she grew up]. The perspective is truly awe-inspiring.

"Every orbit we go over a slightly different part of the Earth ... Whenever I do get to look out, it is glorious. Even the stars have a special brightness. I have seen my 'friend' Orion several times. Taking photos of the Earth is a real challenge, but a steep learning curve. I think I have finally gotten some beautiful shots the last two days. Keeping my fingers crossed that they're in sharp focus."

Soon she would be re-united with her family. Mrs Clark, 41, who joined Nasa in 1996, carried aboard the shuttle a sheet of paper with the photographs and fingerprints of her eight-year-old son, Ian, and his classmates in Houston, where she lived with her husband, Jonathan.

In her last message she wanted to reassure them. "My near vision has gotten a little worse up here so you may have seen pics/video of me wearing glasses. I feel blessed to be here representing our country and carrying out the research of scientists around the world. All of the experiments have accomplished most of their goals despite the inevitable hiccups that occur when such a complicated undertaking is undertaken."

Martha Wilson, Mrs Clark's room-mate at the University of Wisconsin, told The Washington Post: "I heard her speaking to mission control on the internet. There was a smile in her voice and I knew she was loving every minute of it."