By Paul Rincon
BBC News science reporter
Crew members who flew on space shuttle Discovery have been reflecting on the events of their historic flight into space.
Commander Collins said space exploration must go on
The astronauts told a packed press conference at Edwards Air Force Base in California of the wonder and the challenge of their 14-day mission.
The shuttle's commander Eileen Collins praised her crew and said it was "absolutely fantastic" to be back on Earth.
But she added it had been a "bittersweet day", in which her crew had remembered the seven astronauts who died in the Columbia accident and their families.
This was the first shuttle flight since Columbia broke-up trying to re-enter Earth's atmosphere from space in February 2003.
But Discovery's crew agreed that space exploration must go on. The astronauts looked exhausted, yet could not hide their exhilaration after spending two weeks floating 355km (220 miles) above their home planet.
"I feel like going back into space tomorrow," exclaimed mission specialist Soichi Noguchi, who was on his first mission into orbit.
Commander Collins added: "This experience we had was an absolutely wonderful, breathtaking challenge. It was a huge achievement, but just being in space - the human side of being in space - is something I wish I could share with all of you."
Room with a view
The view was sometimes too much to take in, even for experienced members of the crew.
""At night we saw the southern lights, and we flew through the aurora. Beautiful moving lights and colours, sunlights and sunsets," she told reporters.
The prime viewing position even allowed astronauts to see dramatic changes to the Earth as a result of human activity.
Sunrise on Earth, as viewed from the shuttle
"In Africa, I saw massive burning in the central part. We flew over Madagascar, we saw deforestation there. The rivers and streams that normally would be a blueish grey colour are now brown from the erosion of soil," said Commander Collins.
Despite the perfect landing, the mission was beset with problems. Not least of which was a near miss by a suitcase-sized piece of foam shed from Discovery's external tank during launch.
This was the same problem that doomed Columbia; in 2003, a foam chunk only slightly bigger than this came away from the tank on lift-off and punched a hole in its wing.
It allowed super-heated gases to enter the wing when Columbia attempted to return to Earth on 1 February 2003 and tear the orbiter apart.
Two-and-a-half years' work and $1.4bn were supposed to have fixed the problem. Nasa's shuttle fleet has been grounded until an agency "tiger team" has found a solution.
Mission specialist Stephen Robinson was also forced to make an unprecedented spacewalk to pull out two ceramic strips sticking out from beneath the shuttle which could have caused overheating.
The astronaut was carried to Discovery's belly strapped on to the space station's robotic arm: "The operation itself was very simple, but we had to be very careful. [Crew member] Wendy Lawrence was flying the arm using camera views - she has no windows. It was like flying a jet by watching TV," said Robinson.
The astronauts had to admit that the memory of Columbia had, at times, weighed heavy on their minds.
Stephen Robinson made unprecedented repairs to Discovery
Pilot James Kelly admitted he had watched some shuttle systems displays for longer than normal during the return home to look for warning signs of the same phenomena that fatally affected Columbia on its descent.
Kelly also revealed the answer to one of the biggest mysteries of the mission; where he got his nickname "Vegas". Apparently, he had had some luck at cards during downtime as a US Air Force pilot stationed in South Korea - a more mundane explanation than some had hoped.
This was the sort of press conference where the questioning could have gone on all night.
One journalist even touched on religion, asking whether the crew members thought luck, prayer or other forces beyond Nasa's control had saved them from a collision with the largest chunk of foam debris from the external tank during launch.
Collins and mission specialist Charles Camarda carefully sidestepped any suggestion of divine intervention, but many in Nasa will be praying for a swift fix to the foam debris problem so that its fleet can begin flying again.
Commander Collins admitted the shuttle, which made its maiden flight in 1981, was showing signs of its age. But conscious of the criticism, she made an impassioned plea for public support of human space exploration.
"Some people say we should stop flying the shuttle because we've had an accident - frankly two accidents," she said.
"I ask you to please support it, it's very important to us... space exploration is a fantastic part of the human experience."
One day, Collins added, the shuttle would fly its last mission. Despite the arguments against continuing the programme, Nasa is determined that this will not be it.
Five out of Discovery's seven crew members attended the press conference: Collins, Kelly, Robinson, Noguchi and Camarda. Wendy Lawrence and Andy Thomas were absent, said to be undergoing medical tests.