Many question marks still hover over the future of the US shuttle programme and the international space station with which it is linked. But, for a day at least, those concerns were put aside, as an entire country heaved a mighty sigh of collective relief.
After the anxieties which had dogged the two-week mission, it was a faultless, picture-perfect landing yesterday, as first Discovery's back wheels touched the runway at 5.11am, Pacific Time, then the smaller front wheel made contact, and the braking parachute snapped out exactly as scripted, to slow the craft from more than 200mph to a gradual standstill.
The only change in schedule was caused not by any mishap or malfunction on board but by the vagaries of the weather on Earth. After clouds and storms prevented landing at the intended Florida site, Discovery was diverted to Edwards Air Force Base, 60 miles north of Los Angeles.
But that small modification did not dent the celebrations at Nasa, aware of how much was riding on a successful flight by Discovery. The joy reflected, above all, the return of normality: after a two-and-a-half year lay-off following the fiery disintegration of Columbia as it returned to earth in February 2003, the shuttle was back in business.
Michael Griffin, Nasa's administrator, was almost ecstatic as he delivered a first verdict on what has surely been the most scrutinised of all missions. "The crew performed fantastically well. Everywhere you look there's nothing but outstanding success. This is the first step in the sequence to complete construction of the international space station."
Bill Readdy, the agency's chief of space flight operations struck a similar note. "It's going to be really hard to top this mission," he said, pointing to the unprecedented in-flight repairs to the shuttle, when Steven Robinson, attached to a robotic arm, removed pieces of dislodged filler between the craft's all-important heat-resistant ceramic tiles.
He noted too that Nasa had new data on the problem that led to the Columbia disaster, caused by a piece of insulating foam that broke off an external fuel tank and damaged - fatally, it would prove - the craft's protective tiles.
Despite every effort by technicians to correct the fault, an uncannily similar incident occurred when Discovery lifted off on 26 July. Happily, however, the chunk of foam this time missed the shuttle itself. Nasa engineers will thus have more to work with, as they race to have the next launch as soon as possible.
Precisely when that will be is uncertain. The target date is 22 September, when it is hoped Atlantis will blast off into space. But many experts consider that optimistic, given Nasa's insistence that no shuttle will fly until the foam problem is sorted out, once and for all.
"I'm not going to guess," was all Mr Griffin would say, as he parried a barrage of questions from reporters. But he added: "We're going to try as hard as we can to get back in space this year. We've a big construction programme [at the international space station] and we need the shuttle to do it."
In some respects, the remaining five years before the shuttle is phased out in 2010 amounts to a race against time to complete the space station. Thereafter, the US could be dependent on Russia, a prospect that some here do not contemplate with relish - even though the shuttle, which dates back to the 1970s, and the station, now two-thirds finished, will no longer be the focus of the national space programme.
Under plans unveiled by President Bush in January 2004, the goal is now to return Americans to the Moon by 2020 to establish a permanent base that would be the stepping stone for future manned trips to Mars and other planets.
Setting out what he called a "new course" for the US space programme, Mr Bush said the priority would be a new generation of manned space vehicles designed to be flying with a crew in 2014. A decade and a half after that, some say, a manned mission to Mars will be feasible.
But all that is for tomorrow. For Nasa, and indeed for an entire country that was slightly uneasy over its technological mastery of space travel, the safe return of Discovery was a hard-earned moment of satisfaction and celebration.
Upon disembarking, the seven-member crew first went to inspect the tiles on the underbelly of the craft, the cause of so much concern, and where the repairs were carried out. "It looks fantastic," said Eileen Collins, Discovery's commander. Then it was off from California - this time by conventional flight - to Houston, for debriefing and a reunion with their families.