It was the moment science fiction became science fact.
With minute-perfect accuracy, scientists landed a probe on a comet following a 10-year, four-billion-mile journey through the solar system.
There were scenes of joy in the control centre yesterday as the spacecraft made history by becoming the first man-made object to touch down on a comet.
The European Space Agency had predicted that the first signal would arrive back on Earth at 4.03pm confirming that + had touched down after being detached from its mother ship Rosetta.
And at 4.03pm the instruments at the control centre in Darmstadt, Germany, sparked into life as the probe made contact, and furrowed brows were replaced with beaming smiles and tears.
"We are on the comet," announced Dr Stephan Ulamec, Philae's lander manager. "We are sitting on the surface and Philae is talking to us."
Initial jubilation was followed by anxiety, however, when it emerged that the probe's landing harpoons had not activated, meaning that it was simply sitting on the soft surface without being securely attached. Data received at the control centre suggested that Philae might have "bounced" and may be sitting precariously on the comet's surface after "landing twice".
Dr Ulamec added: "It's complicated to land on a comet. It's also complicated to understand what has happened during the landing.
"What we know is that we touched down and we landed on the comet. We had a very clear signal and we also received data from the lander. That is the very good news.
"The not-so-good news is that the anchoring harpoons did not fire. So the lander is not anchored to the surface. Did we just land in a soft-sand box and everything is fine? Or is there something else happening. We still do not fully understand what has happened.
"Some of the data indicated that the lander may have lifted off again...So maybe today, we didn't just land, we landed twice."
Scientists had already spent a nerve-racking 24 hours before the landing trying to work out why Philae would not power up after its 10-year slumber in space. They also realised that the thrusters, designed to help the probe stay on the surface before the anchors were deployed, were not working at all. Without the thrusters, it was feared the probe would drift off into space.
Despite the concerns, they decided to go ahead with the detachment at 8.35am yesterday. The probe made a perfect seven-hour descent on to comet 67P/Churyumov-Gerasimenko.
But last night, scientists were facing the agonising decision of whether to attempt to activate the anchors again and risk pushing the craft back into space, or leave the probe untethered.
Yet the science community was in firm agreement that the €1.6bn mission had been an incredible success.
"It is a milestone for space exploration," said Prof Tom Marsh of the University of Warwick's Astronomy and Astrophysics group. "An incredibly difficult task successfully accomplished at a distance of 520 million miles. It does not get much better than this."
Since it was launched in 2004, Rosetta has travelled four billion miles in its quest to find out, among other things, whether comets could have created life on Earth by bringing water and amino acids. (© Daily Telegraph, London)