Washington: NASA on Wednesday hailed the first-ever landing of a spacecraft on a comet as a "breakthrough moment" in the history of space exploration.
The European Space Agency`s Philae lander detached from the Rosetta spacecraft and touched down on the comet 67P/Churyumov-Gerasimenko, in a complicated maneuver that some experts likened to a bullet meeting another bullet in space.
"We congratulate ESA on their successful landing on a comet today," said John Grunsfeld, astronaut and associate administrator for NASA`s Science Mission Directorate.
"This achievement represents a breakthrough moment in the exploration of our solar system and a milestone for international cooperation."
He also noted that three US space agency instruments are on board Rosetta to map the comet`s nucleus and search for signs of water.
"We are proud to be a part of this historic day and look forward to receiving valuable data," he said.
The 100-kilogram (220-pound) lander separated from its mother ship, Rosetta, after a trek lasting a decade and covering 6.5 billion kilometers (four billion miles).
But the announcement was soon followed by worries that Philae may have landed in soft material and was not properly attached.
