The European Space Agency (ESA) will make history at around 1600 GMT (Thursday midnight, Singapore time) if its three-legged space robot successfully latches itself onto a comet that is hurtling towards the sun.
The ESA's Rosetta probe will release a lander, called Philae, on Wednesday at 0835 GMT (4.35pm Singapore time) at an altitude of 20km above the comet 67P/Churyumov-Gerasimenko, the BBC reported. Touchdown is expected about seven hours after the separation and confirmation of the landing is expected at around 1600 GMT.
Philae is a 100kg science lab that has been piggybacking on its mothership Rosetta since the pair were launched more than a decade ago.
It is designed to detach from Rosetta and land gently on 67P/Churyumov-Gerasimenko, a comet that is now more than half a billion kilometres from Earth and racing towards the Sun, according to the Agence France-Presse.
Astrophysicists hope Philae will survive the perilous descent and use its kit of 10 instruments to analyse the comet's ice and dust - the primeval remnants of the material that built the Solar System some 4.6 billion years ago.
The outcome could confirm, or demolish, a theory that comets pounded Earth in its infancy, bringing it water that became the oceans and carbon molecules that were the building blocks of life.
"This is the first mission that puts a lander down on a comet, so there are a lot of new opportunities to do science," said Gerhard Schwehm, a consultant and manager of the mission from its liftoff until he retired from the space agency last year.
"We will not find life, and we won't be able to answer the question tomorrow how did life emerge on Earth. But if we see organic molecules, we can say 'Oh, the comets could have brought very complex molecules to the early Earth.'"
Watch the video of the Rosetta Mission here.