BERLIN: Scientists are saying their final farewells to the Rosetta space probe ahead of its planned crash-landing on a comet.

The probe was launched in 2004 and took a decade to reach comet 67P/Churyumov-Gerasimenko, where it released a lander in November 2014.

Both Rosetta and its lander Philae have gathered a wealth of data about 67P that have already given scientists significant new insights into the origins and nature of comets.

The European Space Agency plans to steer the probe towards the comet as slowly as possible on Friday so it can take unprecedented close-up images before colliding with the icy surface.

Scientists involved in the project said on Thursday that — even after Rosetta goes silent — they have decades of work ahead of them analysing all the data collected during the mission.

Scientists were astonished to find oxygen molecules in the gassy halo around the comet, and said they appeared to be older than our Solar System.

Scientific models had previously calculated that oxygen as a molecular compound on its own would not have existed at the time the comet was formed, as it would have bonded with other elements like hydrogen. So, how the comet got its oxygen remains a mystery.

Published in Dawn, September 30th, 2016