The European Space Agency has described the landing of its Rosetta probe on the comet 67P/Churyumov– Gerasimenko as “a big step for human civilisation”. Neil Armstrong, who took “a giant leap for mankind” in 1969, would have marvelled at the cautious understatement, for the mission has taken space science to a new frontier. This is the first attempt to orbit and land instruments on a space rock at almost zero gravity. Though the lander may not have grappled itself securely to the surface, the manoeuvre was accomplished. Besides, though space probes have made contact with comets before, this will be the first full contact study of a comet.
In 2005, Nasa’s Deep Impact had lobbed a block of metal into the comet 9P/Tempel 1 to analyse the vapours and dust it raised. The next year, Nasa’s Stardust mission brought back samples and data from the comet 81P/Wild 2 and the asteroid 5535 Annefrank. Astronomers have wanted to know what comets are made of from the earliest times, and contemporary opinion has been divided on whether they are dirty snowballs or icy dirtballs. But now, the question is much larger: could comets have delivered the makings of life to earth?
Complex organic molecules, the precursors of genetic material, are believed to have been synthesised from a “primordial soup” in the earth’s oceans, using energy from lightning. However, comets like 67P hold ice and, if they are found to contain long-chain molecules too, they can provide an alternative explanation for the origin of life. The Rosetta lander, which is equipped with a lab-load of instruments for testing the surface and contents of the comet it has landed on, will help humanity to take “a big step” not only in space science, but also in understanding its own origins.