In a remarkable milestone in space exploration, the European Space Agency (ESA) has succeeded in landing a spacecraft on a comet! Or to paraphrase comic artist Matthew Inman: it still takes most of us multiple attempts to parallel park our cars, yet some folks just used rockets, harpoons and math to land on the surface of a comet! A 10 trillion kilogram chunk of rock, dust and ice; only a couple kilometres across, yet 500 million kilometres away, and moving at 135,000 km/h. And some scientists managed to land a little probe (the size of a refrigerator) on it! No wonder one scientist called it “the most difficult space landing in history”.

ESA’s Rosetta spacecraft (plus robotic lander module Philae) was launched more than 10 years ago. It reached comet 67P/Churyumov–Gerasimenko about three months ago - becoming the first spacecraft to orbit a comet - and yesterday, lander Philae touched down safely on the comet’s surface. Well, “touched down” is perhaps not an accurate description: it seems it bounced twice and landed three times - the first bounce lasted two hours and may have been a kilometre high! Nevertheless, the robotic craft appears to be safe, and is sending images back to Earth.

Together with Rosetta, Philae will complete the most detailed study of a comet ever. Apart from many other experiments, Philae will be searching for complex organic compounds (molecules rich in carbon, hydrogen, nitrogen and oxygen) - some of the building blocks of life. Comets are thought to have delivered a vast quantity of water to Earth, and they may have also seeded Earth with organic compounds.

What an impressive achievement - and what an exciting time for astronomy and space exploration!

PS: see here for a selection of cool pictures related to the landing.