The panic was sparked last week by America's Minor Planet Center, which tracks unidentified, Earth-threatening objects.
It prepared an emergency e-mail warning that the alien lump would skim Earth by 5,600km (3,500 miles) – the distance from London to New York and a very close nearmiss in astronomical terms.
But Moscow-based scientist Denis Denisenko realised the mysterious mass was Rosetta, the European Space Agency probe launched in 2004 on a ten-year mission to chase a comet.
(And who built the plasma interface unit on board Rosetta? If you guessed the Imperial College Space Magnetometer Laboratory, you were right. My colleagues, they are made of awesome.)