I blogged about the Rosetta spacecraft in January after scientists at the European Space Agency successfully revived it after most on-board systems had been shut down and it went into hibernation on its long journey to comet 67P/Churyumov-Gerasimenko. Rosetta is now just days away from arriving at the comet, where it will conduct a detailed 17-month study which will include dispatching a probe called Philae to land on the comet’s surface.
At least, that was the plan. But in mid-July, photographs from Rosetta revealed that 67P/Churyumov-Gerasimenko was a contact binary (low resolution image above). What that means is that the comet, which is four km in diameter, is actually composed of two separate chunks. The news caught scientists by surprise, the BBC reported in mid-July, and while it won’t scuttle the mission, it will necessitate some further analysis to get a handle on the comet’s gravitational field to ensure nothing goes wrong with Rosetta and Philae’s missions.
Rosetta had previously detected water vapour coming from the comet. That discovery was made in late June when the comet was 3.9 AU from the Sun. Launched in 2004, Rosetta will complete its 10-year journey when it arrives at 67P/Churyumov-Gerasimenko on Aug. 6. By that point, the comet will be even closer to the Sun and will be outgassing even more as it heats up and that will be studied by Rosetta as well.