Launched in 2004, Rosetta has spent the past few years in hibernation as it chased the comet across the Solar System. In January of 2014, with its destination in sight, Rosetta woke up and turned on its cameras. At first, the comet looked like a dimensionless pinprick, inactive except for its quiet motion through space. Then, on May 4th a bright cloud appeared around the nucleus.
Holger Sierks of the Max Planck Institute for Solar System Research in Germany explains:
“A flyby is just a tantalizing glimpse of a comet at one stage in its evolution,” points out Alexander. “Rosetta is different. It will orbit 67P for 17 months. We’ll see this comet evolve right before our eyes as we accompany it toward the sun and back out again.”