What happens when you make a low-level flyby of a cometary nucleus?
You get jaw-dropping images.
The above 2-shot mosaic of Comet 67P/Churyumov-Gerasimenko was taken by ESA’s Rosetta orbiter at an effective altitude of just 19.9 kilometers. The resolution is a crisp 1.7 meters per pixel and this frame spans a region of about 3 by 1.7 kilometers. Click on the image to get a larger version.
To illustrate the level of detail, here’s a closeup of one region. The smallest ‘boulders’ on the smooth terrain here are a few meters across. An astronaut standing on this surface and casting a shadow would probably be visible as a 2-3 pixel feature.
Surface features are not all that Rosetta has been seeing. Comet 67P is still about 300 million kilometers from the Sun, it won’t reach perihelion at about 185 million kilometers until August 2015. But things are definitely starting to heat up for the cometary nucleus. The 18 images below span the time from the 31st of January (upper left) to the 25th of March 2015 (lower right) – from 363 million kilometers heliocentric distance to 300 million kilometers.
Jets of sublimated material are already streaming off the surface, carrying tiny solid grains along for the ride and contributing to the solar system’s vast, but tenuous, disk of interplanetary, or zodiacal, dust. This material also poses some significant challenges to Rosetta’s movement and navigation – resulting in a recent hiccup during a flyby.
And on April 15th this remarkable image was taken at 162 km out (14 meters per pixel) – a cometary ‘crescent’.