The Rosetta spacecraft has recorded a "selfie" of its own shadow, projected on the surface of Comet 67P Churyumov-Gerasimenko (67/P). The shadow was the result of the Sun being directly behind the spacecraft when the image was recorded of the icy body.
The Optical, Spectroscopic and Infrared Remote Imaging System (Osiris) was used to record the photograph, which was exposed on February 14, 2014. When the photograph was taken of the comet and Rosetta's shadow, the vehicle was just over 3.6 miles above the surface of the comet. This low altitude allowed for a resolution of slightly over four inches per pixel. Just three days later, the cometary orbiter had traveled to 158 miles away from the icy body. The surface of the comet was examined again, on February 28, from 69 miles away from 67/P.
"An image with this arrangement of the light source and camera really reveals the differences in brightness on the comet's surface. As there are no shadows, this difference must be due to the scattering of the light by the dust particles across the comet's surface," Ekkehard Kührt, from the German Aerospace Center, said.
By studying light and dark regions in the photograph, it is possible to determine the size of dust particles, despite the fact they are far too small to be resolved by the camera.
The fissure seen in the image was nearly directly below the spacecraft when the picture was taken. Because of the alignment, it is almost impossible to tell how far under the surface the crack extends.
Some astronomers are calling this region of the comet Imhotep, after the first known architect and engineer in Egyptian history. The Philae lander, which touched down on the comet, after a few unintentional bounces, is on the other side of the icy body. Images from Philae taken from the surface of the planet show the surface at a resolution of 25 pixels per inch. Researchers hope analysis of the Philae images and data will help answer questions about the inner structure of 67/P, revealing previously-unknown details of the makeup of comets. Early analysis of these high-detail images will be released by investigators in April 2015.
The Rosetta spacecraft was launched on March 2, 2004, and became the first spacecraft to orbit a comet. The vehicle is managed by the European Space Agency (ESA). On its way to the comet, the vehicle was able to examine the planet Mars, as well as two asteroids, 21 Lutetia and 2867 Šteins. The vehicle arrived at the comet on August 6, 2014.
