I had planned to publish this article tomorrow. Alas, @ESA_Rosetta tweeted an adorable Rosetta / Philae Christmas cartoon today that convinced me this article should have a December 25 publication date:
Merry Christmas from #67P, 527 million km from Earth! pic.twitter.com/NhUJAzi7Aq
— ESA Rosetta Mission (@ESA_Rosetta) December 25, 2014
The European Space Agency's Rosetta mission to comet Churyumov-Gerasimenko (aka 67P) launched in 2004 and arrived at its destination earlier this year. One of the mission's first surprise findings came when Comet 67P - assumed to be potato-shaped - resolved to look more like a... rubber duck! Comet 67P is two-lobed, with one lobe distinctly smaller, giving it a familiar shape in human terms. Certainly, "the rubber duck comet" is a less challenging name to pronounce than "comet Churyumov-Gerasimenko!
Above is a full color image of Comet 67P/Churyumov-Gerasimenko that Rosetta took last August through red, blue and green filters. This is how the comet would appear to human eyes, revealing that it is... gray. When this picture was taken, Rosetta was about 120 km (75 mi) distant from Comet 67P, before Philae was deployed. The comet's uniformly gray appearance suggests that any water ice it contains is distributed more or less evenly throughout the comet's two lobes. If there were alternate patches of all-water ice or all-rock we would expect some areas of the comet surface to be brighter than others. The black areas are shadows caused by sunlight streaming across a surface full of steep cliffs and boulders.
Most recent image of Comet 67P taken December 16 by Rosetta, orbiting the comet, with Philae on the surface.
Simulation of Philae on the surface of Comet 67P - Philae is wedged sideways between the base of a cliff and a large rock outcropping, with one of its legs stuck between rocks. After its initial comet touchdown, Philae bounced twice before coming to rest in its current position. Philae was meant to fire harpoons upon landing to anchor itself to the comet and deploy screws in its feet to secure itself in place during its trip around the sun.
These are Philae's 10 science instruments. It is currently unknown to which extent some or all of them can be used during the primary science mission. Philae is now in hibernation mode, as it is stuck in an area of the comet surface that gets only a few hours of sunlight per day - not enough to wake the probe from hibernation. This may change as the comet approaches the sun in coming months. If Philae can be roused from its deep sleep, we may yet obtain a treasure trove of data about what happens when comet 67P approaches perihelion.
For now, let's keep in mind that Philae has been functioning at only a fraction of its intended capacity and yet was already able to return an incredible set of never-before-seen comet data.
Philae's very first picture is a bit of a blur since the lander was bouncing at the time.
Comet close-up: Photo of the cliff right in front of Philae that is blocking its sunlight. The image reveals a number of fissures and fractures. The reflective glare on the rock is caused by the lander.
In addition to data that Philae may yet collect on the comet surface, the Rosetta spacecraft continues to accompany 67P and Philae as they journey towards the inner solar system. Rosetta will orbit the two-lobed comet at altitudes of as little as 6.5 km (4 mi). Already Rosetta has returned spectacular images such as the above - cometary cliff faces that are more than half a mile high (ca.1 km). The whole comet is about 4.5 km (2.8 mi) wide, measured duck head to duck tail.