One of Philae's first images of the surface of its new home, comet 67P/Churyumov-Gerasimenko
Let's recap. Rosetta and Philae spent the last decade hurtling toward a relatively tiny, moving target at a distance of almost 600 million kilometers, course-correcting four times thanks to the gravitational influence of both Earth and Mars, successfully rendezvousing with said comet, carrying out the prescribed launch sequence, free-falling for a nail-biting 7+ hours, and finally, actually touching down on the surface in the exact spot that had been planned. Philae's initial touchdown was unexpectedly brief, however, due to the failure of its harpoons to fire and anchor it to the surface. The probe bounced three times before submitting to the feeble gravitational influence of 67P; by this time, the comet had rotated in such a way that Philae ended up resting in the shadow of a cliff, kilometers away from its planned destination. Even with a successful nudge toward a brighter area, the probe's batteries will probably lack sufficient sunlight to maintain their charge and will likely run out of juice sometime on Saturday, November 15th. Battery failure could spell the end for Philae, but all is not lost! Scientists at the European Space Agency (ESA), the organization behind the mission itself, estimate that Rosetta's landing probe will have collected and transmitted 80-90% of its data by the time its batteries are completely drained.
So what kind of data is Philae collecting, and how will the Rosetta mission help us to understand our place in the Universe? First, Philae's ten scientific instruments will tell us more about the chemical composition of 67P at varying depths, as well as its temperature, density, and magnetic properties. Complex imaging equipment has already begun returning photographs of an alien surface humankind has never seen before. Secondly, the Rosetta spacecraft will continue to orbit the comet even after Philae ceases its transmission. Over the next year, the spacecraft will accompany 67P as it approaches perihelion, or the point in its orbit when it is closest to the sun. As the comet swings through the inner solar system, Rosetta will monitor and record its increased surface activity in order to better understand what happens when comets are heated by the sun's thermal energy. Together, both Rosetta and Philae will assist scientists in building a more accurate and comprehensive picture of the physics and chemistry of comets. These insights may go on to inform theories about the origin of water and/or life in our solar system, which often feature comets as central players.
Despite their prominent role in human legend, comets have actually remained fairly mysterious to astronomers throughout history; however, thanks to modern science, Philae and Rosetta are set to revolutionize our understanding of both these icy bodies and their potentially illuminating role regarding the evolution of our planet and wider solar system. Whether Philae will be brought to life again at some sunny time in the future or whether it will soon go to sleep forever, it has done a superb job epitomizing the human drive toward adventure and discovery.
Three cheers for Philae, and for these few truly monumental days in scientific history.