Last week, 10 years after the Rosetta spacecraft set off on a journey across the solar system, scientists at the European Space Agency announced that it would drop its lander Philae onto 67P/Churyumov-Gerasimenko, a comet it encountered in space in August 2014, and piggyback it as the comet hurtles towards the Sun. Strap in, this is one rough ride. Rosetta who? Launched in March 2004, Rosetta, named after the Rosetta Stone, was reactivated after a record 957 days in hibernation. Composed of an orbiter and lander, Rosetta’s objectives are to study comet 67P in unprecedented detail, prepare for landing the probe on the comet’s surface, and track the comet’s changes through next year using its 21 scientific instruments to document how the comet changes and reacts to a close encounter with the sun. The resulting data will help scientists learn more about the origin and evolution of our solar system and the role comets may have played in seeding Earth with water, and perhaps even life. Just a week ago, Rosetta took a selfie of itself in deep space. It was taken on September 7 with a CIVA camera on Philae, from a distance of 50 km from the comet. The comet 67P Rosetta made history last month when it entered orbit around 67P, the duck-shaped comet that’s 4-km wide. n 67P, whose surface temperatures go down to minus 70°C, has a terrain so uneven that Philae will have to brace for a very rough landing. Rosetta has already captured detailed views of the comet’s landscape — its jagged cliffs, craters and boulders — helping scientists draw their first map of the celestial object. Landing Philae Scientists have named five provisional sites on the comet where Philae will land. The primary site, Site J, is on the head of the comet and offers “unique scientific potential, minimum risk to the lander, good illumination”, ESA said. But it is near two active, gassy pits. The backup site, C, is on the body of the comet. As it approaches 67P, Philae will fire a set of harpoons and tether itself to the frozen surface. Once parked, it will begin collecting scientific data almost immediately, and spend the next several months studying the material both on and beneath the comet’s surface. But since the comet is so far away, scientists won’t have control over the landing. Instead, the commands will be programmed and updated ahead of time. The whole separation, descent and landing procedure is expected to take seven hours.
