This is no ordinary rock. It’s the surface of a comet somewhere between Jupiter and Mars, and it took a European space probe known as Rosetta 10 years to get there before it sent back these unprecedented images today.
Rosetta took these pictures after a series of maneuvers in which it fired thrusters to position itself less than 100 kilometers above the surface of the comet, known as 67P/Churyumov-Gerasimenko. The crucial next step is expected to come in November, when Rosetta will send down a lander to the surface. Scientists hope the lander’s explorations will yield clues not only about this particular comet, but also about the role such chunks of rock and ice have played in celestial history. In the words of my friend Berndt Feuerbacher, a German scientist who is a former president of the International Astronautical Federation: “Comets are relics from the origin of our solar system, kept in a kind of cosmic deep freeze far beyond the outer planets, unchanged in 4.5 billion years.” They provide “a unique opportunity to learn about how our sun, Earth, planets, and even life began.”
The last seven months have been the most critical time in the €1.3 billion project. Before January, Rosetta had spent almost three years in hibernation: it was almost entirely shut down while it was too far from the Sun to draw enough energy for charging its batteries and keeping its instruments running. It drifted instead with the gravitational pull of the Sun and planets.
On that day in January, it was time to begin maneuvering toward the comet. Inside the European Space Agency’s operations center in Darmstadt, Germany, tension grew at the appointed time for Rosetta’s awakening. The scientists would know it had happened when a flat signal on a green monitor finally showed a peak. But 20 minutes after the scheduled time, there was nothing. Feuerbacher told me that there was a deep silence in the room. The European astronaut Thomas Reiter sent Feuerbacher a text message: “Are we a bit late Berndt?”
“Wait, Thomas, wait,” Feuerbacher says he replied. “It’s so far away and has many things to do before telling us she is awake. Open panels, heat up a bit, point its antenna toward Earth, trying to convey, and maybe it fails at the first attempt.”
When the signal on the screen finally spiked a few minutes later, applause burst through the hall. Operations staff put their fists skyward and hugged each other.
After Rosetta’s lander, known as Philae, plunges to the surface of the comet in November, its biggest challenge will be staying there. A comet has such little gravity that Philae could easily bounce from its surface and back into space. But Philae has an anchor to bite into the comet’s surface—a moment that will have everyone in the Darmstadt center holding their breath again.
Alessandro Ovi is the publisher of the Italian edition of MIT Technology Review and has been an advisor to the European Space Agency.