With a long yawn, Rosetta woke up from a luxurious nap. After over 30 months of snoozing, the orbiter was finally close enough to the sun to warm up and power back up. A few sleepy physical adjustments later, she sent a signal home to Europe that she was back on track to meet with her target, a lonely comet.
It took 10 years and a gentle hand from Earth and Mars’ gravity to get there, but Rosetta didn’t just sleep till she arrived. Despite her long deep-space hibernation, she made a few scenic stops en route to her waiting companion, comet 67P/Churyumov-Gerasimenko.
Here’s what she saw:
Boring old Earth and Mars
Credit: ESA/Rosetta mission
OK, so they’re not boring — it’s just that we’ve seen them before. But Rosetta’s treks past us weren’t for sightseeing. Since the orbiter couldn’t make a straight shot to comet 67P, she needed an extra kick from the planets’ forces, known as a gravity assist. This flyby technique can propel or slow down a craft and take months of planning as velocity and directions are tweaked.
Rosetta, for instance, suddenly had to adjust to its new trajectory when it was required to spend 24 minutes in Mars’ shadow. The craft had been taught to react to an absence of sunlight, and the team had to reprogram her to stay calm during that short dark period. (She did.) Rosetta passed by Earth three times and Mars just once.
A diamond in the sky, with Lucy nowhere to be found
Credit: ESA 2012 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/
To practice using the craft’s instruments, Rosetta’s operators guided her past an asteroid for her first flyby — an asteroid discovered in the golden year of 1969. In Earthly terms, asteroid (2867) Steins is a honker of a rock, measuring about 3 miles across (or 5 kilometers). But in space, it’s petite, considering some asteroids are big enough to have their own moons.
Rosetta’s OSIRIS camera captured Steins’ grooved surface, pocked with two craters, in 2008. Trouble was, one of the cameras stopped its observations just minutes before Rosetta’s closest approach, so what we see above is what OSIRIS’ other, wide-angle camera saw at that time. Though the rock and its images are rough around the edges, Steins’ resemblance to a diamond led astronomers to cheerily name its craters after gemstones and other precious minerals.
Ancient space warrior, Lutetia
Credit: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/
Steins’ semi-successful flyby led to some tinkering to get used to Rosetta’s quirks, and the next rendezvous two years later was considerably juicier. The flyby was past a massive asteroid that would require another 40 minutes of a communication halt with Earth to collect images, but the risk paid off: Lutetia was beamed back in brilliant detail.
Lutetia was huge, measuring 80 miles (130 km) in across — and spectacularly old at the ripe age 4.5 billion years old. Coated in craters, it had clearly seen better days. Since its discovery in 1852, the asteroid had been a bit of a mystery. But Rosetta’s close-up showed Lutetia was a remnant from the solar system’s vicious early days, a primitive souvenir from our beginnings that we are humbled to sightsee.