A lot has been made this week of the successful reawakening of the European Space Agency’s Rosetta spacecraft. Rosetta was launched in 2004 to rendezvous with the comet 67P/Churyumov-Gerasimenko. The long chase took it beyond the orbit of Jupiter, and because Rosetta is solar powered it was put into hibernation in June 2011 to save energy. Now that Rosetta has come back closer to the sun (673 million kilometers) there’s enough sunlight to run the spacecraft and ESA scientists waited breathlessly this past Monday to see if the probe’s alarm clock would successfully wake it up again. Rosetta still has a long way to go to catch up with the comet. If all goes well, it’ll make a major course alteration in May, rendezvous with the target in August, and then the lander portion of the spacecraft will land on the comet itself on or about November 11th, 2014. That’s a big deal. There have been fly-bys past several other comets over the decades, but this will be the first landing, the first really good chance to have a look around and analyze samples. That’s important, not just to satisfy our curiosity, but to answer some key questions with practical applications.
My interest in comets was probably peaked as a kid reading Jules Verne’s novel Hector Servadac, also called Off On A Comet. Of course, it wouldn’t actually be possible for a comet colliding with the Earth to scoop up some humans—alive—and allow them to survive throughout a two-year orbit and return safely to Earth. But I loved the adventurous potential of the story, and have even written a (so-far-unpublished) novel inspired by it. As for the reality, there’s lots of inspiration there, too.
We already know that comets are mostly made up of water ice, dry ice (frozen carbon dioxide), and dust. While we look at asteroids for the mining of raw metal ores, their lack of an atmosphere is a big impediment if humans are to work them. All of that ice in comets, on the other hand, could be a ready source of atmospheric gases for human bases on asteroids or in open space. Maybe even more important, that ice can be broken up into hydrogen and oxygen and provide rocket fuel in huge quantities. It’s far too expensive to hoist much fuel out of Earth’s gravity, so there have long been plans to mine ice on the Moon for that purpose. But imagine a huge chunk of raw fuel material already in space, and maybe even going roughly in the direction we want it, say, toward the asteroid belt. We could maneuver the comet by using its own fuel. Comets have already been observed undergoing course changes driven by rockets of their own: powerful bursts of CO2 jetting outward from pockets of dry ice melted by the sun’s heat.
Sure, it’s not quite as simple as just steering a giant cosmic gas station all over the sky, but a carefully-calculated orbit change could certainly place a comet in the neighbourhood of a promising asteroid swarm. Some have even suggested that comets could be used to help provide an atmosphere for Mars so humans could eventually colonize it. And all of these plans depend on learning more about these celestial wanderers through missions like Rosetta.
One thing, though: hijacking and using up a comet for our own purposes would remove one of Nature’s most spectacular shows for future generations. Maybe they’ll forgive us when we can offer them a vacation on scenic Mons Olympus?