If so, how would Earthlings find out about it? While we may be stuck on Earth (most of us, that is), humans have thought up some creative ways to dissect comets and figure out what they're made of. Perhaps the most powerful tool is spectroscopy (defined). While comets are indeed distant, they do reach out and touch us in the sense that they radiate and reflect light. Scientists have learned how to sample the spectrum (defined) of this light and obtain a "fingerprint" of the elements that exist in the body that's radiating or reflecting light.
This is how we know comets are made of different kinds of ices (defined). Each ice -- frozen water, carbon dioxide, ammonia or methane -- has a distinct chemical signature that can be detected and read via spectroscopy (that's how we found poisonous cyanogen gas in Halley's tail).
But wouldn't it be cool to get our grubby mitts on some comet dust? U bet. Been there. Done that. And with a U-2 (not the band). This plane, initially developed for espionage, can fly way above the pollution in our atmosphere. Once U have a U-2, all you need to do is attach sticky plates to it, and you can obtain comet dust for analysis. These studies have helped astronomers further refine the chemistry of comets -- and gain some insight into the chemical state of our early solar system.
What's next with comet science? In 2003, the European Space Agency will launch its Rosetta mission. This spacecraft is to meet Comet Wirtannen as it approaches the sun in 2011, and fly alongside it through perihelion (defined) in 2013. Rosetta will carry two landers to directly sample the comet's surface and radio the results back to Earth. Jules Verne, are you reading?
