Update, Wednesday 11/12: At around 10:30 am ET on Wednesday morning, scientists made history by landing a spacecraft on a comet for the first time ever.
The 220-pound lander Philae was carried to the comet, dubbed 67P/C-G, by a larger probe named Rosetta, launched and operated by the European Space Agency (ESA).
The background: In August, the ESA successfully placed the Rosetta probe, which was launched in 2004, in orbit around a 2.5-mile wide comet named 67P/Churyumov-Gerasimenko. The comet lies between the orbits of Mars and Jupiter, roughly 250 million miles away from earth. On Wednesday, the Rosetta probe is scheduled to release a smaller probe named Philae, which will land on the comet's surface.
As Vox reports, the landing is was to be harrowing, even riskier than the Curiosity rover's landing on Mars, since the comet's surface is not as well-mapped. Philae could have been headed for a crag or any number of unknown, hostile geological features that'll spell its end.
In order to stop such a catastrophe, scientists planned on Philae making a 19-mile descent from its host probe at the slow pace of one meter per second (analogous to two miles per hour). It will also deploy harpoons to latch into the comet's surface as it nears to keep itself steady.
Due to its battery life, Philae will only have about 64 hours to perform its mission of analyzing soil samples and mapping the comets interior via radio waves. Scientists expect to learn about the comet's chemical composition and internal structure, and will use that data to make estimates about the composition of comets in general.
Why it matters: Scientists believe the comet is 4.6 billion years old. Knowing its composition will offer crucial insights into the chemical makeup of the early solar system, as well as Earth's own formation.
If nothing else, a deeper understanding about the solar system can't hurt, just to keep us from more movies like Armageddon.