After 10 years of chasing down Comet 67P—and then landing on it—a robotic space mission has returned a tantalizing discovery: the rubber ducky-shaped rock is home to organic molecules of mysterious composition.

Last week, Europe's Rosetta mission finally deployed its fridge-sized lander to the rocky surface. The lander, called Philae, used some of its last remaining battery power to study the comet and beam any data it could back to Earth.

Its discovery is a big win for science. Made primarily of carbon, organic molecules link together to build the fats, proteins, sugars, and DNA that make up all living organisms on Earth. These molecules are the fundamental building blocks of living things, and they seem to be common throughout the solar system.

It's not clear yet what kind of organics Philae found. They may be as simple as methane (CH4) or methanol (CH4O). But when Popular Science spoke to Stephan Ulamec, the head of the Rosetta lander team, he hinted that the molecules may not be quite so simple. Larger and more complex molecules can produce similar readings on the device that Philae used, he says, and the team needs more time to work out which molecules it detected.