Knock, knock. It's humanity.
The Philae lander in the middle of what might be an alien hive. (via ESA)
If you follow space news at all, you're probably aware that humanity has a doohickey called the Rosetta probe orbiting a comet, specifically comet 67P/Churyumov–Gerasimenko, or "67 Pikachu" for short (not really, I made that up). This was a pretty big deal, since people don't put space probes into orbit around a comet every day...or ever, since it was our first time. Even more groundbreaking, we shot an even smaller doohickey—the Philae lander—onto the comet's surface.
In space, no one can hear comets burp. (via ESA)
Since we've arrived, however, 67 Pikachu has constantly defied our expectations...and one explanation is that it harbors microscopic life. The most important part of this theory is that 67 Pikachu keeps spitting out geysers of gas and water. That's not unusual for a comet as it approaches the sun and heats up, but 67 Pikachu is doing it way too early. It should be too cold for that sort of activity right now, so scientists have speculated that some sort of microscopic life is generating the gas and turning part of the interior to liquid. Also, those geysers are chock-full of hydrocarbons and even amino acids—the materials of life.
67 Pikachu also has a different composition than scientists expected. In particular, it has a hard, black crust over an icy interior. This caused problems when the Philae lander's harpoons failed to stick to the surface as planned, sending the probe tumbling for over a kilometer on the comet's surface before falling into a crater. Some think the black crust could be the hydrocarbon byproducts of microscopic life. This is in part because, being a black surface, this material would heat up very quickly and evaporate when close to the sun—so, the thinking goes, something must be replenishing it. In other spots, there are smooth "seas" of what appear to be water that melted (whether because of internal heat or the sun's rays) and then re-froze.