Scientists say a brief burst of radio activity has been detected at the Arecibo radio telescope in Puerto Rico. This new report resembles previous activity detected in Australia, which has scientist debating possible causes, including solar flares, blitzars, or something even more mysterious. Brian Negin/iStockphoto hide caption

itoggle caption Brian Negin/iStockphoto

Even if we find other life out there, in the depths of space, life here will still be a rare gem that must be worshipped and preserved at all costs. ESO hide caption

itoggle caption ESO

This illustration shows the relative sizes of the habitable-zone planets Kepler-22b, Kepler-69c, Kepler-62e, Kepler-62f and the Earth. NASA/Ames/JPL-Caltech hide caption

itoggle caption NASA/Ames/JPL-Caltech

We're pretty sure these guys are in costumes. (2004 file photo from Comic-Con Convention in San Diego.) Sandy Huffaker/Getty Images hide caption

itoggle caption Sandy Huffaker/Getty Images