Sure, after decades of listening, there is still no message. But with more data to sift through, and new technologies with superior search capabilities, odds of hearing from E.T. are rapidly improving. If the probability in the decade 2011–2021 were x percent, it’s going to be 1,000 times x in the following decade, says Andrew Siemion, director of the Berkeley SETI Research Center. (SETI stands for Search for Extra-Terrestrial Intelligence.)

The reason for E.T. optimism stems largely from several new projects in the works, enhanced with advanced methods for discerning an actual message hidden in the static of cosmic cacophony.

Siemion, speaking in Seattle on February 15 at the annual meeting of the American Association for the Advancement of Science, reported a new release of data from Breakthrough Listen, a major enterprise for recording radio signals from space. Now available for others to analyze, the data dump contains 2 petabytes of information (to store that much, you’d need 2,000 of today’s typical PCs with their puny 1 terabyte hard drives).

Tarter, chair emeritus for SETI Research at the pioneering SETI Institute, described new search projects in the works at the institute, including Laser SETI. It’s a plan to train 96 cameras at a dozen locations around the world to keep a constant vigil for “intelligent” optical signals from space.

Another key driver of increased optimism is the abundance of places to look for life. Thanks largely to the Kepler space telescope’s successful explorations, astronomers now know of thousands of stars possessing planets — and have spotted dozens of rocky, Earth-like planets orbiting their stars at a distance likely to be temperate enough for liquid water, a hopeful indicator of habitability.

And of course, it is still possible that alien life might be hiding closer to home. While it’s very unlikely that any intelligent life abides in our solar system, microbial biology might be viable on moons such as Enceladus (Saturn) and Europa (Jupiter). Robots equipped with tools to extract microorganisms from alien soil and conduct chemical analysis could search for life on site. In the meantime, land- or space-based telescopes might detect signs of biological activity in the atmosphere of distant planets. Certain combinations of molecules in the right ratio would be surefire signatures of life in action.

“The ultimate breakthrough in exoplanetary science will be the detection of a biosignature in the atmosphere of a rocky habitable-zone exoplanet,” astronomer Nikku Madhusudhan noted last year in the Annual Review of Astronomy and Astrophysics. “Defining a unique biosignature remains a theoretical challenge, but several candidate molecules have been suggested.”

No one molecule (not even oxygen) would be a definite sign of life. But multiple life-related molecules detected in the atmosphere of a planet with other suitable conditions (such as a comfy temperature) would be strong evidence. Under Earth-like conditions, various molecules, such as oxygen, ozone, methane, carbon dioxide, nitrous oxide and ammonia could be taken as indicators of biological activity.

“Though there is no single ideal molecule, the combination of multiple species (e.g., oxygen and methane) may be a potential biosignature under the given conditions,” wrote Madhusudhan, of the University of Cambridge in England. “In this regard, a detection of oxygen and methane and/or nitrous oxide along with liquid water on a habitable-zone planet, i.e., an almost exact Earth analog, may be a sure sign of life.”