Science still has no solid proof that life exists beyond Earth. But the more we look around the universe, the more we see the potential for life just about everywhere, including in some really counter-intuitive spots.
Because we've yet to find life elsewhere in our own solar system, the search for life on exoplanets around other stars tends to focus on those in the so-called "goldilocks zone" where conditions would be similar to Earth.
New research from Rice University suggests perhaps the region around a star that's "just right" for life might need to be broadened. It argues that had a few small things been different in the long history of Earth and its neighbors, it could have been Venus that wound up a lush and lively world and our planet could be the searing hell-scape that Venus is today.
"If we find a planet (in another solar system) sitting where Venus is that actually has signs of life, we'll know that what we see in our solar system is not universal," Rice Earth scientist Adrian Lenardic said in a statement Tuesday.
Expanding the goldilocks zone dramatically increases the potential worlds out there that could host life. But what if it isn't even about finding Earth-like environments?
Take Saturn's moon Titan, for starters. This is a bizarre world that looks like our own at first, with lakes, rivers, mountains and even weather, but that doesn't make it a great vacation spot. It's extremely cold with seas that flow because they're filled with liquid methane rather than water and the atmosphere is toxic.
Yet this week a team at Cornell University published research suggesting hydrogen cyanide, created when sunlight interacts with Titan's atmosphere, could be a building block for life there, but probably not anything like life as we know it.
"We are used to our own conditions here on Earth. Our scientific experience is at room temperature and ambient conditions. Titan is a completely different beast," explained the study's lead author, Martin Rahm, in a release Wednesday. "This paper is indicating that prerequisites for processes leading to a different kind of life could exist on Titan, but this only the first step."
Remarkably, the places we can now imagine some sort of life might be able to survive gets even weirder. What if life could exist beyond the rocky worlds we've presumed to be the only likely habitable bodies for so long? Earlier this week, I discussed legendary and prescient science fiction author Ben Bova's belief that Jupiter could host life beneath its dense cloud deck, either living in the air or in condensed oceans.
There's no real evidence to support this sort of a hypothesis, though certainly Bova and others are hoping that NASA's Juno spacecraft may provide some during its mission around Jupiter. If it does turn out life can exist below that gas giant's roiling clouds, presumably it opens up even more possibilities.
This week, astronomers from the University of California at Santa Cruz reported their findings of strong evidence indicating the existence of clouds of water or water ice around the brown dwarf star known as WISE 0855. The dwarf is about five times the mass of Jupiter and essentially a cool failed star only 7.5 light-years away.
"Our spectrum shows that WISE 0855 is dominated by water vapor and clouds, with an overall appearance that is strikingly similar to Jupiter," said Andrew Skemer, lead researcher, in a statement.
The researchers were not looking for signs of habitability at the brown dwarf. But if we follow Bova down the rabbit hole and imagine a habitable Jupiter, it makes sense to consider life could even be found in the outer layers of a star like WISE 0855, where conditions are favorable enough for water vapor to exist.
For now, all these potentially habitable spots around the universe have yet to deliver. Or maybe we haven't looked hard enough just yet.