Image a world where rain falls, collects in lakes and ponds, leaks into the surrounding rock, and vaporizes away, just to fall once again. There’s simply one catch: The world is Saturn’s moon, Titan, where the rain isn’t water; it’s liquid methane.

2 brand-new documents check out how this strangely familiar, waterless “water cycle” manifests on Titan’s surface area. To do so, 2 different research study groups relied on information from the Cassini objective, which ended its remain at the Saturn system in September 2017 The spacecraft flew past the enormous moon more than 100 times, collecting important observations of this weird world as it did so.

A few of those observations revealed researchers something genuinely remarkable: their very first look of liquid presently on the landscape, instead of simple ghosts of such liquid functions “Titan is the only world outside the Earth where we see bodies of liquid on the surface area,” Rosaly Lopes, a planetary researcher at NASA’s Jet Propulsion Lab who dealt with the Cassini objective however wasn’t associated with either of the brand-new documents. “A few of us like to call Titan the Earth of the external planetary system.”

Related: NASA May Choose This Year to Land a Drone on Saturn’s Moon Titan

” Titan is the most fascinating moon in the planetary system. I believe that gets me some opponents, however I believe it’s really real,” Shannon MacKenzie, lead author on among the brand-new research studies and a planetary researcher at Johns Hopkins University’s Applied Physics Lab, informed Space.com. However that does not suggest the moon is simple. “Titan tosses us a great deal of curveballs,” she stated.

MacKenzie’s research study examines one possible curveball: 3 little functions that seemed liquid-filled lakes when Cassini initially found them, however appear to have actually dried up by the time the spacecraft went back to the location. The observations recommend that the liquid either vaporized or leaked into the surrounding planetary surface area.

These “phantom lakes” might be proof of seasonal modifications on the moon, MacKenzie and her coauthors think. (7 Earth years passed in between the spacecraft’s 2 observations of the location, throughout which the northern hemisphere of the moon transitioned from winter season to spring.)

However the scenario might not be rather that easy, considering that the 2 sets of observations were taken by various instruments. Cassini was developed to collect information with either its radar instrument or its visual and infrared light electronic cameras, however not both at the same time. And throughout the spacecraft’s very first pass, the area was too dark to utilize the electronic cameras.

So MacKenzie and her coworkers needed to consider the modification in instruments as a prospective variable. However she’s still positive that something is various in the 2 passes, which it’s quite possible that liquid existed, then vanished. Even if the various signals over the 2 flybys were brought on by some other phenomenon, MacKenzie stated she’s still fascinated by what that might inform us about the weird moon, which is amongst researchers’ possible prospects for where life might be hiding beyond Earth.

” If we’re rather taking a look at some recently recognized products on the surface area, then that’s fascinating, too, due to the fact that the sediments on Titan are actually crucial for prebiotic chemistry,” MacKenzie stated.

However although MacKenzie concentrated on simply 3 ponds that appear to have actually vanished, a lot of lakes stayed noticeable throughout Cassini’s observations of the area. In the 2nd paper released April 15, researchers utilized radar information to study a handful of much bigger lakes.

Throughout Cassini’s really last pass over Titan in April 2017, the spacecraft was set to collect an extremely particular kind of information, called altimetry, over the lake area to determine the height of various compounds. Marco Mastrogiuseppe, a planetary researcher at Caltech, had actually currently utilized comparable information to determine the depths of a few of Titan’s seas, much bigger bodies of liquids, and the Cassini group hoped he would have the ability to do the exact same with lakes.

Mastrogiuseppe and his coworkers did so in their brand-new paper, determining the bottoms of lakes more than 328 feet (100 meters) deep and developing that their contents were controlled by liquid methane “We understood that basically the structure of the lakes is really, really comparable to the among the mare, of the sea,” he stated. “Our company believe that these bodies are fed by regional rains and after that these basins, they drain pipes liquid.”

That recommends that listed below Titan’s surface area, the moon might host yet another function similar to Earth: caverns. In the world, numerous caverns are formed by water liquifying away surrounding rock types like limestone, leaving a kind of landscape called karst, identified by springs, aquifers, caverns and sinkholes.

Scientists studying Titan’s lake area believe that they see comparable karst-type attributes. They likewise have not spotted channels linking all these various liquid functions, which is why Mastrogiuseppe and others presume that a few of the liquid might be permeating into the surrounding surface, similar to karst systems here in the world.

” Titan is actually this world that geologically resembles the Earth, and studying the interactions in between the liquid bodies and the geology is something that we have not actually had the ability to do in the past,” Lopes stated. The brand-new research studies start to make that occur by seeing those interactions playing out reside on another planetary body.

Obviously, it’s a lot more tough to study these interactions up until now away, on a world that has actually never ever been the main focus of an objective. “We have actually been discussing possible objectives with robotic explorers that may crawl down into lava tubes and caverns on the moon and Mars,” Lopes stated. “Could we in the future send out among these to sort of crawl down into this surface and into caverns and discover what’s below there?”

Such an objective most likely will not occur at any time quickly, however NASA is seriously thinking about a job called Dragonfly that would land a drone on the weird moon. If picked, the objective would introduce in 2025 and reach Titan 9 years later on. And if NASA does not select Dragonfly, possibilities are excellent that another objective idea will occur. “Titan’s simply too cool to not return to,” MacKenzie stated.

Both MacKenzie‘s and Mastrogiuseppe‘s documents were released April 15 in the journal Nature Astronomy.

Email Meghan Bartels at mbartels@space.com or follow her @meghanbartels Follow us on Twitter @Spacedotcom and on Facebook