Roughly 70% water, Earth’s surface is covered with rivers, lakes, oceans, mud, and rain clouds. Scientists searching for alien life are searching for planets similar to our own, because experience tells us that life needs water in order to survive.

NASA’s Cassini spacecraft began photographing Titan, one of Saturn’s moons, in 2004. The pictures beamed back to Earth depict strange lakes and rivers. The European Space Agency (ESA)’s Huygens probe splashed into Titan’s mud in 2005, further convincing researchers that Titan was indeed “wet.”

The scientific community agrees that Titan appears Earth-like, but at temperatures around –290°F (–180°C), any water would be in the form of ice. Instead, astronomers believe any wetness on the surface of Titan is a combination of liquid methane, ethane, and other hard-to-freeze elements.

Apparently this moon doesn’t resemble Earth at all. Alex Hayes, a planetary scientist at Cornell University who works on the Cassini radar team, noticed something eerie while observing Saturn’s moon. “Where are all the waves?”

Wind, raindrops, and tides move Earth’s water in every direction. But Cassini has detected no wave action on Titan. It’s pretty strange, especially because, “[w]e know there is wind on Titan, the moon’s magnificent sand dunes prove it,” says Hayes.

Taking into account Titan’s gravity (one seventh that of Earth’s), the nature of fluids on its surface, and its dense atmosphere, Hayes and his colleagues calculated and published the speed needed for waves to form: only two miles per hour!

A strange puzzle, with even stranger solutions. Maybe the lakes are covered with tar, damping wave motion. Or they might be frozen. Or perhaps the wind hasn’t reached two miles per hour… yet.

Most of the lakes are located on Titan’s northern hemisphere, where it has been winter for a few years. The air during winter is colder and thicker, and may be the secret behind the missing waves.

If current climate models are correct, Cassini should be able to detect waves as Titan nears its summer solstice in 2017. Measurements and calculations of waves formed during the summer could tell us the chemical composition of Titan’s lakes… And reveal more about this Earth-like world so unlike Earth.

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA/JPL-Caltech/USGS

Mark Showalter and his research team at the SETI Institute in Mountain View, California, are on a roll. They’ve shown us yet again how much we have to learn about our closest planetary neighbors.

In 2011 and 2012, Showalter’s team discovered two additional moons orbiting Pluto. (The International Astronomical Union recently decided on the names Kerberos and Styx for these moons, despite an overwhelming public vote to name one of them Vulcan.) Using the Hubble Space Telescope, the same researchers recently discovered a new moon orbiting Neptune.

“I got nice pictures of the arcs [segments of the planet’s rings], which was my main purpose, but I also got this little extra dot that I was not expecting to see,” says Showalter.

At 65,400 miles from Neptune, the speedy, newly-discovered moon completes an orbit every 23 hours. This moon is hard to track, but more than 150 archived images from Hubble between 2004 and 2009 enabled Showalter to track down the orbit of the new moon.

“The moons and arcs orbit very quickly, so we had to devise a way to follow their motion in order to bring out the details of the system,” he says. “It’s the same reason a sports photographer tracks a running athlete—the athlete stays in focus, but the background blurs.” (Showalter compares capturing the new moon to Eadweard James Muybridge’s famous racehorse photographs in a blog post earlier this week.)

This 12-mile wide moon is the smallest of the Neptunian system (which currently includes 14 moons), and revolves around Neptune between the orbits of Larissa and Proteus. For now the tiny dot is called S/2004 N 1. The official name may not be put to vote this time (but Star Trek fans can get cracking on ideas).

S/2004 N 1’s discovery brings up additional questions besides its new name. A mini moon like this should have had trouble forming in the neighborhood of much larger moons.

“How you can have a 20-kilometre object around Neptune is a little bit of a puzzle,” says Showalter. “It’s far enough away that its orbit is stable. Once you put it there it will stay there. The question is, how did it get there?”

Triton is Neptune’s biggest moon, orbiting in the direction opposite Neptune’s spin. Astronomers originally thought that a moon of this type would have to be captured by Neptune’s gravity, destroying all smaller moons in the process.

Stay tuned to learn S/2004 N 1’s new name, and perhaps new theories about how it originated in the first place!

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA, ESA, M. Showalter

Within our solar system, few worlds have much in common with Earth. Sure, Venus is about the same size, and Mars may have once (billions of years ago) resembled Earth in terms of its chemistry… But in many ways, Titan, the largest moon of Saturn, seems to be the world most similar to home.

This moon remained a mystery from the time of its discovery in 1655 until the Cassini/Huygens mission managed to peer beneath its veil of thick clouds in 2004. And that mission has made astounding discoveries.

Underneath its obscuring atmosphere, Titan looks shockingly similar to Earth: the lander saw dunes and valleys, as well as beaches and most surprisingly, seas!

We caught the glint of sunlight off these massive methane lakes before, but another near pass by Cassini has allowed us to make a radar map of the topography of Titan’s surface to get a sense of the depth of these alien oceans. It also provided a chance to build upon our understanding of how mountains and valleys here on Earth affect weather patterns around them.

And Cassini has also helped us understand Titan’s unusual atmosphere. A recent NASA press release describes how the moon forms a chemical mix near the surface “like L.A. smog on steroids.” The presence of complex aerosols has long puzzled scientists, but Cassini’s data provided clues to identify the missing link in the process: polycyclic aromatic hydrocarbons (PAHs). (The Academy’s planetarium director recently blogged about a diagram that accompanied that press release.)

Cassini is approaching ten years in orbit around the ringed planet, and its work continues. A future objective is to determine if waves occur on any of Titan’s three largest seas, not too far a stretch given the observations of massive dunes sculpted by wind, but astronomers are still working to piece together the delicate balance of wind, temperature, chemical composition, and viscosity of these alien shores.

Every pass gives us more information about Titan’s clouds and the world beneath them—fleshing out our knowledge of this most familiar-seeming moon.

Josh Roberts is a program presenter and astronomer at the California Academy of Sciences. He also contributes content to Morrison Planetarium productions.

Image: NASA/JPL-Caltech/SSI

At the recent AAAS meeting in Boston, I met Amanda Hendrix from NASA’s Cassini Mission. Dr. Hendrix, a planetary scientist, has been with Cassini since 1999, when Cassini flew by Earth’s Moon. “I became involved with the UVIS (the Ultraviolet Imaging Spectrograph) team to analyze the Moon data. The next year, I began working with the Cassini Project team at JPL as part of the Science Planning team, to plan out the science investigations that would happen during each icy satellite flyby.” Now she uses data from UVIS to study the icy moons of Saturn.

Cassini has returned so many stunning results over the last nine years, I thought I’d get the latest from her. Here’s an excerpt of our email interview.

Where is Cassini right now? What is it studying?

Cassini is in a highly inclined portion of its tour of the system, so that its path is ~60° out of the plane of Saturn’s equator. This provides Cassini’s instruments access to wonderful views of the polar regions of Saturn and Titan, and also a unique perspective on the rings system.

After spending the last couple of years in the equatorial plane, it is great to get some beautiful views of the rings, and to understand how they are evolving on the timescales of a few years. High latitude views of the planet and Titan mean that we can observe critical seasonal variations happening in the Saturn atmosphere (such as the development of the giant “serpent” storm) and the Titan atmosphere (such as the formation of the southern hemisphere polar hood) and on the Titan surface (we can watch for changes in the lakes and seas at the southern and northern polar regions).

Looking for and studying seasonal variations is important because it helps us to piece together the clues to understand solar system processes and will ultimately aid in the study of the formation and evolution of the solar system.

Can you highlight some of Cassini’s recent discoveries?

There are several studies being undertaken to understand the variability (if any) of Enceladus’ activity, and its ice grain and water vapor output, with orbital location. Some models have shown that the gravitational stresses vary, depending on where Enceladus is in its orbit, and this might affect the plume output. So those studies are ongoing and interesting.

On another topic, Cassini images have been used to show that Titan “glows” from deep in its atmosphere, as seen while Titan was in Saturn’s shadow. The likely cause is deeply-penetrating particles (such as cosmic rays) that excite the atmospheric gases. Another discovery is that there could be icebergs—of hydrocarbon ice—floating on the lakes of Titan. This comes from the radar images of the lakes along with calculations that if some amount of Titan atmosphere is contained within the methane ice, it will float rather than sink.

What’s next for Cassini? 

Cassini will remain in the inclined phase of orbits until around February 2015 (it recently passed the peak in inclination and is now heading back down), then it will execute orbits roughly in the equatorial plane (for about a year), and this is when we will have two Dione and three Enceladus flybys. The final close flyby of the moon Rhea took place Saturday, March 9, 2013. We have numerous upcoming Titan flybys to study this intriguing moon and track its seasonal variations.

How much longer will Cassini be operational?

The plan is for Cassini to remain in operation, in orbit at Saturn, until September of 2017. An exciting end-of-mission is being planned, whereby Cassini orbits closer and closer to Saturn, with its orbital periapse (closest point to Saturn in the orbit) between the top of the atmosphere and the inner edge of the D-ring (the innermost ring), at high inclination. Such close passes will tremendously help the instruments on Cassini to measure the internal structure and magnetic field of Saturn, and will allow for a careful measurement of the mass of the rings—which is important in ultimately understanding their age and source! Finally, Saturn’s gravity will capture Cassini and the mission will be over.

What are some of your favorite findings?

The discovery of activity at Enceladus is one of my favorites! That such a small moon puts out so much material, with great effect on the rest of the system, is really astonishing and wonderful. This discovery was great because it was such a multi-instrument discovery and really highlights the utility of synergistic investigations on a mission.

Another one of my favorites is the discovery of liquid lakes on Titan—the only body in the solar system other than Earth with liquid on the surface! The landing of the Huygens probe on the surface of Titan was a really exciting time. Another of my favorite findings was the up-close views of bizarre Iapetus that we obtained during our close flybys with that moon.

Why do the data and images Cassini provides move people so much?

Cassini is such a great mission because the payload includes a complementary instrument suite that allows us to probe nearly every aspect of the Saturn system. The datasets are stunning and moving partly because the Saturn system is very beautiful. The intricate detail revealed in the images is wonderfully mind-boggling!

Recent Cassini image (with Venus hiding in Saturn’s rings): NASA/JPL-Caltech/Space Science Institute