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

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

By Zuberoa Marcos

Humanity has landed several rovers on Mars. The next scientific challenge is to land a boat on Titan.

Titan, Saturn’s largest moon, is one of the most interesting destinations in the Solar System for scientists looking for extraterrestrial life. Discovered on March 25, 1655 by the Dutch astronomer Christian Huygens, Titan has the most Earth-like atmosphere. Just as on Earth, it is composed primarily of nitrogen (95%), methane (approximately 3%), and the remaining 2% percent consists of hydrogen, little vapor water, other hydrocarbons and possibly argon. These atmospheric gases are some of the necessary building blocks for life.

In 2005, the Cassini-Huygens mission studied extensively Titan descending via parachute onto its mysterious surface. It confirmed that lakes, seas and rivers exist and cover much of the satellite’s northern hemisphere. However, the chemical composition of the lakes of Titan is still not well determined.

The Titan Lake In-situ Sampling Propelled Explorer (TALISE) project proposes sending a boat-probe to Saturn’s largest moon that could be propelled by paddles, inflatable wheels or screws. The probe would land in the middle of Ligeia Mare—Titan’s biggest lake and then sail for the coast, taking scientific measurements along the way.

“The detection of additional compounds and the investigation of the influence of both photochemistry and the atmosphere on the chemical composition of liquids of Titan’s lakes it is the next step to understand the satellite’s environment, its relationship with the climate and to analyze the possibility of prebiotic compounds” explained the scientists in the abstract of the project presented in the European Planetary Sciences Congress held in Madrid, Spain last month.

The TALISE project is currently being developed in Spain by SENER, an engineering company, and the Centro de Astrobiología, a research center associated with NASA’s Astrobiology Institute. The hovercraft design is still under consideration but they hope to be ready for a future space science mission call for proposals.

Zuberoa Marcos is a former biologist and current science writer based in Barcelona. She writes articles regularly for Science Today.

Surcando los mares de Titán

Por Zuberoa Marcos

La Humanidad ha posado varios rovers sobre la superficie de Marte. El próximo reto científico es que un barco se pose en Titán.

Titán, la luna más grande de Saturno, es uno de los destinos más interesantes del Sistema Solar para los científicos que buscan vida extraterrestre. Descubierto el 25 de marzo 1655 por el astrónomo holandés Christian Huygens, Titán tiene la atmósfera más parecida a la de la Tierra. Al igual que la de nuestro planeta, se compone principalmente de nitrógeno (95%), aproximadamente el 3% es metano y el 2% restante una mezcla de hidrógeno, vapor de agua, otros hidrocarburos y posiblemente argón. Todo estos gases atmosféricos son ladrillos necesarios para construir vida.

En 2005, la misión Cassini-Huygens estudió minuciosamente Titan al descender en paracaídas y posarse en su superficie. Confirmó que un conjunto de lagos, mares y ríos cubren gran parte del hemisferio norte del satélite. Sin embargo, la composición química de los lagos de Titán sigue siendo desconocida.

El proyecto Explorador in situ de los lagos de Titán (TALISE por sus siglás en inglés) propone enviar un barco-sonda propulsado por paletas o ruedas inflables a la luna más grande de Saturno. La sonda aterrizaría en medio del Ligeia Mare, el lago más grande de Titán, y después navegaría por la costa realizando mediciones científicas a lo largo del camino.

“La detección de compuestos químicos adicionales y el estudio de la influencia de la fotoquímica y de la atmósfera en la composición química de los líquidos que forman los lagos de Titán es el siguiente paso para comprender el medioambiente del satélite, su clima y analizar la posible existencia de compuestos prebióticos”, explicaron los científicos en el resumen del proyecto presentado en el Congreso Europeo de Ciencias Planetarias celebrado en Madrid, España, el pasado mes de septiembre.

El proyecto TALISE está siendo desarrollado por la empresa española de ingeniería SENER y el Centro de Astrobiología, un centro de investigación asociado al Instituto de Astrobiología de la NASA y ubicado en las afueras de Madrid. El diseño del barco está aún en estudio, pero los científicos confían en tenerlo listo para la próxima convocatoria de propuestas para futuras misiones espaciales.

Zuberoa Marcos es bióloga molecular y actualmente trabaja como productora de TV y periodista científica. Escribe de forma regular para Science Today.

Saturn’s moons got all sorts of attention. From Enceladus’ warm “Perrier” ocean to the potential for life on Titan, one of the best-known planets in our Solar System enjoyed particular popularity this week.

In the lab, researchers were able to create the building blocks of life in Titan’s atmosphere. From SPACE.com:

In the lab, researchers simulated possible chemical reactions occurring high up in the nitrogen-rich atmosphere of Titan. They found that various complex molecules, such as amino acids and nucleotide bases, could form without much prodding.

Also in the news this week, the idea that perhaps it was the death of a large, early moon around Saturn that formed its lovely rings. From Universe Today:

[Robin] Canup’s new alternative theory is that Titan-sized moon with a rocky core and an icy mantle spiraled into Saturn early in solar system history. Tidal forces ripped off part of the icy mantle, distributing it into what would become the rings.

The Academy’s own Jack Dumbacher made news this week with research on the family tree of extinct passenger pigeons. DNA extracted from century-old museum specimens reveals that the spectacular passenger pigeon was most closely related to other North and South American pigeons, and not to the Mourning Dove, as was previously suspected. You can read more in the abstract, published in this month’s Molecular Phylogenetics and Evolution.

Now for three news items about beer and flirtation…

Italian researchers recently published a protein library of beer, and according to the Discoblog in Discover:

…better knowledge of the proteins that survive brewing could help improve flavor, aroma, and retention of the foamy head so prized by beer drinkers.

Cheers!

And how about Beers in Space? Popular Science had a story this week about a non-profit space research company that is “about to test an Australian beer that’s brewed and bottled especially for consumption in microgravity.” Apparently, due to numbed taste buds and carbonation, regular beer just won’t do.

Finally, our science-geek neighbors at UCSF posted a very funny, must-see YouTube video late last week, “Most Beautiful Girl in the Lab.”

What turned you on in science news this week? Let us know!