As the key to life on Earth, water has also become the key to looking for life on other worlds…

Water on Earth flows through a cycle that most children learn about in elementary school. Some scientists hope that if we notice a cycle on another planet then it could hint at the existence of liquid water: if we find a cycle, then we may find water, and we may find life. So the idea goes.

Observations of Saturn’s moon Enceladus reveal geyser jets on its south pole. The jets let out a plume of vapor whose magnitude varies according to predictable times. A paper on the plume cycle, published in the journal Nature, analyzes data from NASA’s Cassini spacecraft to study the patterns of ejection from under the ice-covered moon.

“The jets of Enceladus apparently work like adjustable garden hose nozzles,” said Matt Hedman, the paper’s lead author and a Cassini team scientist based at Cornell University. “The nozzles are almost closed when Enceladus is closer to Saturn and are most open when the moon is farthest away.”

The Cassini team observed the jets for the first time in 2005 soon after the spacecraft entered Saturn’s orbit. The team hypothesized that the intensity of the jets would vary over time, but they did not directly observe any variation until they examined over 200 photos taken from the mission.

The images show that the southern plume becomes about four times brighter while Enceladus lies far from Saturn, and dims while it is close. Why? It may have something to do with recent findings about Saturn’s gravitational influence on Enceladus…

The research team believes that Saturn’s gravity squeezes Enceladus and causes the changes in geyser strength. When Enceladus is closer to Saturn, the geyser openings tighten up, allowing less material to escape. When Enceladus relaxes at farther distances, the spray can escape in larger quantities.

“The way the jets react so responsively to changing stresses on Enceladus suggests they have their origins in a large body of liquid water,” said Christophe Sotin, a co-author and Cassini team member. “Liquid water was key to the development of life on Earth, so these discoveries whet the appetite to know whether life exists everywhere water is present.”

So if we follow the water, perhaps we will find life…?

By the way, you can visit Enceladus in Morrison Planetarium! From now through September 5th, check out Fragile Planet at the California Academy of Sciences.

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

Image: NASA/JPL-Caltech/University of Arizona/Cornell/SSI

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

The scientists used data from NASA’s Cassini, Galileo and New Horizons missions (dating from 1996 to 2009) to search the ring systems of Jupiter and Saturn for patterns of cometary disruptions.

In the case of Jupiter, the ripple-producing culprit was the well-known comet Shoemaker-Levy 9, whose debris cloud hurtled through the thin Jupiter ring system during a kamikaze course into the planet in July 1994. Scientists attribute Saturn’s ripples to a similar object—likely another cloud of comet debris—plunging through the inner rings in the second half of 1983. The researchers believe this comet passed through when Saturn was on the other side of the Sun from Earth.

“We now know that collisions into the rings are very common—a few times per decade for Jupiter and a few times per century for Saturn,” said Mark Showalter of SETI and lead author of the paper on Jupiter. “Now scientists know that the rings record these impacts like grooves in a vinyl record, and we can play back their history later.”

The tightness of the rings’ “grooves” gives clues to when the comet debris came hurling through, according to Nature News:

As time passed, this tilt has become a progressively tighter spiral, meaning that the shorter the ripple’s wavelength, the longer ago it was formed.

(Discover has a great NASA video of the rings becoming tighter with age on their site.)

The ripples also give scientists a measurement of the size of the clouds of cometary debris that hit the rings. In each of these cases, the nuclei of the comets were a few kilometers wide before they likely broke apart.

“Finding these fingerprints still in the rings is amazing and helps us better understand impact processes in our solar system,” said Linda Spilker, Cassini project scientist, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “Cassini’s long sojourn around Saturn has helped us tease out subtle clues that tell us about the history of our origins.”

“What’s cool is we’re finding evidence that a planet’s rings can be affected by specific, traceable events that happened in the last 30 years, rather than a hundred million years ago,” said Matthew Hedman, of Cornell and lead author of the Saturn paper. “The solar system is a much more dynamic place than we gave it credit for.”

Image credit: NASA/JPL-Caltech/SETI

As if Saturn wasn’t already considered drop-dead gorgeous. And as if Cassini wasn’t already the luckiest satellite in the skies. Using Cassini’s visual and infrared mapping spectrometer instrument (VIMS), scientists gathered data to create beautiful images and even a video of auroras on the ringed planet. Released just today, these are truly a must see!

Also published today, in the journal Science, independent researchers have calculated the vastness of the BP oil spill by viewing videos of the underwater oil gushing. From Science News:

Crone and Tolstoy used an optical technique known as flow velocimetry. In this approach, the volume of a roiling plume is estimated by using video or a series of photos to measure the movements of a host of distinguishing features over a short period of time. Computers can then calculate likely flow volumes based on the plume’s size and density.

And their numbers exceed the government estimate by about 300,000 barrels (or 12.6 million gallons) of oil.

Earlier this week, scientists published a study in the Proceedings of the National Academy of Sciences (PNAS) describing the affect of dust on Colorado’s snowpack. According to Reuters and Yale Environment 360:

Dust created by intensifying human activities in the southwestern United States has caused snow in the Rocky Mountains to melt earlier over the last 150 years and has reduced runoff into the Colorado River basin by about 5 percent, according to a new study.

For a drought-prone area, this makes a potentially bad situation worse.

So, now for a bit of good news. A month ago, we reported on Conservation International’s launch of a worldwide search for 100 species or so of amphibians that were possibly extinct. This week, they announced three of those species were spotted—two in Africa and one in Mexico. You can read more at the 80beats blog on Discover.

Which science news items caught your eye this week? Let us know!