Scientists discover storms in the tropics of Titan

Aug 12, 2009
This is an adaptive optics image from Gemini Observatory of Titan passing nearly directly in front of Saturn. Titan, as usual, looks quite bland, with no hint of clouds. Credit: Gemini Observatory/AURA/Henry Roe, Lowell Observatory

For all its similarities to Earth -- clouds that pour rain (albeit liquid methane not liquid water) onto the surface producing lakes and rivers, vast dune fields in desert-like regions, plus a smoggy orange atmosphere that looks like Los Angeles's during fire season -- Saturn's largest moon, Titan, is generally "a very bland place, weatherwise," says Mike Brown of the California Institute of Technology.

"We can watch for years and see almost nothing happen. This is bad news for people trying to understand Titan's meteorological cycle, as not only do things happen infrequently, but we tend to miss them when they DO happen, because nobody wants to waste time on big telescopes—which you need to study where the clouds are and what is happening to them—looking at things that don't happen," explains Brown, the Richard and Barbara Rosenberg Professor of Planetary Astronomy.

However, just because weather occurs "infrequently" doesn't mean it never occurs, nor does it mean that astronomers, in the right place at the right time, can't catch it in the act.

That's just what Emily Schaller—then a graduate student of Brown's—and colleagues accomplished when they observed, in April 2008, a large system of storm clouds appear in the apparently dry mid-latitudes and then spread in a southeastward direction across the . Eventually, the storm generated a number of bright but transient clouds over Titan's tropical latitudes, a region where clouds had never been seen—and, indeed, where it was thought they were extremely unlikely to form.

Schaller, now a Hubble Postdoctoral Fellow at the University of Arizona, Brown, and their colleages; Henry Roe, a former Caltech postdoctoral scholar in Brown's group, now at the Lowell Observatory in Flagstaff; and Tapio Schneider, a professor of environmental science and engineering at Caltech, describe their work, and its implications for climate on Titan, in the August 13 issue of Nature.

"A couple of years ago, we set up a highly efficient system on a smaller telescope to figure out when to use the biggest telescopes," Brown says. The first telescope, NASA's Infrared Telescope Facility, on Mauna Kea, takes a spectrum of Titan almost every single night. "From that we can't tell much, but we can say 'no clouds,' 'a few clouds,' or, if we get lucky 'monster clouds,'" he explains.

Schaller explains, "The period during which I was collecting data for my thesis, sadly, corresponded entirely to an extended period of essentially no clouds, so we never really got to show the full power of the combined telescopes. But then, after finishing and turning in my thesis, I walked back across campus to my office to look at the data from the previous night to find that Titan suddenly had the biggest clouds ever. I like to think it was Titan's graduation gift to me. Or perhaps a bad joke."

The day after the telescope's big find (and Schaller's thesis submission), Schaller, Brown, and Roe began tracking the clouds with the large Gemini telescope on Mauna Kea and watched this system evolve for a month. "And what a cool show it was," Brown says.

A major storm erupts in the desert tropics of Titan. Credit: Emily Schaller et al./Gemini Observatory

"The first cloud was seen near the tropics and was caused by a still-mysterious process, but it behaved almost like an explosion in the atmosphere, setting off waves that traveled around the planet, triggering their own clouds. Within days a huge cloud system had covered the south pole, and sporadic clouds were seen all the way up to the equator."

Schneider, an expert on atmospheric circulations, was instrumental in helping to sort out the complicated chain of events that followed the initial outburst of cloud activity.

"The monthlong event has many important implications for understanding the hydrological cycle on Titan," says Brown, "but one of the reasons I am most excited about it is that it shows clouds near the equator—where the [European Space Agency's] Huygens probe landed—for the first time. For a while now, people have speculated that the equatorial regions are simply too dry to ever have significant ."

And yet, the images snapped by the Huygens probe in January 2005, as it descended through Titan's soupy atmosphere and toward the surface, revealed small-scale channels and streams, which looked just like features created by fluids—by water, here on Earth, and on Titan, probably by liquid methane.

Experts had speculated for years on how there could be streams and channels in a region with no rain. The new results suggest those speculations may prove unneccessary. "No one considered how storms in one location can trigger them in many other locations," says Brown.

More information: The paper, "Storms in the tropics of ," appears in the August 13 issue of Nature.

Source: California Institute of Technology (news : web)

Explore further: Staying warm: The hot gas in clusters of galaxies

add to favorites email to friend print save as pdf

Related Stories

Titan Weather: Cloudy Every 15 Years

Nov 01, 2005

About two years ago, before the Huygens probe arrived at Titan, Henry Roe, a graduate student I was working with at Berkeley, discovered clouds on Titan. He was the first person to get images of what he thought ...

More Stormy Weather on Titan

Dec 22, 2004

Titan, it turns out, may be a very stormy place. In 2001, a group of astronomers led by Henry Roe, now a postdoctoral scholar at the California Institute of Technology, discovered methane clouds near the south p ...

Predicting the weather on Titan?

Jan 23, 2006

Using recent Cassini, Huygens and Earth-based observations, scientists have been able to create a computer model which explains the formation of several types of ethane and methane clouds on Titan.

Titan's icy climate mimics Earth's tropics

Oct 02, 2007

If space travelers ever visit Saturn's largest moon, they will find a tropical world where temperatures plunge to minus 274 degrees Fahrenheit, methane rains from the sky and dunes of ice or tar cover the ...

Recommended for you

Staying warm: The hot gas in clusters of galaxies

3 hours ago

Most galaxies lie in clusters, groupings of a few to many thousands of galaxies. Our Milky Way galaxy itself is a member of the "Local Group," a band of about fifty galaxies whose other large member is the ...

A colorful gathering of middle-aged stars

Nov 26, 2014

NGC 3532 is a bright open cluster located some 1300 light-years away in the constellation of Carina(The Keel of the ship Argo). It is informally known as the Wishing Well Cluster, as it resembles scattered ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

docknowledge
not rated yet Aug 13, 2009
Hmmm.. Looks like somebody is gunning for their own dedicated satellite. But...seems reasonable.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.