Scientific Unknowns: Life on Titan?

Sunlight reflecting of one of the lakes of Titan
Image Courtesy: NASA/JPL/University of Arizona/DLR

Of all the places we look for life in the solar system, there is one that has captured my imagination more than any other. Maybe it is because of this obscure moons weirdness, or the possibly of an entirely new biology. Either way I could not discuss life in the solar system and leave it out. So what plausibly and evidence is there for life on Saturn's largest moon? The answer may surprise you.

Here on Earth all life requires water. Water makes a great solvent. This simply means a large variety of different molecules can be taken up by the water. Suspended in liquid water, those molecules can move around to do the things of life. This works great here on Earth and water may even be a good solvent for possible life on Europa. Titan however, is a balmy -290 ^oF, putting water out of the picture. Luckily Titan is covered with another liquid that may be able to fill the same role as water, liquid methane. I need be clear in saying that we have no idea if life can form in liquid methane. Maybe it forms easier in methane than it does in water. While there are some good reasons to think water may be the liquid of choice, we simply don't know. This is what make Titan such an interesting world to explore.

An infrared image of Titan showing Titan's Northern Lakes
Image Courtesy: NASA/JPL/Space Science Institute

So now we have a feel for the plausibility of life on Titan, but what about the evidence? Often in science you test a hypothesis by building a model that produces predictions. Then you test those predictions to see if the model reflects reality. In 2005 a team of astrobiologists published a paper making some suggestions about what we might expect to see if some sort of methanogenic life were enjoying the orange haze of Titan. In 2010 data from the Cassini Huygens probe matched those predictions. So what does that mean? Well it means that this model deserves strong consideration. That said, we should not be quick to accept any claim of alien life. There are a huge multitude of processes not involving life that can change the chemistry of an atmosphere. This evidence is a exciting starting point, but it is not proof.
So when it comes to Titan, even more so than Mars or Europa, I can only say we have no clue if there is any life present. Titan is a moon we have only recently gotten a good look at. Astronomy has a history of dismissing early speculations of life with future observations. Will that pattern hold true on Titan? We need more scientists and more spacecraft to find the answer. Right now I can only say that I don't know, but that I am extremely excited to see the discoveries made as we hunt down the solution.

Updates from Space

Image credit: NASA/JPL/SSI

There has been some exciting news from space over the last week. Here are some of the highlights.

Things are looking dim for the Martian rover Spirit. We haven't heard from this hardy rover in almost a year. Sounds like they will keep trying for a few more months but things don't look good. For a rover that was designed to last 3 months, 5 years is not bad.

On a brighter note, the Messenger spacecraft has dropped into orbit around Mercury. There it can now study Mercury's strange magnetic field. Messenger will also image the 5% of Mercury's surface that has yet to be mapped.

Thought Earth was the only place in the solar system to get spring showers, think again. Scientists using the Cassini spacecraft have gathered evidence of rain showers on Titan. At almost -300 degrees Fahrenheit, Titan's rain is likely a mix of liquid methane and ethane. This weird moon never ceases amazing me.

Weird Hills on the Surface of Titan

Titan is one of the one of the most exciting places in our solar system. This moon of Saturn has liquid methane playing the role of water on its surface, and water ice playing the role of solid rock. We are just beginning to understand the dynamics at work on this moon, in part because it is shrouded in a thick methane atmosphere. This image was taken on December 28th, 2009 and is giving sicentists new puzzle to solve.

The lines you see in the lower left of the image are rifts similar to features called corona on Venus. On Venus, we think they are caused by heat within the planet that puts stress on the rock. Straight features like this could also be created by surface activity like wind or rainfall.

The star-shaped feature to the right also points to some sort of activity happening in this area. “This star-shaped pattern of the hills indicates something significant happening in the middle of the star,” said Steve Wall of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., a Cassini scientist on the radar team. “It might be caused by tectonic forces, such as the forces that pull the crust of a planet apart, or rainfall that leads to erosion, or an ice intrusion like a dike.”

Scientists don't have any answers yet, but either answer would be exciting. If this was caused by rain, it gives us a better understanding of how liquid methane shapes the surface of Titan. If on the other hand it is caused by some sort of internal heat, it raises all new questions on what the inside of Titan is like. We will just have to wait as Cassini continues to unveil this exciting world.

Image Credit: NASA/JPL

A Glimpse of Lakes on Titan

Imagine a world so cold that temperatures like -270 Fahrenheit are not uncommon.Water acts more like rock, and a thick orange atmosphere looms overhead. Instead of water carving up the landscape, you have methane. This is Saturn's moon Titan.

This image is of sunlight bouncing of the lake Kraken Mare taken by the Cassini spacecraft. This lake of liquid methane is larger than the Caspian Sea here on Earth. Titan is a fascinating world because of how it compares to the Earth. “These results remind us how unique Titan is in the solar system,” said Ralf Jaumann, a visual and infrared mapping spectrometer team member on Cassini. “But they also show us that liquid has a universal power to shape geological surfaces in the same way, no matter what the liquid is.”

There has been building evidence for lakes on Titan even before Cassini arrived at Titan. This picture is a elegant piece of evidence confirming those weird lakes. “This one image communicates so much about Titan -- thick atmosphere, surface lakes and an otherworldliness,” said Bob Pappalardo, Cassini project scientist, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “It’s an unsettling combination of strangeness yet similarity to Earth. This picture is one of Cassini’s iconic images.”

Titan is one of the most exciting places in the solar system to explore. I think this just gives a taste of what awaits us.

For more information: Cassini Homepage
Image Credit: NASA/JPL/University of Arizona/DLR

A New Face to Saturn's Rings

Over the last few months, we have been treated to a series of images of long shadows cast across Saturn's rings.  This unique viewing opportunity happens about every 15 years as Saturn approaches equinox.  The low angle of the Sun's rays across the rings has been great for science and, of course, produced some amazing photos.  August 11th was Saturn's equinox, so now the opposite side of the rings is being lit up by the sun.

In this bottom image you can see Titan and the shadow that it's casting on the planet.  Both of these are raw images from Cassini so they're a little rough but still give a sense for Saturn's grandeur.  Click on the images to a larger version.

In my opinion, Cassini has produced more eye candy than any other spacecraft we have put up there.  I hope that Cassini will continue to function for many more years before it is crashed into Saturn.  Imagine what we would see and learn if we sent a Cassini-like mission to each of the outer planets.  I hope the folks at NASA recognize the public interest these images have produced and will try for more missions that will be able to capture the majesty that space has to offer.

All images are credit NASA/JPL/Space Science Institute