All posts for the month June, 2012

Could Well Be!

This artist's concept shows a possible scenario for the internal structure of Titan, as suggested by data from NASA's Cassini spacecraft. Scientists have been trying to determine what is under Titan's organic-rich atmosphere and icy crust. Image credit: A. Tavani

The more we explore the outer solar system with probes like the Cassini spacecraft, the cooler things we discover. This week planetary scientists working with data from that spacecraft announced that there’s a good chance Saturn’s moon Titan has a layer of liquid water hidden beneath that desolate icy surface.

The discovery came from the study of tides on Titan.  This moon is squeezed and stretched as it orbits Saturn, and that is bound to cause some heating in the core.  It’s also a shape-changing process.

The scientists figured out that Titan is not a big rocky ball that would show a slight bulge on its surface as Saturn’s strong gravitational pull tugged on it.  The way they did this is quite ingenious.  They looked at Titan during its 16-day orbit of Saturn.  As it whirls around the huge planet, Titan’s shape changes and scientists could chart those changes.  Titan is not a perfectly round sphere. Instead, it’s slightly elongated like a football. As it orbits Saturn, its  long axis grows when it’s closer to Saturn. Eight days later, when Titan is farther from Saturn, it’s much less elongated and more nearly round. Cassini measured the gravitational effect of that squeeze and pull.  These measurements and the assessment of Saturn’s gravitational pull on Titan provide the best data yet of  Titan’s internal structure and what they show is that for the shape to change as much as it does, Titan likely has a an ocean layer.  It’s not necessarily a huge or deep one, but the fact that it’s there at all is one more step in learning more about Titan’s structure.

Now, I read a few stories here and there about how this supposed ocean is darn near proof that life could exist on Titan.

Not so fast.  The presence of a subsurface layer of liquid water at Titan is not necessarily an indicator for life. There are still a lot of studies to be done before scientists understand what Titan looks like in its interior, and whether or not the conditions are right for life to exist in that ocean, or perhaps at a rock-water interface deep inside.

The implications of an ocean in Titan is an exciting finding, no matter what else is discovered there. This mysterious, cloudy world is slowly yielding up its secrets, and in the process, is opening our minds about what other surprises we’re going to find in, on, or near the worlds of the outer solar system.

A Hell of a Planet

In honor of the transit of Venus, NASA-JPL offered up a look at our “sister” neighbor planet. It’s a gorgeous evening/morning star as seen from Earth, but if you were to travel there, you’d find it be less than gorgeous. Or, you might say it has a terrifying beauty of its own.

Lighting on Venus, as visualized by an artist. Credit: ESA.

“Venus is a fascinating yet horrendously extreme place all at once,” explains Sue Smrekar, a scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Although the surface is hot enough to melt lead due to its runaway greenhouse atmosphere, in many respects it is Earth’s twin [in size, gravity and bulk composition].”

Decades of exploration of Venus using spacecraft in orbit and flying by our “twin” has shown us a volcanic world smothered in clouds, and a world with an oppressive atmosphere that is so heavy it could crush a human standing on its surface. What’s not to like about that? Particularly if you’re a planetary scientist, Venus offers a fascinating place to study. I’ve often heard that it perfectly fits the old vision of what Hell would be like (if it existed): hot, oppressive, inescapable, and torturous. Great place to visit if you can breathe carbon dioxide, stand up to sulfuric acid rain, and you revel in dodging electrical storms and volcanoes.

Well, nothing says every world in the solar system has to be like Earth. In fact, it’s great that we have this array of worlds to study, including Venus. What we learn there and at other places in our solar system will help us understand the worlds we are finding around other stars. Which, poetically enough, will help us understand our own origins as a star and planetary system even more. Think about that as you watch the transit of Venus tomorrow!