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Titan and Dione (the smaller moon) against the face of Saturn (Cassini image)

One of the solar system’s most interesting places just got even more interesting.

Scientists studying data from the U.S./European Cassini probe in orbit around Saturn report (in this week’s Science magazine) that the fog-covered moon Titan most likely has an ocean some 60 miles beneath its icy surface.

The Cassini team infers the ocean from the way the moon flexes due to gravitational tides as it circles Saturn.  The amount of flexing is greater than one would expect if Titan were made entirely of solid rock.

Titan — already the only place in the solar system beside Earth with surface lakes — now joins a small group of water worlds: Europa, Ganymede, and Callisto, all moons of Jupiter.

The ocean had been predicted (below) but it’s nice to have empirical evidence.

What's underneath? And what's that red stuff? Thera Macula, as seen by the Galileo spacecraft.(NASA/JPL/University of Arizona)

The news that Russian scientists have finally drilled through the thick ice covering Antarctica’s mysterious Lake Vostok got me thinking, naturally, of Europa. Biologists hope to find previously unknown forms of life in Vostok, whose waters have effectively been sealed off from the outside world for eons. So, too, Jupiter’s moon might someday yield clues about — or even our first glimpses of — life beyond Earth. Europa is one of the first places to go if you’re searching for aliens, since it also has an ice-capped ocean.

Unfortunately, NASA’s planetary program is broke.

More about that in a minute. First, though, what could we do if we had the money? A team at the Jet Propulsion Laboratory has come up with a concept for a Europa Lander that could be launched as soon as 2021. There are other, competing Europa concepts — an orbiter and a multiple flyby mission — but the lander is to me (forgive my childishness) the coolest. And, as JPL’s Dave Senske told NASA’s Outer Planets Assessment Group yesterday, it would be the “most definitive way to assess what’s on the surface.”

The team envisions a six-legged spacecraft weighing about 100 pounds, which could last on Europa for about a month (Jupiter’s intense radiation limits the lifetime). Equipped with cameras, spectrometers, and a seismometer, the lander would drill or jackhammer a few inches into the ground to collect samples from below the radiation-contaminated zone. One likely landing site, called Thera Macula (above), is streaked with intriguing reddish material that may indicate the presence of organics. There’s reason to suspect that pockets of liquid water exist less than two miles below the surface at Thera Macula. Reaching those underground lakes might be a job for some future Europa cryobot, but not this first lander.

Nobody knows how rough the landing site would be. Galileo and Voyager photos aren’t detailed enough to answer the question, and according to some thinking, Europa’s icy surface could be as rugged as Death Valley’s “Devil’s Golf Course” (pictured below), which poses an obvious risk to a legged lander. Potential sites would have to be scouted from orbit during the month before landing, using a camera similar to the HiRISE now orbiting Mars.

Rough landing zone. (Photo of the "Devil's Golf Course" by Lluís Ribes Portillo)

The JPL team tried very hard to design a mission using technology that’s already, or almost already, in hand. True, nobody’s ever done a precision landing on another planet using LIDAR for last-minute hazard avoidance. But as study team members pointed out at the OPAG meeting, such technology has been in development for more than a decade. They think it’s doable. Which is exciting.

Now the bad news. The Europa Lander would cost as much as $3.5 billion, not counting launch. And NASA has no money for such ambition. The agency’s planetary exploration budget has just been slashed, partly a victim of its own excesses. The Mars program has been among the biggest offenders of late, but advocates of missions to the outer planets have proven little better at bringing down costs. NASA’s top science official, John Grunsfeld, was briefed about the new Europa concepts yesterday, and reportedly liked what he heard. The orbiter and flyby estimates both came in under $2 billion, which is better than previous Europa concepts. Still, Grunsfeld could only quip to the JPL briefers, “Now we just need $2 billion.”

Until something changes, then, we’ll have to settle for Lake Vostok, or science fiction — like this upcoming film, The Europa Report, which takes place, presumably, in some distant, less economically pinched future.

Part of the new geological map of Io published by the Planetary Science Institute and the U.S. Geological Institute.

Jupiter’s innermost moon, Io, is one of the most fascinating planetary bodies in our solar system — with hundreds of volcanoes, it’s the most geologically active, constantly reshaping its surface. Today a group at the Planetary Science Institute have released a new geological map of the moon, integrating four “global mosaics” produced by the United States Geological Survey in 2006. You can download the whole map here (PDF).

David A. Crown, a senior scientists at PSI, explained in the announcement why this map is special:

This new map of Io’s geology provides for the first time a detailed record of the different types of landforms and deposits that form the surface and presents a global context that is important for understanding Io’s internal evolution and volcanic processes, as well as for targeting future observations of Io. Knowledge of Io’s volcanic activity derived from geologic mapping is an important contribution to our understanding of the nature and diversity of volcanism in our solar system.

What makes the map even more interesting is that it’s based off of information collected mostly from the Voyager and Galileo missions. Yes indeed: spacecraft launched over thirty years ago and currently passing the boundary of our solar system are still giving us new things to think about. The two Voyager spacecraft made their closest approach to Jupiter in 1979, which was when we first discovered that Io was geologically active. Galileo, launched in 1989, deepened our knowledge of the Jovian moon though a number of close fly-bys, observing the effects of volcanic eruptions and imaging the surface to show the sheer extent of the activity.

That we can continue to parse this data to reveal even more about our neighbors is a testament to just how much data these planetary missions can dig up, and how much we still have to learn about our own solar system.

Stresses on Mercury's surface, which may have resulted from the cooling and solidification of either impact melt or volcanic fill. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

On a similar note — that is, space missions “living on” well past their standard mission dates, the MESSENGER spacecraft, in orbit around Mercury, just began its first extension this week. It launched in 2004 and entered Mercury’s orbit on March 18, 2011, with a planned mission end on March 17, 2012. NASA announced last November that the mission would be extended another year. The spacecraft is studying many of the same things at Mercury, including the history of its volcanism and how the planet’s topography has changed. As the team announced last October, they’ve mapped nearly the entire planet and are using it, along with data collected from Mariner 10 in 1974-75, to learn how Mercury was shaped by its volcanic activity.

An artist's conception of GJ 1214b

Astronomers announced this week that they’ve confirmed the existence of a new class of planet — a hot, watery, exotic “super-Earth.”

A little over two years ago, astronomers at the Harvard-Smithsonian Center for Astrophysics discovered an exoplanet that we agreed was worth some extra attention. The planet, designated GJ 1214b, is only 2.7 times the diameter of Earth — one of the smallest exoplanets found — and orbits just over a million miles from its star (compare to Earth’s 92 million miles) in a zippy 38-hour ‘year.’

Given its size and density, astronomers speculated that GJ 1214b may very well be covered in deep oceans. The Harvard-Smithsonian team kept studying it, enlisting the Hubble Space Telescope to get more data about the planet’s atmosphere. “We’re using Hubble to measure the infrared color of sunset on this world,” said astronomer Zachory Berta in this week’s release. The data seem to confirm that GJ 1214b has a very steamy atmosphere, thick with water vapor.

Even more intriguing is that due to the temperature (being so close to its red dwarf star makes it around 450 degrees Fahrenheit) and extreme pressures, all that water gets a bit…exotic. Materials “like ‘hot ice’ or ‘superfluid water’ – substances that are completely alien to our everyday experience” would form, according to Berta. We emailed Berta to ask if he could explain these strange materials further.

Frankly, it’s difficult for me to imagine what these exotic forms of water would be like – we have very little experience with them here on Earth. They’re simply how the molecule H2O acts when it is in high pressure and temperature environments …

Our closest point of comparison is that the outer atmosphere might be something like a hot, steamy oven that you would use to bake bread with nice crust. But as you go deeper into the planet, you would encounter these exotic forms of water. I should add, however, that there’s still an enormous uncertainty about the composition of the planet overall. Yes, the observations point to a planet that is rich in water, but what is it mixed with, and in what proportions? Really visualizing the “surface” of this planet (if there is one!) will require us figuring those things out!

But whatever the case, the temperatures are too high for liquid water as we know it to exist on GJ1214b.

We feel obligated to point out that if you’re going to google “hot ice” like we did, the first hit you get is this video; we asked Berta if that’s what he was talking about. He replied, “Sadly, I don’t think the YouTube video would be a great example. It shows water that’s saturated with sodium acetate, and the sodium acetate is crystalizing into the solid form. I’d really rather you didn’t link to it [ed note -- Sorry!], because that’s not what we think is going on.” OK, we crossed it off our “What Hot Ice Might Be Like” list.

Given the existence of water, we also asked Berta if he would “speculate wildly” on the question of life on GJ 1214b:

There’s probably no liquid water anywhere on this planet, so nope, I won’t speculate wildly about what sort of life could live there. Sorry! I can’t imagine it – the temperature would be too high for the large, complex molecules that make life possible to survive. But I will say this, which I think is an important point along the same lines:

What makes me excited about these observations is really the technique, the idea that we can use a telescope to observe the atmosphere of a very distant planet. GJ1214b is too hot for life, but it’s not too difficult for us to imagine that we could make similar observations of the atmosphere of a planet that was a little cooler in temperature than GJ1214b and could potentially host life. Microbial and plant life on Earth have dramatically altered our atmosphere over its history. If they did the same on another planet orbiting another star, observations like these of that planet’s atmosphere might then be able to tell us whether or not there is life elsewhere in our galaxy.

Add two more stripes to this ingenious chart showing all the attempts over the past 50 years to send spacecraft to Mars. Let’s hope that the stripe for the Curiosity Mars Science Laboratory, which launched successfully on Saturday, reaches all the way to the surface of the planet.

Sadly, the stripe for Russia’s Phobos-Grunt Mars spacecraft, currently incommunicado in Earth orbit, appears doomed to end at the outside, “fail” ring, which may also spell the end of the country’s planetary program.

The apparent demise of Phobos-Grunt got me reading up on the history of Russian Mars exploration, looking for stories from happier days.  I hadn’t known about PrOP-M, the first rover (or maybe crawler is a better word) launched to Mars. It ended up failing , too, but it would have been fun to watch had it succeeded.

By 1971 the Soviets had already landed one Lunokhod rover on the moon’s surface. The 10-pound PROP-M, included as a payload on the Mars 3 lander launched in May 1971, was much more modest.  After Mars 3 touched down, the rover, attached to a 15-meter umbilical cord, was designed to shuffle away from the lander on two ski-like contraptions. The video below (queued up here at the 3:51 mark) shows how the rover maneuvered itself.  Unfortunately, Mars 3 went silent immediately after it touched down, and PROP-M was never heard from again. NASA didn’t land its own rover on Mars until 1997, when Sojourner rolled off of the Mars Pathfinder.

When Curiosity touches down on Mars next August, it should tip its electronic head in the direction of PROP-M, wherever it lies on the unforgiving plains of Mars.