'Titan's Lakes Revealed' says the stunning cover of the current issue of Nature. The news isn't really a surprise -- remember that as Huygens approached Titan, there was still some question about whether or not the probe might not splash down in a sea of liquid methane. But here is the hard evidence, culled from the July 22 Titan flyby. The dark patches Cassini 'saw' on radar show little radar reflectivity and, when you add in topographical features, bear the clear signature of lakes. For me, the news evokes a long-ago time when I was growing up in St. Louis. Among my father's books was an old, leather-bound atlas that dated back to the late 19th Century. And one day as I browsed through various maps, I saw the thrilling word 'unexplored' in one corner of the Mato Grosso region of western Brazil. Filling in a map and tracing the great saga of exploration is one of humanity's great themes, one we now extend to entire worlds. That 'Titan's Lakes' headline took me right back to a...

It would be easy to keep this site filled with outer Solar System news, so various and captivating are the images that stream in from our spacecraft. Exoplanet studies keep us focused primarily on nearby stars, but I do want to keep up with Cassini, and decided some time back that Centauri Dreams would leave inner system coverage to others and pick up the pace as we moved to Saturn and beyond. And what a story keeps unfolding there. For Cassini remains healthy and the news from Enceladus intriguing. We've known since last year about the plume erupting on the satellite, leading to speculation of liquid water beneath the ice of its surface. The south polar region of the tiny moon is geologically active in ways that challenge the imagination. After all, isn't the rest of Enceladus as cratered and ancient-looking as the surface of our own Moon? The 'Cold Faithful' model, which patterned the Enceladus geyser on Yellowstone's Old Faithful, has apparently run into problems. Susan Kieffer...

If you've seen the Sierra Nevadas, you know what Bob Brown is talking about when he likens the mountain range found on Titan to those beautiful peaks in the western United States. Brown (University of Arizona) is team leader of the Cassini visual and infrared mapping spectrometer. Cassini was able to resolve features down to 400 meters (1300 feet) on its October 25 flyby. And suddenly we have a mountain range, dunes, and something resembling a volcanic flow under Titan's inscrutable atmosphere. Fascinatingly, at the top of the ridges are deposits of a white material that may be ethane snow or some other form of organic substance. Here's Cassini scientist Larry Soderblom (USGS) on the organics: "There seem to be layers and layers of various coats of organic 'paint' on top of each other on these mountain tops, almost like a painter laying the background on a canvas. Some of this organic gunk falls out of the atmosphere as rain, dust, or smog onto the valley floors and mountain tops,...

This image is simply too beautiful not to run for the weekend, even though it's getting play everywhere. The Sun is, of course, behind Saturn, backlighting the rings to reveal hitherto unseen detail. Image credit: NASA/JPL/Space Science Institute Gorgeous as it is, bear in mind that this is a composite in which the colors have been exaggerated. 165 Cassini images went into its production, taken with the spacecraft's wide-angle camera over a three hour stretch on September 15. Ultraviolet, infrared and clear filter images went into the composite, which was then adjusted to get as close to natural color as possible. Much good science is coming out of these observations, but for now absorb the beauty of the scene, surely a view that will stand as one of Cassini's defining moments.

The imagery from Cassini's twelve-hour pass behind Saturn turns out to have been productive indeed. We pause from things interstellar, then, to admire the beautiful photograph below. The occultation of the Sun put the spacecraft in position to see the rings with exquisite and detail-enhancing backlighting, providing striking visual evidence for their extensive interaction with some of Saturn's smaller moons. Image (click to enlarge): Wispy fingers of bright, icy particles reach several tens of thousands of kilometers outward from Enceladus into the E ring, while the moon's active south polar jets continue to fire away. Credit: Jet Propulsion Laboratory/Space Science Institute. This is Enceladus as we've never seen it before, moving through a highly visible E ring, to which it appears connected by feathery strands of ice crystals. These are surely coming from the moon's south polar geysers, another of Cassini's remarkable discoveries. No clearer evidence that moons like this one have...

The upcoming solar occultation should be quite an event for Saturn-orbiting Cassini. The Sun will pass directly behind the planet from the spacecraft's vantage point, and will remain there for twelve hours. New ring structures may turn up in the resulting images, along with views of the D, F, G and E rings that will be like none ever observed. In addition, the event should allow scientists to map microscopic particles moving within the ring system. "We are all sort of on pins and needles waiting for the results," says Brad Wallis, Cassini Rings Discipline Scientist. "When you get these kinds of high phase angles, very small particles almost focus the light right at the observer. So these faint rings that are so hard to see are going to be considerably brighter and show us details that are just not possible to see in other viewing conditions. All the space between Enceladus and the G ring is probably going to be pretty well lit up. It's really a unique event." By phase angle, Wallis...

The seventh and final instrument aboard New Horizons has now been tested in space and found to return good data. The Pluto-bound spacecraft used its Long Range Reconnaissance Imager (LORRI) to take a picture of the Messier 7 cluster on August 29. Stars down to 12th magnitude are visible in the image, which means the instrument checks out with pre-launch calculations and is operating nominally. "Our hope was that LORRI's first image would prove not only that the cover had opened completely, but that LORRI was capable of providing the required high-resolution imaging of Pluto and Charon," says Andy Cheng, LORRI principal investigator, from Johns Hopkins University Applied Physics Laboratory, which built and operates the spacecraft. "Our hopes were not only met, but exceeded." The mirror remained in focus even after its temperature dropped by more than 50 degrees C (120 degrees F) when its cover door opened. Next for LORRI are observations of Jupiter as New Horizons begins to focus on...

Someone with more cultural insight than Centauri Dreams will have to explain why the designation of Pluto as a planet has captivated so large an audience. The issue is front page on my local newspaper this morning and I'm being asked about it by people who have never shown the slightest interest in space exploration. Perhaps it's the overturning of things memorized long ago, as if someone had changed the multiplication tables, or decided to modify what makes up the letters of the alphabet. Whatever the case, the IAU's draft definition seems to lead to a de facto loss of planetary dignity for Pluto even while maintaining its tenuous identification as one of the tribe. For 'plutons' -- that category to describe planets whose orbits take more than 200 years to complete, with large orbital inclination and eccentricity -- will no doubt soon comprise the vast majority of planets as we discover more and more material in the Kuiper Belt. Which will inevitably lead to an accurate sense that...

The current issue of Nature features a look at Huygens data with a big payoff: rain is falling on Titan, continues to fall as we speak, and will probably keep falling for a long time. Says Christopher McKay (NASA Ames), a co-author of the paper, "The rain on Titan is just a slight drizzle, but it rains all the time, day in, day out. It makes the ground wet and muddy with liquid methane. This is why the Huygens probe landed with a splat. It landed in methane mud." All this from low, methane-nitrogen clouds that are barely visible but appear to be widespread, affecting weather globally. A Nature feature on this work, from which the McKay quote is drawn, can be found here. Methane rains are what you get at temperatures of minus 179 degrees Celsius, as are the river-like features also found by the probe as it descended on January 14, 2005. The latter surely derive from the ceaseless rains as well. McKay says the rain equals roughly two inches a year, about as much as Death Valley gets on...

Xanadu, that bright continent-sized aberration on the surface of Titan, begins to look somewhat familiar in new radar images from the Cassini orbiter. It's surrounded by darker terrain, cut by rivers and filled with hills and valleys. Cassini could identify a crater, probably created by asteroid impact, and flatter areas into which the rivers flow -- these are presumably lakes. Geologically and topographically (and ignoring for a moment the deep freeze), the place does look something like Earth, even if rain there falls in the form of methane. Image: A network of river channels is located atop Xanadu, the continent-sized region on Saturn's moon Titan. This radar image was captured by the Cassini Radar Mapper on April 30, 2006. These winding, meandering river channels start from the top of the image and run like a fork in the road, splitting to the right and left of the image. At Titan's chilly conditions, streams of methane and/or ethane might flow across parts of the region. Credit:...

With New Horizons now six months out and closer to Jupiter than it is to the Sun, the creatively-acronymed Jupiter Encounter Science Team (JEST) has turned in its observation plan. New Horizons will pick up a gravity assist from the gas giant in February of 2007, on its way to the 2015 encounter with the Pluto system. That also means that from January to June of 2007, the spacecraft will make more than 500 observations on everything from the Galilean satellites to the Jovian magnetosphere, with rich results expected. If you are tracking New Horizons, check out the mission locator page. Alan Stern's regular reports are also vital; Stern is principal investigator for the mission and has, throughout planning and launch, used the Web effectively to keep the public informed about its progress. In the latest update, he reports on a rare occultation of a star by Pluto in June. Such events provide the opportunity for studying Pluto's atmosphere, with the interesting result that conditions...

Centauri Dreams incorrectly identified the name of one of the new Plutonian moons yesterday as Nyx. The actual name is Nix, as witness this statement from the International Astronomical Union, quoting Oddbjørn Engvold, general secretary of the organization: "In Greek mythology, Nyx is the goddess of the night, but since asteroid 3908 already bears the Greek name Nyx, we changed Nyx to its Egyptian equivalent, Nix. Hydra was a nine-headed serpent with poisonous blood that had its den at the entrance to Hades, where Pluto and his wife Persephone entered the Underworld." Also on the IAU's agenda at its General Assembly in Prague in late August is a looming question: what is the proper definition of a planet? Pluto's planetary status is clearly at stake, as is that of 2003 UB313, the 10th 'planet' known unofficially as Xena. The Centauri Dreams take is that anything Pluto-sized and over is a planet, and if we wind up with a Solar System of 35 planets, most of them in the Kuiper Belt, so...

Centauri Dreams is told that one reason the name Pluto was chosen for the ninth planet in our Solar System is that the first two letters formed the initials of Percival Lowell. The Boston-born astronomer became world famous for his studies of the so-called 'canals' on Mars, but he devoted the last years of his life to the search for Planet X, a world he was convinced must exist. Dying in 1916, Lowell wasn't around to celebrate Clyde Tombaugh's discovery of Pluto some fourteen years later. In my mind, names play a role not dissimilar from the collapse of the wave function in some versions of quantum mechanics. Perform an observation and from a superposition of states you get a hard data-point. In a similar way, give something a name (see Bradbury's "The Naming of Names") and you make a vaguely understood object or place concrete. We'll get more concrete still with Pluto and its various moons when the New Horizons mission gets there and we start naming craters and peaks. But we didn't...

Enceladus continues to be an unlikely story, a tiny Saturnian moon jetting icy plumes of what seems to be water vapor from the surface of its south pole. Some believe there is even the potential for life here. But how did the 'hot spot' that produces this activity wind up precisely at the pole? We'll know more through future Cassini measurements, but a new study suggests that such a low-density region could cause the moon to roll over, thus moving this material to the polar area while repositioning excess mass at the equator. What's more, the bizarre Uranian moon Miranda may bear witness to the same phenomenon. The theory seems to gibe with other aspects of Enceladus including the surface features Cassini has so vividly imaged. The famous 'tiger stripe' pattern gives evidence of being made up of fault lines caused by tectonic stress. And the temperature variation at the pole also reinforces the reorientation concept. "The whole area is hotter than the rest of the moon, and the...

Was there ever a fifth rocky, terrestrial planet in our Solar System? If so, it was located beyond the orbit of Mars in what is now the asteroid belt. John Chambers (Carnegie Institute of Washington) likes to call the hypothetical world 'Artemis,' and at the 2006 Astrobiology Science Conference in Washington DC this March, he described how the planet might have formed. The trick, of course, is to account for the orbits of the giant planets, which some believe underwent a shift from almost circular to more highly eccentric (elliptical) orbits. If you set up a simulation with Jupiter in a circular orbit, terrestrial worlds form out to about 2.2 AU. From an abstract of Chambers' presentation: Artemis could have formed in a region that was stable before the giant planets' shift, but unstable thereafter, probably between 1.8-2.2 AU. We simulate the giant planets' orbital shift to explore Artemis' demise, varying Artemis' mass and starting location. In each simulation, the giant planets'...

Centauri Dreams has great pleasure in recommending new movie views of the landing of the Huygens probe on Titan, released yesterday by NASA, the European Space Agency and the University of Arizona. The first sequence, titled "View from Huygens on Jan. 14, 2005" offers a spectacular four-minute ride that compresses what would have been seen by the probe during its 2.5 hour descent, using data gathered by the Descent Imager/Spectral Radiometer instrument aboard Huygens. Image: DISR view south at 5 miles above the landing site on Titan, Jan. 14, 2005. (Credits: ESA/NASA/JPL/University of Arizona). "At first, the Huygens camera just saw fog over the distant surface," said Erich Karkoschka, team member at the University of Arizona, Tucson, and creator of the movies. "The fog started to clear only at about 60 kilometers [37 miles] altitude, making it possible to resolve surface features as large as 100 meters [328 feet]," he said. "But only after landing could the probe's camera resolve...