One of the challenges of running a site like Centauri Dreams is that deep space news accumulates so swiftly that it's easy to focus on one issue while another timely story slips away. I don't want to get too far past the European Planetary Science Congress, which ended in Madrid on September 28, without mentioning the interesting discussion of Titan that took place there. A new proposal for landing on the moon and sampling Ligeia Mare, its largest lake, was put forward to join previous Titan exploration proposals, all of them challenging yet doable. Titan Lake In-situ Sampling Propelled Explorer (TALISE) is the brainchild of SENER, a private engineering and technology group that has provided components and subsystems for a wide variety of space missions. The idea is to land a probe in the middle of Ligeia Mare, near Titan's north pole, and embark on a six- to twelve-month cruise to the coast, gathering data all the way. TALISE team member Igone Urdampilleta explains what makes TALISE...

At $2.5 billion, NASA's Curiosity rover didn't cost quite as much as Cassini ($3 billion), but what a relief to Solar System exploration both near and far to have it safely down at Gale Crater. This Reuters story tells me that 79 different pyrotechnic detonations were needed to release ballast weights, open the parachute, separate the heat shield, detach the craft's back shell and perform the rest of the functions needed to make this hair-raising landing a success. All of this with a 14-minute round-trip radio delay that left mission engineers as no more than bystanders. Congratulations to the entire Curiosity team on this triumphant event! As we now move into the next several weeks checking the six-wheeled rover and its instruments out for exploration, let's ponder future targets beyond the Red Planet. For at some point, no matter what we find on Mars, we're going to want to push on to the outer planets, where intriguing moons like Titan, Europa and Enceladus await. The latter's...

When I was a boy, I became fascinated early on with the outer planets. The further out, the better as far as I was concerned, and as you might imagine, I had a special fascination with Pluto. In the summer, I used to haunt the library in the nearby suburb of Kirkwood (in St. Louis, where I grew up), working my way through all the books on astronomy and space I could find. Because I was reading all of them, I would encounter older volumes, some pre-dating the discovery of Pluto, and more recent tomes with details about the planet I didn't know. It didn't matter; I just kept reading. What was fun about all this was that I kept expecting to find something new each time I opened a book, and was sometimes rewarded with a fact that brought this distant realm into perspective. The news that Hubble has now found a fifth moon orbiting Pluto awakens that same sense of satisfaction, for as we keep tuning up our observing skills, we're learning much about the outer system that surprises us. The...

It should come as no surprise to anyone who follows Centauri Dreams that I am a great admirer of Ed Stone, the former director of the Jet Propulsion Laboratory (from 1991 to 2001) and more than any single scientist, the public face of many of our missions to the outer Solar System. Stone's work on space projects began as far back as 1961 with the cosmic ray experiments he designed for the Discoverer satellites, but it was as project scientist for the Voyager missions that he became a familiar figure to audiences worldwide. His tenure at JPL saw missions like Mars Pathfinder, the Sojourner rover, Deep Space 1 and the launches of Cassini and Stardust. That, of course, is only a partial list, but it gives you the drift. This morning I'm thinking about Stone again because of a quote he provided for a recent JPL news release. Here again he's talking about the Voyagers, which are pushing up against the edge of the system: "The laws of physics say that someday Voyager will become the first...

What is it that makes us want the stars? Surely there are philosophical reasons that push us into the universe, and in his book Quest: The Essence of Humanity (2004), Charles Pasternak delves into 'questing' as a drive embedded in the species. But alongside a need to explore I can see two other drivers. One is the urge to know whether life exists elsewhere, and ultimately, whether there are other technological civilizations somewhere in the galaxy. The other is simple survival: We need to move into the universe as a backup plan in case of disaster here on Earth, whether that disaster is caused by an asteroid or a human activity gone awry. This morning I'm musing on all this in the context of recent news from the outer Solar System, where the data we're analyzing from the Cassini mission are matched only by our desire to have still further, more targeted explorations. We learn, for example, that Titan has lakes around its equator. Lakes on Titan aren't a surprise: We've already known...

Mars has always been a tempting destination because of the possibility of life. Thus the fascination of Schiaparelli's 'canals,' and Percival Lowell's fixation on chimerical lines in the sand. But look what's happened to the question of life elsewhere in the Solar System. We've gone from invaders from Mars and a possibly tropical Venus -- wonderful venues for early science fiction -- to a vastly expanded arena where, if we don't expect to find creatures even vaguely like ourselves, we still might encounter bacterial life in the most extreme environments. Astrobiology will push exploration. This is not to say that objects in deep space aren't worth studying in their own right, possible life or not, but merely to acknowledge that if we find life on another world, it deepens our view of the cosmos and fuels the exploratory imperative. A 'second genesis' off the Earth, once confirmed, would heighten interest in other targets where microbial life might take hold, from the cloud tops of...

by Larry Klaes Larry Klaes is a long-time Centauri Dreams contributor, a practitioner of the Tau Zero Foundation and a serious devotee of space exploration and its history. Here he gives us a look at the Pioneer probes that first took us to the outer Solar System, journeys that foreshadowed the later exploits of the Voyagers and the more recent New Horizons mission to Pluto/Charon. It's hard to believe that it's been fully forty years since the Pioneers were launched. They came out of the era when thinking big was the order of the day, Apollo was putting astronauts on the Moon and human expansion into the cosmos seemed inevitable. When we ponder today's budget shortfalls and drifting public attention, it's heartening to recall that era even as we speculate about missions that will follow up on the findings of these two remarkable probes. The early 1970s was an exciting time for lunar and planetary exploration. On the Moon, Apollo was still placing pairs of astronauts on Earth's...

Of all the probe targets in the outer Solar System, Titan is in many ways the most provocative. Not long ago we looked at two concepts -- Titan Mare Explorer (TiME) and AVIATR -- that would get instruments back into Titan's atmosphere and, in the case of TiME, onto one of its northern seas. The allure of this moon is surely what goes on in that atmosphere, a nitrogen brew mixed with methane that generates complex hydrocarbons. We're learning how these fall on the surface to form patterns of dunes made up of organic material, all of this mediated by a weather cycle that involves seasonal change the Cassini spacecraft has strikingly recorded. Kathleen Mandt (Southwest Research Institute) has been studying methane in Titan's atmosphere over time using data both from Cassini and the European Space Agency's Huygens probe (digression: can it really be seven years since Huygens parachuted down through those orange skies? Good grief...) Mandt's team is looking at heavy methane -- methane...

Getting to the stars may involve a sudden breakthrough -- we can't rule out disruptive technologies, nor can we predict them -- but my guess is that interstellar flight is going to be a longer, more gradual process. I can see a sort of tidal expansion into the outer system, forays to Mars, for example, followed by reassessment, retrenchment, then one day deeper study of Jupiter's moons with advanced robotics that can get under Europa's ice. The search for life may become so provocative that we have to explore Titan and Enceladus with human crews, and the imperative for planetary protection may help us further tune up our deep space technologies. The thing is, one wave of exploration inevitably begets another. Let's put no timeframe on that kind of expansion because, like the tides, it may surge at times and then fall back, hostage to budgetary problems and waves of public interest that can as easily ebb. But I could see an eventual civilization that extends throughout the Solar...

I closed last week with two posts about the AVIATR mission, an unmanned airplane that could be sent to Titan to roam its skies for a year of aerial research. It’s a measure of Titan’s desirability as a destination that it has elicited so many mission proposals, and I want to get into the Titan Mare Explorer (TiME) as well, but let’s pause a moment to consider the nature of what we’re doing. Out of necessity, all our missions to the outer system have been unmanned, but as we learn more about long-duration life-support and better propulsion systems, that may change. The question raised this past weekend in an essay in The Atlantic is whether it should. Ian Crawford, a professor of planetary sciences at Birkbeck College (London) is the focus of the piece, which examines Crawford’s recent paper in Astronomy and Geophysics. It’s been easy to justify robotic exploration when we had no other choice, but Crawford believes not only that there is a place for humans in space, but that their...

Yesterday's discussion of the AVIATR mission to Titan inevitably brought up another prominent Titan mission concept: Titan Mare Explorer (TiME). I'll have more to say about this one next week, as today I want to continue talking about AVIATR, but you can once again see how Titan enthralls us with its 'Earth-like' aspects. Need a thick atmosphere around a moon? Titan is your only play, and if, as with TiME, you want to put an instrument package into an off-planet surface lake, you'll be hard pressed to do it anywhere else, at least in this Solar System. These two mission concepts fire the imagination -- they're the kind of thing kids like me used to dream about when we plunked down our money at the newsstand for copies of Galaxy or Fantasy & Science Fiction. It's unlikely, though, that both missions will fly. If TiME, which is a Discovery-class mission finalist and thus cost-capped at $425 million, is chosen, then the odds on AVIATR probably drop. AVIATR, a New Frontiers-class...

Each of our highest priority targets in the outer Solar System offers something unique, from Europa’s internal ocean to the geysers of Enceladus. But Titan exerts the kind of fascination that comes from the familiar. The imagery of lakes and river channels reminds us inescapably of our home world, even if the temperature on the Saturnian moon averages a brisk 94 K, which works out to -291 degrees on the Fahrenheit scale. But because of its thick atmosphere we have options for exploring Titan that are unavailable on the other icy moons, and we’re working with a landscape that is a compelling frozen doppelgänger of Earth, a landscape we’d like to explore up close. As we saw yesterday, part of the outer system puzzle is getting supplies of plutonium-238 up to speed, and there is at least some movement on that front. If we want to get aggressive about exploring Titan, one excellent way to deploy that plutonium is aboard AVIATR (Aerial Vehicle for In-situ and Airborne Titan...

How likely are we to find other planets in the universe that are as habitable as Earth? One key to the puzzle has long been thought to be the presence of Jupiter in our own Solar System. In fact, the presence of the giant planet has become a player in the so-called 'rare Earth' argument that sees Jupiter as just one factor that makes our Solar System unique. Put a gas giant in the proper position in any solar system and, so the argument goes, dangerous objects from the outer system will be deflected, protecting the inner planets and allowing life to flourish. The issue gets a hard look from Jonathan Horner (University of New South Wales) and Barrie Jones (The Open University, UK) in a paper delivered in Canberra in September of 2011. Jupiter as protector has a certain appeal. Voyager, Galileo and other probes have shown us a massive planet that is otherwise cold and forbidding, but a world with enough mass to have huge effects on other objects in the Solar System. Horner and Jones...

We tend to think of interstellar journeys as leaps into the void, leaving the security of one solar system to travel non-stop to another. But a number of alternatives exist, a fact that becomes clear when we ponder that our own cloud of comets -- the Oort Cloud -- is thought to extend a light year out and perhaps a good deal further. There may be ways, in other words, to take advantage of resources like comets and other icy objects for a good part of an interstellar trip. That scenario is not as dramatic as a starship journey, but it opens up possibilities. Let’s say, for example, that we only manage to get up to about 1 percent of lightspeed (3000 kilometers per second) before we run into technical challenges that are at least temporarily insurmountable. Speeds like that take well over 400 years to get a payload to Centauri A and B, but they make movement between planets and out into the Kuiper Belt and Oort Cloud a straightforward proposition. A civilization content to create...

Mindful of the recent work on axial tilt I've reported in these pages, I was interested to learn that Vesta's axial tilt is just a bit greater than the Earth's, about 27 degrees. We've been pondering the consequences of such obliquity on planets in the habitable zone, but in Vesta's case, the issue isn't habitability but water ice. For spurred by the Dawn mission, scientists are looking at whether permanently shadowed craters on the asteroid's surface would allow water to stay frozen all year long. Unlike the situation on the Moon, the answer on Vesta (on the surface at least) seems to be no. Earth's axial tilt is 23.5 degrees, but the Moon's is a scant 1.5 degrees, making the shadow in some lunar craters permanent, a fact that has led to speculation that ice in these locations could be of use to future manned missions there. In contrast, Vesta's obliquity means that it has seasons, so that every part of the surface becomes exposed to sunlight at some point in the year. Even so, says...

The methane/ethane cycle we see on Titan is reminiscent of the water cycle on Earth, which is what people are really talking about when they refer to this frigid place as vaguely 'Earth-like' -- this is not exactly a temperate climate! But we have a long way to go in understanding just how the cycle operates on the distant moon, which is why new work on Titan's sand dunes is drawing interest. By studying the dune fields, we can learn about the climatic and geological history they depict and perhaps get clues about other issues, such as why Titan's lakes of liquid ethane and methane are found mostly in the northern hemisphere. What Cassini is showing us are regional variations among Titan's dunes, a landscape feature that covers some 13 percent of the surface in an area roughly equivalent to that of Canada. But every time we run into an Earth analogue on Titan, we're confronted with major differences. Titan's dunes are made not of silicates but of solid hydrocarbons that wind up as...

A robust new computer model that couples the atmosphere of Titan to a methane reservoir on the surface goes a long way toward explaining not just how methane is transported on the distant moon, but also why the various anomalies of Titan's weather operate the way they do. The model comes out of Caltech under the guidance of Tapio Schneider, working with, among others, outer system researcher extraordinaire Mike Brown. It gives us new insights into a place where the average surface temperature hovers around a chilly -185 degrees Celsius (-300 F). Image: NASA's Cassini spacecraft chronicles the change of seasons as it captures clouds concentrated near the equator of Saturn's largest moon, Titan. (Credit: NASA/JPL/SSI). Titan can a frustrating place for meteorologists to understand because during the course of a year some things happen that, in the early days of research, didn't make a lot of sense. The moon's equator, for example, is an area where little rain is supposed to fall, but...

I hope everyone is having a happy holiday season and looking forward to the upcoming New Year's festivities. In the intervening window, let's look at the outer Solar System. No other spacecraft has ever come as close to Pluto as New Horizons now has, already halfway between the Earth and the distant dwarf planet. It's also worth mentioning that New Horizons is only the fifth spacecraft to venture so deep into the Solar System, following the two Voyagers and the Pioneer spacecraft. July of 2015 will be an extraordinary time as we wait for data return from the mission and begin to find answers to some of the many questions that await us there. But studies from closer to home are continuing to reveal more about Pluto/Charon as well. The Cosmic Origins Spectrograph aboard the Hubble Space Telescope has found evidence for complex hydrocarbon and/or nitrile molecules on the planetary surface. Alan Stern, principal investigator for New Horizons, is behind the study, whose work was recently...

Sub-surface oceans in the Solar System may be far more common than we've realized. We've grown used to contemplating water under the ice of Europa, but similar oceans may well exist on Ganymede and Callisto, and there are signs of a possible ocean beneath Titan, not to mention the unusual activity we continue to observe on Enceladus. Where liquid water in cold objects seems least likely is in the Kuiper Belt, but Guillaume Robuchon and Francis Nimmo (University of California at Santa Cruz) have been making the case for an ocean inside distant Pluto, based on their models of thermal evolution and the behavior of the ice shell. As this article in Astrobiology Magazine points out (and thanks to my friend Antonio Tavani for the pointer to this one), Pluto's outer surface is a thin shell of nitrogen ice covering a shell of water ice. With New Horizons inbound to Pluto/Charon for an April, 2015 encounter, the researchers have been working out what surface features might help us make the...

An area of disrupted terrain called Thera Macula on Jupiter’s moon Europa may be evidence for a body of liquid water with the volume of North America’s Great Lakes encased within the ice. The notion comes from analysis of floating ice shelves that seem to be collapsing. That an ocean exists beneath the ice on Europa should surprise no one, but what is significant about the recent findings is that they suggest a way to exchange nutrients and energy between the surface and the ocean beneath. Such a mechanism changes the nature of the speculation about whether Europa’s ice is thick or thin. The case for astrobiology always seemed stronger if the ice were thin, but it seems that ways to exchange material with the surface may exist in either scenario. At least that’s what this intriguing finding suggests. Britney Schmidt (University of Texas at Austin) is lead author on the paper that appears online in Nature: "One opinion in the scientific community has been, 'If the ice shell is thick,...