New measurements from Cassini, made on a flyby through the plume of Enceladus on March 12, 2008, bolster the case for liquid water in the Saturnian moon. Cassini found negatively charged water ions in the plume, and its plasma spectrometer also traced other kinds of negatively charged ions including hydrocarbons. That adds Enceladus to a fairly select list -- the Earth, Titan and the comets -- where negatively charged ions are known to exist in the Solar System. They're found in Earth's ionosphere, and also in places at the surface where liquid water is in motion, such as waterfalls. Image: Is there liquid water beneath this surface? Portions of the tiger stripe fractures, or sulci, are visible along the terminator at lower right, surrounded by a circumpolar belt of mountains. The icy moon's famed jets emanate from at least eight distinct source regions, which lie on or near the tiger stripes. However, in this view, the most prominent feature is Labtayt Sulci, the approximately...

Here's something to consider re the recent Pluto news: The Hubble maps of the tiny world that were released yesterday show a resolution of roughly 300 miles per pixel. When New Horizons flies by Pluto/Charon in 2015, it will send images with a resolution of 300 feet per pixel. And we've been reminded once again that every time we look deeper into something hitherto unexplored, we're likely to be surprised. The surprise in this case was the significant reddening of the dwarf planet and the time frame in which it occurred, a mere two years. I thought the liveliest part of the teleconference on Pluto yesterday was Marc Buie's response to what had appeared in his datasets. Buie (Southwest Research Institute) was looking at imagery collected by the Hubble Space Telescope from 2002 to 2003 and comparing it with the results of earlier ground-based observations, as well as with Hubble pictures taken in 1994. The dramatic reddening seems to have occurred between 2000 and 2002, even as the...

Collisions between asteroids should be highly energetic affairs, with an average impact speed of close to 5 kilometers per second. We may be looking at the debris of a head-on collision between two asteroids in imagery provided by the Hubble Space Telescope. The object in question, originally thought to have been a comet, is P/2010 A2, discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) sky survey on January 6 of this year. The follow-up Hubble imagery dates from late January, and shows an unusual filamentary pattern near the nucleus. Image: HST picture of the comet-like object called P/2010 A2. The object appears so unusual in ground-based telescopic images that discretionary time on Hubble was used to take a close-up look. This picture, from the January 29 observation, shows a bizarre X-pattern of filamentary structures near the point-like nucleus of the object and trailing streamers of dust. The inset picture shows a complex structure that suggests the object is not a...

Adding punch to the National Research Council's recent report on detecting near-Earth objects is the first asteroid detection by WISE, the Wide-Field Infrared Survey Explorer. We've focused in these pages primarily on WISE's ability to spot nearby brown dwarfs, but the mission is going to map the entire sky in infrared light and its discoveries should range from the inner system to distant galaxies. As an asteroid hunter, WISE is demonstrating it will be second to none, quickly spotting the object now designated 2010 AB78, a finding soon confirmed at visible light wavelengths at the University of Hawaii's 2.2-meter instrument at Mauna Kea. At 158 million kilometers from Earth, the asteroid, some 1 kilometer in diameter, poses no impact threat for the foreseeable future, but all asteroid and comet detections from WISE move nonetheless to the Minor Planet Center in Cambridge (MA) and follow-up observations then establish firm orbital data for newly discovered objects. The thinking is...

What goes on under the clouds of Neptune and Uranus? A new paper reinforces the possibility that there are oceans of liquid diamond in such places, diamond seas with solid diamond icebergs. It's a notion with a pedigree. I'm looking, for example, at a paper by David Stevenson (Caltech) from the Journal de Physique from November of 1984, where I find this: There is clear evidence that many hydrocarbons decompose (or collapse) upon shock compression, probably into graphite and hydrogen. It is very important to establish the range of temperature and C:H ratios for which this decomposition can occur. It is equally important to establish whether an actual phase separation occurs (implying possible formation of a diamond or liquid metallic (?) carbon layer in Uranus and Neptune) or whether a collapsed but intimately mixed C-H structure results. Stevenson's work built on that of Marvin Ross, who suggested the possibility of diamonds in this environment in 1981. Researchers at the University...

The Hubble Space Telescope is capable of extraordinary things, but a 35th magnitude object is beyond its capabilities. In fact, 35th magnitude is 100 times dimmer than what the instrument can see directly. But an ingenious investigation using Hubble's Fine Guidance Sensors (FGS) has turned up the smallest Kuiper Belt Object yet found. Not surprisingly, the method involves an occultation, in which the object discovered passed in front of a background star and revealed itself through the tiny signature of the event. Imagine tracking down something that is only 975 meters across but almost seven billion kilometers from the Sun (a solid 45 AU). By comparison, the smallest Kuiper Belt Object previously seen in reflected light is about fifty times larger. Hilke Schlichting (Caltech) and team took advantage of 4.5 years of FGS data to make the find. The Fine Guidance Sensors provide navigational information to Hubble's attitude control systems by looking at specific stars for pointing. And...

Saturn's moon Iapetus has always had an unusual aspect, one first noted all the way back in the days of Giovanni Cassini (1625-1712), for whom our Saturn orbiter is named. The moon's discoverer, Cassini correctly noted that Iapetus had a bright hemisphere and a dark one, each visible (because of tidal lock) on only one side of the planet as viewed from Earth. We now call the dark hemisphere Cassini Regio in honor of the Italian-born astronomer. Image: Cassini-Huygens spacecraft images of Iapetus' dark, leading side and its bright, trailing side. The high-resolution images shed new light on the long-standing puzzle of how Iapetus got its unusual coloration. Credit: Cassini Imaging Team. So what makes Cassini Regio so dark? Interior activity on the moon itself is one possibility, but the leading theory is that dusty debris from Saturn's moon Phoebe is the source. Now images from the Cassini orbiter have been analyzed, with a paper in Science concluding that Cassini Regio is being...

Although we have no direct observations of objects in the Oort Cloud, we may be able to change that with space missions like Kepler and CoRoT. So argue Eran Ofek (Caltech) and Ehud Nakar (Tel-Aviv University) in a recent paper. If they're right, we'll improve our understanding of the Solar System's planetary accretion disk and get a better feel for the dynamics of planet formation. Right now even the largest telescopes can't find Oort Cloud objects. Where do Kepler and CoRoT fit in? The answer is that they may be able to observe occultations of background stars, a method that has been put to use for Kuiper Belt Objects already, although to date there is only one reported occultation by a KBO. Ofek and Nakar look at the rate of occultation events, creating an estimate that shows the possibility of Kepler detections of Oort objects and presenting statistical methods that can be used to verify that any occultations are real events and not simply noise in the data. Moreover, they think...

Imagine a boat from Earth drifting across an alien sea. Something like that could happen as early as 2022 if Ellen Stofan (Proxemy Research) can talk the powers that be into the venture. Stofan envisions a new mission to Titan, the only other place in the Solar System known to have bodies of liquid on its surface. The methane and ethane lakes revealed by Cassini show some bodies as large as the Black Sea or the Great Lakes of North America. Stofan's target: Ligeia Mare or Kraken Mare, two of the larger possibilities revealed by the orbiter. Image: Radar data from Cassini allowed the creation of this artificially colorized view of Ligeia Mare, with liquid methane/ethane shown in blue. Credit: NASA/JPL/USGS. What an interesting off-shoot from the conventional rover concept, but then, Titan seems to inspire such things. Various types of airship designs have been put forward for studying the Saturnian moon, and at the Aosta conference in July, Giancarlo Genta described the workings of a...

Back when I was a kid I found an old atlas that had been on the family shelves since the early 1900's. I used to browse through it looking at all the places that had changed. The map of eastern Europe was, as you can imagine, a far cry from what it later became, with the pre-World War I world vividly sketched in those musty pages. But what really caught my eye was one of the maps of South America, showing an area of Brazil that was still marked 'unexplored.' It was the only such place I could find on any of the maps, and it filled my adolescent head with thoughts of adventure. I wish I had that atlas nearby to scan from, but the image below gets across the feel of those old maps. Henry M. Stanley I'm not, but exploration has huge appeal, and to get the pure product today, we have to move into space. Out there most everything could be marked 'unexplored.' Sure, we're getting to know the planets, but we've only had a few missions beyond Mars, have yet to see Pluto/Charon close up, and...

Long-time Centauri Dreams readers already know of my admiration for Richard Greenberg's work on Europa, admirably summarized in his 2008 title Unmasking Europa: The Search for Life on Jupiter's Ocean Moon (Copernicus). It's a lively and challenging book, one which Greenberg used to take sharp issue with many of his colleagues, and although he played this aspect of the work down in a phone conversation when I reviewed the book, the animated back and forth makes for a fascinating look at how planetary science gets done. In his book, Greenberg argues forcefully that the thickness of Europa's ice is unlikely to be more than a few kilometers, and that its active resurfacing would make it possible for life-forms below the ice to occasionally be carried above it. That would be good news for our hopes of detecting life, of course, for it would obviate the need to drill through the ice sheet. A spacecraft's electronics might not last long given radiation levels this close to Jupiter, but...

My first glimpse of Ganymede ran like this: Three dead men walked across the face of hell. Their feet groped past frozen rock, now and then they stumbled in the wan light, and always they heard the thin, bitter mumble of wind and felt the cold gnawing at their flesh. Around them there was death, naked stone reaching for a cruel sky of stars, a lean, poisonous whirl of snow which was not snow, that whipped about them and then lay still to crunch under their tread. Jupiter was low in the south, a great shield which glowed amber. That's not today's Ganymede, but a mid-1950's version as seen in Poul Anderson's The Snows of Ganymede (Ace Books, as part of an Ace Double that included Anderson's War of the Wing Men, otherwise known as "The Man Who Counts"). I bought this off a newsstand in St. Louis and remember reading it while waiting for a sandwich to arrive at a lunch counter just off Clayton Rd. I would have been something like nine years old. That memory made the recent news about...

I'm sure there are people who can keep things straight in the shifting world of planetary definitions, but given the fact that I'm still not used to Pluto's demotion, I have to look twice before I write anything on the subject. After checking, then, I confirm that Haumea, the interesting outer system object recently considered as the target of a fast orbiter mission (see this earlier post, and its sequel), is called a 'dwarf planet.' Orbiting in the Kuiper Belt, Haumea joins Eris, Pluto and Makemake in this category, the fourth largest dwarf planet now known in the Kuiper Belt. Dwarf planet Ceres is a main-belt asteroid, and thus not, like the others, a KBO as well. Image: Composite image of computer model frames showing Haumea's red spot as the dwarf planet rotates. Credit: P. Lacerda . What's special about Haumea? Its shape, for one thing. The distant world rotates in 3.9 hours, faster than any other large object in the Solar System. That spin seems to account for Haumea's unusual...

Conservation of energy means we never really get something for nothing. Nonetheless, the idea of propellantless propulsion is profoundly important for our future in space. A solar sail uses momentum from solar photons to get its boost, letting the Sun serve as the energy source so we don't have to carry heavy fuel tanks and can maximize payload. So propellantless propulsion really means finding sources outside the spacecraft itself to do the work. The Interplanetary Gambit Recently I've finished Michel Van Pelt's book Space Tethers and Space Elevators (Copernicus/Praxis, 2009), a treatment of a technology we seldom consider in these pages because it's more practical in terms of near-Earth solutions. But Van Pelt surveys tethers -- and the space elevator idea, which is built around what could be considered a giant tether -- so comprehensively with regard to the implications of leaving the propellant behind that his book is a must read for those of us interested in deep space...

I'm pushed for time this morning but do want to catch up with Cassini news, in particular the recent findings from Enceladus. The plumes of water vapor and ice particles erupting from the moon continue to capture the imagination. Cassini's Ion and Neutral Mass Spectrometer was used during Enceladus flybys in July and October of 2008, with results just released in Nature. Out of all this we get this interesting find, as discussed by Hunter Waite (SwRI), who is lead scientist on the instrument involved: "When Cassini flew through the plume erupting from Enceladus on October 8 of last year, our spectrometer was able to sniff out many complex chemicals, including organic ones, in the vapor and icy particles. One of the chemicals definitively identified was ammonia." William McKinnon (Washington University, St. Louis) calls ammonia "sort of a holy grail for icy volcanism," noting that this is our first unambiguous detection of ammonia on an icy satellite of a giant planet. Finding it is...

If you'll examine the cover of Claudio Maccone's new book carefully, you'll see an interesting object at the lower right. It's a spacecraft with two deployed antennae connected by a tether. The book is Maccone's Deep Space Flight and Communications, whose subtitle -- 'Exploiting the Sun as a Gravitational Lens' -- tells us much about the author's view of how early interstellar missions should proceed. And Maccone devoted a session at the recent conference in Aosta to these matters, making the case for taking advantage of this natural phenomenon. Uses of Gravitational Lensing We've looked at the Sun's gravitational lens, and the FOCAL mission Maccone champions to exploit it, many times here on Centauri Dreams. But for newcomers, gravitational focusing has been an active astronomical tool since 1978, when a 'twin' image of a quasar was found by the British astronomer Dennis Walsh. The gravitational field of a galaxy between the Earth and the quasar had bent the light from the more...

Other than Monday, the week here has been devoted to the outer planets, and before I leave that subject, I want to work in the findings of a team of astronomers looking at the early history of the asteroid belt. Recent numerical simulations suggest that many of the objects found in the 'main belt' between the orbits of Mars and Jupiter actually formed far out in the Solar System, moving inward during a violent spasm of planetary evolution. That points to an early system that, at particular times, underwent upheaval caused by a rearrangement of the gas giant planets. This is the so-called Nice model, so named because much of the work on it was performed at the Observatoire de la Côte d'Azur in Nice. The model proposes that the gas giant planets migrated to their present positions long after the protoplanetary gas disk had dissipated, playing a role in the Late Heavy Bombardment of the inner planets some 3.9 billion years ago, and producing many other effects, including the formation...

Gentry Lee (Jet Propulsion Laboratory) discusses the question of extraterrestrial life on a program called Are We Alone, which airs this evening on the Discovery Channel at 2100 EDT (0100 UTC on the 17th). Lee is chief engineer for the Solar System Exploration Directorate at the Jet Propulsion Laboratory, a veteran of Viking and Galileo, and a co-author of Arthur C. Clarke. He was also involved with Carl Sagan on COSMOS, so he knows something about video productions. Pushing Back Astrobiology As I've noted in the two previous posts, we're moving into an era of re-examination of the Solar System. It's one that leads inevitably to a new understanding of the concept of habitable zones, with life now being considered a possibility on places that were once thought off-limits. Europa is unusual enough, but the evidence for that ocean beneath the ice is persuasive. Can we extend the paradigm all the way out to the Kuiper Belt? If so, missions like the Haumea orbiter or probes to other...

Yesterday's look at a fast orbiter mission to Haumea raises useful questions. The mission, developed conceptually by Thales Alenia Space and presented at Aosta by Joel Poncy, is particularly demanding because this outer system object has no atmosphere. You can make the case for a Neptune orbiter with associated study of Triton, as several readers have already done, but if you want to orbit Haumea, no aerobraking is possible to ease orbital insertion. The Haumea mission, in other words, deliberately pushes the state of the art in both propulsion and power generation. Poncy noted in his talk at the Hotel Europe that his team had adapted an in-house software model to optimize the propulsion possibilities. The team considered only electric or magneto-plasma technologies (for the latter, think VASIMR -- Variable Specific Impulse Magnetoplasma Rocket). They assume a direct trajectory to Haumea with arrival around 2035, when the object is at 49 AU, and they weigh the benefits of a gravity...

One of the surprises of the Aosta conference was Joel Poncy's presentation on a fast orbiter mission to Haumea. Poncy (Thales Alenia Space, France) and colleagues have been developing ideas for the extraordinarily difficult challenge of not just sending a probe to the outer system, but slowing it down for orbital capture. It's one thing to do this, say, for Neptune, where a thick atmosphere can be used for aerobraking, but it's quite another to contemplate doing the same for an airless trans-Neptunian object (TNO) like Haumea. Nonetheless, there are solid reasons for thinking about such a mission. The first is purely scientific. As Poncy did, I'll use outer planet specialist Mike Brown's illustrations of what has happened to our Solar System in the last few decades. The first illustration shows the Solar System most of us grew up with, a system with nine planets that were more or less clearly defined, with what was assumed to be a certain amount of debris and cometary material...