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An Oxygen-Rich Europan Ocean?

by Paul Gilster | Oct 8, 2009 | Outer Solar System | 14 Comments

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...

Planetary Habitability Quantified

by Paul Gilster | Oct 7, 2009 | Astrobiology and SETI | 30 Comments

Habitability is always a matter of definition. Is it a measure of suitability for human life? Or do we take the larger astrobiological view that it's based on suitability for microbial life, in which case we go from a narrowly defined habitable zone here in our Solar System to one that could potentially stretch from the upper atmosphere of Venus to the suspected subsurface aquifers on some Kuiper Belt objects. But these qualitative definitions have thus far lacked a quantitative counterpart, a method to quantify and compare potentially living worlds. The matter has drawn the attention of Abel Mendez (University of Puerto Rico, Arecibo), who discussed his quantitative evaluation of planetary habitability at the Division for Planetary Sciences meeting this week in Fajardo, Puerto Rico. One of his results stands out immediately. Using finely tuned planetary models, Mendez found that among Mars, Venus, Europa, Titan and Enceladus, the latter has the highest subsurface habitability. That...

Dark Energy’s Elusive Signature

by Paul Gilster | Oct 6, 2009 | Exotic Physics | 6 Comments

It's odd to think that there would be a connection between the large-scale structure of the universe and what we hope to achieve with deep space propulsion. But figuring out how things work on the largest scale may offer us valuable clues about what is possible and what is not. If we understand correctly how gravity works at the macro scale, then the evidence for 'dark energy' seems persuasive. Something is causing the universe not only to expand but to accelerate its expansion, and that something must operate against the force of gravity, which ought to be slowing the process down. Which brings us to BOSS, the Baryon Oscillation Spectroscopic Survey, now beginning its operations after taking first light on the night of September 14-15. A part of the Sloan Digital Sky Survey III, BOSS will use the 2.5-meter telescope at Apache Point Observatory in New Mexico to measure the spectra of 1.4 million galaxies and 160,000 quasars by 2014. Out of this we should derive the most accurate data...

Looking Out on a Cosmic Aegean

by Paul Gilster | Oct 5, 2009 | Culture and Society | 33 Comments

Herbie Hancock's Maiden Voyage is one of my favorite CDs, as definitive a statement of Hancock's jazz artistry as, say, A Song for My Father is for Horace Silver's craft, or Giant Steps for John Coltrane's. But Maiden Voyage, particularly the title track, has that sense of relentless, questing motion that energizes me about all journeying. It's restlessness mixed with inevitability, an Odyssean fling with great events in a vast and unknowable sea. Such thoughts come to mind this morning because I've been paging through Giulio Magli's Mysteries and Discoveries of Archaeoastronomy (Copernicus, 2009) while listening to Hancock's work. It's a lively and amusing book, amusing because Magli (Politecnico of Milan) enjoys taking swipes at colleagues as well as earlier scholars, and it plumbs the depths of sites around the world where our ancestors either did or might have aligned their structures with celestial objects. Some of these places remain controversial, because there are a lot of...

Herschel: Lighting Up the Interstellar Medium

by Paul Gilster | Oct 3, 2009 | Deep Sky Astronomy & Telescopes | 0 Comments

Sometimes we're reminded in a stunning way of how much material exists in the star-forming regions of the galaxy. Take a look at the image below, which comes from the Herschel Space Observatory. Herschel's SPIRE camera, which works at wavelengths between 250 and 500 microns, is combined here with data from the observatory's other camera, called PACS, which operates between 70 and 170 microns. The combination reveals detailed images in the far infrared, locating star-forming regions that would otherwise be difficult to detect at a single wavelength. Image: Five-color composite image of a 2 x 2 degree area in the plane of our Galaxy, combining the PACS and SPIRE observations. In this image the SPIRE and PACS images have been combined into a single composite; here the blue denotes 70 microns, the green 160 microns, and the red is the combination of the emission from all three SPIRE bands at 250/350/500 microns. Credit: ESA. The infrared range these instruments cover should tell us much...

Arecibo in Context: Watching for NEOs

by Paul Gilster | Oct 1, 2009 | Asteroid and Comet Deflection | 12 Comments

Some things to keep in mind with regard to near-Earth objects: NASA is working with a Congressional mandate from 2005 that it discover ninety percent of all NEOs that are 140 meters in diameter or greater. The deadline for this task is 2020, and the interim report Near-Earth Object Surveys and Hazard Mitigation Strategies (written by a committee appointed by the National Research Council) says the surveys currently in progress are not capable of meeting this goal. The final report is to appear in December. Now switch to Arecibo. The radio telescope there, run by Cornell University and the National Science Foundation, has run into serious funding questions. NSF must decide whether the current cooperative relationship between Cornell and NSF should continue, and whether the observatory itself should be funded. You may recall that an NSF panel recommended in late 2006 that Arecibo's operating budget be reduced in a series of steps, ultimately taking it from $10.5 million to $4 million...

Heliospheric Crossings (and the Consequences)

by Paul Gilster | Sep 30, 2009 | Interstellar Medium | 21 Comments

Below you'll see that I'm running Mike Brown's sketch of the 'new' Solar System, one I originally ran with our discussion of Joel Poncy's Haumea orbiter paper, which was presented at Aosta in July. The sketch is germane on a slightly different level today because as we look at how our views of the Solar System have changed over the years, we've learned how many factors come into play, including one Brown's sketch doesn't show. For surrounding the planets and nearer regions of the Kuiper Belt is the heliosphere, that bubble of solar wind materials whose magnetic effects help protect the inner system. Image: Our view of the Solar System has gone from relatively straightforward to one of exceeding complexity. Credit: Mike Brown/Caltech. Look at the heliosphere diagram below and you'll see that while the eight planets are comfortably within it, our Pioneers and Voyagers are pushing toward or through the termination shock on their way to the heliopause. Galactic cosmic rays are shown...

Exoplanet Transits: Maxing Out Our Resources

by Paul Gilster | Sep 29, 2009 | Exoplanetary Science | 5 Comments

I'm a great believer in getting the most out of older systems. The computer I do most of my work on is now eight years old. I have access to newer equipment, but I built this box with an eye toward longevity and I'm still happy with it. With the pace of technological change, it's definitely gotten creaky despite additional memory, a new video card and various other upgrades. That means that Windows gets slower and slower on it, but then, I rarely use Windows, being an open source guy to the bone. Linux has always been my choice. Now the nice thing about Linux is that, no matter which version I run (and I've run quite a few by now), I can get snappy performance out of this old box. The astronomical analogy isn't too far to seek -- these days we're talking about building larger and larger Earth-based telescopes, and in fact have just inaugurated the Gran Telescopio Canarias on a 7,874-foot mountaintop in the Canary Islands, an instrument that has the largest segmented mirror -- 10.4...

Notes & Queries 09/28/09

by Paul Gilster | Sep 28, 2009 | Culture and Society | 37 Comments

Modeling a Space-Based Future The submission deadline for the MiniSpaceWorld contest has, according to Tibor Pacher, been extended to November 1. Those with a yen to build scale models with a space theme should be considering the possibilities in the project, an exhibit showcasing everything from current rocket technology to basic principles of physics and astronomy, space travel as seen in science fiction and more. MiniSpaceWorld draws on the inspiration of the Miniatur Wunderland in Hamburg, which does for model railroads what Pacher hopes to do for space-themed modelers and educators. Image: Tibor Pacher, who leads the MSW effort. With the help of the Roland Eötvös Physical Society, the MSW design particulars are now being circulated to 1500 secondary school physics teachers in Hungary, which is the reason for the deadline extension. Full particulars can be found on the site, where I notice that the design contest award ceremony will be held in Budapest on December 5. The Hamburg...

Homing In on Planet Formation

by Paul Gilster | Sep 25, 2009 | Exoplanetary Science | 9 Comments

Protoplanetary disks may not raise the same level of excitement that the discovery of new planets does, but to me, the idea of watching a planetary system form is awe-inspiring. I can't help but wonder whether, going back about five billion years or so, astronomers around some distant star weren't watching the early signs of planetary formation around our own star. Disks in their various stages give us a sense of the continuity of solar system development. Continuity, that is, in the sense that stars seem to form planets as a matter of course. But we're seeing yet more evidence this week that protoplanetary disks can vary markedly from star to star. Now comes news of the dust cloud around 51 Ophiuchi, which turns out to be not one but two distinct disks, an inner one with grains 10 micrometers and larger in diameter (based on infrared observations), and an outer one made up of primarily 0.1 micrometer grains. Image: This graphic compares the inner and outer disk of the 51 Ophiuchi...

Memories of Jupiter Space

by Paul Gilster | Sep 24, 2009 | Outer Solar System | 13 Comments

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...

Relativistic Effects on Solar Sails

by Paul Gilster | Sep 23, 2009 | Sail Concepts | 15 Comments

It's a long way from the back of an envelope to a deployed spacecraft, which is one reason why scientists write papers in journals and gather at conferences. Such venues are where ideas get shaken out, problems identified and solutions proposed. We sometimes talk about realistic technologies like solar sails as if all that remained were to build them, but as Roman Kezerashvili demonstrated at the recent conference in Aosta, there is a range of problems that we are only beginning to consider. Kezerashvili (City University of New York), working with colleague Justin Vazquez-Poritz, has identified a significant area of concern for mission concepts that pass close by the Sun. Often called 'Sundiver' missions (a Gregory Benford coinage, if memory serves), these sails would be so constructed as to survive an extremely close solar pass. Perhaps protected behind an occulter until periherlion, the sail would then be unfurled to receive the full force of the Sun's photons at extremely close...

Regarding METI and SETI Motives

by Paul Gilster | Sep 22, 2009 | Astrobiology and SETI | 30 Comments

by James Benford I first talked to Jim Benford back in 2003, discussing his work (wih brother Gregory) on microwave beam propulsion. He had already run experiments at the Jet Propulsion Laboratory demonstrating acceleration on a lightsail using these techniques, and was then hoping to run an experiment on The Planetary Society's ill-fated Cosmos 1. The founder of Microwave Sciences, Benford's earlier work at Physics International led to the development of the largest high power microwave experimental facility in the country. Along with continuing work on sail beamed propulsion concepts, the physicist has been actively studying questions of SETI and METI, musing on the kind of beacons we might find and the motivations for building them. Herewith some thoughts inspired by recent discussions in these pages. We explored the motives for a civilization broadcasting to the galaxy at large (which I call Beacons, as they're not targeted at specific stars) in one of the two papers we did last...

Interstellar Beacons: A Silence in Heaven?

by Paul Gilster | Sep 21, 2009 | Astrobiology and SETI | 47 Comments

by Jon Lomberg It seems fitting that we should be in the midst of a three-part series on SETI and METI issues. As Larry Klaes reminded me in a recent comment, September 19th was the fiftieth anniversary of the paper that began the modern SETI era, Morrison and Cocconi's "Searching for Interstellar Communications" (available here). Artist, lecturer and polymath Jon Lomberg now adds his own take on the discussion. Pay particular attention to the question of signal duration -- would a METI signal be continuous or intermittent? Much rides on the answer. Lomberg is a familiar figure to Centauri Dreams readers. Creator of the Galaxy Garden (Kona, Hawaii), Jon is an astronomical artist working in many media whose work is known throughout the space community and beyond. Viewers of COSMOS will know that he was chief artist on that project, serving as Carl Sagan's principal artistic collaborator for many years. His splendid work on CONTACT, where he storyboarded many of the film's astronomical...

The Why of METI and SETI

by Paul Gilster | Sep 18, 2009 | Astrobiology and SETI | 53 Comments

?by Larry Klaes About a decade ago while attending a SETI conference, I was listening to a researcher give a talk about detecting messages from other galaxies such as the giant elliptical galaxy Messier 87 and the immense Virgo galactic cluster it resides in. Since M87 is about 60 million light years from the Milky Way, I later asked him why would someone send a message that they could not hope to get a reply to for 120 million years at the least. His reply was rather vague and dissatisfying to me. It was along the lines of they would do it for the sake of being able to sending such a message across such a vast distance and time. I was left with the impression he did not fully think out why any intelligence would send messages across millions of light years of intergalactic space with even less hope of a reply than our token METI (Messaging ExtraTerrestrial Intelligence) effort with Messier 13 in 1974 via Arecibo, for which we will need to wait 50,000 years for the quickest reply...

Surface Feature Found on Haumea

by Paul Gilster | Sep 17, 2009 | Outer Solar System | 9 Comments

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...

CoRoT-7b: A Small, Rocky World Examined

by Paul Gilster | Sep 16, 2009 | Exoplanetary Science | 17 Comments

?I love to run into genuine enthusiasm when someone is doing cutting-edge science, and Didier Queloz (Observatoire de Geneve) has not let me down. Here the astronomer is discussing CoRoT-7b, which new studies have determined is a rocky world: "This is science at its thrilling and amazing best. We did everything we could to learn what the object discovered by the CoRoT satellite looks like and we found a unique system." Amazing indeed. We knew from CoRoT's transit measurements that the radius of this planet was about twice that of Earth. Queloz and team went to work with the HARPS spectroscope (High Accuracy Radial velocity Planet Searcher) at ESO's La Silla site in Chile, gathering fully seventy hours of observations on the system. What emerged was the best mass measurement for an exoplanet yet. Combining that revealed mass -- five times that of the Earth -- with CoRoT's radius readings, we can deduce that CoRoT-7b is about as dense as Earth, and thus almost certainly a rocky world....

Lightcraft Experiments Continue

by Paul Gilster | Sep 15, 2009 | Advanced Rocketry | 26 Comments

?The last time we developed a new way of reaching orbit was back in the 1950s. How useful, then, to come up with one that allows huge weight reduction because it leaves propellant and energy source on the ground. Keeping the fuel at home or harvesting it along the way are key ways to conceptualize missions to the outer Solar System or beyond. But in more immediate terms, laser-beamed lightcraft can give us a relatively inexpensive way to low-Earth orbit as we begin to build a true space-based infrastructure. Eric Davis (IASA) and Franklin Mead (formerly of the Propulsion Directorate, AFRL, now retired and pursuing independent research) envision a ground-based laser beam generator system made up of power supply, laser beam generator/transmitter and related tracking, hand-off and safety systems. As we saw yesterday, the system would power an air-breathing pulsed-detonation engine that feeds off ambient air turned into plasma by the laser from the ground, producing a 'superheated plasma...

Lightcraft: A Laser Push to Orbit

by Paul Gilster | Sep 14, 2009 | Advanced Rocketry | 25 Comments

Not the least of the objections against using laser propulsion to boost a lightsail to the stars is the engineering required to build the system. But theorists like Robert Forward, who originated the laser lightsail idea, never thought we would simply create such a system from scratch. We might ask, then, in the area of laser propulsion, what ideas are being experimented with right now, and might be capable of development into more advanced designs? Enter the Lightcraft Laser lightcraft command the attention here. Extensive work has been done on them at the Air Force Research Laboratory (AFRL), building upon earlier work at the AFRL Propulsion Directorate at Edwards Air Force Base. These early designs aim not at the stars, of course, but at a much more accessible target: Low Earth Orbit. A ground-based laser transmits power to the spacecraft, which collects the incoming energy and uses it to power its propulsion system. The beauty of this is that ambient air becomes the working...

Connecting to the Cosmos

by Paul Gilster | Sep 11, 2009 | Culture and Society | 3 Comments

Learning how we connect with the universe is one of the most fruitful investigations of modern science. No matter how we approach the matter, we're confronted with interesting possibilities. We study how gas giant planets may affect life on inner, terrestrial worlds by diverting asteroids from potential impacts. We look at issues like panspermia, wondering whether life's building blocks (or even life itself) arrived from elsewhere in the cosmos. In recent times, we've examined our Solar System's movements through the galaxy to ask whether there may be clues to periodic mass extinctions on our planet. As we widen stellar habitable zones into galactic ones, our musings take us out into the universe. They also confront us with our own limitations -- our eyes, notes astronomer James Kaler, see wavelengths between 0.00004 and 0.00008 of a centimeter. Kaler calls our visual spectrum "...but one octave on an imaginary electromagnetic piano with a keyboard hundreds of kilometers long." That...

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In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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