by Paul Gilster | Mar 13, 2007 | Outer Solar System |
Every time we get new information about Enceladus, I keep thinking about how the original Orion team would have felt if they really had made the trip to Saturn they once discussed for their fabled atomic rocket. Enceladus, thought Freeman Dyson, looked to be a logical place to refuel because it was believed to be rich in ice and hydrocarbons. But no one in those pre-Cassini days could have imagined what Dennis Matson (Jet Propulsion Laboratory) is now talking about:
“Deep inside Enceladus, our model indicates we’ve got an organic brew, a heat source and liquid water, all key ingredients for life. And while no one is claiming that we have found life by any means, we probably have evidence for a place that might be hospitable to life.”
All of which falls into the ‘never in my wildest dreams’ category, for Enceladus has hardly led the list when one discusses life’s possible venues in the Solar System. But Cassini found geysers ejecting water vapor and ice from the moon’s south polar region back in 2005. And that raised the whole issue of what was producing the needed heat to cause the eruptions. Add to that the fact that some of the molecules found in Enceladus’ plumes require elevated temperatures to form.
One way into the problem is to consider these temperatures as the result of radioactive decay. Let radioactive isotopes of aluminum and iron decay over a period of about seven million years and you generate enough heat to rearrange the mix of ice and rock into a rocky core surrounded by ice. Billions of years later, you should still see a relatively warm core fueled by this radioactive decay and given a boost by Saturn’s tidal pull.
As to those molecules in the plumes, Matson’s new study of same notes the Cassini spectrometer findings: water vapor, methane, carbon dioxide, propane, acetylene and gaseous nitrogen. Matson believes the nitrogen comes from the thermal decomposition of ammonia down where the warm core and liquid water meet. The temperatures involved may go as high as 577 degrees Celsius (1070 degrees Fahrenheit).
So is there an organic-rich mixture below the surface of Enceladus even today? Cassini found hydrocarbon chains in the moon’s plume, which means we can’t rule this scenario out. If so, that hardly means life is present, but a new measurement of the plume’s chemistry during a March 2008 flyby may help to refine the model, and tell us whether this tiny, surprising object is ready to yield still more of its secrets.
The paper is Matson et al., “Enceladus’ plume: Compositional evidence for a hot interior,” Icarus Vol. 187 Issue 2 (April 2007), pp. 569-573, with abstract available here. Bear in mind the contrasting clathrate model, which comes up with an alternative explanation for the Enceladus plumes that does not rely on the presence of liquid water. We now have two solid hypotheses about something quite unusual, and rely on Cassini’s next pass to help us sort out which of these is the most likely explanation.
by Paul Gilster | Mar 12, 2007 | Culture and Society |
When and if we discover extraterrestrial life, the handling of the news will be interesting. Recall the tumultuous media circus following the announcement in the movie Contact. Carl Sagan knew a little about dealing with the press, and the film version gets across what might happen when you start broadcasting public fear and fascination through a cable TV and Net-connected world. Or think of the recent rumblings when the SETI Institute said it was about to make a ‘major announcement,’ which turned out to be business related and not extraterrestrial at all.
And in point of fact, we do have one actual experience of trying to announce extraterrestrial life. That was in 1996, when a team of researchers had submitted a paper, subsequently accepted, to Science. The contents were dynamite, for the authors proposed that the Antarctic meteorite ALH84001 might be evidence of life on Mars. The team had studied four potential biomarkers within the meteorite, which had earlier been determined to be of Martian origin, and the circus soon began.
NASA scheduled a news conference, aware of the public interest that must follow, even though the evidence for life was equivocal at best. But a member of the White House staff spilled the beans to his girlfriend about the upcoming Science story, so the word had already leaked. Add to that the fact that a prepublication version of the story was given to the press earlier than planned. The result: hoping to avoid being scooped, a number of news outlets started distributing the paper to get quotes from experts to bolster their upcoming stories. The work on ALH84001 thus began its journey from interesting paper to ‘discovery.’
Today we have no definitive take on the Martian meteorite, but the fact that there are alternative explanations to the possible biomarkers leads many to doubt their validity. Whatever the case, contrast this situation — researchers working in strict secrecy until the press sniffs out their forthcoming paper — to what may happen with a Mars sample return mission. The scientists who work on the first samples will be operating from the start under public scrutiny, looking both for biohazards and for evidence of life while under pressure to work quickly.
What that calls for, in the eyes of John Rummel (Science Mission Directorate, NASA Headquarters) and Margaret Race (SETI Institute) is a communications plan that has been thought through in advance and will anticipate any outcome. Their recent paper suggests how such a sample receiving facility (SRF) might operate, with dialog involving NASA, policy makers, international partners and teams of experts:
In order to provide for a successful SRF activity, risk management and planetary protection information will have to be balanced with a program of education and outreach, from the scientific perspective, that will focus on the anticipated benefits of Mars exploration and of returning a sample from Mars — while not neglecting the uncertainties associated with the biological potential of Mars. In order to take a comprehensive approach even further, a Mars SRF communication plan must also address how, when, and where the public and scientific community will be informed of results and findings that occur during both the life detection and biohazard testing of the sample. Such information should be structured to properly put it into context, while it also may be delivered without context — in the raw — as a more or less continuous stream, similar to the recent practice of NASA solar system exploration missions.
And that last point bears watching. We know that bringing extraterrestrial life to light will draw intense public interest. The ability of any government agency to contain the outcome in the face of live streaming of data via the Net is questionable. Even as Martian samples are first being examined, various media outlets will be announcing rumor-based results in hopes of positioning themselves ahead of the pack. How well have we thought through the impact of an unequivocal finding of life on another world, even single-celled life? NASA is thinking hard about this, and that’s an indication that Mars remains very much in play as a potential home to some kind of exobiology.
The paper is Rummel and Race, “Got Life? Hours of boredom followed by moments of sheer terror (and that’s just with the press),” in Acta Astronautica 59 (2006), pp. 1160-62. A NASA draft protocol on all this is Rummel, et al. (Eds.), A Draft Test Protocol for Detecting Possible Biohazards in Martian Samples Returned to Earth (NASA/CP-2002-211842), 2002.
by Paul Gilster | Mar 10, 2007 | Culture and Society |
Back in the 1950’s, science fiction magazines were all over the newsstands. That’s significant for Centauri Dreams‘ purposes because these titles spurred many a career in science and a fascination with astronomy, astrophysics and engineering. Many is the scientist I’ve talked to who fondly reminisces about stories that proved inspirational, and in today’s math-challenged world, getting students to start thinking about pursuing work in physics or other sciences is a serious concern.
Which is one reason Paul Raven’s recent essay on the declining fortunes of the science fiction magazines caught my eye. Paul writes Velcro City Tourist Board, the site I turn to when I want to know what’s worth reading on the modern SF scene. He’s well plugged in — Paul writes reviews for Interzone, the fine British magazine, among other things — and for those of us whose SF tastes run to older material, he provides a wonderful way of keeping up with new trends and making sense out of where the field is going.
Image: The first issue of Beyond Fantasy Fiction, from July of 1953. Note the distinctive cover art by Richard Powers. The 1950’s produced many solid titles that have long since vanished. What can we do to recapture that era’s publishing vitality?
Jump back to that 1950’s newsstand a moment. I can remember seeing, at just one drugstore in suburban St. Louis, a wide range of titles: Galaxy, Infinity, Worlds of IF, Astounding, Venture, Amazing, Fantastic Stories, Fantasy & Science Fiction, Fantastic Universe and Satellite. Others were available around town, some of them only briefly (I recall Damon’s Knight’s Worlds Beyond, for example). And a magazine called Beyond, the fantasy offshoot of Galaxy, is a wonderful memory, its exotic covers capturing fascinating and always well-written tales of the unknown.
Compared to that scene, today’s magazine drought is a sad thing indeed. And even among the survivors, which in the US include Analog (the old Astounding), F&SF and Asimov’s, subscriber numbers are nowhere near what they might be, while the brave attempt to translate short fiction markets to the Web still tries to define itself. I suspect good things will eventually come from that attempt (check Strange Horizons), but until then, I worry like Paul Raven about the effect of genre magazine loss:
The magazine markets have always been the proving ground for new novelists in genre, and that’s the best argument for wanting to them to survive that I can think of. Novels will take much longer to die off in dead tree format for an assortment of reasons – the iconic status of the book, the inconvenience and user cost of printing out a novel length manuscript, and so on – although the big publishers are starting to realise that digital is as unavoidable as death and taxes if they want to stay relevant in a wired world. But magazines of all types are already suffering, because there are so many more efficient ways to get hold of bite-sized content.
Internet content is indeed changing the equation. Is it both the cause of the problem and its solution? The major US magazines are available in digital form through venues like Fictionwise, and as one who does a lot of reading on a Palm TX, I see this as an exploitable market. The key will be figuring out how to turn the necessary profit to support an ongoing venture — writers do like to be paid, and so do editors and publishers.
As the experimentation proceeds, one good thing will be a larger marketplace for writers. The current magazines are largely filled with the same names month after month. The lively market of years past has become a much diminished club of insiders with few membership slots open. Paul believes that free content supported by advertising will reinvigorate the magazine scene and provide new opportunities. Perhaps, but I have my doubts in a world that seems to be turning away from text entirely thanks to the enticement of video in all its venues.
Image: The April 1957 issue of Fantastic Universe. Covers like these prompted endless speculation in this young reader about possible futures and our place in the cosmos.
Even as I write that, though, I’m reminded that one thing I’ve always missed when reading magazines in digital format is not just the illustrations but the advertising itself. I like to look at the cover art of new books, for example, and I miss the print formatting of the paper magazine. The online solution will gradually have to work out file formats (and I am not talking about PDF!) that incorporate as much of the visual appeal of a printed volume as possible, while including the digital benefits that are so obvious, such as the search function. And needless to say, doing this without over-burdening the result with DRM (digital rights management) would allow portability between devices.
The key question persists. As SF magazines make the online transition, will they be able to generate readers in sufficient numbers?
I have no answer to that one, but do believe that a viable science fiction scene is a stimulus to the scientific imagination, and one that acts as a powerful recruiter for many of the sciences. Genre magazines seem like a niche, but their effects have always been greater than their numbers suggest. It’s good to see editors like F&SF‘s Gordon van Gelder engaging on this issue (see the comments to Paul’s post), and searching for the model that will take us forward. Let’s hope such editors succeed.
by Paul Gilster | Mar 9, 2007 | Deep Sky Astronomy & Telescopes
Out near the end of the Big Dipper’s handle is a strip of sky the width of two full moons that looks all but empty to the naked eye. But take a closer look, as the ongoing AEGIS survey is doing across the electromagnetic spectrum — from radio and infrared through visible light up to the x-ray regions — and you’ll find more than 150,000 galaxies. AEGIS is examining galaxies up to 9 billion years back in time.
The name stands for the All-wavelength Extended Groth Strip International Survey, and when I first wrote about it, I didn’t have this link to the nineteen papers about the survey that will appear in the Astrophysical Journal Letters in the spring. What’s exciting about the survey is its sheer breadth — no other region of the sky this large has been examined quite so intensively. Cosmologist Jeffrey Newman (Lawrence Berkeley National Laboratory) puts it this way:
“We have looked at this patch of sky with every possible telescope, at wavelengths covering nine orders of magnitude – that’s a wavelength range of a billion, compared to the ability of our eyes to see a range of two. Each provides a little piece of the puzzle of how galaxies evolve.”
Out of that comes a look at galaxies in their adolescence. Some interesting finds have already emerged. How about a galaxy with a double black hole? The galaxy, about six billion light years out, shows a separation of about 4,000 light years between the two black holes, one of them 5 million times the Sun’s mass, the other about a tenth as large. The odd pairing is apparently the result of a merger hundreds of millions of years earlier between two elliptical galaxies, since which time the two black holes have been spiralling towards each other. Unlike other black hole pairings nearer the Earth, this pair is visible in optical wavelengths.
We don’t know how many galaxies may take on this configuration because it takes matter falling into the black holes to make them visible — both black holes would have to be accreting matter to make their nature clear. But the AEGIS discovery of an apparent merger of two elliptical galaxies is helpful because ellipticals are places where new star formation has ceased. That leaves them with little dust to obscure their centers.
A Hubble view of the AEGIS area shows galaxies in an uneven distribution that bears the signature of dark matter — galaxies, so current thinking goes, form where dark matter is concentrated. But Hubble is only one part of AEGIS, which also includes four orbiting and four ground-based telescopes. Many of the galaxies found are familiar, like the spirals or ellipticals near the Milky Way, while others show the random results of violent mergers. Several new gravitational lenses have already been spotted.
Image: This image, taken by NASA’s Hubble Space Telescope, represents a small section of a larger panoramic view of the heavens. The cosmic tapestry unveils galaxies in all shapes, sizes, and colors. Some of the galaxies are nearby; the smaller ones are far away and existed when the universe was only a small fraction of its current age of roughly 14 billion years. Credit: NASA, ESA, M. Davis (University of California, Berkeley), S. Faber (University of California, Santa Cruz), and A. Koekemoer (STScI).
To say that astronomers are enthusiastic about the AEGIS results so far would be an understatement. Here’s Marc Davis (University of California at Berkeley), a co-leader of the project along with Sandra Faber (UC Santa Cruz): “The goal was to study the universe as it was when it was about half as old as it is at present. We’ve gotten such fabulous data; it just blows your socks off.”
Davis is leader of the DEEP2 Galaxy Redshift Survey, which brings spectroscopic data to bear on the AEGIS findings. The result is an unparalleled sampling of galactic evolution whose dataset is still growing, with results expected to affect our understanding of the universe’s development for a long time to come. The overview paper to look at, available here, is Davis et al., “The All-wavelength Extended Groth Strip International Survey (AEGIS) Data Sets,” to be a part of the special issue of Astrophysical Journal Letters that will appear soon.
by Paul Gilster | Mar 8, 2007 | Asteroid and Comet Deflection |
OK, we sometimes encounter scientific terms with large numbers of syllables, but how about this one, perhaps the prize winner: the Yarkovsky-O’Keefe-Radzievskii-Paddack Effect. This multicultural monicker — drawn on the names of a Russian engineer, an American scientist, a Russian astronomer and a NASA aerospace engineer — has something interesting to say about sunlight. As solar radiation heats and cools an asteroid, released energy can change its rotation. In the case of the asteroid 2000 PH5, the effect increases the spin rate to the point where the asteroid may eventually come to spin faster than any asteroid known.
This complicated study used a variety of telescopes to make the case that the asteroid’s rotation period decreases by 1 millisecond every year. That’s a long and slow effect, but the results build over time, and they’re more readily observable because 2000 PH5 approaches Earth every year. The cause is the heating of the asteroid’s surface by the Sun. Stephen Lowry (Queens University Belfast) puts it this way:
“The warming caused by sunlight hitting the surfaces of asteroids and meteoroids leads to a gentle recoil effect as the heat is released. By analogy, if one were to shine light on a propeller over a long enough period, it would start spinning.”
Is this how some binary asteroids have formed, spinning so fast that they eventually break apart? Nobody has ever observed the YORP effect in action before, but it’s thought to play a role in changing asteroid orbits between Mars and Jupiter, perhaps leading some into planet-crossing orbits. With observations from a bevy of telescopes around the world and radar observations from Arecibo and the Goldstone facility in California, the researchers were able to create a 3D model of the asteroid’s shape.
The spin effect thus noted was seen to increase according to theory throughout a four year observing period. Projecting forward with these data, the team sees 2000 PH5 stable for another 35 million years, with its existing 12 minute rotation being reduced to just 20 seconds in that time. No currently known asteroid is rotating so fast. Says Lowry: “This exceptionally fast spin-rate could force the asteroid to reshape itself or even split apart, leading to the birth of a new double system.”
Image: Radar images obtained at the Arecibo facility in Puerto Rico on July 28, 2004, covering one full rotation of asteroid 2000 PH5 (columns 1 and 4). Corresponding shape-model fits to the images are shown in columns 2 and 5. Columns 3 and 6 are detailed 3-D renderings of the shape model itself. Credit: European Southern Observatory.
Another asteroid under study is 1862 Apollo, observed by a different team that finds the asteroid is making one extra rotation per orbit around the Sun every forty years. That’s a gain of more than four minutes a year, making it clear these effects can play a serious role in the way such objects move. No orbital changes from this source will be quick, but over the long haul YORP may help us make better predictions about what near-Earth asteroids are going to do as they make their close approach.
One of two papers slated to appear in Science Express is Lowry, “Direct Detection of the Asteroidal YORP Effect,” which should be online soon. The paper on 1862 Apollo is Kaasalainen et al., “Acceleration of the rotation of asteroid 1862 Apollo by radiation torques,” posted online in advance of print publication by Nature and available here.
