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Meanwhile, Around the Outer Planets…

The outer planets turn out to be far livelier places than we ever expected in those distant pre-Voyager days. Io set the tone, but look at all the activity we’ve found from Enceladus to Triton, and now we’ve got continuing Cassini revelations as well as new interpretations of what the Galileo probe found around Jupiter. Some of this is striking indeed, as witness a paper called to my attention by Larry Klaes and Adam Crowl discussing what may be happening on Europa in terms of energy.

The apparent presence of that sub-ice ocean on Europa has made it of great interest for astrobiology. The problem has been the availability of energy. Christopher Chyba (Princeton University), working with Kevin Hand (Princeton) and Robert Carlson (Caltech) have used data from Galileo’s Near-Infrared Mapping Spectrometer to determine that the Jovian moon could maintain an oxidized ocean. I should have the full text of this one shortly (right now I’m working solely from the abstract), but the gist of the matter is here:

We analyzed chemical sources and sinks and concluded that the radiolytically processed surface of Europa could serve to maintain an oxidized ocean even if the surface oxidants…are delivered only once every 0.5 Gyr. If delivery periods are comparable to the observed surface age (30–70 Myr), then Europa’s ocean could reach O2 concentrations comparable to those found in terrestrial surface waters, even if ~109 moles yr-1 of hydrothermally delivered reductants consume most of the oxidant flux. Such an ocean would be energetically hospitable for terrestrial marine macrofauna. The availability of reductants could be the limiting factor for biologically useful chemical energy on Europa.

If the term ‘macrofauna’ doesn’t get your attention, nothing will. The paper is Hand, Carlson and Chyba, “Energy, Chemical Disequilibrium, and Geological Constraints on Europa,” Astrobiology Vol. 7 (6) (2007), pp. 1006-1022 (abstract). I have two other articles this team published in the same journal last summer but I’m going to hold on those until I can dig into the full text of this latest paper, hoping to place the earlier work in a broader context. So we’ll return to Europa before long for more on this encouraging study.

Meanwhile, we continue to learn more about the changeable surface of Titan, harking back to the announcement of sand dunes on that moon in 2006 and later work examining Titan’s methane lakes. Jani Radebaugh (Brigham Young University) and team, who produced these earlier finds, now look at Cassini radar images showing mountains on Titan. The researchers used light and shadow in the radar images to calculate the slope of the mountains and thus determine their height.

The study indicates that Titan’s mountains are made of water ice, the largest being a scant two kilometers from base to peak. The small scale is interesting in its own right because it suggests erosion. We have a surface whose topography, rather than being the result of impact structures, seems to offer up lively geological processes. Which is not to say that impact craters have not played their own role in some places, but that a more likely explanation for what we are seeing is crustal activity, either through compression or separation of crustal materials.

The Titan paper is Radebaugh et al., “Mountains on Titan observed by Cassini Radar,” Icarus Vol. 192, Issue 1 (December, 2007), pp. 77-91 (abstract).

Comments on this entry are closed.

  • ljk January 7, 2008, 23:00

    Russia to search for life on Jupiter’s moon Europa: report

    MOSCOW, Jan 7 (AFP) Jan 07, 2008

    Russia plans to participate in a European mission to
    investigate Jupiter’s moon Europa and search for simple
    life forms, the Interfax news agency reported on Monday,
    quoting a senior researcher.

    The head of the Space Research Institute, Lev Zelyony,
    said a project to explore the giant gaseous planet Jupiter
    would shortly be included in the programme of the
    European Space Agency (ESA) for the years 2015 to

    Full article here:


  • David January 8, 2008, 4:26

    Years ago, Freeman Dyson wrote that it might be a good idea to look for “frozen fish” orbiting Europa.
    The idea being that a past impact on the moon might have sent stuff into orbit.

  • Administrator January 8, 2008, 8:19

    David, that is a truly Dysonian idea! Do you remember which book or paper it was in? Would love to read that one.

  • ljk January 8, 2008, 8:59

    Maybe we could get Mrs. Pauls to fund an expedition to
    Jupiter based on that idea. :^)

  • Administrator January 8, 2008, 9:13

    A new take on ‘So long and thanks for all the fish,’ that’s for sure!

  • David January 8, 2008, 10:22

    I think I read it in one of his books from the 80’s or 90’s. Sorry, can’t remember much else other than that the book was a collection of rather interesting essays.

  • AlfaCentavra January 8, 2008, 19:14

    For future science on Jupiter’s moon Europa ESA want nuclear technology from Russia. ESA
    haven’t it.

  • Goldstein Hovercraft January 10, 2008, 22:24

    The article by Dyson was titled “”Warm-Blooded Plants and Freeze-Dried Fish” and it can be found here: http://www.theatlantic.com/issues/97nov/space.htm
    Unfortunately, a subscription to The Atlantic is required.

    The article, I believe, was an excerpt from a book by Dyson titled “The Sun, the Genome, and the Internet — Tools of Scientific Revolutions”, and it is reviewed here: http://www.sfsite.com/08b/sun63.htm

    Finally, for those looking for instant gratification (and who on the web isn’t?), Dyson mentions the concept in interview here:

    As Dyson notes, the idea finding fish in orbit around Europa is part of his general strategy for finding extraterrestrial life: Focus on what is easily detectable, rather than on what is probable. This fits in with his concept of pitlamping the Oort Cloud, and in the interview above, he mentions the related concept of looking for warm patches at night on Mars. You can read more about the pit lamping idea here: http://www.leitl.org/docs/public_html/tt/msg11177.html <- recommended reading for those not already familiar with Dyson’s concept!

    Hope this helps!

    Eric Goldstein

  • Administrator January 11, 2008, 9:14

    Eric, these links are tremendously helpful. Thanks! I’m not familiar with ‘pitlamping’, but I’ll examine the link. Dyson’s notion on looking for what is readily detectable certainly resonates, especially since detection ‘on the cheap’ could actually speed the process. The interview with Stewart Brand is highly recommended. What a remarkable man Dyson is.

  • Goldstein Hovercraft January 11, 2008, 10:52

    Glad to help. About pit lamping, I’m sorry, my mistake, the proper spelling is “pit lamping”, with a space between the two words. If you google “pit lamping” and “Dyson”, you’ll be in for a treat.

    From this link: http://www.starastronomy.org/cgi-bin/wwwthreads/showthreaded.pl?Cat=&Board=events&Number=13030

    “Pit lamping” on earth refers to the illegal (in-most places) hunting practice of shining a bright light and then shooting at the reflection of the eyes and then seeing what you shot (hopefully not your hunting partner). He stated that since life on the surface of Europa, Pluto or other KBOs would need to concentrate sunlight in order to survive and thrive, it may exist in the form of “sunflowers” with parabaloid reflectors concentrating sunlight on the vital areas of the organism’s body. He stated that there would be an angle at which sunlight or other light source is relected back the way it came so if one orbited Europa and shined a light source on the surface any sunflowers present would reveal themselves by their reflections. Additionally, the farther from the sun you went to look for these the easier it would become since the efficiency or collecting area of the reflector would have to increase to compensate for the reduced sunlight intensity. In these regions it might be feasible to detect these reflections and it might be possible to do so from Earth itself.”

    This short piece of fiction
    discusses the obvious connection between this idea and the more famous Dyson Sphere idea: http://writings.mike-combs.com/eyeshine.htm

    By the way, if you live in an urban area, you can still try out pit lamping — on a cat! Backing away from a cat who stared curiously back at my flashlight, I was amazed by how I could detect the eyes of the cat at a much greater distance than the cat’s body. Once the cat hid in the bushes, I was surprised to find that I could still track the cat’s movements using the same method — whenever I made a noise, the otherwise camouflaged cat would look back at my flashlight, and its two glowing eyes would reveal its position.

    Finally, for those who read the links above, the question comes up of where life in the Oort cloud would originate. On an early date, my wife and I went to see Dyson give his pit lamping talk at Fermilab, and I like to joke that I fell in love with my wife when she asked him that question of vacuum life’s origin. Dyson pointed out that many icy bodies in the Oort cloud may have sufficient radioactives in the core to warm an interior ocean (and alternatively, two bodies orbiting each other may provide enough tidal heating – like Pluto and Charon). Life could originate in the interior ocean, evolve to exploit the sunlight available on the surface (see the links), and then spread throughout the Oort cloud (again, see the links).

    Eric Goldstein

  • ljk January 23, 2008, 17:17

    Jupiter’s raging thunderstorms a sign of ‘global upheaval’

    New Scientist


    David Shiga

    January 23, 2008

    Towering storms more than 100 kilometres tall have been
    caught punching up through Jupiter’s cloud deck for the
    first time, thanks to a series of Hubble Space Telescope
    and ground-based observations. The rare storms – a sign of
    recent turmoil on the planet – are helping scientists deduce
    what lies hidden beneath the clouds that shroud the solar
    system’s largest planet.

    The Hubble Space Telescope captured the first of the two
    clouds by chance just as it was forming on 25 March 2007.
    A second, very similar cloud appeared just 9 hours later in
    an image taken by a team of amateur astronomers from the

    “It’s pretty clear that there’s a lot going on in Jupiter’s
    atmosphere right now – much more than usual – and these
    storms are probably tied in with that so-called global upheaval,”

    The appearance of the two storms provides information on
    the atmosphere below the cloud deck, de Pater says. In order
    to successfully reproduce the appearance of the storms in
    simulations, the researchers had to set the amount of water
    vapour below the clouds to very high levels – about 300 times
    that measured by the Galileo spacecraft, which sent an entry
    probe into an unusually cloud-free region on Jupiter in 1995….

    Stories on this topic appeared in various sources around the world, including
    the http://story.malaysiasun.com/index.php/ct/9/cid/89d96798a39564bd/id/318173/cs/1/ Malaysia Sun.

  • ljk March 20, 2008, 13:09

    Galileo In-Situ Dust Measurements in Jupiter’s Gossamer Rings

    Authors: Harald Krueger, Douglas P. Hamilton, Richard Moissl, Eberhard Gruen

    (Submitted on 19 Mar 2008)

    Abstract: During its late orbital mission at Jupiter the Galileo spacecraft made two passages through the giant planet’s gossamer ring system. The impact-ionization dust detector on board successfully recorded dust impacts during both ring passages and provided the first in-situ measurements from a dusty planetary ring. In all, a few thousand dust impacts were counted with the instrument accumulators during both ring passages, but only a total of 110 complete data sets of dust impacts were transmitted to Earth.

    Detected particle sizes range from about 0.2 to 5 micron, extending the known size distribution by an order of magnitude towards smaller particles than previously derived from optical imaging (Showalter et al. 2008). The grain size distribution increases towards smaller particles and shows an excess of these tiny motes in the Amalthea gossamer ring compared to the Thebe ring. The size distribution for the Amalthea ring derived from our in-situ measurements for the small grains agrees very well with the one obtained from images for large grains.

    Our analysis shows that particles contributing most to the optical cross-section are about 5 micron in radius, in agreement with imaging results. The measurements indicate a large drop in particle flux immediately interior to Thebe’s orbit and some detected particles seem to be on highly-tilted orbits with inclinations up to 20 deg.

    Comments: 13 figures, 4 tables, submitted to Icarus

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0803.2849v1 [astro-ph]

    Submission history

    From: Harald Krueger [view email]

    [v1] Wed, 19 Mar 2008 17:18:50 GMT (713kb)


  • ljk April 7, 2008, 12:51


    Two missions to the outer Solar System, Laplace (Europa and
    Jupiter Mission) and Tandem (Titan and Enceladus Mission), are
    competing against each other for selection later this year; Emily
    Baldwin summarises the key goals of each ambitious mission.


  • ljk June 3, 2008, 23:35

    Exploring the Outer Solar System with the ESSENCE Supernova Survey

    Authors: A. C. Becker, K. Arraki, N. A. Kaib, W. M. Wood-Vasey, C. Aguilera, J. W. Blackman, S. Blondin, P. Challis, A. Clocchiatti, R. Covarrubias, G. Damke, T. M. Davis, A. V. Filippenko, R. J. Foley, A. Garg, P. M. Garnavich, M. Hicken, S. Jha, R. P. Kirshner, K. Krisciunas, B. Leibundgut, W. Li, T. Matheson, A. Miceli, G. Miknaitis, G. Narayan, G. Pignata, J. L. Prieto, A. Rest, A. G. Riess, M. E. Salvo, B. P. Schmidt, R. C. Smith, J. Sollerman, J. Spyromilio, C. W. Stubbs, N. B. Suntzeff, J. L. Tonry, A. Zenteno

    (Submitted on 29 May 2008)

    Abstract: We report the discovery and orbit determination of 14 trans-Neptunian objects (TNOs) from the ESSENCE Supernova Survey difference imaging dataset. Two additional objects discovered in a similar search of the SDSS-II Supernova Survey database were recovered in this effort. ESSENCE repeatedly observed fields far from the Solar System ecliptic (-21 deg < beta < -5 deg), reaching limiting magnitudes per observation of I~23.1 and R~23.7.

    We examine several of the newly detected objects in detail, including 2003 UC_414 which orbits entirely between Uranus and Neptune and lies very close to a dynamical region that would make it stable for the lifetime of the Solar System. 2003 SS_422 and 2007 TA_418 have high eccentricities and large perihelia, making them candidate members of an outer class of trans-Neptunian objects.

    We also report a new member of the ”extended” or ”detached” scattered disk, 2004 VN_112, and verify the stability of its orbit using numerical simulations. This object would have been visible to ESSENCE for only ~2% of its orbit, suggesting a vast number of similar objects across the sky. We emphasize that off-ecliptic surveys are optimal for uncovering the diversity of such objects, which in turn will constrain the history of gravitational influences that shaped our early Solar System.

    Comments: 5 pages, 1 table, accepted for publication in ApJL

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0805.4608v1 [astro-ph]

    Submission history

    From: Andrew Becker [view email]

    [v1] Thu, 29 May 2008 19:23:06 GMT (17kb)


  • ljk June 20, 2008, 17:18

    Stability of Irregular Satellites of Giant Planets in the Solar System

    Authors: Yue Shen (1), Scott Tremaine (2) ((1) Princeton, (2) IAS)

    (Submitted on 17 Jun 2008)

    Abstract: We conduct a systematic survey of the regions in which distant satellites can orbit stably around the four giant planets in the Solar system, using orbital integrations of up to 10^8 yr. We confirm previous results that (i) prograde and retrograde satellites orbiting within the Hill radius r_H can survive out to radii of \sim 0.5r_H and \sim 0.7r_H, respectively; (ii) stable orbits do not exist at high ecliptic inclinations when the semi-major axis is large enough that the solar tide is the dominant non-Keplerian perturbation.

    More remarkably, our numerical studies reveal that stable satellite orbits exist at distances \gtrsim 2r_H around Jupiter, Uranus and Neptune (but not Saturn). For Uranus and Neptune, in particular, stable orbits are found at distances as large as \sim 10r_H.

    Comments: 13 emulateapj pages; submitted to AJ

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0806.2882v1 [astro-ph]

    Submission history

    From: Yue Shen [view email]

    [v1] Tue, 17 Jun 2008 22:17:53 GMT (920kb)