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Liquid Water in the Kuiper Belt?

As if New Horizons didn’t already have its work cut out for it, now we have the possibility of seeing a frigid geyser going off on Pluto’s companion Charon when the probe arrives in 2015. The process is called cryovolcanism, the movement of liquid water onto the surface where it freezes into ice crystals. New high-resolution spectra obtained at the Gemini Observatory (Mauna Kea) show ammonia hydrates and water crystals spread patch-like across the surface of the distant world.

The suggestion is that liquid water mixed with ammonia is pushing out from deep within Charon, leading to an interesting conclusion. Thus graduate student Jason Cook (Arizona State), who led the team surveying Charon’s surface:

“Charon’s surface is almost entirely water ice. So it must have a vast amount of water under the surface, and much of that should be frozen as well. Only deep inside Charon could water be a liquid. Yet, there is fresh ice on the surface, meaning that some liquid water must somehow reach the surface. The ammonia sitting on the surface provides the clue. It’s the ammonia that helps keep some material liquid. It makes it all feasible. Without ammonia the water could not get out there.”

Pluto and Charon

Start adding up the other places in the Solar System where cryovolcanism is a factor and the list quickly grows. The Uranian moon Ariel, based on Voyager 2 imagery, may well be undergoing the process, and we’ve already seen evidence of water ice reaching out from beneath the surface of Enceladus. Europa, too, shows evidence of water upwelling from within. But unlike these examples, Kuiper Belt Objects like Charon, Quaoar and others are not tidally squeezed (Charon is tidally locked to Pluto). Thus the presence of cryovolcanism has implications for what New Horizons may find elsewhere in the Kuiper Belt.

Image: An artist’s conception of Charon with Pluto in the background. The plumes and brighter spots depicted at left on Charon are thought to be created as water (with some ammonia hydrate mixed in) “erupts” from deep beneath the surface. The material sprays out through cracks in the icy crust, immediately freezes and snows crystalline ice down onto the surface, creating a water-ammonia hydrate ice field. Credit: This composite image includes Pluto and Charon models (enhanced), courtesy of Software Bisque. www.seeker3d.com, with plumes and ice fields added by Mark C. Petersen, Loch Ness Productions. Star field from DigitalSky 2, courtesy Sky-Skan, Inc.

Quaoar, in fact, is possibly laden with ammonia hydrate, a form of ammonia suspected on other KBOs including Charon. Its presence is helpful in this frigid scenario, because ammonia hydrates keep liquid water from freezing solid, making its escape from an inner reservoir to the surface that much easier. Evidence for ammonia hydrates on Charon builds the case for their proliferation in the Kuiper Belt. Says Steven Desch, Cook’s thesis advisor at Arizona State:

“It had been tentatively identified on Charon before by other groups, but the lack of spectral resolution hindered its identification. This clinches it. These spectra are also better than those of other KBOs. I’ve talked to seasoned observers who are convinced for the first time that ammonia hydrates exist on KBOs.”

The possibilities are refreshingly open. From what we know so far, Charon seems rather typical of Kuiper Belt objects. The Gemini observations open the door for reservoirs of water deep beneath the surface of many such objects. Cook believes that if Charon holds an ocean, then all Kuiper Belt objects greater than 500 kilometers across may well have them. There could, in short, be more liquid water — perhaps a lot more — in the Kuiper Belt than on Earth.

The paper is Cook et al., “Near-infrared Spectroscopy of Charon: Possible Evidence for Cryovolcanism on Kuiper Belt Objects,” Astrophysical Journal, Volume 663 (July 10, 2007), pp. 1406-1419 (abstract available).

Comments on this entry are closed.

  • Adam July 20, 2007, 22:34

    Hi Paul

    This is a curious one because it is a tad imprecise to portray cold ammonia-water mixes as “liquid” like regular water – their viscosity is a lot higher so the stuff is more like treacle. In a lot of ways the stuff is analogous to silicate magma. So the KBOs could be described as having “chewy centres”. The bigger KBOs might have warmer interiors if the mix of volatiles in their outer layers is right. Solid state creep of water ices can convect enough heat to chill a cryomagma into solidity. More of stuff like nitrogen acts as an insulator that suppresses creep.

  • Administrator July 21, 2007, 9:01

    Adam, wouldn’t this depend on the proportion of the mix? I like the ‘chewy center’ description, though I wonder if we have enough information on the hydrates involved to make this call. In any case, interesting to see the Kuiper Belt slowly coming into focus. Sometimes I forget how recently we’ve started learning any details about it.

  • philw July 21, 2007, 9:38

    Let’s see, so far we know that water is ubiquitous. We’ve detected many ‘organic’ molecules – molecules with carbon nitrogen and oxygen, including alcohol in space. Now with evidence that KBOs contain liquid water, you don’t think its possible that members of a really advanced civilization might be using the outback of our solar system for moonshine stills?

  • Administrator July 21, 2007, 10:07

    Great scenario! Made to order for, say, Robert Sheckley… Bet they make potent stuff, too.

  • george scaglione July 22, 2007, 11:32

    you know i have had quite a thought in relation to this topic which i have just reviewed here and now. new horizons will arrive at pluto in 2015!!!…2015! 8 years from now.underscores like crazy the importance of our work/discussions here! yeah,8 years is too slow.if we are ever to have a chance of reasonably opening up the solar system – let alone the GALAXY! we have to find something faster. engage warp 5 anyone? well anyhow,my thoughts. thank you very much george

  • andy July 22, 2007, 18:46

    I wonder if the decomposing clathrates hypothesis proposed for the Enceladus geysers would be workable on Charon. If that is the case, perhaps a liquid layer isn’t needed at all.

  • Administrator July 22, 2007, 19:56

    Now that’s an interesting notion! I have no idea how well the model fits, but if it starts looking robust for Enceladus, it will surely get a hard look for Kuiper Belt objects.

  • Adam July 23, 2007, 2:43

    Hi andy

    The kind of crystallisation of the water ice detected is dependent on the initial temperature of the water. I think decomposing clathrates can be ruled out – though there’s certain to be clathrates in the mix of ices on Charon.

  • Darnell Clayton July 23, 2007, 19:40

    I wonder if any of these Kuiper Belt Objects could be used for future missions beyond our star system?

    Like mine the water ice for water and fuel in order to propel ships to travel beyond?

    Just a thought.

  • Administrator July 23, 2007, 19:56

    Darnell, I know there have been a variety of science fiction scenarios for using asteroids as starships, and I’ll bet someone has done a story involving KBOs, though I don’t know for sure. I suspect one of our readers will have a pointer or two, and I’ll be interested to know. As for KBO mission strategies in scientific papers, I haven’t run into one yet but will keep my eyes open. Interesting concept.

  • ljk September 21, 2007, 11:26

    Formation of Kuiper Belt Binaries

    Authors: Hilke E. Schlichting, Re’em Sari

    (Submitted on 19 Sep 2007)

    Abstract: The discovery that a substantial fraction of Kuiper Belt objects (KBOs) exists in binaries with wide separations and roughly equal masses, has motivated a variety of new theories explaining their formation. Goldreich et al. (2002) proposed two formation scenarios: In the first, a transient binary is formed, which becomes bound with the aid of dynamical friction from the sea of small bodies (L^2_s mechanism); in the second, a binary is formed by three body gravitational deflection (L^3 mechanism). Here, we accurately calculate the L^2_s and L^3 formation rates for sub-Hill velocities. While the L^2_s formation rate is close to previous order of magnitude estimates, the L^3 formation rate is about a factor of 4 smaller. For sub-Hill KBO velocities (v less than v_H) the ratio of the L^3 to the L^2_s formation rate is 0.05(v/v_H) independent of the small bodies’ velocity dispersion, surface density and mutual collisions. For Super-Hill velocities (v greater than v_H) the L^3 mechanism dominates over the L^2_s mechanism. Binary formation via the L^3 mechanism competes with binary destruction by passing bodies. Given sufficient time, a statistical equilibrium abundance of binaries forms. We show here that the frequency of long-lived transient binaries drops exponentially with the system’s lifetime and that such transient binaries are not important for binary formation via the L^3 mechanism, contrary to Lee et al. (2007). For the L^2_s mechanism we find that the typical time, transient binaries must last, to form Kuiper Belt binaries (KBB) for a given strength of dynamical friction, D, increases only logarithmically with D. Longevity of transient binaries becomes important only for very weak dynamical friction (i.e. D \lesssim 0.002) and is most likely not crucial for KBB formation.

    Comments: 20 pages, 3 figures, ApJ Refereed

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0709.3107v1 [astro-ph]

    Submission history

    From: Hilke Schlichting [view email]

    [v1] Wed, 19 Sep 2007 21:24:46 GMT (20kb)

    http://arxiv.org/abs/0709.3107

  • ljk October 22, 2007, 11:15

    Detection of methane on Kuiper Belt Object (50000) Quaoar

    Authors: E.L. Schaller, M.E. Brown

    (Submitted on 18 Oct 2007)

    Abstract: The near-infrared spectrum of (50000) Quaoar obtained at the Keck Observatory shows distinct absorption features of crystalline water ice, solid methane and ethane, and possibly other higher order hydrocarbons. Quaoar is only the fifth Kuiper belt object on which volatile ices have been detected. The small amount of methane on an otherwise water ice dominated surface suggests that Quaoar is a transition object between the dominant volatile-poor small Kuiper belt objects (KBOs) and the few volatile-rich large KBOs such as Pluto and Eris.

    Comments: 8 pages, 2 figures, accepted for publication in ApJL

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0710.3591v1 [astro-ph]

    Submission history

    From: Emily Schaller [view email]

    [v1] Thu, 18 Oct 2007 20:07:48 GMT (540kb)

    http://arxiv.org/abs/0710.3591

  • ljk December 5, 2007, 14:32

    Origin of the Structure of the Kuiper Belt during a Dynamical Instability in the Orbits of Uranus and Neptune

    Authors: Harold F. Levison, Alessandro Morbidelli (OCA), Christa Van Laerhoven, Rodney Gomes, Kleomenis Tsiganis

    (Submitted on 4 Dec 2007)

    Abstract: We explore the origin and orbital evolution of the Kuiper belt in the framework of a recent model of the dynamical evolution of the giant planets, sometimes known as the Nice model. This model is characterized by a short, but violent, instability phase, during which the planets were on large eccentricity orbits. One characteristic of this model is that the proto-planetary disk must have been truncated at roughly 30 to 35 AU so that Neptune would stop migrating at its currently observed location. As a result, the Kuiper belt would have initially been empty.

    In this paper we present a new dynamical mechanism which can deliver objects from the region interior to ~35 AU to the Kuiper belt without excessive inclination excitation. Assuming that the last encounter with Uranus delivered Neptune onto a low-inclination orbit with a semi-major axis of ~27 AU and an eccentricity of ~0.3, and that subsequently Neptune’s eccentricity damped in ~1 My, our simulations reproduce the main observed properties of the Kuiper belt at an unprecedented level.

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0712.0553v1 [astro-ph]

    Submission history

    From: Morbidelli Alessandro [view email] [via CCSD proxy]

    [v1] Tue, 4 Dec 2007 15:34:43 GMT (789kb)

    http://arxiv.org/abs/0712.0553

  • ljk December 11, 2007, 11:35

    Detection of Small Kuiper Belt Objects by Stellar Occultations

    Authors: R. Stevenson

    (Submitted on 10 Dec 2007)

    Abstract: Knowledge of the Kuiper Belt is currently limited to those objects that can be detected directly. Objects with diameters less than $\sim$10km reflect too little light to be detected. These smaller bodies could contain most of the mass in the Kuiper Belt while the abundance of these bodies may constrain the distribution of mass. The overall size distribution of bodies within the Kuiper Belt can also be inferred from the relative abundances of sub-km and larger bodies. Stellar occultations are already used to study dark objects in the Solar System, such as asteroids or planetary rings. Occultation by a KBO of a size comparable to, or larger than, that of the Fresnel Scale will result in Fresnel diffraction.

    Detection of diffraction effects requires fast multiple-star photometry, which will be conducted in July 2007 using the Orthogonal Parallel Transfer Imaging Camera (OPTIC) mounted on the University of Hawaii 2.2m telescope on Mauna Kea.

    This paper details how knowledge of the mass and structure of the outer Solar System may be obtained through the detection of serendipitous stellar occultations.

    Comments: Published in Proceedings of the 14th Young Scientists Conference on Astronomy and Space Physics, Kyiv, Ukraine, April 23-28, 2007

    Subjects: Astrophysics (astro-ph)

    Journal reference: YSC’14 Proceedings of Contributed Papers (eds. G. Ivashchenko, A. Golovin), Kyiv, Kyivskyi Universytet, pp. 77-81, 2007

    Cite as: arXiv:0712.1550v1 [astro-ph]

    Submission history

    From: Ganna Ivashchenko [view email]

    [v1] Mon, 10 Dec 2007 17:43:15 GMT (6kb)

    http://arxiv.org/abs/0712.1550

  • ljk December 14, 2007, 12:38

    An Outer Planet Beyond Pluto and Origin of the Trans-Neptunian Belt Architecture

    Authors: Patryk Sofia Lykawka, Tadashi Mukai

    (Submitted on 13 Dec 2007)

    Abstract: Trans-Neptunian objects (TNOs) are remnants of a collisionally and dynamically evolved planetesimal disk in the outer solar system. This complex structure, known as the trans-Neptunian belt (or Edgeworth-Kuiper belt), can reveal important clues about disk properties, planet formation, and other evolutionary processes. In contrast to the predictions of accretion theory, TNOs exhibit surprisingly large eccentricities, e, and inclinations, i, which can be grouped into distinct dynamical classes. Several models have addressed the origin and orbital evolution of TNOs, but none have reproduced detailed observations, e.g., all dynamical classes and peculiar objects, or provided insightful predictions.

    Based on extensive simulations of planetesimal disks with the presence of the four giant planets and massive planetesimals, we propose that the orbital history of an outer planet with tenths of Earth’s mass can explain the trans-Neptunian belt orbital structure. This massive body was likely scattered by one of the giant planets, which then stirred the primordial planetesimal disk to the levels observed at 40-50 AU and truncated it at about 48 AU before planet migration. The outer planet later acquired an inclined stable orbit (greater than 100 AU; 20-40 deg) because of a resonant interaction with Neptune (an r:1 or r:2 resonance possibly coupled with the Kozai mechanism), guaranteeing the stability of the trans-Neptunian belt.

    Our model consistently reproduces the main features of each dynamical class with unprecedented detail; it also satisfies other constraints such as the current small total mass of the trans-Neptunian belt and Neptune’s current orbit at 30.1 AU. We also provide observationally testable predictions.

    Comments: 80 pages, 24 figures, 7 tables. Accepted for publication in The
    Astronomical Journal

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0712.2198v1 [astro-ph]

    Submission history

    From: Patryk Sofia Lykawka [view email]

    [v1] Thu, 13 Dec 2007 17:18:20 GMT (2795kb)

    http://arxiv.org/abs/0712.2198

  • ljk January 22, 2008, 13:35

    Evidence of N2-Ice On the Surface of the Icy Dwarf Planet 136472 (2005 FY9)

    Authors: S.C. Tegler, W.M. Grundy, F. Vilas, W. Romanishin, D. Cornelison, G.J. Consolmagno

    (Submitted on 21 Jan 2008)

    Abstract: We present high signal precision optical reflectance spectra of 2005 FY9 taken with the Red Channel Spectrograph and the 6.5-m MMT telescope on 2006 March 4 UT (5000 – 9500 A; 6.33 A pixel-1) and 2007 February 12 UT (6600 – 8500 A; 1.93 A pixel-1). From cross correlation experiments between the 2006 March 4 spectrum and a pure CH4-ice Hapke model, we find the CH4-ice bands in the MMT spectrum are blueshifted by 3 +/- 4 A relative to bands in the pure CH4-ice Hapke spectrum. The higher resolution MMT spectrum of 2007 February 12 UT enabled us to measure shifts of individual CH4-ice bands. We find the 7296 A, 7862 A, and 7993 A CH4-ice bands are blueshifted by 4 +/- 2 A, 4 +/- 4 A, and 6 +/- 5 A. From four measurements we report here and one of our previously published measurements, we find the CH4-ice bands are shifted by 4 +/- 1 A. This small shift is important because it suggest the presence of another ice component on the surface of 2005 FY9. Laboratory experiments show that CH4-ice bands in spectra of CH4 mixed with other ices are blueshifted relative to bands in spectra of pure CH4-ice.

    A likely candidate for the other component is N2-ice because its weak 2.15 micron band and blueshifted CH4 bands are seen in spectra of Triton and Pluto. Assuming the shift is due to the presence of N2, spectra taken on two consecutive nights show no difference in CH4/N2. In addition, we find no measureable difference in CH4/N2 at different depths into the surface of 2005 FY9.

    Comments: The paper will appear in Icarus. It has 33 pages, 2 tables, and 7 figures. Replaced version fixed typo in abstract

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0801.3115v1 [astro-ph]

    Submission history

    From: Stephen Tegler [view email]

    [v1] Mon, 21 Jan 2008 01:02:50 GMT (93kb)

    http://arxiv.org/abs/0801.3115

  • ljk February 5, 2008, 10:23

    The Taiwanese-American Occultation Survey: The Multi-Telescope Robotic Observatory

    Authors: M. J. Lehner, C.-Y. Wen, J.-H. Wang, S. L. Marshall, M. E. Schwamb, Z.-W. Zhang, F. B. Bianco, J. Giammarco, R. Porrata, C. Alcock, T. Axelrod, Y.-I. Byun, W. P. Chen, K. H. Cook, R. Dave, S.-K. King, T. Lee, H.-C. Lin, S.-Y. Wang

    (Submitted on 4 Feb 2008)

    Abstract: The Taiwanese-American Occultation Survey (TAOS) operates four telescopes to search for occultations of stars by Kuiper Belt Objects. This paper provides a detailed description of the TAOS multi-telescope system.

    Comments: 11 pages, 11 figures. Submitted to PASP

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0802.0303v1 [astro-ph]

    Submission history

    From: Matthew Lehner [view email]

    [v1] Mon, 4 Feb 2008 18:39:55 GMT (1472kb)

    http://arxiv.org/abs/0802.0303

  • ljk March 6, 2008, 12:02

    The Ratio of Retrograde to Prograde Orbits: A Unique Way to test Kuiper Belt Binary Formation Theories

    Authors: Hilke E. Schlichting, Re’em Sari

    (Submitted on 3 Mar 2008)

    Abstract: With the discovery of Kuiper Belt binaries that have wide separations and roughly equal masses new theories were proposed to explain their formation. Two formation scenarios were suggested by Goldreich and collaborators: In the first, dynamical friction that is generated by the sea of small bodies enables a transient binary to become bound ($L^2s$ mechanism); in the second, a transient binary gets bound by an encounter with a third body ($L^3$ mechanism).

    We show that these different binary formation scenarios leave their own unique signatures in the relative abundance of prograde to retrograde binary orbits. This signature is due to stable retrograde orbits that exist much further out in the Hill sphere than prograde orbits. It provides an excellent opportunity to distinguish between the different binary formation scenarios observationally.

    We predict that if binary formation proceeded while sub-Hill velocities prevailed, the vast majority of all comparable mass ratio binaries have retrograde orbits. This dominance of retrograde binary orbits is a result of binary formation via the $L^2s$ mechanism, or any other mechanism that dissipates energy in a smooth and gradual manner. For super-Hill velocities binary formation proceeds via the $L^3$ mechanism which produces a roughly equal number of prograde and retrograde binaries.

    Comments: 16 pages, 4 figures, submitted for publication in ApJ

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0803.0329v1 [astro-ph]

    Submission history

    From: Hilke Schlichting [view email]

    [v1] Mon, 3 Mar 2008 21:05:10 GMT (29kb)

    http://arxiv.org/abs/0803.0329

  • ljk May 1, 2008, 10:26

    The Warped Plane of the Classical Kuiper Belt

    Authors: Eugene Chiang, Hyomin Choi

    (Submitted on 29 Apr 2008)

    Abstract: By numerically integrating the orbits of the giant planets and of test particles for four billion years, we follow the evolution of the location of the midplane of the Kuiper belt. The Classical Kuiper belt conforms to a warped sheet that precesses with a 1.9 Myr period. The present-day location of the Kuiper belt plane can be computed using linear secular perturbation theory: the local normal to the plane is given by the theory’s forced inclination vector, which is specific to every semi-major axis.

    The Kuiper belt plane does not coincide with the invariable plane, but deviates from it by up to a few degrees in stable zones. A Kuiper belt object keeps its free inclination relative to the Kuiper belt plane nearly constant, even while the plane departs from the trajectory predicted by linear theory. The constancy of free inclination simply reflects the undamped amplitude of free oscillation. Current observations of Classical Kuiper belt objects are consistent with the plane being warped by the giant planets alone, but the sample size will need to increase by a few times before confirmation exceeds 3-sigma in confidence.

    In principle, differences between the theoretically expected plane and the observed plane could be used to infer as yet unseen masses orbiting the Sun, but carrying out such a program would be challenging.

    Comments: Astronomical Journal, in press

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0804.4687v1 [astro-ph]

    Submission history

    From: Eugene Chiang [view email]

    [v1] Tue, 29 Apr 2008 20:05:46 GMT (378kb)

    http://arxiv.org/abs/0804.4687

  • ljk May 15, 2008, 22:57

    Pluto’s Light Curve in 1933-1934

    Authors: Bradley E. Schaefer, Marc W. Buie, Luke Timothy Smith

    (Submitted on 14 May 2008)

    Abstract: We are reporting on a new accurate photographic light curve of Pluto for 1933-1934 when the heliocentric distance was 40 AU. We used 43 B-band and V-band images of Pluto on 32 plates taken on 15 nights from 19 March 1933 to 10 March 1934. Most of these plates were taken with the Mount Wilson 60″ and 100″ telescopes, but 7 of the plates (now at the Harvard College Observatory) were taken with the 12″ and 16″ Metcalf doublets at Oak Ridge. The plates were measured with an iris diaphragm photometer, which has an average one-sigma photometric error on these plates of 0.08 mag as measured by the repeatability of constant comparison stars.

    The modern B and V magnitudes for the comparison stars were measured with the Lowell Observatory Hall 1.1-m telescope. The magnitudes in the plate’s photographic system were converted to the Johnson B- and V-system after correction with color terms, even though they are small in size. We find that the average B-band mean opposition magnitude of Pluto in 1933-1934 was 15.73 +- 0.01, and we see a roughly sinusoidal modulation on the rotational period (6.38 days) with a peak-to-peak amplitude of 0.11 +- 0.03 mag.

    With this, we show that Pluto darkened by 5% from 1933-1934 to 1953-1955. This darkening from 1933-1934 to 1953-1955 cannot be due to changing viewing geometry (as both epochs had identical sub-Earth latitudes), so our observations must record a real albedo change over the southern hemisphere. The later darkening trend from 1954 to the 1980s has been explained by changing viewing geometry (as more of the darker northern hemisphere comes into view).

    Thus, we now have strong evidence for albedo changes on the surface of Pluto, and these are most easily explained by the systematic sublimation of frosts from the sunward pole that led to a drop in the mean surface albedo.

    Comments: Icarus in press, 24 pages

    Subjects: Astrophysics (astro-ph)

    Cite as: arXiv:0805.2097v1 [astro-ph]

    Submission history

    From: Bradley E. Schaefer [view email]

    [v1] Wed, 14 May 2008 15:46:42 GMT (642kb)

    http://arxiv.org/abs/0805.2097