Conditions on TNOs size and density for having extant liquid water

h2ouniverse · Oct 17, 2008

Some months ago Mr Desch et al. from Arizona Sate University had published this:http://spacescience.arc.nasa.gov/agu/abstracts/Deschetal.pdfIn their interesting approach, they conducted a parametric study on how dense or large a transneptunian body shall be to still host a layer of liquid water-ammonia. The time-dependent analysis shows (as opposed to previous static analyses) a longer permanence of liquid phases when starting from a homogeneous undifferentiated cold ball. The only initial assumption that is not that conservative imho is the NH3/H2O ratio of 0.1 (a little bit high?). But for the rest, their analysis is conservative in that:* it neglects the initial accretion heat (assumes homogeneous initial temperature of 50K)* it considers only long-lived nucleotides radiogenic energy (no Al26)* it assumes no tidal heating* it assumes no initial differentiationIt infers that most objects beyond radius 600km should still have today a liquid layer, and that most objects beyond radius 400km have had such a layer for more than 1 billion years. Note that they do not predict any solid convection for bodies smaller than Triton, which limits the heat loss (hence not contradicting the non-differentiation of Callisto's core) <img src="http://sitelife.space.com/ver1.0/Content/images/store/6/14/b68f569b-4e56-4c21-9e24-f0e2751b9b81.Medium.jpg" alt="" /> (from Desch, Cook & Hawley, 2007)

3488 · Oct 17, 2008

Hi Joel,What would enable a largish TNO, assuming no tidal purtabations & / or no large moons in elliptical orbits to maintain liquid watern inside?Is is internal pressure, keeping the H2O from freezing despite extremely low temperatures?Callisto is a good case in point. Third largest moon in the solar system after Ganymede & Titan, only just smaller than Mercury (though only about a third of the mass), but is as dead as a dinosaur, but may have a briny layer under the ice rich crust on the boundary of the undifferentiated mantle. Ganymede, Titan & Europa too may have subsurface oceans (though not proven beyond doubt in any case), but these are large bodies, possibly having enough radioactive materials & tidal heating (a bit like volcanic Io with Jupiter, but on a vastly reduced scale) to keep the interiors warm (Earth & Ganymede apear to be the most differentiated solid bodies known in the solar system), but also perhaps the larger Uranian moons & Triton also having deep reserviours of liquid water. Eris, Pluto, Haumea, MakeMake, 1 Ceres, etc possible too?I have reposted the graph below as I have contrast enhanced it, making it easier to see. <img src="http://sitelife.space.com/ver1.0/Content/images/store/0/3/00a94014-05d5-4a41-9324-aeef92678e42.Medium.jpg" alt="" /> Andrew Brown.  <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

h2ouniverse · Oct 17, 2008

When I now position the main TNOs on Desch's diagram (with large uncertainties on density and size, plus sometimes the non-spherical factor as for Haumea)  I get that: <img src="http://sitelife.space.com/ver1.0/Content/images/store/0/6/60f6d54f-485a-46f8-960b-c8fd46926c95.Medium.jpg" alt="" /> http://sitelife.space.com/ver1.0/Forums/#One can see that Charon, 2002TC302 and Quaoar are borderline (for the last two, depending on their actual density and size). But 6 objects (Triton, Eris, Pluto, Haumea, Makemake, Sedna) would make it. The prospect of a liquid layer on Haumea, inside a fast rotating scalene ellipsoid, would be very exciting...Let's hope that they are right.Btw, Quaoar, Eris, Pluto, Haumea present cristalline ice signatures.

h2ouniverse · Oct 17, 2008

When this time I put on Desch's diagram a set of fictitious bodies that I've called "TIKB" ("Teleported In Kuiper Belt"), that have the density and size of known cisneptunian bodies, but placed as a thought experiment in the conditions of Desch's calculation (no initital differentiation, 50K init temperature, no tidal heating), I get that: <img src="http://sitelife.space.com/ver1.0/Content/images/store/15/11/6fcc2788-449d-4a2c-9b72-298c19f762b0.Medium.jpg" alt="" />One can see that Ceres, Dione, Umbriel would have frozen solid just few hundreds of millions years ago under those Kuiper Belt conditions, with Ariel on the borderline. But Dione, Ariel and Umbriel should receive some tidal heating, moving the extant-water-line to their left. And Ceres initial and current temperature, even assuming no accretional heat, cannot be below 170K on average (due to its proximity to the Sun) => shifting temperatures by more than 100K => extant-water-line should shift to the left too for the real Ceres...Of course Enceladus without tidal heating would not make it but that is not a surprise...What is striking is that we find the usual suspects (Dione, Ariel, Titania, Oberon) in or close to the water pond, and they are precisely the ones exhibiting chasmae. Unlike Tethys or Iapetus that have a low density. The case of Rhea is less blatant (Rhea is undifferentiated...) but it lies at the border of their modelling (density < 1.3) and should be below their extrapolated curve.Best regards.

h2ouniverse · Oct 17, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Hi Joel,What would enable a largish TNO, assuming no tidal purtabations & / or no large moons in elliptical orbits to maintain liquid watern inside?Is is internal pressure, keeping the H2O from freezing despite extremely low temperatures?Posted by 3488</DIV> Hi Andrew,The answer of the authors is: radiogenic heating, combined with absence of solid convection (that accelerates heat dissipation) and presence of a NON-differentiated rock+ice external layer that provides for a lower thermal conductivity hence better insulation. Also they have taken into account the depression of melting temperature due to ammonia, and the latent fusion heat. When doing a static calculation, one misses the effect of latent fusion heat. They claim that when melting the volatile mantle, some radiogenic energy is absorbed as latent heat, then released hundreds of millions years later when the water-ammonia re-freezes, slowing the re-freezing. So there is a time effect, energy storage... Radiogenic energy is much higher at the beginning (a factor of 9 wrt nowadays for long-lived isotopes) so having a mechanism that stores that youth energy and releases it after billions of years is interesting.Note that their model does not work (and they do not claim so) when solid convection is at play, as it must have been on large bodies like Callisto. Also on large bodies with a lot more heating (radiogenic and/or tidal) the differentiation becomes total and you can get catastrophic overturns of the iceshelf and huge losses of volatiles and heat to space.Here they computed that the external layers should remain solid and very hard, that solid convection would not occur (Rayleigh coefficient) and the outer layer should not collapse. Just crack from time to time and vent a little bit...

3488 · Oct 17, 2008

Hi Joel,Yes I would have thought radioisotopic heating was the cause. Even then, for TNO sized bodies, would even those have lost their heating over the age of the Solar System?Yes I was aware of crystalline ice on Eris, Haumea, Quaoar & Charon. Seems srange that Pluto does not show it, though that signature is likely to be hidden under methane ice.Also it seems strange why some bodies such as Rhea & Callisto are undifferentiated, yet some like Ganymede, Dione, Ariel, Titania & Oberon appear to be. Those five really have seen considerable activity in the past & maybe even a little right now. Ganymede is certainly a special case, as appeared to have had a spurt of activity approx 750 MYA - 1 GYA, most likely resulting in being pulled into a more elliptical orbit temporarily, restarting geological activity on the gian, planet sized moon. Reason for which I suspect is a passing massive object (rogue planet unattached to a star), possibly passing through the outer solar system. Just a hare brained idea, I know, but seems to fit.Perhaps many TNOs were effected by this? Just my <img src="http://sitelife.space.com/ver1.0/Content/images/store/11/10/5b1791bf-7e5a-4b25-ba81-4dfa84f67b85.Medium.gif" alt="" /> worth.Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

h2ouniverse · Oct 17, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Hi Joel,Yes I would have thought radioisotopic heating was the cause. Even then, for TNO sized bodies, would even those have lost their heating over the age of the Solar System? Posted by 3488</DIV> Hi Andrew,May I suggest you read the initial link? (Desch's article). Some of their arguments make sense to me. Note that they do not use Al26 and still come to these conclusions. The notion that a body in the 1000-2000km class should have frozen solid long ago is inherited from the days when computations were limited to static cases. The ability to run time-wise simulations over 4.6 billion years has apparently changed a lot these perceptions.Also, unlike what you suggested, pressure is NOT favorable for liquid water. That might have been on the contrary one of the reasons for the non-differentiation of Callisto's core. The reason is that on a large body like Callisto, gravity will generate pressures at depth below 100km that prevent from melting water (hot ices). In that conditions, the radiogenic heating cannot melt water and so the differentiation cannot occur unless you have a lot of radiogenic heating plus tidal heating (as Ganymede had). That explains why paradoxically Callisto is thought to be differentiated between say 10km and 100km depth (approximately!!!!). With a subsurface ocean on top of a giant undifferentiated core. For a TNO, the gravity is not sufficient to block this process. For once, a smaller size is favorable... The key becomes then to have enough silicate/metallic material to get radiogenic energy AND to have a structure and external layers materials that insulate this warming core from space by limiting the conductive losses.We'll see when NH flies by Charon. Just 6 years and 9 months to wait.Best regards.

silylene old · Nov 10, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Hi Joel,Yes I would have thought radioisotopic heating was the cause. Even then, for TNO sized bodies, would even those have lost their heating over the age of the Solar System?Yes I was aware of crystalline ice on Eris, Haumea, Quaoar & Charon. Seems srange that Pluto does not show it, though that signature is likely to be hidden under methane ice.Also it seems strange why some bodies such as Rhea & Callisto are undifferentiated, yet some like Ganymede, Dione, Ariel, Titania & Oberon appear to be. Those five really have seen considerable activity in the past & maybe even a little right now. Ganymede is certainly a special case, as appeared to have had a spurt of activity approx 750 MYA - 1 GYA, most likely resulting in being pulled into a more elliptical orbit temporarily, restarting geological activity on the gian, planet sized moon. Reason for which I suspect is a passing massive object (rogue planet unattached to a star), possibly passing through the outer solar system. Just a hare brained idea, I know, but seems to fit.Perhaps many TNOs were effected by this? Just my worth.Andrew Brown. Posted by 3488</DIV> I thought that Andrew may particularly like this new report, which was originally in Icarus.   http://www.newscientist.com/article/dn16009-mysterious-changes-seen-on-distant-dwarf-planet.html<h1>Mysterious changes seen on distant dwarf planet </h1><ul class="markerlist"><li>21:24 10 November 2008 by Rachel Courtland </li><li>The surface of the largest known 'plutoid' appears to have changed in recent years, according to new measurements of how elements are layered on its icy surface. But astronomers cannot explain the cause of the apparent change.</li></ul>Eris is the largest known object beyond the orbit of Neptune, weighing nearly a third more than Pluto. It travels on an elongated path around the Sun that takes about 560 years to complete.Astronomers think the distant world is covered by a layer of frozen methane and small amounts of nitrogen ice. When it comes near the Sun, these ices are thought to vaporise from sunlit portions of the surface and condense onto regions in shadow.Eris is now near its farthest point from the Sun, so it is expected to be cold and inactive. But a new study suggests the dwarf planet's surface may have changed in the last few years."We're really scratching our heads," says author Stephen Tegler of Northern Arizona University in Flagstaff.<h3 class="crosshead">Pass through</h3>Tegler and colleagues probed Eris's supposedly inactive surface by measuring how methane ice absorbed the Sun's light.Methane absorbs some wavelengths of light more strongly than other wavelengths. Weakly absorbed light can therefore pass through the methane layer and reach greater depths beneath the surface, although the exact depth is difficult to estimate.By studying different wavelengths - or 'bands' - of light in Eris's spectrum using the 6.5-metre MMT observatory in Arizona, the researchers concluded that the concentration of nitrogen seems to increase with depth.That result, based on observations of five wavelength bands in 2007, contradicts observations made in 2005 with the 4.2-m William Herschel Telescope in Spain. The 2005 observations, which measured two bands of light, suggested that nitrogen is more abundant closer to the surface.<h3 class="crosshead">Icy weather?</h3>Both sets of observations are valid, say researchers, but they can't yet come up with an explanation for the difference.One possibility is that Eris experienced some recent change in weather that altered the top several centimetres of its surface, Tegler says.But changes in weather are difficult to explain when Eris is so far from the Sun. "It's very hard to imagine that something that dramatic would be happening on a relatively short time scale", says Mike Brown of Caltech, who was not involved in the study.Another possibility is that methane and nitrogen vapour erupted from Eris's interior, eventually condensing down to form a new layer of ice, says co-author William Grundy of Lowell Observatory in Flagstaff, Arizona.<h3 class="crosshead">Volcanic eruption</h3>No one is sure whether Eris is warm enough to boast this kind of 'cryovolcanism', but "an eruption isn't out of the question", Grundy told New Scientist.NASA's New Horizons mission, which is set to fly past Pluto in 2015, could help determine whether the erstwhile planet ever boasted similar eruptions. "If a shrimpy little body like Pluto can do it, Eris can too," Grundy says.Alternatively, the two teams might have observed different parts of the dwarf planet. New measurements suggest Eris boasts an Earth-like day, rotating on its axis once every 26 hours.Future observations could track the planet's appearance over multiple rotations to determine whether Eris has a patchy composition, Grundy says. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

MeteorWayne · Nov 10, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Posted by silylene</DIV> Very interesting. I too will be head scratching. As I say SOOOO many times, nice catch!! <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

3488 · Nov 11, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>I thought that Andrew may particularly like this new report, which was originall...........................................appearance over multiple rotations to determine whether Eris has a patchy composition, Grundy says. Posted by silylene</DIV>You bet silylene. I think this is absolutely wonderful, thank you very much for bringing this to our attention here.Pinning down the rotation rate too. Much quicker than Pluto's. Wonder what the axial tilt is??? We now know that Dysnomia is not in an Erisynchronous orbit as Charon is in a Hadeosynchronous orbit with Pluto. Dysnomia appears to orbit Eris once every fortnight or so, Eris rotates once ever 26 hours. Wonder what the rotational direction is?It certainly looks as if Eris is giving up a few secrets & perhaps before too long a crude map could be made of the dwarf planet.Volcanism of some sort, certainly cryovolcanoes if proven. Certainly with this, Eris is differentiated, more in common with Ganymede, Titan, Triton, Ariel, Dione, Enceladus & Europa in this respect rather than Callisto & Rhea.I would have thought that Eris would be a dead world, but this new evidence suggests that to not be so. Perhaps Eris looks more like Neptune's Triton in close up, few, small impact craters. Smoothish terrain with large areas of cryovolcanic frozen lava lakes.I wonder if New Horizons 2 / ARGO could swing past post Neptune if selected???????? Would be worth the extra fuel to make the necessary change in direction possible.  Fascinating stuff. Bit preoccupied with sorting data & images & upset with the demise of Phoenix right now (though expected) but this is a welcome diversion. I think this finding will help get New Horizons 2 / ARGO approved.Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

h2ouniverse · Nov 12, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>Andrew Brown. Posted by 3488</DIV> Hi Silylene and Andrew,I saw the article only yesterday. Thanks for these great news. That Eris would have had atmospheric activity (evaporation/recondensation cycles) is not a surprise. Given its perihelion at 39AU, that is logical (as for Pluto). Cryovolcanism would be interesting and I do believe in the differentiation scernario, and too on the presence of liquid deep underground. Whether this potential deep underground ocean is able to percolate to the surface is another kettle of fish.There is another potential explanation though for the phenomenon on Eris => could be a mere "summer" effect on the pole as suggested by the authors:http://arxiv.org/abs/0811.0825v1excerpt: "We suggest a mechanism to explain the apparent increase in nitrogen with depth. Specifically, if we are seeing Eris 50 degrees from pole-on (Brown and Schaller, 2008), the pole we are seeing now at aphelion was in winter darkness at perihelion. Near perihelion, sublimation could have built up atmospheric pressure on the sunlit (summer) hemisphere sufficient to drive winds toward the dark (winter) hemisphere, where the winds would condense. Because nitrogen is more volatile and scarcer than methane, it sublimated from the sunlit hemisphere relatively early in the season, so the early summer atmosphere was nitrogen rich, and so was the ice deposited on the winter pole. Later in the season, much of the nitrogen was exhausted from the summer pole, but there was plenty of methane, which continued to sublimate. At this point, the atmosphere was more depleted in nitrogen, as was the ice freezing out on top of the earlier deposited nitrogen rich ice"The good surprise is that this means that even at 96AU, an object may still present activity/variability. Best regards.

h2ouniverse · Nov 12, 2008

Replying to: <DIV CLASS='Discussion_PostQuote'>I would have thought that Eris would be a dead world,Andrew Brown. Posted by 3488</DIV> Hi Andrew, If you see the size-density diagram I've posted extrapolating from Desch's diagram you can see Eris is way way inside the blue (waterish) zone... Eris, Triton and Pluto do not even fit in the original diagram.  <img src="http://sitelife.space.com/ver1.0/Content/images/store/1/3/d1174f29-185f-4d4b-b330-e4631359aacb.Medium.jpg" alt="" />Replying to: <DIV CLASS='Discussion_PostQuote'>.I wonder if New Horizons 2 / ARGO could swing past post Neptune if selected???????? Would be worth the extra fuel to make the necessary change in direction possible. Andrew Brown. Posted by 3488</DIV>IIUC, that seems to be the plan from the promoters of the misison, with Triton fly-by a main objective of the mission, and hesitation between Trojan-Triton-KBO and Triton-KBO:http://www.lpi.usra.edu/opag/march_08_meeting/presentations/hammel.pdfBest regards.

h2ouniverse · Nov 18, 2008

now also an article on SDC http://www.space.com/scienceastronomy/081118-st-dwarf-planet.html

h2ouniverse · Feb 12, 2009

Some news on the "water" front:this abstract for the coming Lunar and Planetary Science Conference:http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1994.pdfThe author assesses another heat source: serpentinization. At a given point in the text he claims that his figure 1 shows effects comparable in amplitude to radiogenic heating especially for smaller bodies (Enceladus, Ceres). He brings the argument that on mid-sized bodies, percolation of water occurs deeper into the core, providing for chemical energy release through serpentinization.If true, that would bring water to the mill (pun intended) for those who believe in extant water on several of these bodies.

3488 · Feb 14, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>now also an article on SDC http://www.space.com/scienceastronomy/081118-st-dwarf-planet.html Posted by h2ouniverse</DIV>Thank you very much Joel,It looks like Eris may have an axial tilt of approx 40 degrees based on the looking directly at 50 degree point on Eris(the large inclination matters not as this is based on the plane of Eris's heliocentric orbit).Come on NASA, get NH2 / ARGO approved NOW, get her on her way, encounter a main belt asteroid, Jovian Trojan, Saturn, Neptune / Triton & Eris. It can be done & should be done. Replying to: <DIV CLASS='Discussion_PostQuote'>Some news on the "water" front:this abstract for the coming Lunar and Planetary Science Conference:http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1994.pdfThe author assesses another heat source: serpent..........................Posted by h2ouniverse</DIV>Very interesting Joel.One point, regarding water percolation into potential cores. If the body is very heavily differentiated, i.e Ganymede, Titan, Europa, Io, Triton, Pluto, Eris, etc would any H2O if present deep down not get to the core as the surrounding mantles would be too dense or am I being too dense??????Enceladus, 1 Ceres, Quaoar, etc, may not be too dense internally so I could imagine the scenario working there, but the others I mentioned, are they not too large & massive???Much great stuff from the Lunar & Planetary Science Conference, it will take me quite some time to go through it all. Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

h2ouniverse · Feb 15, 2009

Replying to: <DIV CLASS='Discussion_PostQuote'>If the body is very heavily differentiated, i.e Ganymede, Titan, Europa, Io, Triton, Pluto, Eris, etc would any H2O if present deep down not get to the core as the surrounding mantles would be too dense or am I being too dense??????Enceladus, 1 Ceres, Quaoar, etc, may not be too dense internally so I could imagine the scenario working there, but the others I mentioned, are they not too large & massive???. Posted by 3488</DIV> Hi Andrew,As far as I understand his rationale, the author considers the depth at which cracks in the rocky core are not overcome by pressure, thusly letting the water flow down. AFAIRC, it is not a matter of density (drill a vertical well into ocean's bottom and water will fill it anyway) but of gravity and crust resistance (at a given time the pressure caused by gravity will force the well walls towards each other and "heal" the hole). The lower the gravity in the upper core, the more likely it is to keep unhealed cracks long enough for water to penetrate it.Note that there is more water in Earth's crust under oceans than under continents at iso-depth. Best regards.

h2ouniverse · Feb 16, 2009

Another interesting article in the L&P Science Conference:http://www.lpi.usra.edu/meetings/lpsc2009/pdf/2222.pdfthis time pointing to NH3 or NH4 on Charon's surface. That would confirm at worst the presence of ammonia (hence depression of melting point) andat best can be a marker of cryovolcanism.That bodes well for a water(water-ammonia) layer on Charon, and on other large TNOs (Triton, Eris, Pluto, Makemake, 2007 OR10...).

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