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Thread: Callisto colonization -- some crazy ideas

  1. #181
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    Reddit turns out to have its own folder for Callisto-related space articles--and one for Ganymede as well.

    https://www.reddit.com/r/Callisto/

    https://www.reddit.com/r/Ganymede/
    Do good work. —Virgil Ivan "Gus" Grissom

  2. #182
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    A cycler vessel could with little fuel pass between Callisto and another prograde Jovian moon (e.g., Ganymede or an outer asteroidal moon with a mining/manufacturing colony, like Himalia).

    https://ui.adsabs.harvard.edu/abs/20....286P/abstract
    Last edited by Roger E. Moore; 2020-May-02 at 06:08 PM.
    Do good work. —Virgil Ivan "Gus" Grissom

  3. #183
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    Callisto produces ultraviolet aurorae on Jupiter, among other interesting things in this new paper.

    https://ui.adsabs.harvard.edu/abs/20.....85B/abstract
    Callisto in the Magnetosphere of Jupiter
    Belenkaya, E. S.
    Abstract: The study of the Galilean satellites can help clarify the structure of the magnetospheric magnetic field from observations of their projections along magnetic field lines in the atmosphere/ionosphere of Jupiter, where patches of auroras appear. UV auroras in projections on the ionosphere of Io, Europe and Ganymede occur almost permanently, while the observation of the track of Callisto is difficult. One of the reasons is that the Callisto projection lies near or inside Jupiter's bright main oval. Another reason is that Callisto is not constantly in the sub-Alfvenic flow of magnetospheric plasma. The interaction of Callisto with the magnetospheric plasma of the planet is an actual problem widely discussed in the literature, which sheds light on the key processes occurring in the Jovian system.
    Publication: Solar System Research, Volume 54, Issue 2, p.85-95
    Pub Date: April 2020
    Do good work. —Virgil Ivan "Gus" Grissom

  4. #184
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    The abstracts of these two papers are so long they might perhaps be the papers themselves. They provide a wealth of information on processes that could be repeated for a Callisto or Ganymede colony. By all means, click, read and enjoy.

    https://ui.adsabs.harvard.edu/abs/20....610F/abstract
    Towards a Moon Village: Community Workshops Highlights
    Foing, Bernard H.
    41st COSPAR Scientific Assembly, abstracts from the meeting that was to be held 30 July - 7 August at the Istanbul Congress Center (ICC), Turkey, but was cancelled. See http://cospar2016.tubitak.gov.tr/en/, Abstract id. PEX.2-7-16.
    Pub Date: July 2016

    https://ui.adsabs.harvard.edu/abs/20...7163K/abstract
    Towards a Moon Village: Young Lunar Explorers Report
    Kamps, Oscar; Foing, Bernard; Batenburg, Peter
    EGU General Assembly 2016, held 17-22 April, 2016 in Vienna Austria, id. EPSC2016-17163
    Pub Date: April 2016

    This paper is particularly relevant to the topic.

    https://ui.adsabs.harvard.edu/abs/20....814S/abstract
    What Will We Actually Do On the Moon?
    Sherwood, Brent
    Abstract: Descriptions are provided for eleven specific, representative lunar activity scenarios selected from among hundreds that arose in 2006 from the NASA-sponsored development of a "global lunar strategy." The scenarios are: pave for dust control; establish a colony of continuously active robots; kitchen science; designer biology; tend the machinery; search for pieces of ancient Earth; build simple observatories that open new wavelength regimes; establish a virtual real-time network to enable public engagement; institute a public-private lunar development corporation; rehearse planetary protection protocols for Mars; and expand life and intelligence beyond Earth through settlement of the Moon. Evocative scenarios such as these are proposed as a communications tool to help win public understanding and support of the Vision for Space Exploration.
    Publication: Space Technology and Applications International Forum-Staif 2007: 11th Conf Thermophys.Applic.in Micrograv.; 24th Symp Space Nucl.Pwr.Propulsion; 5th Conf Hum/Robotic Techn &Vision Space Explor.; 5th Symp Space Coloniz.; 4th Symp New Frontrs &Future Con. Proceedings held at Albuquerque, New Mexico, 11-15 February 2007. AIP Conference Proceedings Volume 880. Edited by Mohamed S. El-Genk. Melville, NY: American Institute of Physics, 2007., p.814-822
    Pub Date: January 2007

    The representative lunar activity scenarios that, when modified, apply specifically to Callisto colonization would be: pave non-melting roads and lots; establish a colony of continuously active robots for colony maintenance and construction (and robot repair); kitchen science; designer biology; search for geologically interesting rocks and ices with clues to the history of the solar system; build simple observatories that open new wavelength regimes; establish a virtual real-time network to enable public engagement; institute a public-private lunar development corporation; rehearse protection protocols for setting up colonies farther in toward Ganymede and Europa; and expand life and intelligence beyond Earth through extraterrestrial settlement.
    Do good work. —Virgil Ivan "Gus" Grissom

  5. #185
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    More information on what are sometimes called "shell worlds," e.g., a moon or planet with a thick solid ice crust over a subsurface liquid ocean. Callisto, Ganymede, Europa, Titan, Enceladus all qualify as shell worlds at present. The second paper is wholly present through the link, but the first paper is missing except for the abstract. How much tidal heating could be had from a world like Callisto or Ganymede remains to be seen, much less whether that energy could be harnessed for a colony on either world.


    https://ui.adsabs.harvard.edu/abs/20...2899H/abstract
    Ocean Tidal Dynamics and Dissipation in the Thick Shell Worlds
    Hay, H.; Matsuyama, I.
    Abstract: Tidal dissipation in the subsurface oceans of icy satellites has so far only been explored in the limit of a free-surface ocean or under the assumption of a thin ice shell. Here we consider ocean tides in the opposite limit, under the assumption of an infinitely rigid, immovable, ice shell. This assumption forces the surface displacement of the ocean to remain zero, and requires the solution of a pressure correction to ensure that the ocean is mass conserving (divergence-free) at all times. This work investigates the effect of an infinitely rigid lid on ocean dynamics and dissipation, focusing on implications for the thick shell worlds Ganymede and Callisto. We perform simulations using a modified version of the numerical model Ocean Dissipation in Icy Satellites (ODIS), solving the momentum equations for incompressible shallow water flow under a degree-2 tidal forcing. The velocity solution to the momentum equations is updated iteratively at each time-step using a pressure correction to guarantee mass conservation everywhere, following a standard solution procedure originally used in solving the incompressible Navier-Stokes equations. We reason that any model that investigates ocean dynamics beneath a global ice layer should be tested in the limit of an immovable ice shell and must yield solutions that exhibit divergence-free flow at all times.
    Publication: American Geophysical Union, Fall Meeting 2017, abstract #P43C-2899
    Pub Date: December 2017

    https://arxiv.org/abs/1804.07727
    [Submitted on 20 Apr 2018]
    Ocean tidal heating in icy satellites with solid shells
    Isamu Matsuyama, Mikael Beuthe, Hamish C. F. C. Hay, Francis Nimmo, Shunichi Kamata
    As a long-term energy source, tidal heating in subsurface oceans of icy satellites can influence their thermal, rotational, and orbital evolution, and the sustainability of oceans. We present a new theoretical treatment for tidal heating in thin subsurface oceans with overlying incompressible elastic shells of arbitrary thickness. The stabilizing effect of an overlying shell damps ocean tides, reducing tidal heating. This effect is more pronounced on Enceladus than on Europa because the effective rigidity on a small body like Enceladus is larger. For the range of likely shell and ocean thicknesses of Enceladus and Europa, the thin shell approximation of Beuthe (2016) is generally accurate to less than about 4%.The time-averaged surface distribution of ocean tidal heating is distinct from that due to dissipation in the solid shell, with higher dissipation near the equator and poles for eccentricity and obliquity forcing respectively. This can lead to unique horizontal shell thickness variations if the shell is conductive. The surface displacement driven by eccentricity and obliquity forcing can have a phase lag relative to the forcing tidal potential due to the delayed ocean response. For Europa and Enceladus, eccentricity forcing generally produces greater tidal amplitudes due to the large eccentricity values relative to the obliquity values. Despite the small obliquity values, obliquity forcing generally produces larger phase lags due to the generation of Rossby-Haurwitz waves. If Europa's shell and ocean are respectively 10 and 100 km thick, the tide amplitude and phase lag are 26.5 m and <1 degree for eccentricity forcing, and <2.5 m and <18 degrees for obliquity forcing. Measurement of the obliquity phase lag (e.g., by Europa Clipper) would provide a probe of ocean thickness.
    Do good work. —Virgil Ivan "Gus" Grissom

  6. #186
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    Could Callisto or Ganymede be converted for colonization into double-shelled worlds? Could they have an atmosphere generated (by means detailed elsewhere in this thread) and then contained by an artificial shell built over top of and supported by the atmosphere, to prevent leakage? Such an outer shell might also contain and even generate heat by acting as a giant greenhouse.

    https://ui.adsabs.harvard.edu/abs/20...1075R/abstract
    Shell Worlds: An Approach to Making Large Moons and Small Planets Habitable
    Roy, Kenneth I.; Kennedy, Robert G.; Fields, David E.
    Abstract: The main problem with terraforming is finding planets with workable initial parameters: large enough, temperate enough, wet enough, axial spin not too fast or too slow, a magnetic field, etc. We consider a novel method of creating habitable worlds for humanity by enclosing airless and sterile planets, moons, and even large asteroids within engineered shells supported by breathable atmospheres. Beneath the shell an earthlike environment could be formed similar in almost all respects to that of Earth except for gravity, regardless of the distance to the sun or other star. These would be natural worlds, not merely large habitats, stable across historic timescales at least, each comprising a full self-sustaining ecology, which might evolve in interesting and distinct directions over time. This approach requires no fundamental breakthroughs in science or physics but does require progress in energy production, space transportation, and environmental and materials sciences.
    Publication: SPACE TECHNOLOGY AND APPLICATIONS INTERNAT.FORUM-STAIF 2004: Conf.on Thermophys.in Microgravity; Commercial/Civil Next Gen.Space Transp.; 21st Symp.Space Nuclear Power & Propulsion; Human Space Explor.; Space Colonization; New Frontiers & Future Concepts. AIP Conference Proceedings, Volume 699, pp. 1075-1084 (2004).
    Pub Date: February 2004

    https://ui.adsabs.harvard.edu/abs/20.....32R/abstract
    Shell Worlds - An Approach To Terraforming Moons, Small Planets and Plutoids
    Roy, K. L.; Kennedy, R. G., III; Fields, D. E.
    Abstract: One big problem with the traditional terraforming approach is finding planets with workable initial parameters: large enough, temperate enough, wet enough, axial spin not too fast or too slow, a magnetic field, etc. A novel method to creating habitable environments for humanity by enclosing airless and otherwise useless sterile planets, moons, and even large asteroids within engineered shells is proposed. These shells are subjected to two primary opposing internal forces: compression caused by gravity and tension caused by atmospheric pressure. By careful design, these two forces can cancel each other out resulting in a net stress on the shell of zero. Beneath the shell an earthlike environment could be created similar in almost all respects to that of Earth except for gravity, regardless of the distance to the sun or other star. These would be small worlds, not merely large habitats, possibly stable across historic timescales. Each would contain a full, self-sustaining ecology, which might evolve in interesting directions over time.
    Publication: Journal of the British Interplanetary Society, vol. 62, p. 32-38
    Pub Date: 2009

    https://ui.adsabs.harvard.edu/abs/20....238R/abstract
    Shell worlds
    Roy, Kenneth I.; Kennedy, Robert G., III; Fields, David E.
    Abstract: The traditional concept of terraforming assumes ready availability of candidate planets with acceptable qualities: orbiting a star in its "Goldilocks zone", liquid water, enough mass, years longer than days, magnetic field, etc. But even stipulating affordable interstellar travel, we still might never find a good candidate elsewhere. Whatever we found likely would require centuries of heavy terraforming, just as Mars or Venus would here. Our increasing appreciation of the ubiquity of life suggests that any terra nova would already possess it. We would then face the dilemma of introducing alien life forms (us, our microbes) into another living world. Instead, we propose a novel method to create habitable environments for humanity by enclosing airless, sterile, otherwise useless planets, moons, and even large asteroids within engineered shells, which avoids the conundrum. These shells are subject to two opposing internal stresses: compression due to the primary's gravity, and tension from atmospheric pressure contained inside. By careful design, these two cancel each other resulting in zero net shell stress. Beneath the shell an Earth-like environment could be created similar in almost all respects to that of Home, except for gravity, regardless of the distance to the sun or other star. Englobing a small planet, moon, or even a dwarf planet like Ceres, would require astronomical amounts of material (quadrillions of tons) and energy, plus a great deal of time. It would be a quantum leap in difficulty over building Dyson Dots or industrializing our solar system, perhaps comparable to a mission across interstellar space with a living crew within their lifetime. But when accomplished, these constructs would be complete (albeit small) worlds, not merely large habitats. They could be stable across historic timescales, possibly geologic. Each would contain a full, self-sustaining ecology, which might evolve in curious directions over time. This has interesting implications for SETI as well.
    Highlights
    ► Moons, dwarf planets, and large asteroids can be enclosed in engineered shells.
    ► Internal air pressure cancels gravity’s compression; net shell stress is zero.
    ► Artificial light needed; low-gravity but otherwise Earth-like environment inside.
    ► Sidesteps moral hazard of settling rare extrasolar worlds w/aliens (us).
    ► It can be built around any star — interesting implications for SETI.
    Publication: Acta Astronautica, Volume 82, Issue 2, p. 238-245.
    Pub Date: February 2013

    https://ui.adsabs.harvard.edu/abs/20....364R/abstract
    Shell Worlds: The Question of Shell Stability
    Roy, K. L.; Kennedy, R. G., III; Fields, D. E.
    Abstract: The initial idea of shell worlds was first proposed in the January 2009 edition of JBIS. In that paper the stability of the shell around a central world was not discussed at any length except to say that it was stable due to forces induced by gravity. This paper demonstrates in a qualitative and quantitative manner that a material shell supported by atmospheric pressure around a moon or small planet is indeed stable and does not require active measures to remain centered, provided that the central body is large enough. The minimal size of the central body to provide this stability is discussed.
    Publication: Journal of the British Interplanetary Society, vol. 67, p. 364-368
    Pub Date: 2014
    Last edited by Roger E. Moore; 2020-May-03 at 01:59 PM.
    Do good work. —Virgil Ivan "Gus" Grissom

  7. #187
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    The Earth's Moon isn't "dead" after all. The giant impact at Aiken Basin long ago seems to have sparked a long-running series of moonquakes stemming from magma upheavals in the core, coming out on the Moon's opposite side around the Ocean of Storms, which was a magma upwelling itself.

    Now, given that Callisto and other Galilean moons suffered giant impacts in the past, could they also be undergoing moonquakes and seismic/tectonic disturbances? Callisto was hit hard at Valhalla and Asgard.

    https://www.space.com/moon-ridges-re...-activity.html
    Newly discovered ridges on the moon's surface are leading scientists to think that the moon might have an active tectonic system. Using data from NASA's Lunar Reconnaissance Orbiter (LRO), researchers have discovered a number of ridges with exposed bedrock, free of lunar regolith, or powdery lunar "soil," spread across the moon's nearside surface. These ridges, speckled with boulders, could be evidence that, not too long ago, tectonic activity broke apart the moon's surface.

    https://www.sciencealert.com/we-just...nically-active
    The new findings suggest that the ridges are still surging upward. But the combination of the ridges with the magma-filled cracks presents a possible explanation: the South Pole-Aitken Basin. This is a colossal impact crater on the far side of the Moon. At 2,500 kilometres (1,550 miles) across, it covers a quarter of the lunar surface, and is one of the biggest known impact craters in the Solar System. It's possible, the team proposes, that this impact shook the Moon to its core. This could have produced a system of cracks on the near side, which then filled with magma. The rising ridges are then, in this model, the ongoing response to that partially Moon-shattering event long ago.
    Do good work. —Virgil Ivan "Gus" Grissom

  8. #188
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    Why are Ganymede and Callisto different? They're practically twins in so many ways. A decade ago, research showed that Jupiter's habit of flinging around comets and other space debris created giant impacts on the surfaces of Ganymede and Callisto, melting the surface ice and letting the impactor debris sink down to the moons' cores. Ganymede, being closer in, caught the most debris and got the bigger core, and thus the most gravity.

    https://phys.org/news/2010-01-explan...sto-moons.html
    https://ui.adsabs.harvard.edu/abs/20....164B/abstract
    https://www.sciencedaily.com/release...0124162151.htm
    https://www.scientificamerican.com/a...llisto-comets/
    January 24, 2010
    Researchers offer explanation for the differences between Ganymede and Callisto moons
    by Southwest Research Institute
    Differences in the number and speed of cometary impacts onto Jupiter's large moons Ganymede and Callisto some 3.8 billion years ago can explain their vastly different surfaces and interior states, according to research by scientists at the Southwest Research Institute appearing online in Nature Geoscience Jan. 24, 2010.

    Dr. Amy C. Barr and Dr. Robin M. Canup of the SwRI Planetary Science Directorate created a model of melting by cometary impacts and rock core formation to show that Ganymede and Callisto's evolutionary paths diverged about 3.8 billion years ago during the Late Heavy Bombardment, the phase in lunar history dominated by large impact events.

    "Impacts during this period melted Ganymede so thoroughly and deeply that the heat could not be quickly removed. All of Ganymede's rock sank to its center the same way that all the chocolate chips sink to the bottom of a melted carton of ice cream," says Barr. "Callisto received fewer impacts at lower velocities and avoided complete melting."

    In the Barr and Canup model, Jupiter's strong gravity focuses cometary impactors onto Ganymede and Callisto. Each impact onto Ganymede or Callisto's mixed ice and rock surface creates a pool of liquid water, allowing rock in the melt pool to sink to the moon's center. Ganymede is closer to Jupiter and therefore is hit by twice as many icy impactors as Callisto, and the impactors hitting Ganymede have a higher average velocity. Modeling by Barr and Canup shows that core formation begun during the late heavy bombardment becomes energetically self-sustaining in Ganymede but not Callisto.
    Do good work. —Virgil Ivan "Gus" Grissom

  9. #189
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    Two different takes on how to colonise large water-ice moons & other worlds in our Solar System and others. First is a detailed plan to melt the water-ice and turn the moons into ocean worlds, perhaps making them "shell worlds" covering the atmosphere with a material to keep the air from being lost. Second is the plan to leave the moons icy and unmelted, but dig below the surfaces to form colonies near the subsurface water oceans.

    A. Frasier's "Universe Today" column, "How Do We Terraform Jupiter’s Moons"
    https://forum.cosmoquest.org/archive.../t-160975.html
    https://forum.cosmoquest.org/showthr...’s-Moons

    B. https://arxiv.org/abs/2003.09231
    The subsurface habitability of small, icy exomoons
    J. Tjoa, M. Mueller, F.F.S. van der Tak
    [Submitted on 20 Mar 2020]
    Assuming our Solar System as typical, exomoons may outnumber exoplanets. If their habitability fraction is similar, they would thus constitute the largest portion of habitable real estate in the Universe. Icy moons in our Solar System, such as Europa and Enceladus, have already been shown to possess liquid water, a prerequisite for life on Earth. We intend to investigate under what circumstances small, icy moons may sustain subsurface oceans and thus be "subsurface habitable". We pay specific attention to tidal heating. We made use of a phenomenological approach to tidal heating. We computed the orbit averaged flux from both stellar and planetary (both thermal and reflected stellar) illumination. We then calculated subsurface temperatures depending on illumination and thermal conduction to the surface through the ice shell and an insulating layer of regolith. We adopted a conduction only model, ignoring volcanism and ice shell convection as an outlet for internal heat. In doing so, we determined at which depth, if any, ice melts and a subsurface ocean forms. We find an analytical expression between the moon's physical and orbital characteristics and the melting depth. Since this expression directly relates icy moon observables to the melting depth, it allows us to swiftly put an upper limit on the melting depth for any given moon. We reproduce the existence of Enceladus' subsurface ocean; we also find that the two largest moons of Uranus (Titania & Oberon) could well sustain them. Our model predicts that Rhea does not have liquid water. Habitable exomoon environments may be found across an exoplanetary system, largely irrespective of the distance to the host star. Small, icy subsurface habitable moons may exist anywhere beyond the snow line. This may, in future observations, expand the search area for extraterrestrial habitable environments beyond the circumstellar habitable zone.
    Last edited by Roger E. Moore; 2020-May-12 at 01:01 AM.
    Do good work. —Virgil Ivan "Gus" Grissom

  10. #190
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    An interesting bit of Galilean satellite history possibly explained, with reference to Callisto's position and characteristics.

    https://arxiv.org/abs/2005.05132
    [Submitted on 11 May 2020]
    Photoevaporation of the Jovian circumplanetary disk I. Explaining the orbit of Callisto and the lack of outer regular satellites
    N. Oberg, I. Kamp, S. Cazaux, Ch. Rab
    The Galilean satellites are thought to have formed from a circumplanetary disk (CPD) surrounding Jupiter. When it reached a critical mass, Jupiter opened an annular gap in the solar protoplanetary disk (PPD) that might have exposed the CPD to radiation from the young Sun or from the stellar cluster in which the Solar System formed. We investigate the radiation field to which the Jovian CPD was exposed during the process of satellite formation. The resulting photoevaporation of the CPD is studied in this context to constrain possible formation scenarios for the Galilean satellites and explain architectural features of the Galilean system. We constructed a model for the stellar birth cluster to determine the intracluster far-ultraviolet (FUV) radiation field. We employed analytical annular gap profiles informed by hydrodynamical simulations to investigate a range of plausible geometries for the Jovian gap. We used the radiation thermochemical code ProDiMo to evaluate the incident radiation field in the Jovian gap and the photoevaporation of an embedded 2D axisymmetric CPD. We derive the time-dependent intracluster FUV radiation field for the solar birth cluster over 10 Myr. We find that intracluster photoevaporation can cause significant truncation of the Jovian CPD. We determine steady-state truncation radii for possible CPDs, finding that the outer radius is proportional to the accretion rate... [P]hotoevaporative truncation explains the lack of additional satellites outside the orbit of Callisto.... [P]hotoevaporation can disperse the disk before Callisto is able to migrate into the Laplace resonance. This explains why Callisto is the only massive satellite that is excluded from the resonance.
    Do good work. —Virgil Ivan "Gus" Grissom

  11. #191
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    When it comes to sending humans to Jupiter, nuclear thermal propulsion is the way to go. (Cargo can go the slower, energy-cheap way.) Here is a short course on that type of engine.

    https://theconversation.com/to-safel...-answer-137967
    Do good work. —Virgil Ivan "Gus" Grissom

  12. #192
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    Lightbulb

    A reminder, mostly for myself, that a complete description of Callisto orientation terms and maps is found at:

    https://forum.cosmoquest.org/showthr...y-and-so-forth

    semi-buried in the Astronomy folder. Five orientation maps are attached for the reader's interest.
    Attached Images Attached Images
    Do good work. —Virgil Ivan "Gus" Grissom

  13. #193
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    A collection of random thoughts.

    1. The hovering, rocket-powered sky crane used by Mars rover Curiosity would be a great way to land equipment on Callisto without using rockets, which risk melting the surface and sticking the spacecraft in refrozen ice. Rockets, however, could use compressed air at cold temperatures, so as not to melt anything too much.

    2. The surface of Callisto is so rough that some means should be devised to build roadways/ pathways across the surface, using:
    a. actual bulldozer vehicles, robotic
    b. space mirrors to focus the Sun's rays to melt a "parking lot" or pathway (sun's light awfully weak here, but building big mirrors cheaply still possible)
    c. space explosion of nuclear weapon to create brief, superhot "sun" to melt an area flat.
    A large amount of rocks and solid debris is expected, so even a melted flat surface could be rough.

    It is possible that micrometeorites might have softened up the surface to create an ice regolith, easier to drive on and smoothing off the rocks, but we will see.

    3. You can warm up the surface only so much around a colony without risking disaster. Too much waste heat, and the surface will melt and either:
    a. stay as a short-term lake or pond, flooding everything, or
    b. melt then refreeze, trapping everything.
    Waste heat should be strictly monitored. Heat will also produce an atmosphere, which is not an entirely bad thing.

    4. An artificial atmosphere can be produced around Callisto, supposing enough surface heat is directed toward this goal at some place. This has been discussed before here. As with Titan, an atmosphere would burn up meteoroids and dust, saving colonists and equipment, plus it would introduce light scattering, making it easier to get about on the surface. However, it might spoil astronomical observations, but why put telescopes on the surface? Leave them in space. A cycle might develop in which part of the atmosphere freezes out again in the antisolar hemisphere, the side not facing the Sun at any time, or even on the solar hemisphere (day side) if cold enough. This "frost" might cover equipment, however.

    5. The main point in colonizing Callisto is to establish a vital and renewable human population in the Outer Solar System. Maintaining the human population is the key point. Mining the other small moons of Jupiter would bring enormous resources to Callisto (and Ganymede, if also colonized).

    6. However, if establishing a human colony here is too difficult at a given time, and no atmosphere is to be created, just cover the world in exploratory robots and see if the world can be mined for materials for a human colony in the Jovian vicinity.

    7. A possible colony configuration would be one started in a small crater. If the crater floor can be smoothed out, a gigantic balloon could be inflated inside, covering the floor and reaching to the crater walls. (Envisioning a crater under 100 meters diameter here.) Once inflated, the top of the balloon is covered with ice sprayed over it by little snow blower machines. Melt the top ice a little, let it refreeze, and it's solid. When the top is frozen rigid, the colony is created inside the balloon itself, which cannot now deflate. (Add internal pillars and tent poles just in case.)

    8. In case Callisto is geologically active, because of ancient cracking from massive asteroid strikes (like the Moon) or its internal ocean, just don't build anything over a fault system.
    Last edited by Roger E. Moore; 2020-May-30 at 01:46 PM.
    Do good work. —Virgil Ivan "Gus" Grissom

  14. #194
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    It is worth noting than, because Callisto has no atmosphere, an orbiting vehicle can drop very close to the ground without fear of impact, so long as no surface features get in the way. How this might be useful remains to be seen, but one does think about things like the skyhook used during World War II and the Cold War.

    https://en.wikipedia.org/wiki/Fulton...ecovery_system
    Do good work. —Virgil Ivan "Gus" Grissom

  15. #195
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    Quote Originally Posted by Roger E. Moore View Post
    A collection of random thoughts.

    1. The hovering, rocket-powered sky crane used by Mars rover Curiosity would be a great way to land equipment on Callisto without using rockets, which risk melting the surface and sticking the spacecraft in refrozen ice. Rockets, however, could use compressed air at cold temperatures, so as not to melt anything too much.

    2. The surface of Callisto is so rough that some means should be devised to build roadways/ pathways across the surface, using:
    a. actual bulldozer vehicles, robotic
    b. space mirrors to focus the Sun's rays to melt a "parking lot" or pathway (sun's light awfully weak here, but building big mirrors cheaply still possible)
    c. space explosion of nuclear weapon to create brief, superhot "sun" to melt an area flat.
    A large amount of rocks and solid debris is expected, so even a melted flat surface could be rough.

    It is possible that micrometeorites might have softened up the surface to create an ice regolith, easier to drive on and smoothing off the rocks, but we will see.

    3. You can warm up the surface only so much around a colony without risking disaster. Too much waste heat, and the surface will melt and either:
    a. stay as a short-term lake or pond, flooding everything, or
    b. melt then refreeze, trapping everything.
    Waste heat should be strictly monitored. Heat will also produce an atmosphere, which is not an entirely bad thing.

    4. An artificial atmosphere can be produced around Callisto, supposing enough surface heat is directed toward this goal at some place. This has been discussed before here. As with Titan, an atmosphere would burn up meteoroids and dust, saving colonists and equipment, plus it would introduce light scattering, making it easier to get about on the surface. However, it might spoil astronomical observations, but why put telescopes on the surface? Leave them in space. A cycle might develop in which part of the atmosphere freezes out again in the antisolar hemisphere, the side not facing the Sun at any time, or even on the solar hemisphere (day side) if cold enough. This "frost" might cover equipment, however.

    5. The main point in colonizing Callisto is to establish a vital and renewable human population in the Outer Solar System. Maintaining the human population is the key point. Mining the other small moons of Jupiter would bring enormous resources to Callisto (and Ganymede, if also colonized).

    6. However, if establishing a human colony here is too difficult at a given time, and no atmosphere is to be created, just cover the world in exploratory robots and see if the world can be mined for materials for a human colony in the Jovian vicinity.

    7. A possible colony configuration would be one started in a small crater. If the crater floor can be smoothed out, a gigantic balloon could be inflated inside, covering the floor and reaching to the crater walls. (Envisioning a crater under 100 meters diameter here.) Once inflated, the top of the balloon is covered with ice sprayed over it by little snow blower machines. Melt the top ice a little, let it refreeze, and it's solid. When the top is frozen rigid, the colony is created inside the balloon itself, which cannot now deflate. (Add internal pillars and tent poles just in case.)

    8. In case Callisto is geologically active, because of ancient cracking from massive asteroid strikes (like the Moon) or its internal ocean, just don't build anything over a fault system.
    A landing spacecraft will be starting in full sunlight in open space, and will then do a long insertion/landing burn. The best way to avoid sticking to the ice is probably to not even try, and instead provide some kind of platform to allow a rover to come to equilibrium with the surface before attempting to drive. This would cost far, far less mass than a cold gas thruster system operating at ice-safe temperatures.

    Liquid water is not stable in vacuum. All but the most extreme heat sources will cause sublimation, not melting.

  16. #196
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    Quote Originally Posted by cjameshuff View Post
    A landing spacecraft will be starting in full sunlight in open space, and will then do a long insertion/landing burn. The best way to avoid sticking to the ice is probably to not even try, and instead provide some kind of platform to allow a rover to come to equilibrium with the surface before attempting to drive. This would cost far, far less mass than a cold gas thruster system operating at ice-safe temperatures.

    Liquid water is not stable in vacuum. All but the most extreme heat sources will cause sublimation, not melting.
    Sensible, given the extreme cold of the surface (max 170-185 K). Occurs to me that new materials will have to be developed that won't stick or crack or shatter when made into Callisto wheels.
    Last edited by Roger E. Moore; 2020-May-30 at 03:38 PM.
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    Lightbulb

    Quote Originally Posted by Roger E. Moore View Post
    A reminder, mostly for myself, that a complete description of Callisto orientation terms and maps is found at:

    https://forum.cosmoquest.org/showthr...y-and-so-forth

    semi-buried in the Astronomy folder. Five orientation maps are attached for the reader's interest.
    Attached here is an orientation map for Solar directions on Callisto (day side, night side, subsolar point, etc.). It does not coordinate with the other maps, as Jupiter's and Callisto's orbits orbital planes are not perfect circles nor perfectly aligned with each other's plane of movement or with the Sun.
    Attached Images Attached Images
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    The speed of coronal mass ejections can be used to improve predictions of radiation hazards for astronauts in deep space (going to or from Callisto, for example) and earth orbit.

    https://phys.org/news/2020-06-space-...atellites.html
    https://agupubs.onlinelibrary.wiley....9/2020SW002507

    Severe space‐weather is driven by huge eruptions of solar material, known as coronal mass ejections (CMEs), travelling through interplanetary space and disturbing the Earth's own magnetic field system. Using solar imagers to measure the speed of CMEs close to the Sun, it is possible to forecast the arrival time of a CME at Earth. Operators of technological systems which are vulnerable to space weather then have the opportunity to take action to limit the damage. But how useful is this information? Not all CMEs trigger a severe storm, thus CME arrival time forecasts will lead to lots of `false alarms' wherein action is taken when it is not needed. In some situations, this may be acceptable; better safe than sorry. In others, repeatedly taking unnecessary action will prove more costly than the potential space‐weather damage itself. In this study, we outline a simple way to quantify the value of knowing CME arrival time and show that the speed of the CME at Earth is a useful extra piece of information that can be used to reduce the number of false alarms and make forecasts more valuable.
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    A proposal to give Mars a magnetic field that might be perfectly useful on Callisto--and cheaper in materials cost, too. However, this will work only on solid colonized Callistos, not melted/oceanic ones. Callisto's radius is 2,410 km compared to 3,400 km for Mars, so the circumference comparison, Callisto to Mars, is proportionately the same.

    https://arxiv.org/abs/2006.05546
    Fundamental Physical and Resource Requirements for a Martian Magnetic Shield
    Marcus DuPont, Jeremiah W. Murphy
    [Submitted on 9 Jun 2020]
    Mars lacks a substantial magnetic field; as a result, the solar wind ablates the Martian atmosphere, making the surface uninhabitable. Therefore, any terraforming attempt will require an artificial Martian magnetic shield. The fundamental challenge of building an artificial magnetosphere is to condense planetary-scale currents and magnetic fields down to the smallest mass possible. Superconducting electromagnets offer a way to do this. However, the underlying physics of superconductors and electromagnets limits this concentration. Based upon these fundamental limitations, we show that the amount of superconducting material is proportional to B^−2ca^−3, where Bc is the critical magnetic field for the superconductor and a is the loop radius of a solenoid. Since Bc is set by fundamental physics, the only truly adjustable parameter for the design is the loop radius; a larger loop radius minimizes the amount of superconducting material required. This non-intuitive result means that the "intuitive" strategy of building a compact electromagnet and placing it between Mars and the Sun at the first Lagrange point is unfeasible. Considering reasonable limits on Bc, the smallest possible loop radius is ~10 km, and the magnetic shield would have a mass of ~10^19 g. Most high-temperature superconductors are constructed of rare elements; given solar system abundances, building a superconductor with ~10^19 g would require mining a solar system body with several times 10^25 g; this is approximately 10% of Mars. We find that the most feasible design is to encircle Mars with a superconducting wire with a loop radius of ~3400 km. The resulting wire diameter can be as small as ~5 cm. With this design, the magnetic shield would have a mass of ~10^12 g and would require mining ~10^18 g, or only 0.1% of Olympus Mons.
    Last edited by Roger E. Moore; 2020-Jun-12 at 10:12 PM.
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    Could something like that save Earth from flares or be used to generate power without a lot of surface area?

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    Quote Originally Posted by Roger E. Moore View Post
    A proposal to give Mars a magnetic field that might be perfectly useful on Callisto--and cheaper in materials cost, too. However, this will work only on solid colonized Callistos, not melted/oceanic ones. Callisto's radius is 2,410 km compared to 3,400 km for Mars, so the circumference comparison, Callisto to Mars, is proportionately the same.
    I’m having trouble seeing how it would be relevant to Callisto. The key atmospheric loss mechanism is that the escape velocity is so low that a reasonably warm atmosphere will have significant loss over thousands of years. Callisto is significantly more distant from the sun than Mars, so solar wind would be a much smaller issue there and it isn’t clear it would be that important for Mars either.

    It might be useful for reducing surface radiation if not bothering with terraforming, allowing for easier habitat construction and longer outside stays in suits.

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