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View Full Version : Mount Lookitthat in a realistic sense



Roger E. Moore
2018-Aug-29, 07:22 PM
A story told by Carl Sagan, courtesy of the WayBack Machine.

https://archive.org/stream/TheCosmicConnectionCarlSagan/The%20Cosmic%20Connection%20Carl%20Sagan_djvu.txt

Sagan, Carl. The Cosmic Connection: An Extraterrestrial Perspective. New York: Dell Publishing Co., 1973

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“...Just before the remarkable spacecraft observations of Venus of 1968, I submitted a paper to Nature, the British scientific journal, in which I summarized these conclusions and deduced that only the hot-surface model was consistent with all the evidence. I had earlier proposed a specific theory, in terms of the greenhouse effect, to explain how the surface of Venus could be at such high temperatures. But my conclusions against cold-surface models in 1968 did not depend upon the validity of the greenhouse explanation: It was just that a hot surface explained the data and a cold surface did not. Because of my interest in exobiology, I would have preferred a habitable Venus, but the facts led elsewhere. In a paper published in 1962, I had concluded from indirect evidence that the average surface temperature on Venus was about 800 degrees F and the average surface atmospheric pressure about fifty times larger than at the surface of Earth.

“In 1968, an American spacecraft, Mariner 5, flew by Venus, and a Soviet spacecraft, Venera 4, entered its atmosphere. By the year 1974 there had been five Soviet instrumented capsules that entered the Venus atmosphere. The last three touched down and returned data from the planetary surface. They were the first craft of mankind to land on the surface of another planet. The average temperature on Venus turns out to be about 900 degrees F; the average pressure at the surface appears to be about ninety atmospheres. My early conclusions were approximately correct, just slightly too conservative….

“…Theory and spacecraft interact in other ways. For example, Venera 4 radioed its last temperature/ pressure point at 450 degrees F and twenty atmospheres. The Soviet scientists concluded that these were the surface conditions on Venus. But ground-based radio data had already shown that the surface temperature must be much higher. Combining radar with Mariner 5 data, we knew that the surface of Venus was far below where the Soviet scientists concluded Venera 4 had landed. It now appears that the designers of the first Venera spacecraft, believing the models of cold-surface theoreticians, built a relatively fragile spacecraft, which was crushed by the weight of the Venus atmosphere far above the surface—much as a submarine, not designed for great depths, will be crushed at the ocean bottoms.

“At the 1968 Tokyo meeting of COSPAR, the Committee on Space Research of the International Council of Scientific Unions, I proposed that the Venera 4 spacecraft had ceased operating some fifteen miles above the surface. My colleague, Professor A. D. Kuzmin, of the Febedev Physical Institute, in Moscow, argued that it had landed on the surface. When I noted that the radio and radar data did not put the surface at the altitude deduced for the Venera 4 touchdown, Dr. Kuzmin proposed that Venera 4 had landed atop a high mountain. I argued that ground-based radar studies of Venus had shown mountains a mile high, at most, and that it was exceptionally unlikely Venera 4 would land on the only fifteen-mile-high mountain on Venus, even if such a mountain were possible. Professor Kuzmin replied by asking me what I thought was the probability that the first German bomb to fall on Leningrad in World War II would kill the only elephant in the Leningrad zoo. I admitted that the chance was very small, indeed. He responded, triumphantly, with the information that such was indeed the fate of the Leningrad elephant.

“The designers of subsequent Soviet entry probes were, despite the Leningrad zoo, cautious enough to increase the structural strength of the spacecraft in each successive mission. Venera 7 was able to withstand pressures of 180 times that at the surface of the Earth, a quite adequate margin for the actual Venus surface conditions. It transmitted twenty minutes' worth of data from the Venus surface before being fried. Venera 8, in 1972, transmitted more than twice as long. The surface pressure is not at twenty atmospheres, and the spectacular Mount Kuzmin does not exist.”

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The situation with the fictional Mount Kuzmin is somewhat analogous to that in Larry Niven’s SF novel, A Gift from Earth, which appeared in 1968. The setting is on a human-colonized world called Plateau, after its most significant geological feature: a mesa 40 miles high. Except for the environment at the top of the mesa, Plateau is a Venus-type world with an unbreathable atmosphere that becomes denser and hotter the closer one gets to the planet’s surface. Forty miles up, however, the air is breathable. The settlers almost perished while searching for a landing spot on Plateau until the mesa appeared out of the hellish atmosphere. The mesa was named Mount Lookitthat after the ship captain’s cry when he saw it. The plateau atop Mount Lookitthat would have a surface area of about 80,000 square miles, if it is half the size of California (per the book).

I suspect Mount Lookitthat would actually be too large for the planet’s crust to support it and it would immediately begin sinking if it really existed.

In the real world (but not our world), we have Olympus Mons, the highest mountain on a terrestrial planet anywhere in the solar system. The biggest shield volcano ever known, Olympus Mons rises 25 km above the surrounding surface and is 624 km in diameter at its base. That’s about 16 miles high and 374 miles across, with a caldera/summit measuring 56 miles by 37 miles—a lot smaller than Mount Lookitthat, but no slouch.

The question is, what would be the biggest possible mountain that could exist on a terrestrial-type exoplanet?

Roger E. Moore
2018-Aug-29, 07:25 PM
Part of the reason for my fascination with Mount Lookitthat is because it is a nice example of a limited colony: you literally cannot live anywhere else on the planet except on the mountaintop. Similar examples of limited colonies might turn out to be a planet's north and south poles, a planet's equator, a very deep crater or depression on the surface (Hellas, on Mars, where the atmospheric pressure is greatest), or under the sea. Anyway, I digress.

Roger E. Moore
2018-Aug-30, 12:18 PM
See, I think the key here is not just the thickness of the crust of the planet. It could also be the speed of rotation, which would allow for higher mountains at the equator if the centrifugal force acts against the planet's gravity.

Take a smaller-than-Earth sized planet with active volcanism, so it has a hot core and semimolten mantle with magma, and have a volcano appear right on the equator and grow from there. If the planet spins fast enough (8 hour day?), then the volcano could grow to outstanding height. Could you live on top? No, except in a buried or domed colony, but "Top of the world, Ma!" Haven't sorted out the math, yet, though.

grant hutchison
2018-Aug-30, 12:35 PM
See, I think the key here is not just the thickness of the crust of the planet. It could also be the speed of rotation, which would allow for higher mountains at the equator if the centrifugal force acts against the planet's gravity.

Take a smaller-than-Earth sized planet with active volcanism, so it has a hot core and semimolten mantle with magma, and have a volcano appear right on the equator and grow from there. If the planet spins fast enough (8 hour day?), then the volcano could grow to outstanding height. Could you live on top? No, except in a buried or domed colony, but "Top of the world, Ma!" Haven't sorted out the math, yet, though.The scale height of the atmosphere would change in proportion to the extra height your mountain was able to attain. So no advantage from rotation, as far as I can see.

Grant Hutchison

Roger E. Moore
2018-Aug-30, 01:18 PM
The scale height of the atmosphere would change in proportion to the extra height your mountain was able to attain. So no advantage from rotation, as far as I can see.

Grant Hutchison

Oh.... yeah, so no advantage to getting out of a poisonous atmosphere, but at least you'd get a bigger mountain. :)

This got me to wondering about a close-in planet around an M dwarf. Perhaps the tidal force exerted on a slowly rotating captured-resonance planet in 3:2 (3 days to 2 years) might also tug an equatorial mountain to a greater height.

In that situation, being on the mountain might be an advantage if there was an equatorial ocean. The severe tidal forces might cause the ocean to form two giant waves/tides/tsunamis on opposite sides of the planet, both on a more-or-less direct line from their sun. The mountain would provide enough altitude to escape the gigantic wave coming by twice a day.... a day here being multiple Earth days long, and the year here being multiple Earth days long, less than 30 in either case most likely.

Roger E. Moore
2018-Aug-30, 01:27 PM
Just remembered, The Future is Wild: A Natural History of the Future, by Dougal Dixon (2002), had a section talking about the exotic biosphere atop a plateau on a far-future Earth, such as huge but light four-winged birds. Will look up my copy at home to see how high this plateau was supposed to be. It resulted from multiple crustal plates overlapping each other on the eastern side of a supercontinent.

=========== LATE ADD ==============

Found it online. I got a few things wrong, but got the basic idea. This is based on the BBC production of the book.


https://web.archive.org/web/20180830155249/http://speculativeevolution.wikia.com/wiki/Great_Plateau

Great Plateau
in: The Future is Wild, Future is Wild 100 MYF, Asia, and 5 more

The Great Plateau rises up out of the sea, towering 33,000 feet (10,000 meters) above sea level. These inhospitable slopes, full of unstable rocky debris, are home to a number of species.

Since the Cretaceous period to the Eocene epoch of the Paleogene period, about 96-45 million BC, Australia became separated from Antarctica, slowly moving north across the Pacific Ocean towards Asia. Where the two continental plates met, one was pushed below the other, creating a subduction zone to the southeast of the Asian landmass. As the ocean lithosphere - the rigid outer layer of Earth - was drawn down into the mantle and melted, new magma was produced, resulting in large amounts of volcanic activity.

Now, in 100 million AD, Australia's short life as a single continent is over, and it has finally fused with the southeastern edge of Asia and later the northeastern edge (combining with a bit of northwestern North America as well). Seafloor sediments and rock between the two landmasses have been compressed, sheared, ground together and thrust up into a massive mountain chain. This new chain exceeds the proportions of the Himalayas, the highest mountain range of the Quaternary.

Like the Himalayas in their time, these new mountains continue to rise. As the tectonic plates crush against one another, they simultaneously compress the rock downwards into Earth's mantle and upwards into the sky. Further compression has raised a large block of Southeast Asia to form the Great Plateau, the broadest tract of uplands on the surface of the planet. This immense plateau, surrounded by mountains, towers over the shallow shelf seas which cover much of the landmass.

Newly-formed mountains are sharp and jagged. It takes time for the constant assault of rain, wind, frost and running water to erode them into rounded shapes. In 100 million AD, the Himalayas are mere hills - undulation in the center of the continent. The Great Plateau, on the other hand, consists of ranges of pointed pinnacles and knife-edged crests dropping away into slopes of fragmented rock and scree. The valleys and basins between the ridges have filled with newly-eroded debris and formed upland plains, surrounded by peaks reaching up to 33,000 feet (10,000 meters) - higher than any mountains of the past.

How will life survive at this altitude? The climate of the weather-beaten peaks of the Great Plateau will certainly be harsh, but Earth during 100 million AD is warm and volcanic activity has thrown large amounts of carbon dioxide into the atmosphere, making survival easier. There are ample resources for life to flourish.

The Great Plateau, this system of high plains and basins, hemmed in by the highest mountains in the world, is not the dry, cold desert one might expect. Back during the reign of humanity, high-altitude mountain systems such as the Himalayas were home to little more than hardy desert herbs, shrubs and small rodents. Not so the valleys and plains of the Great Plateau, 100 million years on. These are rolling grasslands.

At the outer edges of the Great Plateau, the steep, debris-covered slopes are swept by winds bringing seasonal rains up from the Shallow Seas. The heavy rainfall and loose soil make for an unstable surface, prone to mudslides and rock falls. However, in many areas the surface is stabilized by plant life evolved to cope with just such conditions.

The oceanward slope of the Great Plateau is green with true grasses. Ridges and banks of vegetation undulate down into the layer of cloud drifting up from the sea. Beyond a narrow coastal plain, sunlight glints on the crest of the waves.

Earthquakes are common, as the plateau is still being pushed up, and it is on the center of the the meeting-point of multiple tectonic plates.

Roger E. Moore
2018-Aug-30, 03:59 PM
Various answers to how high a mountain can possibly be on any planet.


https://worldbuilding.stackexchange.com/questions/99157/what-is-the-highest-possible-mountain-on-an-earth-like-world

http://www.hk-phy.org/articles/mount_high/mount_high_e.html

https://www.natureworldnews.com/articles/11196/20141215/mountains-wont-taller-heres-why.htm

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High mountains can generate visible atmospheric waves that act to slow down a planet's rotation, particularly if the atmosphere is thick.


http://www.nature.com/articles/s41561-018-0157-x

Atmospheric mountain wave generation on Venus and its influence on the solid planet's rotation rate

Navarro, T.; Schubert, G.; Lebonnois, S.
07/2018

The Akatsuki spacecraft observed a 10,000-km-long meridional structure at the top of the cloud deck of Venus that appeared stationary with respect to the surface and was interpreted as a gravity wave. Additionally, over four Venus solar days of observations, other such waves were observed to appear in the afternoon over equatorial highland regions. This indicates a direct influence of the solid planet on the whole Venusian atmosphere despite dissimilar rotation rates of 243 and 4 days, respectively. How such gravity waves might be generated on Venus is not understood. Here, we use general circulation model simulations of the Venusian atmosphere to show that the observations are consistent with stationary gravity waves over topographic highs---or mountain waves---that are generated in the afternoon in equatorial regions by the diurnal cycle of near-surface atmospheric stability. We find that these mountain waves substantially contribute to the total atmospheric torque that acts on the planet's surface. We estimate that mountain waves, along with the thermal tide and baroclinic waves, can produce a change in the rotation rate of the solid body of about 2 minutes per solar day. This interplay between the solid planet and atmosphere may explain some of the difference in rotation rates (equivalent to a change in the length of day of about 7 minutes) measured by spacecraft over the past 40 years.

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How to detect very large mountains on exoplanets.


https://arxiv.org/abs/1801.05814

Finding Mountains with Molehills: The Detectability of Exotopography

Moiya A.S. McTier, David M. Kipping
(Submitted on 17 Jan 2018)

Mountain ranges, volcanoes, trenches, and craters are common on rocky bodies throughout the Solar System, and we might we expect the same for rocky exoplanets. With ever larger telescopes under design and a growing need to not just detect planets but also to characterize them, it is timely to consider whether there is any prospect of remotely detecting exoplanet topography in the coming decades. To test this, we devised a novel yet simple approach to detect and quantify topographical features on the surfaces of exoplanets using transit light curves. If a planet rotates as it transits its parent star, its changing silhouette yields a time-varying transit depth, which can be observed as an apparent and anomalous increase in the photometric scatter. Using elevation data for several rocky bodies in our solar system, we quantify each world's surface integrated relief with a "bumpiness" factor, and calculate the corresponding photometric scatter expected during a transit. Here we describe the kinds of observations that would be necessary to detect topography in the ideal case of Mars transiting a nearby white dwarf star. If such systems have a conservative occurrence rate of 10%, we estimate that the upcoming Colossus or OWL telescopes would be able to detect topography with <20 hours of observing time, which corresponds to ~400 transits with a duration of 2 minutes and orbital period of ~10 hours.

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Brief note on the highest mountain on Ceres, which could be an active cryovolcano. Interesting, wonder what the habitability of the volcano crater is, with mining.


http://adsabs.harvard.edu/abs/2017AstSR..13...11V

Features of the structure of Ceres surface

Vidmachenko, A. P.
10/2017

Some of the craters on the surface of planet have a clearly volcanic origin, and a number of them may be active. The object was to have much more impact craters, than there are now. This means that the surface of Ceres is subject to strong geological activity. There were found only 16 craters larger than 100 km in diameter; the largest crater, the Keruan basin, reaches a total of 280 km. It is believed that the ice beneath the surface of Ceres weakens the bark, causing it to smooth over time. The rather dark surface of Ceres is dotted with more than 130 bright spots. Most of them are, most likely, shock meteorite craters. The brightest spot on Ceres consists of two large and many small parts, located in the crater of Okator, 92 km in diameter and 4 km in depth. An analysis of white spots shows that they contain salts formed in the presence of water. This indicates the presence of hydrothermal energy sources in the bowels of a dwarf planet. In addition to salt, ice was involved in the formation of these spots. The second brightest crater of Ceres with a diameter of 6 km is Oxo. It is located, as it were, in the depth of the hole formed in the failure of rocks. The largest mountain of Ceres, Akhuna, has been geologically active for the last billion years, and perhaps is still active. This mountain was formed as a result of cryoeruptions. The existence of cryovolcanoes on the planet confirms the assumption about the probable presence in its bowels of reservoirs from salt water. Thus, observations of the "Dawn" probe show, that Ceres is a relatively active object. The presence of carbonates on the surface indicates that in its interior there existed, or still exist, hydrothermal processes that threw these substances onto the surface.

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Very high mountains interfere with acoustic wave propagation.


http://meetingorganizer.copernicus.org/EGU2017/EGU2017-17917.pdf

Model for predicting mountain wave field uncertainties

Damiens, Florentin; Lott, François; Millet, Christophe; Plougonven, Riwal
04/2017

Studying the propagation of acoustic waves throughout troposphere requires knowledge of wind speed and temperature gradients from the ground up to about 10-20 km. Typical planetary boundary layers flows are known to present vertical low level shears that can interact with mountain waves, thereby triggering small-scale disturbances. Resolving these fluctuations for long-range propagation problems is, however, not feasible because of computer memory/time restrictions and thus, they need to be parameterized. When the disturbances are small enough, these fluctuations can be described by linear equations. Previous works by co-authors have shown that the critical layer dynamics that occur near the ground produces large horizontal flows and buoyancy disturbances that result in intense downslope winds and gravity wave breaking. While these phenomena manifest almost systematically for high Richardson numbers and when the boundary layer depth is relatively small compare to the mountain height, the process by which static stability affects downslope winds remains unclear. In the present work, new linear mountain gravity wave solutions are tested against numerical predictions obtained with the Weather Research and Forecasting (WRF) model. For Richardson numbers typically larger than unity, the mesoscale model is used to quantify the effect of neglected nonlinear terms on downslope winds and mountain wave patterns. At these regimes, the large downslope winds transport warm air, a so called "Foehn" effect than can impact sound propagation properties. The sensitivity of small-scale disturbances to Richardson number is quantified using two-dimensional spectral analysis. It is shown through a pilot study of subgrid scale fluctuations of boundary layer flows over realistic mountains that the cross-spectrum of mountain wave field is made up of the same components found in WRF simulations. The impact of each individual component on acoustic wave propagation is discussed in terms of absorption and dispersion and a stochastic model is constructed for ground-based acoustic signals in mountain environments.

Roger E. Moore
2018-Aug-30, 07:21 PM
Some of the features inside the caldera of Olympus Mons are interesting in that one could picture building a colony within one of the sunken craters, inside the caldera rim, with a heavy-gas atmosphere that would not leak out right away. It would not necessarily have to be a breathable atmosphere (maybe enough to allow a light spacesuit or even shirtsleeve-and-oxygen mask outfit), but it could be useful for agricultural or industrial purposes. The atmosphere would be temporary on a centuries-long basis.

The articles below include photos and drawings.


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https://www.lpi.usra.edu/meetings/lpsc2011/pdf/2386.pdf

FORMATION AND EVOLUTION OF SURFACE AND SUBSURFACE STRUCTURES WITHIN THE LARGE CALDERA OF OLYMPUS MONS, MARS

C. B. Beddingfield and D. M. Burr
2011

A series of ridges and troughs, interpreted as contractional and extensional features, occur within Olympus Mons’ largest caldera. These features trend sub-parallel to the rim and sub-circumferential to the caldera center. Ridges occur within a radial distance of ~16 km from the center and troughs (graben) occur at a radial distance of 16 km to 32 km. Here we use these features in conjunction with physical caldera collapse models to suggest an associated subsurface structural configuration for Olympus Mons as well as a previous evolution of the caldera roof.

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http://www.psrd.hawaii.edu/May11/PSRD-Mars_volc_timeline.pdf

Timeline of Martian Volcanism

Martel, L. M. V.
05/2011

A recent study of Martian volcanism presents a timeline of the last major eruptions from 20 large volcanoes, based on the relative ages of caldera surfaces determined by crater counting. Stuart Robbins, Gaetano Di Achille, and Brian Hynek (University of Colorado) counted craters on high-resolution images from the Context Camera (CTX) on Mars Reconnaissance Orbiter to date individual calderas, or terraces within calderas, on the 20 major Martian volcanoes. Based on their timeline and mapping, rates and durations of eruptions and transitions from explosive to effusive activity varied from volcano to volcano. The work confirms previous findings by others that volcanism was continuous throughout Martian geologic history until about one to two hundred million years ago, the final volcanic events were not synchronous across the planet, and the latest large-scale caldera activity ended about 150 million years ago in the Tharsis province. This timing correlates well with the crystallization ages (~165-170 million years) determined for the youngest basaltic Martian meteorites.

Roger E. Moore
2018-Aug-30, 07:24 PM
See, I think the key here is not just the thickness of the crust of the planet. It could also be the speed of rotation, which would allow for higher mountains at the equator if the centrifugal force acts against the planet's gravity.

Take a smaller-than-Earth sized planet with active volcanism, so it has a hot core and semimolten mantle with magma, and have a volcano appear right on the equator and grow from there. If the planet spins fast enough (8 hour day?), then the volcano could grow to outstanding height. Could you live on top? No, except in a buried or domed colony, but "Top of the world, Ma!" Haven't sorted out the math, yet, though.

Occurs to me that if the volcano/mountain appeared off-center of the equator, the world would wobble a great deal (if it had no large moon) and would go through severe obliquities, much as Mars does now.

Roger E. Moore
2018-Sep-04, 02:18 PM
https://scitechdaily.com/mars-has-some-of-the-tallest-mountains-in-the-solar-system/

Mars Has Some of the Tallest Mountains in the Solar System

By Andrew Good, Jet Propulsion Laboratory August 30, 2018


Complete copy-pasta taken out by moderator.
Do NOT copy-paste whole website texts, which may be copyrighted!
A link with a short description is more than enough.

Roger E. Moore
2018-Sep-05, 02:22 AM
Some of the features inside the caldera of Olympus Mons are interesting in that one could picture building a colony within one of the sunken craters, inside the caldera rim, with a heavy-gas atmosphere that would not leak out right away. It would not necessarily have to be a breathable atmosphere (maybe enough to allow a light spacesuit or even shirtsleeve-and-oxygen mask outfit), but it could be useful for agricultural or industrial purposes. The atmosphere would be temporary on a centuries-long basis.

https://www.ianllanas.com/projects/NE4J5

This is what I was thinking of, can't believe I found it. The caldera of Olympus Mons could be filled with air that could not quickly escape. You'd still get hard radiation from space, bad, but maybe you could deflect or shield against it.


Great image.

Roger E. Moore
2018-Sep-05, 02:24 AM
All in all, though, the best way to make a mountaintop necessary for a colony is to have the mountaintop sticking out of a toxic sea: an island. The mountain could be ginormous, but all you care about is the little livable spot on top. A bit like Noah's Ark on Mt. Ararat, or bad SF films like Waterworld.