A Cometary Transformation

by Paul Gilster on January 25, 2007

Somehow I missed Mike Brown’s recent thoughts on 2003 EL61, the oddly elongated Kuiper Belt object that’s as big as Pluto along its longest dimension. Fortunately, the BBC recently covered the story. At the American Astronomical Society meeting in Seattle, Brown (Caltech) had discussed the instability of the object’s orbit, pointing out that it is headed for an eventual encounter with Neptune. A possible outcome: Two million years from now, 2003 EL61 may be a comet. “When it becomes a comet,” says Brown, “It will be the brightest we will ever see.”

Adam January 25, 2007 at 20:31

Hi Paul

Of course in 2 million years I hope EL61 is either real estate or has been chewed up by industry. Would be a waste for it to boil-away as a comet.

There’s a paper from the 2004 STAIF conference on terraforming small bodies, but there’s nothing much available about it online but the abstract…

Title:
Shell Worlds: An Approach to Making Large Moons and Small Planets Habitable
Authors:
Roy, Kenneth I.; Kennedy, Robert G.; Fields, David E.
Affiliation:
AA(The Ultimax Group Inc, Oak Ridge, TN 37830 . KIRoy@ultimax.com), AB(The Ultimax Group Inc, Oak Ridge, TN 37830 ), AC(Tamke-Allan Observatory, Harriman, TN 37748 )
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). (AIPC Homepage)
Publication Date:
02/2004
Origin:
STI
Keywords:
space research, Moon, planets, human factors, atmospheric chemistry, ecology, energy resources, transportation, environmental factors, design, failure analysis,
Abstract Copyright:
(c) 2004: American Institute of Physics
DOI:
10.1063/1.1649675
Bibliographic Code:
2004AIPC..699.1075R
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.

…interesting feature is the rigid shell for a sky. That’s how the ancients viewed “the heaven” – a gigantic transparent shell, upon which the clouds and heavenly bodies moved. Out past Pluto, with an artificial Sun, such a scenario might well come true.

Administrator January 25, 2007 at 21:46

Engineered shells — fascinating concept. I’ll try to scare this one up at one of the local university libraries.

Adam January 26, 2007 at 0:14

The shell supported by atmospheric pressure would be quite stable too, kind of self-stabilised because any shift in the shell would be counteracted by the pressure asymmetry it would create. I wonder how they planned to get around meteorite damage? Would be pretty substantial over time.

Another possibility is the hollow pressurised shell without any interior planet. Such an object would provide a huge living

Adam January 26, 2007 at 0:23

oops… typo on that last one. I hit ‘submit’ too soon.

…a huge living volume. Just how big? Just a bit smaller than the Jeans radius would insure against unintentional gravitational collapse. I think the strength of the shell would give out before it got that big.

Juan Casares January 26, 2007 at 1:06

“large, dense, rugby-ball-shaped … with a fast rotation rate.”

Almost sounds like a spaceship!

Adam January 26, 2007 at 7:39

To give that last post some figures a shell filled with air at its surface average of density, temperature and pressure (1.225 kg/m^3; 288.15 K; 101.325 kPa) and the Jean’s mass is 69,500 km across. For straight oxygen at 0.2 bar the diameter is 141,900 km – almost as big as Jupiter.

Within all that air the visibility would rapidly decline within a few hundred kilometres – our atmosphere is the equivalent of 8 km of air at surface average density etc. Light is absorbed/scattered by that thickness so we receive just 70% of the light from the Sun. The amount of absorption/scattering increases exponentially, so 80 km of air reduces light to 2.8% of its space value, and 800 km reduces it to less than a quadrillionth.

Such an air-shell would need internal ‘suns’ of its own and from space would look rather like a gas-giant planet, just a lot lighter in mass. The Jupiter scale air-shell’s gas mass would be less than 5 times the Moon’s mass, 6% of Earth.

Strange indeed. Karl Schroeder has written an SF novel set in such a world, “Sun of Suns”, with a ‘steam-punk’ retro-tech feel. Personally I’d rather hard regolith beneath my feet and at least 10% earth gravity.

Dave GIll January 26, 2007 at 7:59

To show the immense progress that weather forecasting has made, I can state with high confidence that when 2003 EL61 puts on its show, it will be cloudy in Ohio.

ljk January 26, 2007 at 9:34

Just shells made from comets?

C’mon, people – think WAY outside the box, or the Shell,
as it may be:

http://www.aeiveos.com:8080/%7Ebradbury/MatrioshkaBrains/index.html

Adam January 26, 2007 at 22:51

Hi Larry

You’re a fan of that concept aren’t you? Personally I think it’s bogus, but who can say? Running the equivalent of 10^26 humans at once (10^42 mips) is quite a bit of brain-power, but what’s the point if they’re all in a shared VR?

Adam

andy January 27, 2007 at 19:36

I’ve always liked the “supercomet” concept. Makes you wonder if, in some extrasolar system, a Pluto-like object has been kicked into the inner regions of a planetary system, and what would happen to it. Once we get systematic direct detection of extrasolar planets (as opposed to the radial velocity stuff we have now), we might find that bright comets or possibly even supercomets could be more easily detected than planets. There’s an abstract to a paper I’ve seen about this but right now I can’t find it.

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