Carl Sagan's bonkers idea—life inside a comet

Carl Sagan’s bonkers idea—life inside a comet
Comet 2012 S1 ISON in outburst, seen on November 15, 2013. Credit: Damian Peach

Establishing a sustained human presence somewhere other than Earth is a vital part of humanity's future, no matter what. We know that Earth won't last forever. We don't know exactly which one of the many threats that Earth faces will ultimately extinguish life here, but life will be extinguished completely at some future point.

Colonizing moons or planets is one way to do it. But that's really hard. We may make it to Mars before too long, but we don't know how successful we'll be at establishing a presence there. There are an awful lot of 'ifs' when it comes to Mars.

The only other option is space habitats. That makes sense; there's much more space out there than there is on planets and moons. And space habitats have been on the minds of thinkers, writers, and scientists for a long time.

Gerard K. O'Neill is probably the most well-known thinker when it comes to space habitats. In 1977 he published the seminal book on space habitats, called "The High Frontier: Human Colonies in Space." O'Neill in his time popularized what is now called the "O'Neill Cylinder."

The O'Neill Cylinder

The O'Neill Cylinder lay the groundwork for space habitat design. It consisted of two counter-rotating cylinders, one nested inside the other. The counter-rotation provided stability and gravity. The atmosphere would be controlled, and the habitat would be powered by solar, and perhaps fusion.

The McKendree Cylinder

Other designs from other people followed O'Neill's. Notable among them is the McKendree Cylinder. The McKendree would be gargantuan compared to the O'Neill Cylinder. Thanks to carbon nanotubes, it would have more surface area than the United States. It was designed by NASA Engineer Tom McKendree and introduced in the year 2,000 at the NASA "Turning Goals into Reality Conference."

There've been other ideas for massive, high-tech space habitats, including the Bernal Sphere and the Stanford Torus. All of these designs are typical of engineers and technologists. Lots of high-tech, lots of steel, lots of machinery. But the engineers and scientists behind those designs weren't the only ones thinking about humans in space.

Carl Sagan was too. And he had a very different idea of what space habitats could be.

Carl Sagan’s bonkers idea—life inside a comet
Interior view of an O’Neill Cylinder. There are alternating strips of livable surface and “windows” to let light in. Credit: Rick Guidice, NASA Ames Research Center
So Crazy It Just Might Work

But the craziest idea for space habitats has got to be Carl Sagan's, from his 1985 book "Comet."In "Comet" Sagan suggested that humans could seek refuge in, and even colonize, actual comets travelling through our solar system. Using all the advanced technologies thought about in Sagan's time—but which don't exist yet—comets could be transformed into humanity's salvation. His idea is a world apart from the high-tech, highly-engineered, gleaming habitat designs that most people think of when they think of space habitats.

I'm a fan of Sagan's. Like many in my generation, I was influenced by his TV series Cosmos. I loved it and it's stuck with me. His book "The Demon-Haunted World" taught us what scientific skepticism can be, and how useful it is.

Sagan's is the most surprising—and perhaps bleakest—view of space habitats. Life inside comets sounds shocking, and maybe even foolish, but as Sagan explains, there is some reasoning behind the idea.

Remember that when Sagan wrote about this, thermonuclear war between the superpowers was a "thing," and thinkers like Sagan felt a sense of imminent danger. That sense of foreboding may have contributed to his "comets-as-space-habitas" idea. Plus, he was just an innovative thinker.

Carl Sagan’s bonkers idea—life inside a comet
The OSIRIS narrow-angle camera aboard the Rosetta spacecraft captured this image of comet 67P/Churyumov-Gerasimenko on September 30, 2016. Does it look habitable, or potentially habitable, to you? Credit: ESA/Rosetta/MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Sagan's thinking behind using comets as space habitats starts out something like this: if there are about a hundred thousand comets crossing Earth's orbit, and another hundred trillion in the Oort Cloud, their combined surface area is roughly equal to about a hundred million Earths. And with advanced technology, Sagan proposed that these comets could be captured and colonized and sent on orbits and trajectories desirable to humans.

Comets are rich in minerals, water ice, and biological compounds. Or so it was thought at the time. That means raw material for manufacturing, water to drink and to supply oxygen, biological compounds for bio-engineering, and even the raw material for rocket fuel. Add a fusion reactor for power, and

comets could end up being the convenience stores of the solar system.

Physicist Freeman Dyson, an innovative thinker himself, had something to add to Sagan's comet idea. In "Comet," Sagan tells of Dyson's ideas around genetic engineering, and that one day we should be able to engineer forms of life that could thrive on comets, and meet some of our needs. Dyson talks about a giant, genetically engineered tree that could grow on a comet, planted in snow rich in organic chemicals. The tree would supply us with fresh oxygen.

This sounds extremely far-fetched: humans living inside comets travelling through space, with giant genetically engineered trees and fusion power plants. I try to remind myself that many things we take for granted now were once thought to be laughable. But even though parts of the comet-as-space-habitat idea sound fanciful—like the giant tree—there may be the seed of a practical here, with humans hitching rides on comets, molding them to our purposes, and extracting resources like minerals and fuel from them.

Carl Sagan’s bonkers idea—life inside a comet
High cliffs on the surface of Comet Churyumov–Gerasimenko as imaged by the Rosetta spacecraft. Credit: (CC BY-SA 3.0 IGO): ESA, Rosetta spacecraft, NAVCAM; Additional Processing: Stuart Atkinson

Sagan was an agile creative thinker. He's clearly riffing when he outlines his ideas for life on comets. He's like the John Coltrane of space science.

It seems doubtful that we would go to the trouble to turn comets into actual habitats. It's probably more science fiction that science. But the future is unwritten, and given enough time, almost anything might be possible.


Explore further

Image: ESA, NASA's SOHO sees bright sungrazer comet

Source: Universe Today
Citation: Carl Sagan's bonkers idea—life inside a comet (2016, November 15) retrieved 26 June 2019 from https://phys.org/news/2016-11-carl-sagan-bonkers-idealife-comet.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
23 shares

Feedback to editors

User comments

Nov 15, 2016
If we have the tech to build self sustaining habitats in comets and large artificial constructs, then we can do the same thing deep underground here. Give us a decade of completely automated mining and manufacturing and we could have more than enough capacity to feed the world. Let the surface farms dwindle and revert back to nature as we automate our food production system and drive the cost of food down to essentially free.

Nov 15, 2016
Problem with the comet idea is that they tend to move fast (relative to Earth) so that 'capturing' them to bring them into an orbit where all the engineering can happen may not be feasible. The alternative would be to get everything needed there in one go - which would be hugely expensive compared to parking them in an easily accesible place.

Remember that when Sagan wrote about this, thermonuclear war between the superpowers was a "thing,"

And it still is. Only that instead of 2 superpowers we now have three - which doesn't really help the situation.

Nov 15, 2016
A better idea may be to look for Trojans or objects in the asteroid belt to hollow out and spin up. Maybe there are some which have enough water to make it feasible*. The distance to these doesn't vary to the extremes that the one to comets does.

If we could alter the course of comets a little bit when we could even combine the advantages of bot: crash a comet into an asteroid. Impart the water and maybe also start off the spin. But that would be some _very_ tricky shot.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more