Weird Life: Must Life Be Based on Carbon and Water?1 John Millam2 and Ken Klos3
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Weird Life: Must Life Be Based on Carbon and Water?1 John Millam2 and Ken Klos3 When we look up into the sky, it is hard not to think about how vast the universe is. Our universe is estimated to contain around 100 billion galaxies with each galaxy having around 100 billion stars. And most of those stars are expected to harbor planets. That is a mind-boggling number of stars and possible planets. This leads inevitably to questions about whether there is life on planets orbiting those distant specks of light. If so, what might it look like? Are there alien civilizations out there with intelligence and technology similar to or even more advanced than our own? If so, can we communicate with them? Why Even Consider “Weird Life”? The Search for Extra-Terrestrial Intelligence (SETI) was inaugurated in the early 1960s to scan the heavens for any signals that might be coming from extraterrestrial civilizations. One thing is certain; SETI proponents are firmly convinced that we will eventually find extraterrestrial life. For example, astronomer Frank Drake who helped found SETI stated, “At this very minute, with almost absolute certainty, radio waves sent forth by other intelligent civilizations are falling on the Earth” (our italics).4 Astronomer Carl Sagan was just as confident about the certainty of extraterrestrial life. He wrote, “Given sufficient time and an environment which is not entirely static, the evolution of complex organisms is, in this view, inevitable. The finding of even relatively simple life forms on Mars or other planets in our solar system would tend to confirm this hypothesis” (our italics).5 Together with Frank Drake he also wrote, “There can be little doubt that civilizations more advanced than the earth’s exist elsewhere in the universe” (our italics).6 SETI: A Twenty-First Century Perspective We have come a long way since SETI was inaugurated 50 years ago. What have we found so far? No confirmed detections of extraterrestrial civilizations. While this does not strictly rule out the existence of extraterrestrials, it does place some strong limits on how prevalent advanced intelligent life might be. For example, we can effectively rule out extraterrestrial civilizations with a level of technology equal to or greater than our own out to a distance 1 Full permission is given to reproduce or distribute this document, or to rearrange/reformat it for other media, as long as credit is given and no words are added or deleted from the text. 2 Dr. John Millam received his PhD in theoretical chemistry from Rice University in 1997, and currently serves as a programmer for Semichem in Kansas City. 3 Mr. Ken Klos received his MS in environmental studies from the University of Florida in 1971, and worked as an environmental/civil engineer for the state of Florida. 4 Timothy Ferris, “Seeking an End to Cosmic Loneliness,” The New York Times Magazine, October 23, 1977, 97. 5 I. S. Shklovskii and C. Sagan, Intelligent Life in the Universe (San Francisco, CA: Holden-Day, 1966), 411. 6 Carl Sagan and Frank Drake, “The Search for Extraterrestrial Intelligence,” Scientific American, 232, May 1975, 80. Weird Life: Must Life Be Based on Carbon and Water? John Millam and Ken Klos of 50 light-years.7 Partial searches extend that conclusion out to 4,000 light-years and for advanced civilizations (type I on the Kardashev scale) out to 40,000 light-years.8 No evidence of extraterrestrial visitation. A belief that some reports of UFOs (unidentified flying objects) represent sightings of alien spacecraft is widely popular, but we do not have credible evidence of extraterrestrial visitation.9 Other solar systems are not similar to our own. When SETI was starting in the ‘60s, it was widely believed that not only would most stars have planets, but that these alien solar systems would be very similar to our own. If this were the case, habitable Earth-like planets should be very common. As of August 2014, we now have the confirmed detection of close to two thousand extra-solar planets with a large number of additional planetary candidates. This gives us the ability to make some preliminary conclusions, although the detection techniques are not sufficiently robust and have not been carried out for long enough to make decisive claims.10 One thing that has been discovered is that there are numerous ways that a solar system can differ from our own in ways that are hostile to life.11 For example, a number of Jupiter-like gas giant planets have been found to be orbiting close to their stars or with highly eccentric (non-circular) orbits.12 Either scenario is disastrous for rocky planets like Venus, Earth, and Mars, and therefore makes life in those solar systems highly unlikely. Requirements for habitability increased greatly. Originally, SETI enthusiasts assumed that only a few conditions were required for an extra-solar planet to be a reasonable candidate for harboring life. However, astronomers today know that hundreds of conditions are required for any kind of advanced life—and this list continues to grow as new discoveries are made. 13 This has led some astronomers to adopt the “rare earth” hypothesis—that complex life is exceptionally rare in the universe.14 Our failure to find any evidence for extraterrestrial life, combined with mounting evidence that habitable planets are exceptionally rare, provides a powerful one-two punch against the whole idea of intelligent life on other planets.15 7 Andrew J. Lepage, “Where They Could Hide: The Galaxy Appears Devoid of Supercivilizations, but Lesser Cultures Could Have Eluded the Ongoing Searches,” Scientific American, July 2000, 40-41. 8 Ian Crawford, “Where Are They? Maybe we are alone in the galaxy after all,” Scientific American, July 2000, 38- 43. 9 Hugh Ross, Ken Samples, and Mark Clark, Lights in the Sky & Little Green Men (Colorado Springs, CO: NavPress, 2002). 10 Kevin W. Plaxco and Michael Gross, Astrobiology, second edition (Baltimore, MD: John Hopkins University Press, 2011), 266-271. 11 Jeff Zweerink, “A Recap of Unexpected Exoplanet Finds?” Today’s New Reason To Believe on May 22, 2014 (http://www.reasons.org/articles/a-recap-of-unexpected-exoplanet-finds). 12 Sam Flamsteed, “Impossible Planets,” Discover, September 1997, 78–83. Hugh Ross, The Creator and the Cosmos, 3rd ed. (Colorado Springs: NavPress, 2001), 187. 13 “What were 2 parameters in 1966 grew to 8 by the end of the 1960s, to 23 by the end of the 1970s, to 30 by the end of the 1980s, to the current list of 123 [as of 2001],” Hugh Ross, 187 with a partial listing on p. 188-193. This subsequently jumped to 153 as of 2002, Hugh Ross, Ken Samples, and Mark Clark, p. 185-189. As of 2008, the list stands at 402 fine-tuned parameters (Hugh Ross, “Part 2. Fine-Tuning for Intelligent Physical Life,” http://www.reasons.org/files/compendium/compendium_part2.pdf, accessed September 18, 2014). 14 Peter D. Ward and Donald Brownlee, Rare Earth (New York: Copernicus Books, 2000). 15 Stephen Webb, If the Universe is Teeming with Aliens … Where is Everybody? Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life (New York, New York: Copernicus, 2002). See also Robert Naeye, “OK, Where Are They?” Astronomy, July 1996, 38-43. 2 Weird Life: Must Life Be Based on Carbon and Water? John Millam and Ken Klos “Weird Life”—Reassessing the Case for SETI So, is that the end of the story? Not by a long shot according to many SETI enthusiasts. Despite setbacks, some SETI proponents are even more optimistic than ever that they will find evidence for extraterrestrial life. As an example, Andrei Finkelstein, director of the Russian Academy of Sciences’ Applied Astronomy Institute, recently declared that extraterrestrials definitely exist, and that we’re likely to find them within two decades.16 One reason for this optimism is that scientists are increasingly recognizing that life can survive under a much broader range of conditions than previously thought possible. For example, the discovery of extremophilic organisms has shown us that some microorganisms can exist under exceptionally harsh conditions that were once thought too inhospitable for life. 17 Equally impressive is the discovery of complex communities of life forms around deep sea hydrothermal vents.18 These amazing creatures live under extreme temperatures and pressures with no sunlight for photosynthesis. For energy, microbes process the noxious chemical brew coming from the vents and they in turn serve as the base for the local food chain. If even conventional life can thrive under such hostile conditions, then what about life that might be different from anything currently known? Early attempts to answer this question ranged from fanciful to highly speculative; but the emerging field of astrobiology is seeking to address the issues of unconventional life based on credible scientific principles. A large number of ideas have emerged about just what kinds of life might exist, where it might arise, and where it might be found. For the purposes of this paper, we will divide all proposed alternative life forms into two basic categories: “exotic life” and “weird life.” The first kind—“exotic life”—refers to organisms that are similar to known life but utilize a different set of biomolecules. For example, scientists are experimenting with microbes that incorporate non-standard amino acids, use different molecules to form the backbone of DNA/RNA, or use non-universal genetic codes. 19 Other recent research has focused on incorporating non-natural nucleic acids into DNA.20 Since “exotic life” still fundamentally relies on carbon for its basic makeup and needs water as its internal solvent, it would likely require the same basic environmental conditions that known life requires.