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Type of Document	Dissertation
Author	Dorn, Evan D
Author's Email Address	public AT lrdesign.com
URN	etd-05272005-071800
Persistent URL	http://resolver.caltech.edu/CaltechETD:etd-05272005-071800
Title	Universal biosignatures for the detection of life
Degree	PhD
Option	Computation and Neural Systems
Advisory Committee	Advisor Name Title Christoph Adami Committee Chair Christof Koch Committee Member Demitri Psaltis Committee Member Joseph L. Kirschvink Committee Member Kenneth H. Nealson Committee Member
Keywords	NDLTD Innovative ETD Award 2006 carboxylic acids artificial life meteorites digital life astrobiology neural networks amino acids
Date of Defense	2005-02-11
Availability	unrestricted
Abstract My goal is to identify processes of life that leave measurable effects on an organism's environment, but which are not tied to any particular biochemistry, in order to build a conceptual framework for the search for extraterrestrial life. To this end, I test a pair of phenomena that appear in both terrestrial (biochemical) life and in digital life. Because these two life forms are different and unrelated, any phenomenon measurable in both is suggested to be universal. The Monomer Abundance Distribution Biosignature (MADB) is any measurement of the relative concentrations of related chemical compounds that cannot be explained by abiotic processes. I observe that living systems synthesize specific chemical compounds at rates that maximize their fitness. As a result, life-bearing environmental samples exhibit compounds in abundance ratios that are clearly not the result of abiotic synthesis because those ratios belie the formation kinetics and thermodynamics that would constrain abiotic synthesis. Often, biotic samples contain high concentrations of specific large, complex molecules that are never seen in abiotic synthesis and cannot be explained unless highly specific catalysts (i.e., enzymes) are present, and energy is expended to drive thermodynamically unfavorable reactions. I catalog this effect as it appears in terrestrial biochemical systems, including amino acids and carboxylic acids, and demonstrate the universality of selection's action on the monomeric composition of life forms by studying analogous examples in digital life. I suggest how this phenomenon provides a route to the detection of even unusual or unforeseen biochemistries, and give examples of detection methods using pattern-recognition techniques that may allow us to empower an autonomous system with the general ability to detect life forms. The Layered Trophic Residue Biosignature (LTRB) is any observation of stratification in solute chemistry that indicates metabolic activity by a sequence of diverse communities. When multiple chemical resources are available, natural selection drives adaptive radiation and the formation of specialist phenotypes. Competition ensures that specialists consume resources in decreasing order of energetic potential when resources diffuse through a medium near a boundary. The result is strata of chemicals appearing in order of redox potential, which is best explained by the presence of life.
Files	Filename       Size       Approximate Download Time (Hours:Minutes:Seconds)     28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access    AminoAcids.xls 1.10 Mb 00:05:06 00:02:37 00:02:17 00:01:08 00:00:05   avida_1.6ED1.tgz 904.61 Kb 00:04:11 00:02:09 00:01:53 00:00:56 00:00:04   avida_1.6ED2.tgz 1.94 Mb 00:08:59 00:04:37 00:04:02 00:02:01 00:00:10   avida_2.0b7.tgz 3.47 Mb 00:16:04 00:08:16 00:07:14 00:03:37 00:00:18   biosignature_movie_1.mpg 1.01 Mb 00:04:40 00:02:24 00:02:06 00:01:03 00:00:05   biosignature_movie_2.mpg 1.37 Mb 00:06:21 00:03:16 00:02:51 00:01:25 00:00:07   CarboxylicAcids.xls 268.80 Kb 00:01:14 00:00:38 00:00:33 00:00:16 00:00:01   config_chapter2A.tgz 7.67 Kb 00:00:02 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01   config_chapter2B.tgz 7.04 Kb 00:00:01 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01   config_chapter3.tgz 11.50 Kb 00:00:03 00:00:01 00:00:01 < 00:00:01 < 00:00:01   config_chapter4.tgz 12.43 Kb 00:00:03 00:00:01 00:00:01 < 00:00:01 < 00:00:01   config_chapter7.tgz 6.63 Kb 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01   LTRB_movie.mpg 936.87 Kb 00:04:20 00:02:13 00:01:57 00:00:58 00:00:04   README-ListOfFiles.pdf 71.38 Kb 00:00:19 00:00:10 00:00:08 00:00:04 < 00:00:01   Thesis-DornED-2005.pdf 5.53 Mb 00:25:36 00:13:10 00:11:31 00:05:45 00:00:29