Introduction
Deep in space, dust is diffracting light, and providing clues to the materials it is passing through, materials that have existed since the early days in the 'life' of the universe.
There happens to be a strong correlation between patterns of light absorption by some dust clouds and that made by small hollow spheres the size of common (earthly) bacteria. This led Fred Hoyle and N. Chandra Wickramasinghe to propose the theory of Panspermia, where life was seeded on earth from space (1 Klyce). While this idea has been ridiculed, this correlation still exists.
One alternate explanation may be that this is a coincidence caused by a similar evolution of bacteria-like organisms, the dust of a life that evolved on (an)other planet(s) from similar chemical backgrounds and where the systems have met some catastrophic end (star system goes nova, collisions, etc). The universe is about 3 times older than the earth, so there is plenty of time for life to have evolved on other planets in other system, provided that the necessary conditions and material were available: the only caveat being what would cause such an improbable coincidence of development.
The existence of other suitable planets seems less and less of a question as we continue to discover more and more planets around other stars, but for such similar life to have such a similar chemical basis there would have to be some method of disbursing the basic chemical compounds used in the formation of life through space. The method does not need to be organic (life based): stellar novas are the #1 basic method of disbursing chemical elements into space after the fusion of hydrogen into those elements during the life of the star. These events are catastrophic certainly, but as the expelled gases expand and cool there is opportunity for all kinds of chemical combinations to take place, easily allowing the formation of even complex molecules. Perhaps there is just some unknown astro-chemical preference for the formation of carbon based life precursor molecules and that they are common throughout the universe. Perhaps the dust balls noted by Hoyle and Wickramasinghe are the signatures of large 'organic' hydrocarbon molecules we are unfamiliar with.
Speculation is fun for all, but what evidence do we have to support such seemingly far-fetched science fiction? Surprisingly, the evidence is substantial. From {the farthest reaches of the Universe}, across own solar system, and to the farthest reaches of our own Earth, evidence of pre-biotic formation of life surround us. This paper will walk you through the evidence, painting a picture of how life could have come to form on Earth.
Evidence
Evidence comes from a number of sources.
From The Universe
So far over 130 different molecules have been discovered in interstellar clouds (2 anon 2004). Most contain a small number of atoms, and only a few molecules with seven or more atoms have been found so far. The most abundant family of molecules in the interstellar medium, after molecular hydrogen and carbon monoxide, are the polycyclic aromatic hydrocarbon (PAH) molecules. These molecules contain about 10% of all the interstellar carbon (3 Bregman &
Temi).
In the farthest depths of the universe polycyclic aromatic hydrocarbon (PAH) molecules have been found by the Spitzer Space Telescope, 10 billion light-years away (4 Hill 2005). Other deep space organic compounds that have already been found are the 7-atom vinyl alcohol (5 anon 2001), the 8-atom molecule propenal and the 10-atom molecule propanal (2 anon 2004), all in interstellar clouds of dust and gas near the center of the Milky Way Galaxy, all some 24,000 light-years away - a distance so far, the molecules could not have come from earth.
Finding bigger molecules might be more difficult, as we have to know what the 'signatures' of those particles are. This is difficult because those particles need to be modeled first to see what their diffraction patterns would be, and we would have to know what the molecules were to model them. This would be similar to the difficulties encountered by Hoyle and Wickramasinghe in matching the dust spectrum to dried bacteria (1 Klyce) and by Rosalind Franklin in unraveling DNA patterns and other folded proteins with crystallography before their structure was fully understood (6 anon).
A little closer to home, the signatures of polycyclic aromatic hydrocarbon (PAH) molecules were found again, this time in the vicinity of a protostellar source, S140 (3 Bregman & Temi). The source, about 3,000 light-years away, is a star in the process of forming. This fact provides more evidence that this hydro-carbon based material was already available at this point of the star's, stage of formation. By extension, it also means that the material was available at the time of any planet's formation.
Traditionally chemists have referred to these compounds as organic molecules because of their association with organic processes. With these discoveries of such molecules in outer space and, presumably, from non-living sources, it seems that a new paradigm is needed. I will refer to these cosmic based complex hydro-carbon compounds hereafter as "Pre-Organic Compounds", or
POCs.
From The Solar System
In the immediate stellar neighborhood we have data from our gas giants and their moons. The IRIS-Voyager infrared spectrometer detected prebiotic molecules on Titan as well as complex organic molecules on Jupiter and Saturn. The Cassini satellite found an organic "factory" of hydrocarbons in the upper atmosphere of Titan (7 Martinez 2005). Carbonaceous material has also been observed in the immediate surroundings of Comet Halley's nucleus, implying these materials are also readily available in the OORT cloud surrounding the planets (8 Encrenaz 1986). These findings, tells us that such POCs are formed in an interstellar medium by non-living procedures. Furthermore, even if they are not uniformly available in the early formation of the system, they are certainly available for transport from such locations where they are available to any planets in the stellar system.
Moving farther in, we have detected a host of POCs on meteors. Mono- and dicarboxylic acids, dicarboximides, pyridine carboxylic acids, a sulfonic acid, and both aliphatic and aromatic hydrocarbons (9 Pizzarello et al 2001) have been found. In addition, hollow, bubble-like hydrocarbon globules, similar to early membraneous formations (10 Watson 2002), and "polyols," components of the nucleic acids RNA and DNA, constituents of cell membranes and cellular energy sources (11 Koczor 2001 & 12 Cooper et al 2001) have been detected in material from meteors as well.
Meteors could also be a source of elements that would otherwise be rare on the surface of the early earth. The steps taken in creating DNA or RNA (one of a number of possible precursors to the advent of DNA on Earth) are unclear. Most of the necessary raw materials and elements for forming RNA-like molecules are readily available at Earth's surface - except for rare elements like phosphorus. At least one study argues that meteorites could have provided the rare elements needed by the early self replicating molecules in readily accessible forms like P2O7, one of the more biochemically useful forms of phosphate, similar to what's found in ATP (13 Reddy 2004). Support for this also comes from the record of meteor bombardment of the moon, which indicates that meteors were much more common during the early days of this planet. There is also reason to believe there may also have been a peak of meteor activity just before the earliest known life appeared, some 3.9 to 3.8 billion years ago (14 Hartmann et al 2000 & 15 Ehrenfreund et al 2002).
The Earth Back Then
There have been experiments on what might have been happening outside the earth's atmosphere in conditions simulating the early solar system. Scientists made glycine, alanine and serine, three of the basic parts of proteins from which all life is made, by simulating conditions that are commonplace in interstellar space and shining ultraviolet light on deep-space-like "ices" (16 Burton 2002 & 17 anon 2002) - again pointing to a ready source of pre-formed amino acids from space and removing the necessity of their formation somewhere on earth. This is also beginning to stretch the definition of "Pre-Organic Compound" (POC) to it's limit, for amino acids are the molecules that living organisms are made from.
As we can see, these POC molecules may have formed outside of the earth. If these molecules did come to earth from space, the next question is what earth was like in those early days and what kind of existence was possible. This would have been before free oxygen
(Ocolor="#000080">
2) was readily available in the atmosphere. While early models of the earth assumed a reducing atmosphere, recent modeling of the Earth's early atmosphere suggests more neutral conditions (e.g.
H
2O, N
2, CO
2) may have existed (15 Ehrenfreund et al 2002). Even so, most researchers still accept that
O
2 experienced a large increase near 2.3 billion years ago, long after life first evolved, and the evidence indicates that
O
2 was less than ~10
-3 current levels during the Archean if not lower (18 Kasting & Pavlov 2001), so the earliest life form(s) were likely based on some other energy transfer system than one using free oxygen (ie some kind of anaerobic system).
The Earth Now
One way to determine possible environments and energy systems that were once on earth and that may have been involved in early life development we can look at what are called "extremeophiles" - archaic bacteria like organisms, living under what appears to us to be extreme conditions. The reasoning behind this is dual-pronged; first, these extreme environments may match, and even be the norm, in early-Earth conditions. Second, it is likely that any such remnant environment would also be inhabited by remnants of early life forms - forms such as these "extremeophiles."
One area that may exhibit such properties is the deep ocean floor around the thermal vents, where life today is still a bizarre chemistry for organisms compared to what we know. Recently, simulating such conditions amino acids were combined into peptides (19 Simpson 1999), and the oldest evidence for life may be thermophile remnants in Greenland rocks that are 3.7 to 3.9 billion years old, where some researchers have concluded that the grains contained carbon of biological origin (20 Hart 2005). Similar research synthesized the critical compound pyruvic acid (CH
3-CO-COOH) from CO in the presence of iron-sulphide at 250 C and pressures equivalent to a depth of 7 km within the rock (21 Earle 2000).
Another element that comes into play with these kinds of areas is radioactive energy and it's effect of the polymerization of larger molecules. The geological record includes widespread evidence for organic accretion and polymerization around radioactive mineral grains (22 Parnell 2003). This may have been a mechanism to help concentrate the necessary molecules in the same locations.
There are many types of anaerobic bacteria, but the real interest here is in the "Archaea" - a life form similar to bacteria but from a separate and earlier domain of life, and found in many extreme environments. Some Archaea, belonging to the methanogens (methane producing microorganisms), are found in cold deep sea sediments called methane seeps at 1,640 to 3,280 feet beneath the surface, where the pressure compresses methane and traps it in a lattice of water ice crystals to form gas hydrates at temperatures of 45 degrees Fahrenheit or even warmer, depending on the crystal structure and depth. (23 Siegel 2005). The Archaea found at the seeps were completely surrounded by sulfate reducing bacteria in a symbiotic relationship that utilized both methane and sulfates for energy (24 Ferdelman et al 2005).
From the Bottom Up
This gives us ideas of where the first forms of life may have developed, but to get to there from the chemicals and energy sources mentioned previously, we need to look at the simplest molecules that can be formed and then move up towards the more complex ones.
First off we have some peptides built out of existing amino acids under conditions similar to possible early earth conditions: under the hot, anaerobic, aqueous conditions of a setting with magmatic exhalations, amino acids are converted into peptides. Peptides were formed from phenylalanine, tyrosine, and glycine (25 Huber & Wchterhuser 1998).
Next we turn to self-replicating molecule experiments. First, a self-replicating 32-amino-acid peptide can autocatalyse its own synthesis by accelerating the amino-bond condensation of 15- and 17-amino-acid fragments in solution (26 Kauffman 1996). Then there is the amino adenosine triacid ester (AATE) that replicates by attracting to one of its ends anester molecule, and to its other end an amino adenosine molecule. These molecules react to form another AATE. The "parent" and "child" AATE molecules then break apart and can go on to build still more AATE molecules (27 Mallove 1990).These experiments are such convincing demonstrations of self-replication by non-living molecules that even extremely skeptical organizations like AnswerInGenesis (AIG) do not dispute the formation of the phenylalanine, tyrosine, and glycine peptides (28 Sarfati) or that the AATE molecules formed new ones (29 Sarfati 2002).
Another experiment shows how cell-like membranes can be formed from common chemicals like calcium chloride, sodium carbonate, copper chloride, sodium iodide, hydrogen peroxide and starch and that they contain chemical reactions (30 Ball 2004), and another shows that these compounds are common in meteor "ices" and that the meteor compounds do form vesicles with the addition of water (31 Dworkin et al 2001).
Formation of amino acids by bacteria is also well documented, but researchers have cause a "new" amino acid to be formed by one, p-aminophenylalanine, or pAF (32 Suh 2003). This demonstrates that the 20 amino acids that are commonly used by all life on Earth are not necessarily special to the formation of life here. Instead, it is likely that they were just the most useful ones available at the time.
Finally, there is the evidence that viruses may be older than our commonly accepted life forms: coat proteins in all viral types that infect all three of the modern domains of life - Eukarya, Bacteria, and Archaea - have conformational similarities, despite the fact that the genetics underlying them are quite different. This implies a common "ancestor" for all these forms of viruses that predates the three domains of life over 3 billion years ago. These viruses could be remnants of a pre-DNA world that was based on RNA replication, remnants that have lost their individual ability to reproduce by adapting to use the replication methods of the DNA world (33 Rice et al 2004).
Conclusions
It seems to me that the building blocks needed for the beginning of life were plentiful, not just on Earth but in space in general and from the earliest of times. They have been around since long before even the Earth formed from the cosmic debris left behind by the life and death cycle of previous stars and planets, back to the beginning of time. These "seeds of life" no doubt extend through the far reaches of the universe as well as the depths of time.
It also seems to me that the natural processes for forming more complex structures from those basic building blocks were likely prevalent on the earth 4.5 billion years ago in a variety of forms, levels of completion and locations. We see that meteors bring not only pre-organic compounds (POCs), energy and rare nutrients, but compounds that can form cell like vesicles to concentrate the chemical interactions. Radioactivity may add energy to the equation, concentrating organic molecules, or deep earth thermal vents may be an additional source.
We end with a scenario that has a random combination of plentiful and multitudinous POCs forming amino acids all over the earth, with membranous systems to contain and concentrate those molecules and their interactions within a protocell type capsule. We also see that random combination of plentiful and multitudinous amino acids into peptides and proteins is feasible, and that concentration and recombination within the membranous protocells enhances the probability that random combinations of them into the first "replicators" (the predecessors to RNA and DNA) is not as far fetched as it seemed at first. A simple building block process where the probability of a successful combination is almost inevitable: it is no longer a matter of "if" but of "when" it will occur under these conditions ...
These "seeds of life" also existed in a world of constant motion, from the constant motion of sub-atomic particles to the interplay of atoms and molecules in chemical combinations, to the ebb and flow of various gases and liquids at different temperatures and densities, to the sometimes violent impact of meteors and eruptions. The existence of the first self-replicators would be little more than a slightly novel extension of this chemical existence, not much more remarkable than catalyzed reactions, their first "food" would have been the chemicals around them.
Once a self-replicating chemical system occurs, however, the frequency and ability of it to reproduce will necessarily outpace the random chemical action from which it came, and the ones that are better able to adapt to and take advantage of the environment will outpace their competition ... they will evolve. From there it is but a small step to the first cell with the components and processes that we would classify as life. Life seems inevitable when given the conditions that existed for the beginning of life.
That is my take on the possibilities for the formation of life on earth.
Enjoy
Post Script
I am adding this to be perfectly clear on my intentions. For me the search for the elusive transition from non-life to life has to be two pronged:
(A) From the bottom up - looking for what happens naturally in a variety of environments to build more and more complex molecules from the materials available. This search also includes simulating a variety of early earth environments and possible environments on other planets (mars) or moons
(europa). These molecules are the building blocks for the foundation, making towers by building onto them until the clouds are reached is the quest.
(B) From the top down - reducing life to a bare minimum, also in a variety of environments to find what can be done away with from the evolved systems and still have a (possibly crude and likely inefficient) forms of life. The variables will likely change with different environments and sources of energy that go with them. This is also where LUCA comes into the picture ("it is widely accepted that ... there was a period where RNA carried out the roles now performed by proteins and DNA"). Taking the skyscraping towers of today and deciphering the support structure, going back through time, paring it down to the bare minimums to find what the first original huts may have looked like.
This specific {topic thread} deals with (A), the bottom up approach, and involves known processes with known, verified results. A future essay may deal with (B), the top down approach, and how we got to RNA and DNA and other advanced molecules from previous stages. There is still a substantial gap between them, but as such research is done from both sides an awareness will build about how near one is to the other, very much like the way the (Golden Gate bridge was built from each side of the bay in closing increments (and even though most engineers of the day said it could not be done). It is also possible that future experiments based on the bottom up approach could result in a self-replicating proto-molecular system that fills some definitions of life without developing either RNA or DNA - presupposing either is similar to presupposing the hand of a designer.
I apologize for the length, but this is a compilation I have made over the last two to three years of points that to me constitute an overview of the state of current knowledge.
Thank you.
References:
(1) Brig Klyce (no date). Hoyle and Wickramasinghe's Analysis of Interstellar Dust. Cosmic Ancestry [Electronic version]. Retrieved 5Nov2005 from
Analysis of Interstellar Dust and Selected Resources. by Brig Klyce
(2) (anon) (2004 Jun 22) Scientists discover two new interstellar molecules. Brightsurf Science News [Electronic version]. Retrieved 5Nov2005 from
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(3) Jesse Bregman and Pasquale Temi (no date) Identifying Polycyclic aromatic hydrocarbon (PAH) molecules in Space. NASA Space Science and Astrobiology Division [Electronic version]. Retrieved 5Nov2005 from
http://spacescience.arc.nasa.gov/displaypage.cfm?page=Bre...
(4) Gay Yee Hill (2005 Jul 28) Spitzer Finds Life Components in Young Universe. NASA News Archives [Electronic version]. Retrieved 5Nov2005 from
NASA -
Spitzer Finds Life Components in Young Universe
(5) (anon) (2001 Oct 1) Scientists Toast the Discovery of Vinyl Alcohol in Interstellar Space. Spacedaily [Electronic version]. Retrieved 5Nov2005 from
http://www.spacedaily.com/news/life-01zi.html
(6) (anon) (no date) Rosalind Elsie Franklin (1920 - 1958). BBC Historical FIgures [Electronic version]. Retrieved 5Nov2005 from
BBC - History: Historical Figuresfranklin_rosalind_elsie.shtml
(7) Carolina Martinez (2005 Apr 25) Organic Materials Spotted High Above Titan's Surface. NASA News Archive [Electronic version]. Retrieved 5Nov2005 from
http://sse.jpl.nasa.gov/news/display.cfm?News_ID=10716
(8) T. Encrenaz (1986) Search for organic molecules in the outer solar system. Adv Space Res. 1986;6(12):237-46. PMID: 11537827. PubMed abstract[Electronic version]. Retrieved 5Nov2005 from
PubMed&
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(9) S. Pizzarello, Y. Huang, L. Becker, R.J. Poreda, R. A. Nieman, G. Cooper, & M. Williams (2001 Sep 21) Organic Content of the Tagish Lake Meteorite. Science Vol 293 p2236-2239 [Electronic version]. Retrieved 5Nov2005 from
http://web99.arc.nasa.gov/PDF/tagish.pdf
(10) Catherine E. Watson (2002 Dec 11) Researchers Find Possible Precursors to Early Life on Earth in Meteorite. NASA News Archive [Electronic version]. Retrieved 5Nov2005 from
NASA -
Researchers Find Possible Precursors to Early Life on Earth in Meteorite
(11) R. Koczor (2001 Dec 20) Sweet Meteorites. Science & NASA [Electronic version]. Retrieved 5Nov2005 from
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(12) G. Cooper, N. Kimmich, W. Belisle, J. Sarinana, K. Brabham & L. Garrel (2001 Dec 20) Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth. Nature 414, p879 - 883 [Electronic version]. Retrieved 5Nov2005 from
Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth | Nature
(13) F. Reddy (2004 Aug 26) Phosphorus from meteorites. Astronomy [Electronic version]. Retrieved 5Nov2005 from
http://www.astronomy.com/asy/default.aspx?c=a&id=2423
(14) W.K. Hartmann, G. Ryder, L. Dones, & D. Grinspoon (2000 Jul 18) The Time-Dependent Intense Bombardment of the Primordial Earth/Moon System. Origin of the Earth and Moon p493-512, University of Arizona Press, Robin M. Canup and Kevin Righter, eds. Excerpt [Electronic version]. Retrieved 5Nov2005 from
http://www.boulder.swri.edu/...mann-etal-2000-lhb-review.pdf
(15) P Ehrenfreund, W Irvine, L Becker, J Blank, J R Brucato, L Colangeli, S Derenne, D Despois, A Dutrey, H Fraaije, A Lazcano, T Owen, F Robert and an International Space Science Institute ISSI-Team (2002 Oct 10) Astrophysical and astrochemical insights into the origin of life. Reports on Progress in Physics vol 65 p1427-1487 abstract [Electronic version]. Retrieved 5Nov2005 from
Attention Required! | Cloudflare
(16) K. Burton (2002 Mar 27) NASA Scientists Create Amino Acids in Deep-Space-Like Environment. NASA News Archives [Electronic version]. Retrieved 5Nov2005 from
NASA - NASA Scientists Create Amino Acids in Deep-Space-Like Environment
(17) (anon) (2002 Mar 27) NASA Scientists Create Amino Acids in Deep-Space-Like Environment. NASA Astrobiology News Archives with links [Electronic version]. Retrieved 5Nov2005 from
http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=1319
(18) J.F. Kasting & A.A. Pavlov (2001 Jun 26) Archean Earth and Contemporary Life: The Transition from an Anaerobic to an Aerobic Marine Ecosystem (Sponsored by NASA Astrobiology Institute). Edinburgh International Conference Centre: Sidlaw [Electronic version]. Retrieved 5Nov2005 from
http://gsa.confex.com/...1ESP/finalprogram/abstract_7607.htm
(19) S. Simpson (1999 Jan 9) Life's First Scalding Steps. Science News, Vol. 155, No. 2, p24 [Electronic version]. Retrieved 5Nov2005 from
http://www.sciencenews.org/pages/sn_arc99/1_9_99/bob1.htm
(20) S. Hart (2005 Oct 5) Hydrothermal Vents - Life's First Home? NASA Astrobiology News Archives [Electronic version]. Retrieved 5Nov2005 from
http://nai.arc.nasa.gov/news_stories/news_detail.cfm?arti...
(21) S. Earle (2000 Aug) Origin of life in a hot iron-sulphur environment. Earth Science News [Electronic version]. Retrieved 5Nov2005 from
Error
(22) J. Parnell (2003 Mar 20) Mineral Radioactivity Promotes Organic Complexity On Rocky Planets (#1119). Lunar and Planetary Science Conference XXXIV, Poster Session II [Electronic version]. Retrieved 5Nov2005 from
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1119.pdf
(23) L.J. Siegel (2005 Oct 5) Café Methane. NASA Astrobiology News Archives [Electronic version]. Retrieved 5Nov2005 from
http://nai.arc.nasa.gov/news_stories/news_detail.cfm?arti...
(24) T. Ferdelman, C. Borowski, N. Knab & H. Lbner (2005) Anaerobic methane oxidation in marine systems. Max Planck Institute for Marine Microbiology [Electronic version]. Retrieved 5Nov2005 from
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(25) C. Huber and G. Wchterhuser (1998 Jul 31) Peptides by activation of amino acids with CO on (Ni,Fe)S surfaces: implications for the origin of life. Science 281(5377) p670-672 [Electronic version]. Retrieved 5Nov2005 from
http://ecoserver.imbb.forth.gr/microbiology/s-e-papers/e-papers/peptideformationbyc_nifes.pdf
(26) S.A. Kauffman (1996 Aug 8) Self-Replication: Even peptides do it. Nature 382 [Electronic version]. Retrieved 5Nov2005 from
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(27) E.F. Mallove (1990 May 9) Self-Reproducing Molecules Reported by MIT Researchers. MIT Tech Talk [Electronic version]. Retrieved 5Nov2005 from
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(28) J. Sarfati (no date) Did scientists create life . or did the media create hype? Answers in Genesis article [Electronic version]. Retrieved 5Nov2005 from
Missing Link
| Answers in Genesis
(29) J. Sarfati (2002 Dec 26) Self-replicating enzymes? Answers in Genesis TJ Archive Volume 11 Issue 1 [Electronic version]. Retrieved 5Nov2005 from
Missing Link
| Answers in Genesis
(30) P. Ball (2004 Apr 26) Mineral brew grows 'cells'. Nature News archive [Electronic version]. Retrieved 5Nov2005 from
Mineral brew grows 'cells' | NatureSign in required, abstract available at
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&sp-sfvl-field=subject%7Cujournal&sp-t=results
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(31) J.P. Dworkin, D.W. Deamer, S.A. Sandford, and L.J. Allamandola (2001 Jan 30) Self-assembling amphiphilic molecules: Synthesis in simulated interstellar/precometary ices. Proceedings of the National Academy of Science vol. 98 no. 3 p815-819 [Electronic version]. Retrieved 5Nov2005 from
Just a moment...
(32) C. Suh (2003 an 13) Researchers create novel life form. Science & Technology (no pub) United Press International [Electronic version]. Retrieved 5Nov2005 from
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(33) G. Rice, L. Tang, K. Stedman, F. Roberto, J. Spuhler, E. Gillitzer, J.E. Johnson, T. Douglas & M. Young (2004 May 18) The structure of a thermophilic archaeal virus shows a double-stranded DNA viral capsid type that spans all domains of life. Proceedings of the National Academy of Science vol. 101 no. 20 p7716-7720 [Electronic version]. Retrieved 5Nov2005 from
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Appendix A: Background Information from the references.
The purpose of this appendix is two-fold.
(1) Some articles are quite long and they often get into many other details, so the sections excerpted here are the pertinent ones to the essay above, and
(2) Some articles are volatile on the web and may disappear or be edited or have the urls changed, so this allows the wording to be retained as captured on 5Nov2005.
Each entry is numbered to correspond to the references used above and a link to the article (as of 5Nov2005) is provided for ease of use. I have also made some parenthetical comments (not indented) at the ends of some entries.
A1 - Hoyle and Wickramasinghe's Analysis of Interstellar DustAnalysis of Interstellar Dust and Selected Resources. by Brig Klyce... Now, however, that organic polymers in space are abundant and may be necessary for life is well accepted. Today we often see stories about things like vinegar among the stars, or "buckyballs" from space as "the seeds of life". To that extent the scientific paradigm for the origin of life on Earth has already shifted.
But Hoyle and Wickramasinghe were not satisfied. In the middle 1970s, they turned their attention to an apparent anomaly in the spectrum. It had a low, broad "knee" centered at about 2.3 wavelengths per micrometer (the slight convexity on the slope at the left side of the graph). This spectral feature could be explained if the grains of dust were of a certain size, and hollow. After trying almost everything else first, in 1979, they looked at the spectrum for bacteria. Dried bacteria refract light as irregular hollow spheres, and their size range is appropriate. The match between the spectrum for dried bacteria (solid line) and the ones from the interstellar grains (dots, triangles and squares) was nearly perfect. Thinking without prejudice, Hoyle and Wickramasinghe concluded the grains probably were dried, frozen bacteria.
A2 - Scientists discover two new interstellar moleculesBrightsurf Science News and Current Events - Page Not FoundA team of scientists using the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) has discovered two new molecules in an interstellar cloud near the center of the Milky Way Galaxy. This discovery is the GBT's first detection of new molecules, and is already helping astronomers better understand the complex processes by which large molecules form in space.
The 8-atom molecule propenal and the 10-atom molecule propanal were detected in a large cloud of gas and dust some 26,000 light-years away in an area known as Sagittarius B2. Such clouds, often many light-years across, are the raw material from which new stars are formed.
So far, about 130 different molecules have been discovered in interstellar clouds. Most of these molecules contain a small number of atoms, and only a few molecules with eight or more atoms have been found in interstellar clouds. Each time a new molecule is discovered, it helps to constrain the formation chemistry and the nature of interstellar dust grains, which are believed to be the formation sites of most complex interstellar molecules.
Starting with previously reported propynal (HC2CHO), propenal (CH2CHCHO) is formed by adding two hydrogen atoms. By the same process propanal (CH3CH2CHO) is formed from propenal.
After these molecules are formed on interstellar dust grains, they may be ejected as a diffuse gas. If enough molecules accumulate in the gas, they can be detected with a radio telescope. As the molecules rotate end-for-end, they change from one rotational energy state to another, emitting radio waves at precise frequencies. The "family" of radio frequencies emitted by a particular molecule forms a unique "fingerprint" that scientists can use to identify that molecule. The scientists identified the two new aldehydes by detecting a number of frequencies of radio emission in what is termed the K-band region (18 to 26 GHz) of the electromagnetic spectrum.
Complex molecules in space are of interest for many reasons, including their possible connection to the formation of biologically significant molecules on the early Earth. Complex molecules might have formed on the early Earth, or they might have first formed in interstellar clouds and been transported to the surface of the Earth.
A3 - Identifying Polycyclic aromatic hydrocarbon (PAH) molecules in Spacehttp://spacescience.arc.nasa.gov/displaypage.cfm?page=Bre...Polycyclic aromatic hydrocarbon (PAH) molecules are the most abundant family of molecules in the interstellar medium after molecular hydrogen and carbon monoxide, and contain about 10% of all the interstellar carbon.
Recently, a spectral database has become available from the Infrared Space Observatory that contains objects in which we have found the C-H PAH stretch feature (near 3.26 m) in absorption. Using the database of isolated neutral PAHs generated by the Ames Astrochemistry Laboratory, we can match the interstellar feature fairly well with a mixture of PAH molecules. However, the mixture is not unique and does not tell us which particular PAHs are present in space. This is demonstrated in the Figure which shows two fits to the absorption observed towards the protostellar source S140. The laboratory database contains only a few PAHs as large as those expected to survive the rigors of the interstellar medium, so it is perhaps not surprising that a precise match is still not possible. Techniques for obtaining lab spectra of larger PAHs exist, but making large PAHs for lab studies is very difficult. Once such lab data exist, being able to directly compare lab and interstellar spectra without using uncertain models could provide the first identification of individual PAHs in space.
A4 - Spitzer Finds Life Components in Young UniverseNASA -
Spitzer Finds Life Components in Young Universe
NASA's Spitzer Space Telescope has found the ingredients for life all the way back to a time when the universe was a mere youngster.
Using Spitzer, scientists have detected organic molecules in galaxies when our universe was one-fourth of its current age of about 14 billion years. These large molecules, known as polycyclic aromatic hydrocarbons, are comprised of carbon and hydrogen. The molecules are considered to be among the building blocks of life.
"This is 10 billion years further back in time than we've seen them before," said Dr. Lin Yan of the Spitzer Science Center at the California Institute of Technology in Pasadena, Calif. Yan is lead author of a study to be published in the August 10 issue of the Astrophysical Journal. Previous missions - the Infrared Astronomical Satellite and the Infrared Space Observatory - detected these types of galaxies and molecules much closer to our own Milky Way galaxy. Spitzer's sensitivity is 100 times greater than these previous infrared telescope missions, enabling direct detection of organics so far away.
Since Earth is approximately four-and-a-half billion years old, these organic materials existed in the universe well before our planet and solar system were formed and may have even been the seeds of our solar system.
Spitzer's infrared spectrometer split the galaxies' infrared light into distinct features that revealed the presence of organic components. These organic features gave scientists a milepost to gauge the distance of these galaxies. This is the first time scientists have been able to measure a distance as great as 10-billion light years away using the spectral fingerprints of polycyclic aromatic hydrocarbons.
"These complex compounds tell us that by the time we see these galaxies, several generations of stars have already been formed," said Dr. George Helou of the Spitzer Science Center, a co-author of the study. "Planets and life had very early opportunities to emerge in the universe."
A5 - Scientists Toast the Discovery of Vinyl Alcohol in Interstellar Spacehttp://www.spacedaily.com/news/life-01zi.htmlAstronomers using the National Science Foundation's 12 Meter Telescope at Kitt Peak, AZ, have discovered the complex organic molecule vinyl alcohol in an interstellar cloud of dust and gas near the center of the Milky Way Galaxy. The discovery of this long-sought compound could reveal tantalizing clues to the mysterious origin of complex organic molecules in space.
"The discovery of vinyl alcohol is significant," said Barry Turner, a scientist at the National Radio Astronomy Observatory (NRAO) in Charlottesville, Va., "because it gives us an important tool for understanding the formation of complex organic compounds in interstellar space.
The astronomers were able to detect the specific radio signature of vinyl alcohol during the observational period of May and June of 2001. Their results have been accepted for publication in the Astrophysical Journal Letters.
A6 - Rosalind Elsie Franklin (1920 - 1958)
BBC - 404: Not Found
Franklin was an expert in using x-ray crystallography to study imperfectly crystalline matter, such as coal. She started work on the DNA by making very thin threads of it, bundling them and hitting them with a super-fine x-ray beam. She soon discovered the two forms of DNA. The easily photographed A form was dried, while the B form was wet.
While much harder to photograph, her pictures of the B form showed a helix. Since the water would be attracted to the phosphates in the backbone, and the DNA was easily hydrated and dehydrated, she guessed that the backbone of the DNA was on the outside and the bases were therefore on the inside. This was a major step forward in the search for the structure of DNA.
In November 1951 Franklin presented her A and B form data to an audience that included James Watson, who was working in Cambridge with Francis Crick on the x-ray crystallography of protein. On hearing her lecture, the two men built their first model of DNA: a triple helix with the bases on the outside. However, in May 1952, Franklin got her first good photograph of the B form of DNA, showing a double helix. This was another major breakthrough. Franklin then continued working on the A form, having decided it would provide more data.
In early 1953, Watson and Crick saw some draft work by the American scientist Linus Pauling, and were given access to Franklin's data and her B form photographs showing DNA to be a multiple helix. From his work on proteins, Crick realised that her data implied an anti-parallel double helix. Franklin had reached this conclusion with regards to the A form, but had yet to apply this theory to the other form.
Both projects were nearing the finish, but Franklin was pipped at the post. Franklin herself had written a draft paper on 17 March 1953, but was unable to publish before Watson and Crick, who were published the following day. Watson and Crick had broken a gentleman's agreement by working on DNA when they had claimed otherwise, and Franklin had offered valid criticism of their first model.
A7 - Organic Materials Spotted High Above Titan's Surfacehttp://sse.jpl.nasa.gov/news/display.cfm?News_ID=10716During its closest flyby of Saturn's moon Titan on April 16, the Cassini spacecraft came within 1,027 kilometers (638 miles) of the moon's surface and found that the outer layer of the thick, hazy atmosphere is brimming with complex hydrocarbons.
Scientists believe that Titan's atmosphere may be a laboratory for studying the organic chemistry that preceded life and provided the building blocks for life on Earth. The role of the upper atmosphere in this organic "factory" of hydrocarbons is very intriguing to scientists, especially given the large number of different hydrocarbons detected by Cassini during the flyby.
... Complex mixtures of hydrocarbons and carbon-nitrogen compounds were seen throughout the range of masses measured by the Cassini ion and neutral mass spectrometer instrument.
"We are beginning to appreciate the role of the upper atmosphere in the complex carbon cycle that occurs on Titan," said Dr. Hunter Waite ...
Hydrocarbons containing as many as seven carbon atoms were observed, as well as nitrogen-containing hydrocarbons (nitriles). Titan's atmosphere is composed primarily of nitrogen, followed by methane, the simplest hydrocarbon.
Interstellar clouds produce abundant quantities of organics, which are best viewed as the dust and grains incorporated in comets. This material may have been the source of early organic compounds on Earth from which life formed. Atmospheres of planets and their satellites in the outer solar system, while containing methane and molecular nitrogen, are largely devoid of oxygen. In this non-oxidizing environment under the action of ultraviolet light from the Sun or energetic particle radiation (from Saturn's magnetosphere in this case), these atmospheres can also produce large quantities of organics, and Titan is the prime example in our solar system. This same process is a possible pathway for formation of complex hydrocarbons on early Earth.
A8 - Search for organic molecules in the outer solar system.National Center for Biotechnology Information entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11537827&query_hl=2
Recent developments of millimeter astronomy have led to the discovery of more and more complex molecules in the interstellar medium. In a similar way, attempts have been made to detect complex molecules in the atmospheres of the most primitive bodies of the Solar System, i.e. outer planets and comets, as well as in Titan's atmosphere. An important progress has been achieved thanks to the continuous development of infrared astronomy, from the ground and from space vehicles. In particular, an important contribution has come from the IRIS-Voyager infrared spectrometer with the detection of prebiotic molecules on Titan, and some complex organic molecules on Jupiter and Saturn. Another important result has been the observation of carbonaceous material in the immediate surroundings of Comet Halley's nucleus. In the near future, the search for organic molecules in the outer Solar System should benefit from the developments of large millimeter antennae, and in the next decade, from the operation of infrared Earth-orbiting spacecrafts (ISO, SIRTF) .
A9 - Organic Content of the Tagish Lake Meteoritehttp://web99.arc.nasa.gov/PDF/tagish.pdfThe Tagish Lake meteorite fell last year on a frozen lake in Canada and may provide the most pristine material of its kind. Analyses have now shown this carbonaceous chondrite to contain a suite of soluble organic compounds (~100 parts per million) that includes mono- and dicarboxylic acids, dicarboximides, pyridine carboxylic acids, a sulfonic acid, and both aliphatic and aromatic hydrocarbons. The insoluble carbon exhibits exclusive aromatic character, deuterium enrichment, and fullerenes containing "planetary" helium and argon. The findings provide insight into an outcome of early solar chemical evolution that differs from any seen so far in meteorites.
A10 - Researchers Find Possible Precursors to Early Life on Earth in MeteoriteNASA -
Researchers Find Possible Precursors to Early Life on Earth in Meteorite
The Tagish Lake meteorite fell to Earth over the Yukon Territory of Canada on Jan. 18, 2000. Parts of the meteorite were collected and kept frozen in an unprecedented level of cleanliness to ensure that it was not contaminated by any terrestrial sources.
Through extensive testing using, in part, electron microscopes, the researchers found numerous hollow, bubble-like hydrocarbon globules in the meteorite. They believe these organic globules, the first found in any natural sample, are very similar to those produced in laboratory simulations designed to recreate the initial conditions present when life first formed in the universe.
"While not of biological origin themselves, these globules would have served very well to protect and nurture primitive organisms on Earth," said Dr. Michael Zolensky, an author of the paper and a researcher in the Office of Astromaterials Research and Exploration Science at NASA's Johnson Space Center in Houston. "They would have been ready-made homes for early life forms."
Last year, researchers at NASA's Ames Research Center in Moffett Field, Calif., announced that they had made basically identical hydrocarbon globules in the laboratory from materials present in the early solar system and interstellar space.
"What we have now shown is that that these globules were in fact made naturally in the early solar system, and have been falling to Earth throughout time," Zolensky said.
A11 - Sweet MeteoritesPage Not Found | Science Mission DirectorateA NASA scientist has discovered sugar and several related organic compounds in two meteorites - providing the first evidence that another fundamental building block of life on Earth might have come from outer space.
Dr. George Cooper and co-workers from the NASA Ames Research Center found the sugary compounds in two carbon-rich (or "carbonaceous") meteorites. Previously, researchers had found inside meteorites other organic, carbon-based compounds that play major roles in life on Earth, such as amino acids and carboxylic acids, but no sugars.
"Finding these compounds greatly adds to our understanding of what organic materials could have been present on Earth before life began," Cooper said. "Sugar chemistry appears to be involved in life as far back as our records go." Recent research using ratios of carbon isotopes have pushed the origin of life on Earth to as far back as 3.8 billion years, he said. (An isotope is one of two or more atoms whose nuclei have the same number of protons but different numbers of neutrons.)
Scientists have long believed meteorites and comets played a role in the origin of life. Raining down on Earth during the heavy bombardment period some 3.8 billion to 4.5 billion years ago, they brought with them the materials that may have been critical for life, such as oxygen, sulfur, hydrogen and nitrogen. Sugars and the closely related compounds discovered by Cooper, collectively called "polyols," are critical to all known life forms. They act as components of the nucleic acids RNA and DNA, constituents of cell membranes and cellular energy sources.
A12 - Carbonaceous meteorites as a source of sugar-related organic compounds for the early EarthCarbonaceous meteorites as a source of sugar-related organic compounds for the early Earth | NatureThe much-studied Murchison meteorite is generally used as the standard reference for organic compounds in extraterrestrial material. Amino acids and other organic compounds important in contemporary biochemistry are thought to have been delivered to the early Earth by asteroids and comets, where they may have played a role in the origin of life. Polyhydroxylated compounds (polyols) such as sugars, sugar alcohols and sugar acids are vital to all known lifeforms”they are components of nucleic acids (RNA, DNA), cell membranes and also act as energy sources. But there has hitherto been no conclusive evidence for the existence of polyols in meteorites, leaving a gap in our understanding of the origins of biologically important organic compounds on Earth. Here we report that a variety of polyols are present in, and indigenous to, the Murchison and Murray meteorites in amounts comparable to amino acids. Analyses of water extracts indicate that extraterrestrial processes including photolysis and formaldehyde chemistry could account for the observed compounds. We conclude from this that polyols were present on the early Earth and therefore at least available for incorporation into the first forms of life.
A13 - Phosphorus from meteoriteshttp://www.astronomy.com/asy/default.aspx?c=a&id=2423Phosphorus plays a central role for life on Earth. It is an intimate part of life's architecture, contained in the salts that stiffen vertebrate bones and in phospholipids that form the walls of all living cells. It is linked to life's fundamental fuel, adenosine triphosphate (ATP), the energy storehouse that powers just about every physiological action. Even the lengthy genetic sequences of DNA and RNA ” the blueprints for life itself ” lie cradled within the twisting embrace of a pair of helical backbones built from phosphorus.
Yet for all its biological importance, the element is in remarkably short supply on Earth. According to recent studies, hydrogen atoms outnumber phosphorus atoms by 49 million to 1 in Earth's oceans, 2.8 million to 1 in the universe at large, and 203 to 1 in bacteria. Phosphorus fares a little better with oxygen atoms, which outnumber it by 25 million to 1 in the oceans, 1,400 to 1 in the cosmos, and 72 to 1 in bacteria. For every atom of phosphorus counted in such a census, carbon and nitrogen atoms appear, respectively, 974 and 633 times more often in the oceans, 680 and 230 times more frequently in the universe, and in numbers 116 and 15 times greater in bacteria.
Because phosphorus is much rarer in the environment than in life, understanding the behavior of phosphorus on the early Earth gives clues to life's orgin," said Matthew Pasek, a doctoral candidate at the University of Arizona's Lunar and Planetary Laboratory. Working with Dante Lauretta, assistant professor of planetary sciences at the university, Pasek argues that iron meteorites could have brought more phosphorus to Earth than occurs naturally. He presented his ideas at the 228th American Chemical Society national meeting in Philadelphia on Tuesday.
... Pasek and Lauretta began looking at meteorites as a possible source of the element. Meteorites contain several different phosphorus-bearing minerals, but the most important, said Pasek, is iron-nickel phosphide, also known as schreibersite. This metallic compound is extremely rare on Earth, but iron meteorites are peppered with schreibersite grains or even pinkish-colored veins of the mineral. Iron meteorites became the focus of the study because schreibersite is between 10 and 100 times more common in iron meteorites than other types.
Last April, Pasek, Lauretta, and undergraduate student Virginia Smith, mixed schriebersite with de-ionized water at room temperature. They then analyzed the liquid mixture using nuclear magnetic resonance. "We saw a whole slew of different phosphorus compounds being formed," Pasek said. "One of the most interesting ones we found was
P2O7, one of the more biochemically useful forms of phosphate, similar to what's found in ATP." The analysis revealed numerous phosphate salts in different states of oxidation, Pasek told Astronomy.
A14 - The Time-Dependent Intense Bombardment of the Primordial Earth/Moon System
EvC Forum: Harvard to sponsor abiogenesis project
Thanks.
(a bit gaudy)
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