Is Earth Exceptional?
The Quest for Cosmic Life
Mario Livio & Jack Szostak . 2024 . 576.83 LIVIO . Cedar Mill Library
- Chemistry escapes me. Too many un-descriptive "historical" names for processes, substances, molecules. Hence chapters 2, 3, and 4 are as difficult to internalize as lists of the crowned heads of Europe (and the wars they started, won, and mostly lost)
p001 Chapter 1: A Freak Chemical Accident or a Cosmic Imperative?
p022 Galileo: "I do not feel obligated to believe that the same God who has given us our senses, reason, and intelligence, wishes us to abandon their use"
p025 Chapter 2: The Origin of Life: The RNA World
p033 Ribonuclease P !RNase P
broad class of RNA+Protein molecules that cut specific cellular RNAs in specific ways
- p033 The RNA does the work, the attached protein neutralizes the large negative charge of the RNA molecule
p033 Sidney Altman and colleagues added Mg++ magnesium ions, achieving similar neutralization
- p034 discoveries of many self-cleaving RNAs that catalyze chemical reactions
p034 Walter Gilbert catchphrase RNA World
p037 Yale biochemist Thomas Steitz The ribosome is a ribozyme
p039 Chapter 3: The Origin of Life: From Chemistry to Biology
p043 formose synthesis, sugar from formaldehyde
p046 British chemist John Sutherland
p048 pH buffer and catalyst makes 2-aminooxazole 2AO synthesis efficient, systems chemistry example
p048 2AO plus glyceraldehyde produces [[ https://en.wikipedia.org/wiki/Ribose_aminooxazoline | RAO
p057 Where did SO₂ come from? Volcanic eruptions. Pinatubo released enough SO₂ haze to cool Earth for 2 years.
p067 Appendix: Chemical Structures and Reactions
p073 Chapter 4: The Origin of Life: Amino Acids and Peptides
p083 Chapter 5: The Origin of Life: The Road to the Protocell
p087 dipolar membrane molecules amphiphilic, hydrophobic and hydrophilic ends, self-assembly of bilayer membranes
- p087 early Earth environment origin difficult to explain
p089 fatty acids spontaneously assemble into bilayers in water, model protocells
p091 Alexander Oparin proposed coaverate aggregates of polymers
- p091 RNA molechttps://en.wikipedia.org/wiki/Red_edgeules might have "colonized" the surface of mineral particles, but attraction forces distort them
- p092 condensation of nucleotides into chains is endothermic in water, hydrolyzing separation exothermic
- p093 Drying RNA in warm CO₂ can polymerize, but carbonic acid breaks bonds
p094 Leslie Orgel
p094 imidazole activated nucleotide release
p094 leaving group detaches during reaction
- p095 growing ice crystals concentrates dissolved compounds between them
p096 alkaline carbonate lakes concentrate dissolved phosphate
- p097 perhaps suitable environments for nucleotide and RNA synthesis
p100 Szostak Lab U. Chicago chemistry depertment
- p101 non-enzymatic RNA copying very different from biological copying
- p101 spending months in the laboratory can save you several hours in the library
p102 imidazole-activated dinucleotide, "bridged substrate"
- p103 higher copying at lower concentrations
- p104 similarities to replication of simpler RNA viruses infecting bacteria, but simpler
p105 circular genome avoids starting/ending point, viroids
- p106 beginning replication methods would not have been complex
p106 virtual circular genome model VCG
- p107 temperature cycling separates and joins randomly, copying in different places, eventually complete replication
- hypothetical, testing under way
p107 Albert Eschenmoser hypothetical progenitor nucleic acid that led to RNA
- p108 showed a diverse collection of artificial nucleic acids can be viable genetic polymers
- p108 Whatever the original nucleic acid, RNA always wins; the copying process preferentially generates RNA
- p109 fatty acid membranes highly permeable to inbound nutrients and outbound wastes without evolved pores or channels
- p109 experiments demonstrate primordial cells can grow and divide in many different ways
p109 micelles, molecular aggregates that can grow and divide
- p110 growing membranes vary in shape, leading to budding and new vesicles
- p111 osmotic pressure swells RNA-filled vesicles with water and more RNA
- p111 "competitive growth" favors protocells containing RNA that replicates faster
- p112 increased concentration outside the protocell reduces osmotic pressure, reshapes the vesicle, perhaps dividing it
p112 divalent magnesium citrate can protect a protocell from rupture
- p112 doesn't effect fatty acid membranes
- p113 membranes also stabilized by ribose and adenine nucleotides
p113 Sarah Keller University of Washington slkeller@uw.edu, B.A. Physics Rice 1989, PhD Biophysics Princeton 1995
- p117 easiest-to-make amino acids tend to pair-bond strongly
- p117 genetic code partly deterministic, partly "frozen historical accident"
p119 Chapter 6: Putting it All Together: From Astrophysics and Geology to Chemistry and Biology
- p135 Many chemical processes only at surface, evidence of surface origin of like, NOT hydrothermal vents
- p136 experiment show temperature cycles enable seemingly contradictory requirements.
- p136 environment cycling between high and low temperatures seems required for nonenzymatic RNA replication
- p137 Darwin's prescient "warm little pond"; volcanic hot springs, and asteroid impact craters
- p138 evolving ribozymes requires maintenance of larger genome
p138 hypothetical life on Mars might originate from impact ejecta; 12% of Chixhulub ejecta reached Earth escape velocity
p141 Chapter 7: Extraterrestrial Life on Solar System Planets?
- p143 Thin Mars atmosphere (2ppm of Earth mass per square meter, not much more than an industrial high vacuum), no magnetic field. Mars is 2ppm Earth, 999998 ppm Moon, with far less sunlight and similer peak corona mass ejection radiation levels.
- p144 Elon Musk wants to die on Mars, just not on impact
p151 1976 Viking Labelled Release (LR) experiment
p151 Gilbert Levin still insisted that he found life in 2019 Scientific American article.
p152 Dirk Schulze-Makuch suggested life in Martian hygroscopic salts, killed by LR water
p152 Carl Sagan "If there is life on Mars, we should do nothing with Mars. Mars belongs to the Martians, even if the Martians are only microbes."
- p156 Martian mineral processes can produce subsurface abiotic methane.
p156 Sample Analysis at Mars (SAM) on Mars Science Laboratory Curiosity Rover found 0.4 ppb methane.
p157 ESA ExoMars Trace Gas Orbiter found nothing up to 2019
p157 ESAMars Express Orbiter reported a methane spike above Gale crater in 2019
p161 Perseverance samples dried up river delta on west rim of Jezero Crater 2022 May, sample return mission planned after 2033
p167 Chapter 8: Extraterrestrial Life on Solar System Moons?
p174 charged particles bombarding Europa produce 40 tonnes of oxygen per hour over Europa's 1e13 square meter surface
- Europa surface temperature 50K to 140K, oxygen will be gas, not liquid or solid
- Europa escape velocity 2 km/s, rms thermal velocity less than 400 m/s, but charged particle bombardment might remove it
- Europa atmospheric density 2.4e18 to 14e18 atoms per square meter, 24 to 140 micrograms per square meter.
p178 Cassini scientists conclude Enceladus rotation wobble from subsurface ocean
- p179 Cassini Enceladus flybys of Enceladus detected phosphate, hydrogen cyanide, and more methane than abiotic geology predicts
p180 Saturn's rings 100 million years old according to Luciano Iess
- p180 other disagree about "young" rings
- p181 many astrobiologists consider Enceladus a most attractive extraterrestrial life search target
p187 Jupiter Icy Moons Explorer JUICE will reach Jupiter in 2031, orbit Ganymede in 2034
p189 Chapter 9: Life Out There: The Astronomical Quest
- p194 exoplanet oceans and lakes reflect their star's light with "glint"; observed on a Titan methane lake:
Listig-Yaeger, J. et. al., "Detecting Ocean Glint on Exoplanets Using Multiphase Mapping". Astronomical Journal 156. no. 6 (December 2018). pdf
p195 NASA EPOXI mission
- p195 a 6 meter space telescope could measure glint for one to ten nearby habitable-zone exoplanets
p196 Massive star, short duration. 10*Msun -> 20M years not 5B, hence no biospheres above 1.5*Msun
p196 M-dwarf stars more common, 0.5*Msun -> 60B years, longer timespan for evolution of life
- KL however, if intelligent life consumes/destroys its planet, most have already done so.
p197 Perhaps not; young M-dwarf stars frequently flare, sterilizing planets before steady main sequence. Habitable zone closer, planets more likely to tide-lock
- p198 JWST may detect atmospheres, but not biosignatures
p198 Sara Seager MIT says JWST might detect atmospheric water vapor (how many observation hours needed? JWST probably overbooked.
- p199 biosignatures only suggestive, not proof.
p199 unequivocal techno-signatures may be only proof
p199 Earth's Great Oxidation Event 750 to 460 Mya
- p200 acidity of oceans increased 30% over the last 250 years
- p200 one million species (out of estimated 8.7 million) threatened with extinction
- p202 exoplanet biosignature gasses: molecular oxygen, ozone, nitrous oxide, plus water (vapor?) and methane
- p202 molecular oxygen strong reflected light in the 760 nanometer band, does not overlap other gases
- dim red or near-infrared
p203 titanium dioxide photocatalysts can abiotically split liquid water and produce oxygen
- p206 Present day methane concentration 1.6ppm, limited by oxygen
carbon dioxide plus methane plus no oxygen might indicate exolife
p208 Vegetation Red Edge VRE, plants scatter 750 nm to 1100 nm
- p209 no known abiotic sources, though exoplanet vegetation may differ
p215-6 TRAPPIST-1 41 l-y away, 9% Sun mass, 4 planets, no atmospheres (book out of date?)
p218 Large Ultraviolet Optical Infrared Surveyor proposed for 2039
p219 Chapter 10: Life as We Don't Know It: The Design of Natural and Unnatural Life-Forms
p221 Magnetite facilitates homochirality Citation needed "2023"
p223 PNAS 2015 Hardy artificial life with different genetic material "just around the corner"
- p225 Haldane 1954 Ammonia solvent instead of water Citation Needed
p231 Chapter 11: The Hunt for Intelligence: Preliminary Thoughts
p233 Most observable SETI civilizations old. astroengineering, infrared, powerful infrared sources
- mentions modified planets, however, practically ALL mass and power and HEAT SINK is off planet.
- also, Carnot efficiency is better at colder temperatures, and structure/bit stability is an exponential of (1/T)
- p237 "Vicinity of high energy sources" ... no, too noisy and expensive and unstable, not nearly enough kT ln(2) Shannon bits because T is high. Speed is speed of light; actually SLOWER in a deep gravity well
- p238 Calculations that assume intelligence isotropically announces itself
Authors haven't read Saberhagen's Berserker novels, perhaps not recent news.
p242 Stigler's law of eponymy: no scientific discovery is named after its original discoverer.
p245 Brandon Carter claims (Anthropic Principle) typically intelligent civilizations do not have time to evolve, Earth is a very rare outlier
- Silly; there are 6 to 20 billion Sun-like (G-type) stars in the Galaxy. Even if "rare" is one in a million, that is 6 to 10 thousand civilizations.
- Livio makes a UV/Ozone argument. seemingly assuming land intelligence only
- p250 war or pandemic could wipe out current civilization, but not intelligent life.
- p252 hundreds of millions of potentially habitable planets in "Goldilocks zone" of stars in the Milky Way, many other galaxies
- but what giant tools will we need to look for them? My guess is MANY MANY "cold" dishes in the Kuiper belt
p253 Crick, F.H.C., and L.E. Orgel. “Directed Panspermia.” Icarus 19, no. 3 (1973): 341-346
p257 Chapter 12: The Hunt for Intelligence: The Searches
- p259 Many SETI radio surveys, few stars surveyed, data grossly insufficient
And why would ET broadcast isotropic radio rather than use narrow beam laser?
Saberhagen Berserkers machine intelligences that destroy all life (and detect broadcasting species)
p259 The Wow! Signal 1977 August 15, Sagittarius, 72 second window 1420 MHz 33 standard deviations above radio noise Ohio State Big Ear Radio Telescope 33 meter dish
p260 Chinese 500m FAST radio telescope 70 Mhz to 3 GHz, cost $180M, 2008 to 2016
- 9110 people relocated, $269M spent to create a radio-quiet area
- tradeoff between actual mission and tourist cellphones
- only a steerable 300m diameter patch illuminates the receiver aperture
p261 BLCI1 2019 Breakthrough Listen Candidate 1 at Parkes Ra:wqdio Observatory, probably interference
p261 candidates HD 139139 and KIC 8462852 Tabby's Star
Andrew Vanderberg "In astronomy we have a long history of not understanding something, thinking it’s aliens, and later finding out it’s something else ... The odds are pretty good that it’s going to be another one of those."
p262 Tabby Star up to 22% irregular fluctuations; no radio/optical SETI signals, in Cynus 1450 ly distant
- p262 Our radio broadcast signals have reached only 1% of Milky Way so far (?)
- p262 Probable time of return radio signal 1500 years in future
p271 Chapter 13: Epilogue: And Immanent Breakthrough?
- p275 initial synthesis of activated nucleotides a major gap in current understanding
- p285 Acknowledgements
- p287 Selected Further Reading
- p301 Lustin-Yaeger et. al. 2018, "Detecting Ocean Glint on Exoplanets Using Multiphase Mapping," Astronomical Journal 156 no. 6 December
- p311 Index