AST 248, Lecture 14

James Lattimer

Department of Physics & Astronomy 449 ESS Bldg. Stony Brook University

April 6, 2020

The Search for Intelligent Life in the Universe [email protected]

James Lattimer AST 248, Lecture 14 Development of Complexity

Catastrophe Theory

I Consider a potential function V (x) = x 3 + ax.

I When a < 0 there is both a stable minimum (dots) and an unstable maximum in the potential.

I As a is slowly increased, the equilibrium system moves smoothly to smaller x: p xeq = −a/3.

I When a = 0, the stable minimum disappears, and for a infinitesimally positive, the system moves abruptly to a new equilibrium very far removed from the old.

James Lattimer AST 248, Lecture 14 Boolean Networks

A logical system composed of units or nodes that can be in either on or off states (analogy, lightbulbs). One could have a system of N nodes, each connected to K other nodes. Whether a node is on or off is determined by the state of the conected neighbors and a set of logical rules. For example, suppose K = 2, so that node A is connected to nodes B and C, and the logical rules are: if B and C are both on or off, then A is turned on. If B is on and C is off or vice versa then A is turned off. Beginning from an initial state, the network takes a step and alters the state of each node, if necessary, to comply with the logical rules. Since some state of the network will eventually repeat an earlier state, the system will enter a repeating cycle. The length of the cycle could be as short as one step (i.e. the system is fixed) or extremely large. A large network will behave chaotically. In between these extremes, Boolean networks show interesting behavior, such as quickly reverting to cyclical behavior, known as an attractor.√ For example, if N = 100, 000 and K = 2 there are about N = 316 different cycles, each about 316 steps long. This is surprisingly orderly behavior: out of the 1030,000 possible states, it will end up in one of these 316 cycles. Thus the vast majority of the system’s possible states are never visited after the limit cycle is obtained. As the network goes into a limit cycle, about 70% of the nodes become frozen, with the other 30% randomly varying. When the frozen sea forms marks a phase transition between chaos and order.

James Lattimer AST 248, Lecture 14 Stuart Kauffman has applied this model to genes to describe genetic regulatory networks and to the development of complex . He examines how one goes from an undifferentiated egg by repeated division to differentiated cell types: red blood cells, retinal cones, etc. Genes are the nodes of a Boolean network and cell types are the attractors or limit cycles; cell division represents a timestep. He reasons that cell specialization is obtained for free from the connectivity rules. The number of genes in is about 100,000 and the number of cell types is about 256, close to its square root. This scaling also seems to work for other organisms. Furthermore, about 70% of the genes are permanently turned on in all cell types.

James Lattimer AST 248, Lecture 14 How Small Can Organisms Be?

Smallest bacteria and archaea I Carsonella ruddii contains a circular chromosome of 159,662 base pairs with a high coding density (97%) with many overlapping genes and reduced gene length. Number of predicted genes is 182, lowest in record. I Nanoarchaeum equitans discovered in a hydrothermal vent, about 400 nm in length, and containing 490,885 base pairs. Genes for several vital metabolic pathways are missing; they cannot synthesis nucleotides, amino acids or . But it has DNA repair mechanisms and can carry out DNA replication, transcription and translation. I Mycoplasma is the smallest free-living with 580,000 base pairs and 517 genes. Numerous genes essential for life are missing. Minimal Genome Project I A study headed by Craig Venter to find the smallest working set of genes necessary for an organism to live and reproduce successfully. Mycoplasma was subjected to random gene knockouts, with each knockout mutant being tested for signs of life. Roughly one third of the knockouts that resulted in a non-viable mutant were from genes that had a function that was unknown at the time. About 300 genes seem to be necessary for survival. I It is also planned to create a synthetic chromosome and inject it into Mycoplasma with the original genetic material removed to attempt to create artifical life. I Intent will be to develop a new fuel or agent for environmental remediation.

James Lattimer AST 248, Lecture 14 Nanobes

I Filamental structures found in rocks and sediments in 1996. I Might be smallest form of life, 10 times smaller than the smallest bacteria, C. ruddi (160 kbp) Mycoplasma (580 kbp), or archaeum, Nanoarchaeum (491kbp). I Smallest nanobes are 20 nm in diameter. I Debate concerning if they contain DNA. I Similar to life-like structures in ALH84001, the Martian meteorite. I Commercially interesting in plastics manufacturing. I Recovered from sandstone rock retreived from 3-5 km under ocean bed where pressure is 2000 atm and T = 115 − 170◦ C. I Could be implicated in some and calcification of teeth and arterial walls. I It is suggested this could be a new form of life, but most biologists are doubtful at this stage that they are independent life forms. I Main argument against, lacking DNA/RNA evidence, is they are simply too small. I What can nanobes tell us about life’s origins?

James Lattimer AST 248, Lecture 14 Life and Collective Behavior

Evolution occurs whenever an hereditary change by chance improves its efficiency of survival and its rate. The obvious route is to become bigger: I offers better protection against changes in physical environment; I it can invoke division of labor so that different parts become specialized; I it can prey on smaller creatures. There is always room at the top, but limits are imposed by the physics of and muscles and gravity. But what about becoming smaller? Microbes have been around a long time, so they must be successful. I they can grow rapidly; I you can parasitize something which is larger. Carried to an extreme, perhaps you lose all capacity to reproduce or metabolize on your own (think viruses). Limits to becoming smaller imposed by the size of a single ribosome, 18 nm. With RNA and , a size limit is closer to 50–100 nm. Nanobes can be as small as 20 nm. Perhaps each nanobe contains only a part of the living system, so a large collection of nanobes is actually necessary to be the functional equivalent of a single cell. Nanobes may represent an extreme degree of collective behavior, not dissimilar from the gene swapping (horizontal gene transfer) between prokaryotes that led to eukaryotes. The boundary between living organisms and non-life now becomes murky, indeed.

Adapted from V. Nanjundiah, J. of Biosciences 25, 9 (2000)

James Lattimer AST 248, Lecture 14 Major Stages of

4.5 Gyr Formation of Earth 4.1 Gyr First chemofossil evidence of life (disuputed) Life was anaerobic, chemoautotrophs, utilize H2S 3.9 Gyr End of Late Heavy Bombardment of inner solar system 3.5 Gyr First microfossil evidence, first evidence for photosynthetic life First photosynthesizers utilized H2S.

2.7 Gyr Cyanobacteria develop aerobic using H2O

2.4 Gyr Buildup of O2 in atmosphere, avoidance of “Oxygen Catastrophe” Development of Eukaryota through endosymbiosis (mitochondria and chloroplasts); nuclear membrantes, , sexual reproduction, flexible cell walls, internal scaffolding (cytoskeleton). Perhaps connected with large bacteria Magnetobacter with organelles of magnetite (Fe3O4), connection to development of Earth’s core and magnetic field at the same time. enables identical DNA replication, 1000-fold DNA size increase 1.2 Gyr Earliest evidence for multicellular organisms, including animals and plants 545 Myr Cambrian Explosion leading to proliferation of animal diversity over a 40 Myr period. Only major period of family diversification in geologic record. Causes: O2 levels, genetic complexity, Snowball Earth, absence of predators.

James Lattimer AST 248, Lecture 14 475 Myr Plants develop means to live on land, evolving from algae. 440 Myr First major extinction (Late Ordovician) 400 Myr Amphibians and insects colonize land. 360 Myr Dense Carboniferous forests, resulting in coal and oil. 250 Myr Permian extinction leading to dinosaur domination 210 Myr Late Triassic extinction

200 Myr First charcoal observed in strata, evidence that O2 levels are near present values. 65 Myr K-T extinction of dinosaurs leading to mammalian domination 60 Myr Last common ancestor of primates 7 Myr Hominid develops, last common ancestor of humans, gorillas and chimpanzees 0.2 Myr First (Homo sapiens) fossils 0.05 Myr Upper Paleolithic Revolution and exosomatic symbols and projectile weapons: emergence of true intelligence? 0.03 Myr Extinction of Neanderthals 0.012 Myr Extinction of Homo Floresiensis

James Lattimer AST 248, Lecture 14 Evolution of First Animals 3D laser scan

UC Riverside scientists claim to have found the first ancestor of animals, the 555 Myr old wormlike Ikaria wariootia in Australia. It’s the earliest known bilaterian (has a front, back, two symmetrical sides and openings at Ikaria wariootia each end connected by a gut). oval impressions near burrows The earliest multicelluar organisms (sponges, algae), in contrast, had variable shapes. Bilateral symmetry gives the ability to move purposefully and a common way to organize bodies. They were found in Ediacaran Period deposits in Nilpena, South Australia, associated with nearby fossilized burrows. The animal sizes are about 2-7 mm long and 1-2.5 mm wide and all images would just fit into the burrows. UC Riverside Another animal-like organism, Dickinsonia, with oval sizes from 1 inch to several feet, Dickinsonia were also among the first large animals at 550 Myrs old, but were evolutionary dead ends and not ancestors of any present-day animals.

James Lattimer AST 248, Lecture 14 Evolution of Information Capacity

DNA and Information DNA carries information in a computer-like way. Each base-pair contains two bits of information (The prior uncertainty is the number of equiprobable alternatives N = 4, so the information content of a message that narrows those alternatives down to 1 is log2 N = 2.) We will use the genome length to measure the information content, but note that this can be misleading:

I Much of the human genome, as well as other complex organisms, contains junk DNA that does not seem to contain useful information. It does not contribute to information content. In humans, the useful DNA is a mere 2% of the total. Amoebae have a genome 80 times that of humans but a considerably smaller percentage is useful coding.

I Conversely, DNA contains additional information to that contained in a simple reading of base-pairs because genes are often regulated by the activation of several other genes in a regulatory network.

James Lattimer AST 248, Lecture 14 Information and the Nervous System

The nervous system, especially the brain, also contains information, but the storage is more complicated.

I The brain contains 10 billion neurons, each connected to 1000 - 10,000 others.

I Neuron positions require little information. A part in a billion accuracy requires about 90 bits per neuron or a total of 120 Mbytes (1 byte = 8 bits). The main information is in the connections. We will need the address of each neuron: 10 billion can be stored with 34 bits (234 = 17 billion), plus an additional bit to specify the on/off state of each. Each synapse involves at least 1000 neurons bringing the total to 35,000 bits per synapse. There are 1010 = 10 billion synapses, involving a total of 3.5 · 1014 bits or nearly 0.05 petabytes.

James Lattimer AST 248, Lecture 14 Information and Evolution

I Initially, DNA was limited by error-rate during reproduction to around 10 million base-pairs. I Error-correcting (proteins) evolved to increase the length of DNA by about 100. I Increased specialization of cells accounts for an increase of another factor of 10 in genome length. I Ulitmately, DNA length is limited by chemistry to its present length. I At the same time this limitation was reached, an alternative method of storing information developed, involving the nervous system. I Nervous systems quickly evolved into brain stems and brains. I The multiple-connectivity of neurons vastly increases information storage. I No one can deny that by any method of measurement there has been a broad overall trend toward increased information content.

I But is a trend observed in all evolutionary lineages? No, parasites are a good example. It might be that even a majority of lineages have no progressive trend.

I In those lineages that show progressive trends over long times, there are many reversals and re-reversals in the shorter term, so that the progress is undermined. James Lattimer AST 248, Lecture 14 Why does information content increase during evolution? A consequence of . I Random genetic error (), horizontal gene transfer, sexual recombination, and migratory mixing all increase genetic variation, the available alternatives, so they decrease the available information content.

I Natural selection is a winnowing of the available alternatives, and thus increases the information content.

I Natural selection is thus nonrandom in the direction of improvement (survivability and reproductivity).

I Relatively small changes in the genome have produced major differences in organisms. The chimpanzee genome differs from a human’s by about 2%. A qualitative change in intelligence accompanied small quantitative increase. Big brains, tools (chimpanzees, elephants, ravens), culture and linguistic abilities (apes, whales, dolphins) and self-awareness (elephants, dolphins, apes) aren’t uniquely human. The key step might have been the development of projectile weapons and exosomatic symbols: symbolic intelligence (messaging without direct use of – decorated clothing, jewelry, paintings, ornate weapons). Further dramatic increases in information capacity occur because of civilization. I Societal specialization I Language I Technology (tools, books, computers)

James Lattimer AST 248, Lecture 14 Primate Evolution

James Lattimer AST 248, Lecture 14 Hominid Evolution

James Lattimer AST 248, Lecture 14 Phylogeny

James Lattimer AST 248, Lecture 14 Molecular Clocks Over time, mutations build up in DNA at a reliable rate. If a length of DNA found in 2 species differs by 4 bases and the entire DNA length changes by 1 base per 25 Myrs, the 2 versions are separated by 100 Myrs and their common ancestor lived 50 Myrs ago. A molecular clock can definitely say that one time period is twice as long as another, but cannot assign fixed times. Calibration against independent evidence about dates, such as the fossil record or sampling over evolutionary timescales, is necessary. Small sizes and changes in functionality of studied proteins can hamper calibration.

James Lattimer AST 248, Lecture 14 Adam and Eve The most recent common ancestor (MRCA, the most recent individual from which all organisms in the group are directly descended) of all currently living humans can be traced genetically by matrilineal and patrilineal paths, effectively tracing the family tree backward in time. Eventually, the lineages converge.

I Matrilineal: mitochondrial DNA (mtDNA) traces the Mitochondrial Eve (female MRCA). Seems to have lived about 140,000 years ago in Ethiopia, Kenya or Tanzania, using the molecular clock technique of correlating elapsed time with observed genetic changes. I Patrilineal: Y-chromosome traces the Y-chromosomal Adam (male MRCA). Seems to have lived about 60,000 – 90,000 years ago in Africa using molecular clock and genetic marker techniques. Both female and male MRCAs lived much longer ago than their joint MRCA, who is estimated to have lived only around 3000 BC. The identical ancestors point was about 5400 BC, when all humans can be divided into two groups: those who left no descendants today and those who are common ancestors of all living humans. Put another way: this is the most recent time when everybody today had the same set of ancestors. James Lattimer AST 248, Lecture 14 Ancestry

Proof that Mitochondrial Eve (or Y-chromosomal Adam) exists.

I All humans alive today form the set S. The set of all women who were mothers of the members of S is S 0, and the size of S 0 must be no larger than the size of S (each of us has only 1 mother). But it is more likely that the size of S 0 is much smaller than the size of S (each woman typically has more than 1 child). 00 I Repeat the proces to form set S and so on: each succeeding set is smaller than before. Finally, the set S n0 will contain 1 woman.

I This woman was not the only woman alive then; she had many contemporaries. But none of them left decendents along the matrilineal line.

I Once a mitochondrial Eve is established, further births cannot remove her status as an ancestor of all women. But further deaths can shift the title of mitochondrial Eve to a later individual. This happens, for example, during a population bottleneck (e.g., a plague reduces enormously the number of humans).

James Lattimer AST 248, Lecture 14 Ancestry and the MRCA

I The number of your ancestors must increase as you go back into the past. The number of ancestors doubles with each generation going back, unless some of the ancestors are duplicated. After 30 generations, number of ancestors would be at most 230 ≈ 1 billion.

I However, the number of humans on the Earth decreases as you go into the past. 30 generations was 900 years ago, when the world’s population was 300 million.

I There is, therefore, a higher likelihood, as you go into the past, of finding an individual who was an ancestor of any random person alive today. Go back far enough, and it becomes a certainty: this was the time of the MRCA. It’s estimated to have been about 170 generations back. At this time, one couple formed the MRCA. Others were ancestors of some humans but not all, and still others were not ancestors of anyone living today.

James Lattimer AST 248, Lecture 14 MRCA

www.pbs.org/wgbh/nova/neanderthals/mtdna.html

James Lattimer AST 248, Lecture 14 Evolutionary Implications

I Even at a microscopic level, evolutionary advantages of complex and/or specialized structures imply that they will develop. I Several significant physical conditions seem necessary for intelligence to develop: land, O2 atmosphere, relatively stable climate. I It is a fact of life that major catastrophic events will randomly change the direction and pace of evolution; on Earth, the net effect has been to enhance evolution because events did not completely extinguish life and new ecological niches were created. I Major terrestrial-based changes, such as earthquakes, volcanos, continental drift, have a limited or gradual impact. Possible exception: Snowball Earth and the Cambrian Explosion. I Sudden catastropic changes seem to be connected to random, extraterrestrial events such as asteroidal impacts, supernovae and gamma-ray bursts. I Relatively small changes in the genome produce major differences in organisms. The human and chimpanzee genomes differ by about 2%. I Although gorillas and chimpanzees have been evolving separately from humans for the same time span (all three have the same common ancestor), they have not beome intelligent. Is intelligence the logical outcome of evolution? James Lattimer AST 248, Lecture 14 Recent References of Interest

I The debate concerning ’gene-first’ or ’-first’ origin theories of life: http://sciencecases.lib.buffalo.edu/cs/collection/ detail.asp?case_id=643&id=643 Look at the indicated .pdf file.

I A comprehensive summary of Earth’s history, the origin and development of life, evolution, diversity, extinctions, and fossils, especially hominid fossils. http://www.maropeng.co.za/content/page/maropeng-exhibition- highlights Check out the Exhibition guide link. Be sure to look at all its “Read more” links.

James Lattimer AST 248, Lecture 14 Catastrophes and Evolution

I Extinction was not widely accepted before 1800. I Extinction was established as a fact by Georges Cuvier in 1796, critical for catastrophism, he also opposed Lamarckian evolution theories. I Over 99% of all species that have ever existed are now extinct. I Extinctions occur at an uneven rate. I There have been 6 major and many minor (up to 20) extinctions observed in the fossil record. Nearly all divisions among geological eras, eons and periods are marked by extinctions and originations. Cambrian-Ordovician transition 488 Myr A series of extinctions that eliminated many brachiopods and tribolites. Ordovician-Silurian transition 444 Myr Second largest extinction. Late Devonian 360 Myr A series of extinctions near the Devonian-Carboniferous transition, lasted 20 Myr with several pulses. Permian-Triassic extintinction 251 Myr Earth’s largest extinction killed 96% of all marine species and 70% of land species (plants, insects, vertebrates). Ended dominance of mammal-like reptiles and led to dinosaur dominance. Triassic-Jurassic extinction 200 Myr Last of large amphibians extinguished. Cretacious-Tertiary extinction 65 Myr About 50% of all species, including dinosaurs, were extinguished. Holocene extinction, now About 70% of biologists view the present as a mass extinction, due to human intervention. Not universally accepted as many argue there are significant differences from extinctions.

James Lattimer AST 248, Lecture 14 Major Extinctions

Rohde & Muller, Nature, 2005

James Lattimer AST 248, Lecture 14 Theories of Extinctions

I A theory should

I explain all the losses, not just a few groups like dinosaurs

I explain why some organisms survived and others didn’t

I be based on events that actually happened. I Flood basalt events, triggered by extensive volcanic activity, have been recorded 11 times and each is connected to an extinction event. I Sea level falls have been recorded 12 times and 7 are associated with extinctions. I Asteroid impacts producting craters over 100 km wide have been recorded once and associated with a mass extinction. These could produce intense volcanic activity as well as prolong heating or cooling due to deposition of soot and aerosols into atmosphere. I Asteroid impacts producing craters less than 100 km wide have been recorded over 50 times, but most not connected to any extinctions. I Other astronomical events, like supernovae and gamma ray bursts, could irradiate the Earth and destroy the ozone layer among other things. It’s been suggested a supernova was connected with the Ordovician-Silurian transition, but this is only weakly supported by evidence. I Other terrestrial events connected with global warming or cooling, like Snowball Earth or continental drift.

James Lattimer AST 248, Lecture 14 The Late Permian Extinction

Magnetism reveals world-wide glaciations have occurred.

James Lattimer AST 248, Lecture 14 The Late Permian Extinction

Oxygen generated by aerobic photosynthesis eliminated methane and initiated global cooling.

James Lattimer AST 248, Lecture 14 The Cretaceous-Tertiary Boundary Layer

Raton Pass, NM

Gubbio, Italy James Lattimer AST 248, Lecture 14 The Cretacious-Tertiary Boundary Layer

James Lattimer AST 248, Lecture 14 Cretacious-Tertiary Extinction Available evidence points strongly to an asteroid impact: Iridium enhancements In 1980, Alvarez, Alvarez, Asaro and Michels discovered that sedimentary layers at the K-T boundary contain concentrations of iridium and other rare-earth elements between 30 and 130 times normal. These elements are rare in the Earth’s crust, having been drained to Earth’s core when the Earth was molten as part of the Earth’s differentiation. But the same elements are corresondingly abundant in asteroids and comets. The amount of the excess iridium suggested an impactor of 10-15 km diameter. 2 3 2 1/3 4πR⊕d = 4πR /3 ⇒ R = (3R⊕d) d = 0.1 cm, R⊕ = 6373 km ⇒ R = 5 km Spherules Droplets of rock melted by high temperatures Shocked quartz Formed under high pressure conditions Soot Ashes in amounts consistent with burning most of Earth’s biota Worldwide distribution Liklihood A 10-km body will impact the Earth about once per 100 million years, and the K-T extinction occurred 65 Myr ago. Craters Several craters with ages of 65 Myrs found: Chicxulub, Mexico; Boltysh crater in Ukraine; Silverpit crater in the North Sea Crater size An impactor produces a crater 20 times its own size, so a 10-km impactor makes a 200 km crater. Chicxulub crater is about 180 km in diameter.

James Lattimer AST 248, Lecture 14 Chicxulub Crater w.tdn.uufi jkorteni/space/boundary www.student.oulu.fi/

James Lattimer AST 248, Lecture 14 Spherule Distribution

James Lattimer AST 248, Lecture 14 Alternative Extinction Theories

James Lattimer AST 248, Lecture 14 Simple Crater Formation

Craters are always circular.

Energy comes from kinetic of impactor and is much larger than the equivalent release of chemical energy (TNT).

Impact speed is the Earth’s escape speed plus the original space velocity.

James Lattimer AST 248, Lecture 14 Lesson 3: Crater - Overhead 2 Impact Effects

I Equate kinetic energy of impactor with gravitational potential energy. Establishes an estimate of impact velocity that is equivalent to the Earth’s escape velocity. s 1 2 GmM⊕ 2GM⊕ −1 mvesc = ⇒ vesc = = 11 km s ' 25, 000 mph 2 R⊕ R⊕ In fact, an impactor is likely to crash with about 50% more velocity. I The kinetic energy per projectile mass m is 1 v 2 = 1.3 · 1012 erg g−1 ' 100 × TNT. 2 I A 1 km-diameter projectile has a mass 4π m = ρ(D/2)3 = 1.6 · 1015 g 3 which strikes with an energy equivalent to 1.6 · 105 MT of TNT. I A general rule of thumb is that, on the Earth, a meteoroid will create a crater that is about 20 times bigger than itself. I On the Moon, the crater will be about 12 times the size of the impactor. James Lattimer AST 248, Lecture 14 Impacts Do Happen!

Comet Shoemaker-Levy 9, 1994

Peekskill, NY, 1992

James Lattimer AST 248, Lecture 14 Tunguska, Siberia, 1908

James Lattimer AST 248, Lecture 14 Carancas, Peru, 2007

On September 15 2007 a chondritic meteorite hit near Carancas, Peru and poisioned about 30 villagers that approached the impact site (600 more had provoked psychosomatic ailments). The impact caused boiling of arsenic-contaminated ground water from natural deposits. The local province is turning this into a tourist attraction.

James Lattimer AST 248, Lecture 14 Has No One Been Killed By A Meteorite?

10,700 BC End of Pleistocene: Great Lakes impacts linked to worldwide deposits of mammal bones and extinctions including wooly mammoths and saber-tooth tigers; disappearance of Clovis Culture 3123 BC K¨ofelsimpact event in Austria; impactor trajectory recorded on a Sumerian clay tablet 2807 BC Large impact in Indian Ocean caused megatsunamis 2200 BC Sudden fall of Sumerian civilization linked to impact 207 BC Bavarian impact of 0.7 mile diameter asteroid 536 BC Two impacts off Australia lead to megatsunamis and linked to reduced sunlight and crop failures in China and Mediterranean 580 AD Fireball near Bordeaux destroys Orleans 1348 AD Fireballs and earthquake in Carinthia kills 40,000 1430 AD Chinese fleet of Zhou Man destroyed, more than 173 ships, by comet 1490 AD Meteorite falls in Ch´ıng-yang, Shaanxi, China, killing more than 10,000 1631 AD 20,000 fatalities from a seige followed by a cataclysmic meteor impact in Magdeburg, Germany 1907 AD Family killed by meteorite in Hsin-p´ai,Weng-Li, China 2001 AD Red rain of Kerala, India, from comet disintegration

James Lattimer AST 248, Lecture 14 Impacts

Chapman and Morrison, Nature, 1994

James Lattimer AST 248, Lecture 14 Impact Rate Revised

NASA NEO Science Definition Team, 2003

James Lattimer AST 248, Lecture 14 Impact Rate Revised

Wikipedia

James Lattimer AST 248, Lecture 14 Impact Fatalities

Chapman and Morrison, Nature, 1994

James Lattimer AST 248, Lecture 14 Impact Fatalities

Rumpf, Lewis and Atkinson 2017

James Lattimer AST 248, Lecture 14 Impact Fatalities: Land vs. Water

Rumpf, Lewis and Atkinson 2017

James Lattimer AST 248, Lecture 14 Fatalities Per Year

Chapman and Morrison, Nature, 1994

James Lattimer AST 248, Lecture 14 Impact Fatality Estimates

Simulation of 100,000 years duration, keeping worst event per decade Asteroid/comet # # % Fatal Average Average Annual risk diameter (m) events fatal events yield (MT)∗ fatalities∗ of fatal event 13-99 9792 949 10 18 43 000 1 in 100 100-199 173 124 72 300 280 000 1 in 800 200-499 31 29 94 2000 700 000 1 in 3500 500-999 3 3 100 35 000 13 million 1 in 30 000 All 9999 1105 11 170 120 000 1 in 90 ∗per fatal event Simulation of 1 million years duration, keeping worst event per century Asteroid/comet # # % Fatal Average Average Annual risk diameter (m) events fatal events yield (MT)∗ fatalities∗ of fatal event 13-99 8563 2619 31 30 92 000 1 in 382 100-199 1065 736 69 300 310 000 1 in 1359 200-499 311 295 95 3900 1.8 milion 1 in 3390 500-999 45 44 98 29 000 14 million 1 in 22 727 1000-1999 14 14 100 220 000 180 million 1 in 71 429 2000+ 2 2 100 2 million 1.7 billion 1 in 500 000 All 10 000 3710 37 2 600 2 million 1 in 270 ∗per fatal event J. Lewis, U. of Arizona

James Lattimer AST 248, Lecture 14 Fatality Odds For USA

Terrorism−→

C. R. Chapman

James Lattimer AST 248, Lecture 14 Fatality Rates

C. R. Chapman

James Lattimer AST 248, Lecture 14 Impact Probability

Boslough et al. 2012

James Lattimer AST 248, Lecture 14 Prediction Consequences Nature of Problem Mistaken or exaggerated media report of near-miss or near-term predicted impact causes panic and demands for official action. Probability of Happening Has already occurred, and likely to happen again. Most likely way of impact hazard becoming of urgent concern to public officials. Warning Time Page-one stories develop in hours with officials being totally surprised. Mitigation Public education in science and risk, in particular. Development of critical thinking concerning risk. Science education and journalism need improvement. Examples

I Near miss by 100-m asteroid 60,000 km away. Will people believe official statements? I Mistaken famous astronomer predicts impact in 10 years, but report not withdrawn for days. I Official IAU prediction of 1-in-a-few-hundred impact possibility later in century; not refined until later (Asteroid 1997 XF11). I Grotesque media hype of one of above cases. From C. R. Chapman, Southwest Research Institute

James Lattimer AST 248, Lecture 14 Mitigation

I The energy needed to pulverize an impactor that has a kinetic energy of 1 MT is about 0.0001 MT. −8 I The energy needed to deflect an impactor is about 3 · 10 of that needed to pulverize it. Power of sunlight:  R 2  d −2 P = 4.3 · 1016 erg/s 1 km 1 AU Acceleration: a = 2P/(Mc). Deflection distance: ∆ = at2/2

Pt2  d −2  1 km   t 2 ∆ = = 1.4 km Mc 1 AU r 1 yr I For ∆ ' 8000 km, the size of the Earth, t ' 76 yrs. is needed if the impactor is at a mean distance of 1 AU from the Sun and is about 1 km in radius. I The space shuttle main engines could deflect a 1-km body with a lead time of about 30 years. I Delta 2 1st stage rocket could deflect 100-m body with lead time of 6 months. I Danger of a bomb attack is that it could lead to many impactors producing damage over a wider range with a cumulative effect at least as large if not larger than the original impactor. James Lattimer AST 248, Lecture 14