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• Astrobiology – “Life in the Universe” • Astrobiology – “Life in the Universe” Jason T. Olona – Sandia High School • Astrobiology is a field of science that gets a lot of laughs… Astrobiology: branch of science concerned with the study of the origin of life on Earth and the possible variety of life elsewhere. (OR) Astrobiology: Study of the origins, evolution, distribution, and future of life in the universe. • Synonymous with “exobiology,” “cosmobiology,” and “bioastronomy.” • BIG QUESTION: • Our study of astronomy has taught us that we have always been wrong in the past whenever we have claimed that earth is somehow unique… • Center of the Solar system? Center of the Universe? Sun is a special star? Planets are special? Life is special? • Copernican Principle: there is nothing special about our place in the universe. If life has developed here, why not elsewhere? • To answer this question, we have to ask ourselves… What is life? - Reproduction, growth, energy utilization, (metabolism), response to stimuli, evolutionary adaptation, ordered structure of cells, heritable blueprint (DNA). - Problem? Are we defining life on earth, or life in the universe? • What is life? • Life on Earth based on organic molecules (Carbon) • True question – is organic biochemistry as likely or unlikely in the universe at large? Behold! The great replicator molecules! • Life as we know it is based on amino acids. • SPONCH (CHNOPS) – rare or common in universe? • Life also needs ENERGY! Could life form from other things? SURE? Carbon based life = us. Silicon based life? Maybe… Is water necessary? What about just a liquid? Hypothetical solvents – ammonia, sulfuric acids, formamide, hydrocarbons, and (at temperatures much lower than Earth's) liquid nitrogen, or hydrogen • Origin of life on earth: 2 major theories 1) Life started here on Earth 2) Panspermia: Life (or the molecules that are necessary for life) came from somewhere else. Comets? Mars? • Early Earth – Hydrogen, ammonia, methane, and water vapor. • Primordial soup – take elements, add energy, make new stuff! • Urey-Miller experiment Stanley Miller and Harold Urey (1930) Added water, methane, ammonia, and hydrogen to mimic early - None of these experiments have Earth atmosphere. created DNA, rather they have showed Result was organic that biological molecules can be created molecules – amino acids! by non-biological means. • Origin of life – • Inorganic molecules to organic molecules (4.5 billion years ago) • First DNA and RNA (4.5-4.0 billion years ago) • First cells – prokaryotes “LIFE” (4 billion years ago) • Cells – eukaryotes (2 billion years ago) • Multicellular life – (1 billion years ago) • First land animals (500 million years ago) Assumptions of Mediocrity Why do we assume extraterrestrial life exists? 1. Because life on Earth depends on just a few basic molecules 2. Because the elements that make up these molecules are common to all stars 3. If physics is the same everywhere(!), given enough time, life must have originated elsewhere in the cosmos. What would life on other planets look like? What would life on other planets look like? • Study extremophiles • Extremophiles – • Thermophiles – heat tolerant up to 122 C • Psychrophiles – cold tolerant down to -25 C • Acidophiles – pH values near 0 • Alkaliphiles – pH levels of 13 (bleach) • Halophile – 10 times saltier than the ocean • Barophile – 1000 atmospheric pressure • Xerophile – little water • Radiation – Deinococcus radiodurans (1000x radiation we could withstand) • Vacuum of Space – Tardigrades! • So… what do we look for? • Habitable Zone – water in liquid form. Distance from star. • Biomarker: evidence of the presence of life, especially a global indication of life on a planet that could be detected remotely (unusual atmospheric composition). • Ex: Photosynthesis changed earth’s atmosphere to 20% oxygen. Should look for planets earth sized or gas presence that is difficult to explain without life. -Gases that may be signs of life - Nitrous oxide, methane, and oxygen • Biomarker: evidence of the presence of life, detected remotely (unusual atmospheric composition). • Ex: Photosynthesis changed earth’s atmosphere to 20% oxygen. Should look for planets earth sized or gas presence that is difficult to explain without life. -Gases that may be signs of life - Nitrous oxide, methane, with oxygen • “Life is the hypothesis of last resort” - Carl Sagan • "When you hear hoofbeats, think of horses not zebras“ (we must exhaust all other explanations for what we are seeing before we claim to have found evidence for life on other worlds). - Possibilities in our Solar System – Mars? Europa? Enceladus? Titan? • So… If Copernican principle is correct, biology could be common. Why not intelligent life? Fermi Paradox: if life and intelligence are common, why haven’t we found them? Or they found us? • Possible answers: maybe life is common but intelligence isn’t? Maybe there hasn’t been enough time? Maybe advanced species make it a practice to not interfere? Interstellar travel is HARD and EXPENSIVE– extremely slow and energetically expensive. • SETI – Search for Extra Terrestrial Intelligence • If you want to bridge interstellar distances, use EM spectrum! • Talk is cheap! Travels at speed of light and low energy cost. • Earth is already on the air – AM radio broadcasts since 1920s • TV since 1950s • What are we looking for? • Problem: signals need to be from intelligent sources, rather than naturally occurring. • Narrow “bandwidth, pulsed signals, very little frequency “drift” • So far, no detections. But the search continues! • Aracibo message: • Other messages: Pioneer 10 and 11 plaque & Voyager Record Let’s Consider the Chances… • How old is the universe? 13.8 Billion years old. • Stars in Milky Way? Conservative 250 Billion • Like our Sun? Conservative 100 Billion in Milky Way • How many galaxies? Conservative 200 Billion • How many exoplanets? Confirmed 4,000 in Milky Way • Like Earth? About 50 confirmed in Milky Way Our chances of finding life in the universe is directly proportional to how long we look (aka how long our civilization lasts)... • Drake Equation – • goal is to estimate N = number of civilizations in our galaxy. * • N = R Fp ne Fl Fi Fc L Each letter stands for a particular variable. * N = R Fp ne Fl Fi Fc L * - R = rate at which stars like out sun form – about 10 every year - Fp = fraction of these stars with planets - ne = The number of planets per solar system that can incubate life - Fl = fraction of habitable planets that actually develop life. - Fi = planets that develop intelligent life - Fc = probability that intelligent societies that invent technology - L =lifetime of societies that use technology If N = 1… just us? Carl Sagan’s guess, N = a few million Drake = 10,000 or conservative 500 www.seti.com to tinker with equation. • What is the problem with the Drake equation? • We only have one data point – Earth So is this equation a little biased? It has to be! We can only make assumptions based on things we know. .
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