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The search for life in the Universe ASTR 201 Friday, September 13, 2013 Outline of Week #2 What are we searching for? Why are we searching now? Introduction to Astrobiology The Scientific Method Friday, September 13, 2013 What are we searching for? How do we define life? common attributes of bacteria, beetles, mushrooms, a maple tree, kittens, and your Mom versus a crystal, a fire, or the ocean? made of cells? reproduce/spread? grow? respond/move? Necessary and sufficient conditions? not just one condition, but need 6 to define life as we know it. given difficulties in defining life on Earth, then scientific search for life generally assumes Earth-like as a starting point Friday, September 13, 2013 The key properties of life on Earth Friday, September 13, 2013 Are your favorite ETs from books & movies Earth-like? Friday, September 13, 2013 A wider variety of possibilities … ? Friday, September 13, 2013 Extremophiles on Earth Friday, September 13, 2013 What would count as evidence? Friday, September 13, 2013 What would count as evidence? Fossilized evidence of life found on Mars Friday, September 13, 2013 What would count as evidence? Fossilized evidence of life found on Mars Fossilized evidence of life found in a meteorite Friday, September 13, 2013 What would count as evidence? Fossilized evidence of life found on Mars Fossilized evidence of life found in a meteorite Evidence of photosynthesis in atmosphere of extra-solar planet Friday, September 13, 2013 What would count as evidence? Fossilized evidence of life found on Mars Fossilized evidence of life found in a meteorite Evidence of photosynthesis in atmosphere of extra-solar planet Signal from alien civilization (SETI) Friday, September 13, 2013 What would count as evidence? Fossilized evidence of life found on Mars Fossilized evidence of life found in a meteorite Evidence of photosynthesis in atmosphere of extra-solar planet Signal from alien civilization (SETI) Living organisms found on a meteorite, comet or asteroid Friday, September 13, 2013 What would count as evidence? Fossilized evidence of life found on Mars Fossilized evidence of life found in a meteorite Evidence of photosynthesis in atmosphere of extra-solar planet Signal from alien civilization (SETI) Living organisms found on a meteorite, comet or asteroid Friday, September 13, 2013 Aliens visit us What would count as evidence? Fossilized evidence of life found on Mars Fossilized evidence of life found in a meteorite Evidence of photosynthesis in atmosphere of extra-solar planet Signal from alien civilization (SETI) Living organisms found on a meteorite, comet or asteroid Friday, September 13, 2013 Aliens visit us Alien artifacts found on nearby planet What would count as evidence? Fossilized evidence of life found on Mars Fossilized evidence of life found in a meteorite Evidence of photosynthesis in atmosphere of extra-solar planet Signal from alien civilization (SETI) Living organisms found on a meteorite, comet or asteroid Friday, September 13, 2013 Aliens visit us Alien artifacts found on nearby planet Living biosystem within the Solar System Why are we searching now? Debate over life on other worlds is not new ~300 BC, Greek philosophers debated “What is the Universe made of?” [Plato, Aristotle, Thales, Anaximander ...] ** atomists Earth & heavens made of fire, earth, water, air Aristotelians Four elements confined to Earth, heavens made of ether/quintessence so long as number of atoms is each element has its own properties infinite, then natural to create other (Earth travels towards centre of worlds and life. the Universe, fire rises from it), thus the Earth is the centre and there are no other worlds. Friday, September 13, 2013 Is Earth the only “world”? Earth was long thought to be the only “world” For thousands of years, the five naked-eye planets have been known Mercury, Venus, Mars, Jupiter, and Saturn However, the nature of these objects was largely unknown until the advent of the telescope Friday, September 13, 2013 The Moon as another world In 1609, Galileo showed that the Moon is a world with mountains, valleys, craters, etc. He also speculated that the lunar maria might be oceans of water Kepler suggested that the Moon had an atmosphere and inhabitants! Bruno burned at the stake Friday, September 13, 2013 Percival Lowell’s Mars In the late 1800’s, astronomer Percival Lowell made detailed maps of Mars, identifying numerous “canals” He concluded that a Martian civilization had made these canals to transport water from the poles to cities close to the equator Friday, September 13, 2013 In the News The south pole of Mars shows that the Red Planet isnʼt always dull, dusty, and barren 1 By Sebastian Anthony on September 6, 2013 at 9:58 am What you see is an image of Mars’ south pole, captured by the European Space Agency’s Mars Express Orbiter. It is distinctly different from the dusty, barren, not-attractive landscapes that we usually associate with the Red Planet, but it’s still most definitely Mars. The huge white swirl in the middle is Mars’ permanent southern polar ice cap. It mostly consists of water ice, like the poles here on Earth. In the winter, as temperatures fall to around -153 Celsius (-243 F), carbon dioxide freezes, forming a few-meter-deep layer of dry ice. When the winter ends and sunlight strikes the dry ice, it sublimates into gas, creating massive winds that travel at 250 mph (400 kph). Friday, September 13, 2013 The Solar System’s habitable zone Friday, September 13, 2013 Places to look in the Solar System Europa Mars Titan Enceladus Friday, September 13, 2013 Are there other suns? Ancient astronomers speculated that stars were like the Sun but much further away Confirmation of this idea required measurement of stellar distances One technique for measuring distances is called stellar parallax Friday, September 13, 2013 The first detections of stellar parallax Ancient astronomers tried to detect stellar parallax with the naked eye, but were unsuccessful In 1838, Friedrich Bessel became the first to measure the parallax of another star (61-Cygni) he found a parallax of 0.3 arcseconds, corresponding to a distance of about 700,000 AU! (11 LY) later in 1838, Thomas Henderson measured a parallax of 0.76” for Alpha Centauri, placing it only 270,000 AU away (4.3 LY) Friday, September 13, 2013 Do other stars have planets? Given that the Sun is a fairly ordinary star, it seems reasonable to imagine that other stars may have planets too However, it is extremely difficult to detect a (relatively) small, faint planet very close to a bright star Despite several decades of effort, no so-called extra-solar planets had been detected as of the early 1990’s However, the first such planet (51 Pegasi) was detected in 1995 We now know of about 600 extra-solar planets! Friday, September 13, 2013 Techniques for finding extra-solar planets Friday, September 13, 2013 How many planets are there in the observable Universe? We will make a very rough estimate of the number of planets in the observable universe, and for the sake of argument, let’s be very pessimistic … assume that 1% of stars have planets (likely about 1-30%) assume that each of these stars has only 1 planet assume our Galaxy contains 100 billion stars assume the observable universe contains 100 billion galaxies likely to be considerably higher Together, this implies that the observable universe contains 100 billion * 100 billion * 1 * 0.01 planets more likely 200-400 billion 100 billion billion planets in total (1020) While this calculation is overly simplistic, there clearly is no shortage of locations in which life may exist! Friday, September 13, 2013 In the News 905 Planets around 697 Stars 154 Confirmed (Kepler & community) 3,573 Kepler Candidates and Confirmed Planets Date of last update: 2013-09-05 From the NASA Exoplanet archive at http://exoplanetarchive.ipac.caltech.edu/ Friday, September 13, 2013 Friday, September 13, 2013 Summary of why search now? New discoveries on the environments that host life and the range in types of life found on Earth suggest that life is very hardy Universe if full of stars, now learning full of planets too. Scientific/technological advances make it possible to search for habitable planets and varieties of life. Friday, September 13, 2013 Some Review Questions Chapter 1, page 14 - Could try #1, 4, 12, 17 1. Why are scientist interested in the possibility of life beyond the Earth? 4. What are extrasolar planets? In what way does their discovery make it seem more reasonable to imagine finding life elsewhere? 12. A habitable planet is (a) a planet that has oceans like Earth, (b) a planet that has life of some kind, (c) a planet that may or may not have life, but has environmental conditions under which is seems that life could arise or survive. 17. If we sent one of our current spacecraft to a nearby star (besides the Sun), the trip would take about (a) a decade, (b) 100 years, (c) 100,000 years. Friday, September 13, 2013 Astrobiology - Given that we have not yet found life beyond Earth, the search for such life is obviously very challenging - simply pointing telescopes at the sky hasn’t been successful - there is a need for good strategies in deciding how best to increase our chances of finding life elsewhere - The science of Life in the Universe is called Astrobiology - The primary goals of astrobiology include - understanding the conditions necessary for life on Earth (and possibly the conditions required for life in general) - looking for places in the universe which have these conditions - trying to actually detect extraterrestrial life Friday, September 13, 2013 Fields related to astrobiology Astronomy & Planetary Science (where to search) Physics & Chemistry (universality of the Laws) Biology (define life) Geology (define habitable) Engineering (build equipment, rockets, etc.) Mathematics, Statistics, Computer Science (modelling) Philosophy Friday, September 13, 2013 Is biology also universal? Friday, September 13, 2013 Is biology also universal? Transition from chemistry to biology occurs under many condition (extremophiles), and quickly (like early Earth) Extremophiles on Earth Friday, September 13, 2013 Text Fossil evidence of blue-green algae (cyanobacteria) were producing oxygen (contributing to our atmosphere) for at least 2.7 billion yrs. also complex molecules in the ISM. Where will we discover new life? 1. In a test tube? 2. Bacterial goo on Titan? 3. Biomarkers in an exoplanet atmosphere? 4. Calling us up on an interstellar laser phone? Chances of finding microbial life seem good, yet that predated intelligent life on Earth by 3-4 billion years. Friday, September 13, 2013 The Scientific Method How do we distinguish between good & bad science? accept, observe guess testable prediction revise, or discard flashlight example can still fail since rarely have all the facts, or the data you really want, and scientists are human (intuition, beliefs ...) not all knowledge is science Friday, September 13, 2013 Friday, September 13, 2013 Observe Occam’s Razor Verifiable Friday, September 13, 2013 “Only a Theory” What does that mean exactly? Does it mean it’s just a guess? a guess is more like a hypothesis than a theory. A theory is an idea that is based on several verifiable observations, and has been tested and confirmed by others, giving it broad support. Theory of Evolution Theory of Gravity Friday, September 13, 2013 Some More Review Questions Chapter 1, p 14 Could try #6, 14, 20 Chapter 2, p46 Could try #4, 5, 12, 14, 15 Science or Nonscience: test statements #19-28. Friday, September 13, 2013 Some Review Questions Chapter 1, p 14 Could try #6, 14, 20 6. What do we mean by “universality” of physics and chemistry? Although we do Chapter 2, p46biology is similarly universal, what evidence makes it seem not know yet whether that it might be? Could try #4, #5, #12, #14 Accordingor to current scientific test understanding, life on #19-28. Earth (a) was exceedingly 14. Science Nonscience: statements improbably, (b) arose quite soon after conditions allowed it, (c) may have been inevitable, but took billions of years to arrive. 20. Failure to find life on any other world would mean (a) the whole subject had been a waste of time, (b) we must have done something wrong, since life has to exist beyond Earth, (c) we have learned important lessons about the conditions that made life on Earth possible. Friday, September 13, 2013 Some Review Questions 12. What is the difference between a hypothesis and a theory in science? 14. What is Occam’s razor? Given an example of how it applies. 15. Why doesn’t science accept personal testimony as evidence? Explain. 4. Who first proposed the Earth is a planet orbiting the Sun, and roughly when? Why didn’t this model gain wide acceptance in ancient Greece? 5. Briefly describe and contrast the different views of the atomists and the Aristotelians on the subject of extraterrestrial life. Chapter 2, p46 Could try #4, 5, 12, 14, 15 Science or Nonscience: test statements #19-28. Friday, September 13, 2013 For Week #3 Review Chapter 3 from the textbook * Assignment 1 will be posted on Tuesday Familiarize yourself with course website Lecture materials are posted online http://www.astro.uvic.ca/~venn/a201.html Friday, September 13, 2013