Phys 214. Planets and Life

Transcription

1 Phys 214. Planets and Life Dr. Cristina Buzea Department of Physics Room (Please use PHYS214 in subject) Lecture 1. Course overview January 7th

2 Phys 214. Planets and life Textbook required Life in the Universe Second Edition 2007 By Jeffrey Bennett & Seth Shostak Other reading resources: 1. Astrobiology: A Multi-Disciplinary Approach (2004) by Jonathan Lunine 2. An Introduction to Astrobiology (2004) by Iain Gilmour, Mark A. Sephton 3. Planets and Life: The Emerging Science of Astrobiology (2007) by Woodruff T. Sullivan & John Baross Other information on the website:

3 Planets and Life - Overview What is life? Common ancestor of life on Earth The elements of life and where were they made The Cosmic calendar How big is the Universe Solar system, planets, moons, small bodies How did the solar system formed Planetary nebulae Extrasolar planets Habitability Overview of possible places for life in the Solar system

4 What is life? 1. Order 2. Reproduction 3. Grows and develops 4. Energy 5. Responds to the environment 6. Evolutionary adaptation Molecules in living organisms exhibit order. They are arranged in patterns that make cell structures. Exception: crystals. Spiral patterns in two single celled organism Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

5 What is life? 1. Order 2. Reproduction 3. Grows and develops 4. Energy 5. Responds to the environment 6. Evolutionary adaptation Living organisms reproduce or are products of reproduction. Exceptions: Viruses - incapable or reproducing on their own, need a living organism. Prions - infectious proteins, agents of mad cow disease. A single-celled organism (amoeba) dividing into two cells. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

6 What is life? 1. Order 2. Reproduction 3. Grows and develops 4. Energy 5. Responds to the environment 6. Evolutionary adaptation Living organisms grow and develop in patterns in part by heredity, traits passed to an organism from its parents. Exception: fire Nile crocodile emerging from its shell. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

7 What is life? 1. Order 2. Reproduction 3. Grows and develops 4. Energy 5. Responds to the environment 6. Evolutionary adaptation Life uses energy from the environment to create and maintain patterns of order within their cells, to reproduce and grow. Exceptions: Some organisms can survive for very long period of times in dormant state. Tube worms living near deep-sea vents obtain energy from chemical reactions made possible in part by heat released from the volcanic vent. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

8 What is life? 1. Order 2. Reproduction 3. Grows and develops 4. Energy 5. Responds to the environment 6. Evolutionary adaptation Life interacts with the surroundings and responds to environmental changes. Exceptions: human-made devices (thermostat) A jackrabbit s ears flush with blood, the blood flow adjusts automatically to help the animal maintain a constant temperature by adjusting the heat loss from the ears. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

9 What is life? 1. Order 2. Reproduction 3. Grows and develops 4. Energy 5. Responds to the environment 6. Evolutionary adaptation Life evolves as a result of the interactions between organisms and the environment, leading over time to evolutionary adaptations that make species better suited for the environment. A pygmy seahorse is camouflaged in its coral surroundings. Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley

10 Cells: the basic units of life Bacteria Amoebas Plant cells Animal cells Copyright 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley Some organisms consist of single cells, others are complex structures with trillions of cells working cooperatively, having specialized tasks.

11 Life on Earth- a common ancestor All Earth life uses only left-handed amino acids. Every living cell on Earth uses the same molecule - ATP - to store and release energy! All life on Earth passes hereditary information in the same way with DNA

12 Life on Earth- a common ancestor Based on biochemical and genetic relationships, life is classified into 3 domains. Mutations the molecular basis for evolution.

13 Life on Earth Just 4 elements - O, C, H, N - make up about 96% of the mass of typical living cells. Most of oxygen is part of WATER molecules.

14 The elements of life were made in stars! Older stars are mostly made up of H and He. The elements of life C, O, N, and heavier elements were formed by nuclear fusion in stars. Younger stars, like our Sun, contain higher proportions (up to 2%) of their mass in the form of heavier elements. Galaxies are recycling plants, reusing material expelled from dying stars to make new generations of stars and planets

15 We are star stuff! The process of stellar and galactic recycling operate throughout the Milky Way, as well as every similar galaxy in the Universe. Perhaps most other star systems have the necessary raw ingredients to build Earth-like planets & LIFE.

16 The Big Bang According to current astronomical data, the Universe is approximately 14 billion years old 14,000,000,000.

17 The Cosmic Calendar Jan 1 The Big Bang Feb The Milky Way Many generations of stars lived and died in the subsequent months, enriching the galaxy with heavier elements. The Big Bang is on Jan 1st, and the present is the stroke of midnight on Dec 31. Each month is a little more than one billion years, each day ~ 40 million years, each second more than 400 years. Sept Solar System & Earth (about 4.5 billion years ago) Sept 22 early life on Earth (more than 3.5 billion years ago) living organisms remained microscopic in size until Dec 17

18 The Cosmic Calendar Dec 17 Cambrian explosion (545 million years ago) Incredible animal diversity Dec 26 Rise of dinosaurs Dec 30 Dinosaurs extinction (65 million years ago) The death of dinosaurs allowed other species to evolve. Dec 31, 9 pm early hominids (human ancestors) 60 million years later after dinosaurs extinction

19 The Cosmic Calendar Dec 31, 11:58 pm Modern humans evolve The entire history of human civilization fits into just the last half-minute! The fact that the Universe is so much older than Earth means that could be many worlds that had plenty of time for life to arise and evolve.

20 How big is the Universe? The age of the universe poses some limitations on the portion of the universe that we can observe with telescopes, due to the limited value of the speed of light. When we look to great distances, we are also looking far back into the past. By counting the galaxies in the photo, the observable universe has an estimate of about 100 billion galaxies.

21 Number of stars in the observable universe The Universe has an estimate of 100 billion galaxies. Milky Way has an estimate of 100 billion stars. 100 billion x 100 billion = 10,000,000,000,000,000,000,000= stars Due to the incredible size of the universe, our search for extraterrestrial life will probably be limited to within our Milky Way.

22 The Solar System

23 Two major types of planets Terrestrial & Jovian. Terrestrial planets - small, made mostly of rock & metals with high densities, near the Sun Jovian planets -large, made mostly of gases and liquids with low densities, far from the Sun

24 Small bodies and dwarf planets orbiting the Sun

25 Small bodies orbiting the Sun

26 Moons Terrestrial planets have few moons. Mercury and Venus have no moons. Mars has two very small moons, probably captured asteroids. Moons are common for Jovian planets,totalling at least 150 moons together.

27 Nebular theory The formation of the solar system according to the nebular theory has four steps: 1. Contraction into a planetary nebula 2. Condensation 3. Accretion 4. Clearing

28 Planetary Nebulae

29 Extrasolar planets

30 Habitability Requirement for liquid water The habitable zone becomes increasingly smaller and closer-in for stars of lower luminosity. Galactic constraints

31 Earth Habitability climate stability 1. Moon: stability of Earth tilt

32 Earth Habitability climate stability 3. Global magnetic field - protects Earth from the energetic particles of the solar wind - impairs solar wind stripping of Earth atmosphere

33 Environmental requirements for habitability Potential liquids for life Life needs: 1) Source of molecules from which to build living cells 2) Source of energy to fuel metabolism 3) Liquid medium most likely water

34 Moon and Mercury The less likely habitable places in the Solar System - much smaller than Earth (gases escaped into space) - lost their internal heat (no plate tectonics and volcanism Mercury The closest planet to the Sun Dayside temperature 425deg C Night temperature -175 deg C Moon Mercury

35 Venus Strong greenhouse effects CO 2 more than 96% of Venus atmosphere (1% CO 2 for Earth atmosphere) - Surface temperature 470 o C - Pressure 90 times higher than at Earth surface - sulfuric acid clouds

36 Mars Polar temperatures at the winter pole 130 o C (CO 2 condenses into dry ice) At the summer pole CO 2 sublimates into gas The difference in the atmospheric pressure induces pole-pole strong winds and global dust storms The moons of Mars

37 Mars

38 Mars had once flowing water! Now the surface pressure is too low for liquid water. Mars retains enough internal heat for underground liquid water. Water on Mars

39 Water on Mars

40 Life on Mars? Martian meteorite contains microscopic structures interpreted as fossils of ancient life. Coincidental patterns: The face on Mars The Happy face on Mars!

41 Jovian planets (gas giants)

42 Moons of Jovian planets Jupiter moon Ganymede and Saturn moon Titan are larger than planet Mercury Saturn s moon Titan (2,575 km) Mercury (2,440 km radius) Ganymede (2,634 km), Callisto (2,403 km), Io (1,821 km), Europa (1,565 km)

43 Moons of Jovian planets Io (1,821 km), Europa (1,565 km), Titan (2,575 km) Many moons are planetlike in almost every way except their orbits. Some moons are geologically active, others have water, other atmosphere. Io is the most volcanically active world in the Solar System. Europa has occasionally water or ice floating on its surface. Titan has an atmosphere thicker than the Earth. Large moons around jovian planets offer a second category (after terrestrial planets) of potentially habitable worlds.

44 Jupiter s s moon Io Strong tidal stresses and heating make Io the most active body of the Solar system.

45 Jupiter s s moon Europa Europa is covered with an ice shell. Gravitational measurements and surface feature suggest a liquid water ocean under the outer layer of ice

46 Saturn s s Moon Titan Pressure 1.5 time the one of Earth Surface temperature 180 o C. Atmosphere 90% nitrogen, but almost no oxygen. Rivers and lakes of liquid methane.

47 Saturn s s Moon Enceladus Has liquid water below the surface exhibiting cryovolcanism. Geysers erupt from its surface due to pockets of liquid water at temperatures of 0 o C, despite a surface temperature of -200 o C.

48 What conditions can life survive? Extremophile organisms - that live and some can survive only in the extreme conditions. Thermophiles - deep-sea hydrothermal vents (121 o C) Endolithic Bacteria - living in rocks Xerophile - dry conditions Radioresistant - withstand massive doses of radiation Endospores - special cells allowing to become dormant Vacuum, heat, pressure, radiation, long preservation (bacteria revived and cultured after some 25 million years of encapsulation in the guts of a resin-trapped bee.)

49 Bacteria survives trip to the Moon Interior view of Surveyor 3 TV camera; surviving microorganisms cultured from the polyurethane foam insulation. Surveyor 3 landed on the moon on April 20, Culture plate from 3 camera foam sample showing Streptococcus mitis. a common harmless bacteria from the nose, mouth& throat in humans. Streptococcus mitis survived: launch space vacuum 3 years of radiation exposure deep-freeze at an average temperature of only 20 K no nutrient, water or energy source

50 Impacts and extinctions At least 5 major mass extinctions, including the K-T (cretaceous-tertiary boundary) occurred on Earth. The rate of extinction for plants and animals over the past 500 millions years.

51 Impacts 25 million particles each day Add a total of 20,000-40,000 tons per year Many asteroids crosses the Earth s orbit. 50 m meteor? The question is not whether but WHEN a future impact occur.

52 Impacts and extinctions

53 Phys 214. Planets and Life Dr. Cristina Buzea Department of Physics Room (Please use PHYS214 in subject) Wednesday - Questionnaire