Terrestrial Planet Formation
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Geological Timeline
Geological Timeline In this pack you will find information and activities to help your class grasp the concept of geological time, just how old our planet is, and just how young we, as a species, are. Planet Earth is 4,600 million years old. We all know this is very old indeed, but big numbers like this are always difficult to get your head around. The activities in this pack will help your class to make visual representations of the age of the Earth to help them get to grips with the timescales involved. Important EvEnts In thE Earth’s hIstory 4600 mya (million years ago) – Planet Earth formed. Dust left over from the birth of the sun clumped together to form planet Earth. The other planets in our solar system were also formed in this way at about the same time. 4500 mya – Earth’s core and crust formed. Dense metals sank to the centre of the Earth and formed the core, while the outside layer cooled and solidified to form the Earth’s crust. 4400 mya – The Earth’s first oceans formed. Water vapour was released into the Earth’s atmosphere by volcanism. It then cooled, fell back down as rain, and formed the Earth’s first oceans. Some water may also have been brought to Earth by comets and asteroids. 3850 mya – The first life appeared on Earth. It was very simple single-celled organisms. Exactly how life first arose is a mystery. 1500 mya – Oxygen began to accumulate in the Earth’s atmosphere. Oxygen is made by cyanobacteria (blue-green algae) as a product of photosynthesis. -
The Multifaceted Planetesimal Formation Process
The Multifaceted Planetesimal Formation Process Anders Johansen Lund University Jurgen¨ Blum Technische Universitat¨ Braunschweig Hidekazu Tanaka Hokkaido University Chris Ormel University of California, Berkeley Martin Bizzarro Copenhagen University Hans Rickman Uppsala University Polish Academy of Sciences Space Research Center, Warsaw Accumulation of dust and ice particles into planetesimals is an important step in the planet formation process. Planetesimals are the seeds of both terrestrial planets and the solid cores of gas and ice giants forming by core accretion. Left-over planetesimals in the form of asteroids, trans-Neptunian objects and comets provide a unique record of the physical conditions in the solar nebula. Debris from planetesimal collisions around other stars signposts that the planetesimal formation process, and hence planet formation, is ubiquitous in the Galaxy. The planetesimal formation stage extends from micrometer-sized dust and ice to bodies which can undergo run-away accretion. The latter ranges in size from 1 km to 1000 km, dependent on the planetesimal eccentricity excited by turbulent gas density fluctuations. Particles face many barriers during this growth, arising mainly from inefficient sticking, fragmentation and radial drift. Two promising growth pathways are mass transfer, where small aggregates transfer up to 50% of their mass in high-speed collisions with much larger targets, and fluffy growth, where aggregate cross sections and sticking probabilities are enhanced by a low internal density. A wide range of particle sizes, from mm to 10 m, concentrate in the turbulent gas flow. Overdense filaments fragment gravitationally into bound particle clumps, with most mass entering planetesimals of contracted radii from 100 to 500 km, depending on local disc properties. -
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Formation of the Solar System (Chapter 8)
Formation of the Solar System (Chapter 8) Based on Chapter 8 • This material will be useful for understanding Chapters 9, 10, 11, 12, 13, and 14 on “Formation of the solar system”, “Planetary geology”, “Planetary atmospheres”, “Jovian planet systems”, “Remnants of ice and rock”, “Extrasolar planets” and “The Sun: Our Star” • Chapters 2, 3, 4, and 7 on “The orbits of the planets”, “Why does Earth go around the Sun?”, “Momentum, energy, and matter”, and “Our planetary system” will be useful for understanding this chapter Goals for Learning • Where did the solar system come from? • How did planetesimals form? • How did planets form? Patterns in the Solar System • Patterns of motion (orbits and rotations) • Two types of planets: Small, rocky inner planets and large, gas outer planets • Many small asteroids and comets whose orbits and compositions are similar • Exceptions to these patterns, such as Earth’s large moon and Uranus’s sideways tilt Help from Other Stars • Use observations of the formation of other stars to improve our theory for the formation of our solar system • Use this theory to make predictions about the formation of other planetary systems Nebular Theory of Solar System Formation • A cloud of gas, the “solar nebula”, collapses inwards under its own weight • Cloud heats up, spins faster, gets flatter (disk) as a central star forms • Gas cools and some materials condense as solid particles that collide, stick together, and grow larger Where does a cloud of gas come from? • Big Bang -> Hydrogen and Helium • First stars use this -
The Subsurface Habitability of Small, Icy Exomoons J
A&A 636, A50 (2020) Astronomy https://doi.org/10.1051/0004-6361/201937035 & © ESO 2020 Astrophysics The subsurface habitability of small, icy exomoons J. N. K. Y. Tjoa1,?, M. Mueller1,2,3, and F. F. S. van der Tak1,2 1 Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands e-mail: [email protected] 2 SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands 3 Leiden Observatory, Leiden University, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands Received 1 November 2019 / Accepted 8 March 2020 ABSTRACT Context. Assuming our Solar System as typical, exomoons may outnumber exoplanets. If their habitability fraction is similar, they would thus constitute the largest portion of habitable real estate in the Universe. Icy moons in our Solar System, such as Europa and Enceladus, have already been shown to possess liquid water, a prerequisite for life on Earth. Aims. We intend to investigate under what thermal and orbital circumstances small, icy moons may sustain subsurface oceans and thus be “subsurface habitable”. We pay specific attention to tidal heating, which may keep a moon liquid far beyond the conservative habitable zone. Methods. We made use of a phenomenological approach to tidal heating. We computed the orbit averaged flux from both stellar and planetary (both thermal and reflected stellar) illumination. We then calculated subsurface temperatures depending on illumination and thermal conduction to the surface through the ice shell and an insulating layer of regolith. We adopted a conduction only model, ignoring volcanism and ice shell convection as an outlet for internal heat. -
Mars Mars Is the Fourth Terrestrial Planet. It Is Smaller in Size Than
Mars Mars is the fourth terrestrial planet. It is smaller in size than Earth and Venus, but larger than Mercury. Of the planets, Mars is the most hospitable to visiting humans, as it has an atmosphere, though it has no oxygen and is very thin. In the early days of the solar system, Mars has had liquid water on its surface, which is proved by the existence of various minerals that require liquid water to form. The current atmosphere of Mars is too thin and cold for liquid water to exist for long periods of times. Still, there is evidence of terrain shaped by flowing liquids, which are probably temporary flows or floods caused by the melting of ice in the ground. Mars has seasons like the Earth, and ice caps at the poles that grow and shrink over the course of the year. They consist of water ice and CO2 ice, the latter varying more with the seasons. One year on Mars is a bit less than two Earth years. Mars has two moons, Phobos and Deimos. They are very small compared to Mars, and are likely to be asteroids captured by Mars's gravity in the distant past. Giant planets and their moons The outer four planets of the solar system are known as the giant planets, because of their large size (compared to the terrestrial planets). The giant planets of our solar system can be further divided into two categories: gas giants (Jupiter and Saturn) and ice giants (Uranus and Neptune). The gas giants consist mainly of hydrogen (up to 90%) and helium, while the ice giants are mostly "ices" such as water and ammonia, with only some 20% of hydrogen. -
Planets of the Solar System
Chapter Planets of the 27 Solar System Chapter OutlineOutline 1 ● Formation of the Solar System The Nebular Hypothesis Formation of the Planets Formation of Solid Earth Formation of Earth’s Atmosphere Formation of Earth’s Oceans 2 ● Models of the Solar System Early Models Kepler’s Laws Newton’s Explanation of Kepler’s Laws 3 ● The Inner Planets Mercury Venus Earth Mars 4 ● The Outer Planets Gas Giants Jupiter Saturn Uranus Neptune Objects Beyond Neptune Why It Matters Exoplanets UnderstandingU d t di theth formationf ti and the characteristics of our solar system and its planets can help scientists plan missions to study planets and solar systems around other stars in the universe. 746 Chapter 27 hhq10sena_psscho.inddq10sena_psscho.indd 774646 PDF 88/15/08/15/08 88:43:46:43:46 AAMM Inquiry Lab Planetary Distances 20 min Turn to Appendix E and find the table entitled Question to Get You Started “Solar System Data.” Use the data from the How would the distance of a planet from the sun “semimajor axis” row of planetary distances to affect the time it takes for the planet to complete devise an appropriate scale to model the distances one orbit? between planets. Then find an indoor or outdoor space that will accommodate the farthest distance. Mark some index cards with the name of each planet, use a measuring tape to measure the distances according to your scale, and place each index card at its correct location. 747 hhq10sena_psscho.inddq10sena_psscho.indd 774747 22/26/09/26/09 111:42:301:42:30 AAMM These reading tools will help you learn the material in this chapter. -
Outer Planets: the Ice Giants
Outer Planets: The Ice Giants A. P. Ingersoll, H. B. Hammel, T. R. Spilker, R. E. Young Exploring Uranus and Neptune satisfies NASA’s objectives, “investigation of the Earth, Moon, Mars and beyond with emphasis on understanding the history of the solar system” and “conduct robotic exploration across the solar system for scientific purposes.” The giant planet story is the story of the solar system (*). Earth and the other small objects are leftovers from the feast of giant planet formation. As they formed, the giant planets may have migrated inward or outward, ejecting some objects from the solar system and swallowing others. The giant planets most likely delivered water and other volatiles, in the form of icy planetesimals, to the inner solar system from the region around Neptune. The “gas giants” Jupiter and Saturn are mostly hydrogen and helium. These planets must have swallowed a portion of the solar nebula intact. The “ice giants” Uranus and Neptune are made primarily of heavier stuff, probably the next most abundant elements in the Sun – oxygen, carbon, nitrogen, and sulfur. For each giant planet the core is the “seed” around which it accreted nebular gas. The ice giants may be more seed than gas. Giant planets are laboratories in which to test our theories about geophysics, plasma physics, meteorology, and even oceanography in a larger context. Their bottomless atmospheres, with 1000 mph winds and 100 year-old storms, teach us about weather on Earth. The giant planets’ enormous magnetic fields and intense radiation belts test our theories of terrestrial and solar electromagnetic phenomena. -
The Solar System Cause Impact Craters
ASTRONOMY 161 Introduction to Solar System Astronomy Class 12 Solar System Survey Monday, February 5 Key Concepts (1) The terrestrial planets are made primarily of rock and metal. (2) The Jovian planets are made primarily of hydrogen and helium. (3) Moons (a.k.a. satellites) orbit the planets; some moons are large. (4) Asteroids, meteoroids, comets, and Kuiper Belt objects orbit the Sun. (5) Collision between objects in the Solar System cause impact craters. Family portrait of the Solar System: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, (Eris, Ceres, Pluto): My Very Excellent Mother Just Served Us Nine (Extra Cheese Pizzas). The Solar System: List of Ingredients Ingredient Percent of total mass Sun 99.8% Jupiter 0.1% other planets 0.05% everything else 0.05% The Sun dominates the Solar System Jupiter dominates the planets Object Mass Object Mass 1) Sun 330,000 2) Jupiter 320 10) Ganymede 0.025 3) Saturn 95 11) Titan 0.023 4) Neptune 17 12) Callisto 0.018 5) Uranus 15 13) Io 0.015 6) Earth 1.0 14) Moon 0.012 7) Venus 0.82 15) Europa 0.008 8) Mars 0.11 16) Triton 0.004 9) Mercury 0.055 17) Pluto 0.002 A few words about the Sun. The Sun is a large sphere of gas (mostly H, He – hydrogen and helium). The Sun shines because it is hot (T = 5,800 K). The Sun remains hot because it is powered by fusion of hydrogen to helium (H-bomb). (1) The terrestrial planets are made primarily of rock and metal. -
Kuchner, M. & Seager, S., Extrasolar Carbon Planets, Arxiv:Astro-Ph
Extrasolar Carbon Planets Marc J. Kuchner1 Princeton University Department of Astrophysical Sciences Peyton Hall, Princeton, NJ 08544 S. Seager Carnegie Institution of Washington, 5241 Broad Branch Rd. NW, Washington DC 20015 [email protected] ABSTRACT We suggest that some extrasolar planets . 60 ML will form substantially from silicon carbide and other carbon compounds. Pulsar planets and low-mass white dwarf planets are especially good candidate members of this new class of planets, but these objects could also conceivably form around stars like the Sun. This planet-formation pathway requires only a factor of two local enhancement of the protoplanetary disk’s C/O ratio above solar, a condition that pileups of carbonaceous grains may create in ordinary protoplanetary disks. Hot, Neptune- mass carbon planets should show a significant paucity of water vapor in their spectra compared to hot planets with solar abundances. Cooler, less massive carbon planets may show hydrocarbon-rich spectra and tar-covered surfaces. The high sublimation temperatures of diamond, SiC, and other carbon compounds could protect these planets from carbon depletion at high temperatures. arXiv:astro-ph/0504214v2 2 May 2005 Subject headings: astrobiology — planets and satellites, individual (Mercury, Jupiter) — planetary systems: formation — pulsars, individual (PSR 1257+12) — white dwarfs 1. INTRODUCTION The recent discoveries of Neptune-mass extrasolar planets by the radial velocity method (Santos et al. 2004; McArthur et al. 2004; Butler et al. 2004) and the rapid development 1Hubble Fellow –2– of new technologies to study the compositions of low-mass extrasolar planets (see, e.g., the review by Kuchner & Spergel 2003) have compelled several authors to consider planets with chemistries unlike those found in the solar system (Stevenson 2004) such as water planets (Kuchner 2003; Leger et al. -
Comparative Habitability of Transiting Exoplanets
Draft version October 1, 2015 A Preprint typeset using LTEX style emulateapj v. 04/17/13 COMPARATIVE HABITABILITY OF TRANSITING EXOPLANETS Rory Barnes1,2,3, Victoria S. Meadows1,2, Nicole Evans1,2 Draft version October 1, 2015 ABSTRACT Exoplanet habitability is traditionally assessed by comparing a planet’s semi-major axis to the location of its host star’s “habitable zone,” the shell around a star for which Earth-like planets can possess liquid surface water. The Kepler space telescope has discovered numerous planet candidates near the habitable zone, and many more are expected from missions such as K2, TESS and PLATO. These candidates often require significant follow-up observations for validation, so prioritizing planets for habitability from transit data has become an important aspect of the search for life in the universe. We propose a method to compare transiting planets for their potential to support life based on transit data, stellar properties and previously reported limits on planetary emitted flux. For a planet in radiative equilibrium, the emitted flux increases with eccentricity, but decreases with albedo. As these parameters are often unconstrained, there is an “eccentricity-albedo degeneracy” for the habitability of transiting exoplanets. Our method mitigates this degeneracy, includes a penalty for large-radius planets, uses terrestrial mass-radius relationships, and, when available, constraints on eccentricity to compute a number we call the “habitability index for transiting exoplanets” that represents the relative probability that an exoplanet could support liquid surface water. We calculate it for Kepler Objects of Interest and find that planets that receive between 60–90% of the Earth’s incident radiation, assuming circular orbits, are most likely to be habitable. -
1 Towards a Molecular Inventory of Protostellar
TOWARDS A MOLECULAR INVENTORY OF PROTOSTELLAR DISCS Glenn J White (1), Mark A. Thompson (1), C.V. Malcolm Fridlund (2), Monica Huldtgren White (3) (1) University of Kent, UK, [email protected] (2) ESTEC, NL, (3) Stockholm Observatory, Sweden Abstract solid, atomic and ionised material in the pre- planetary environment. The chemical environment in circumstellar discs is a unique diagnostic of the thermal, physical and Details of the survey chemical environment. In this paper we examine the structure of star formation regions giving rise to low We are carrying out a survey of nearby star mass stars, and the chemical environment inside formation regions to them, and the circumstellar discs around the developing stars. • Search in the optical/IR region for triggered/induced solar-type star formation. Introduction We measure the boundary conditions, such as external pressure of ionised gas that Life develops from a sequence of organic chemical triggering the star formation using radio processes that develop sufficient complexity to lead observations, and from molecular line to mutating and self-replicating sentient organisms. tracers, estimate the internal pressure in the Cellular structures, formed following selective molecular gas. evolution along the Tree of Life, emerged from the • Characterise the properties of the central reactions amongst these simple organic compounds, protostellar core and protostellar discs at which were derived from cosmically abundant submm, mid and near-IR wavelengths, by elements and molecules that are abundant in space. measuring the spectral energy distributions Much of this early chemical inventory was delivered and the atomic and molecular inventory of a to the surfaces of planets, including the Earth, during sample of circumstellar discs the early phase of massive cometary bombardment of • Measure the chemical inventory of gas- the earth - e.g.