DOCSLIB.ORG

Dawn Mission Reveals Dwarf Planet Else in the Solar System

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Dawn Mission Reveals Dwarf Planet Else in the Solar System Fossil Planet With lowlands, highlands, weird white spots, and even a pyramid, the largest object in the asteroid belt is unlike anything Dawn mission reveals dwarf planet else in the solar system. by Eric Betz IN THE BEGINNING, with a mass equivalent to just 4 percent of that contained in Earth’s Moon. What was OUR SOLAR SYSTEM left is what we still see today. One-third of that mass is held by a single WAS A VIOLENT PLACE. world, Ceres. At 590 miles (950 kilometers) NASA’s Dawn mission Radiation from neighboring massive across, it’s our solar system’s largest asteroid captured Ceres from stars bombarded our small part of a large and the only dwarf planet this side of Pluto. Ceres 8,400 miles (13,600 kilometers) away in molecular cloud — a many light-years-wide It’s also a relic of our violent origins. May as it spiraled body of gas and dust resembling the Eagle This icy body is the current focus of into ever-lower Nebula’s “Pillars of Creation” — as the NASA’s Dawn mission — a small spacecraft orbits. ALL IMAGES: NASA/ JPL-CALTECH/UCLA/MPS/DLR/IDA, whole expanse coalesced like a figure skater that’s powered its way across the inner solar EXCEPT WHERE NOTED pulling her limbs in tight for a spin. system since 2007 using unconventional Some 99.8 percent of the mass drew to ion propulsion. The engine allowed Dawn the center, forming our Sun. And out of the to become the first mission to ever orbit firmament 4.6 billion years ago, tiny bits of two extraterrestrial bodies. Astronomers dust, like particles in a smoke cloud, stuck spent 14 months studying the asteroid together to create ever-larger clumps. Vesta before embarking for Ceres in 2012. Grains grew into pebbles; pebbles “Ceres, and Vesta before it, are intact formed planetesimals. protoplanets — bodies that were growing But this process was still in its early days to planethood when their growth was when a supernova blast rang out, seeding stopped by external forces,” says Dawn radioactive elements across the still-forming Principal Investigator Chris Russell of the inner realm of planets, which trapped heat University of California, Los Angeles. inside any worlds already gathered together. “They have a record of the earliest days of Meanwhile, something pivotal took the solar system. They were there and expe- place between 2 and 3 astronomical units rienced it and have evolved little. ... We are from our young Sun (1 AU is the average returning to the scene of the crime to inter- Earth-Sun distance) in the present-day view the witnesses.” asteroid belt. As Jupiter, the largest planet, Now, these fossil planets are teaching took shape, it had catastrophic effects on a astronomers what our solar neighborhood group of planetesimals. was like when Earth saw its first sunrise. The gaseous giant perturbed the region Solar system models use bodies like and stopped its mass from ever coalescing Vesta and Ceres as building blocks for ter- to become a terrestrial planet. restrial planets. Ceres is likely similar to the Jupiter may have flung much of the planetesimals that brought Earth its oceans. mass to the solar system’s outer reaches, And our planet’s iron core might have leaving what’s now called the asteroid belt formed from a number of Vesta-like worlds. “Almost everything we see on Ceres was Eric Betz is an associate editor of Astronomy. unknown before we arrived,” Russell says. He’s on Twitter: @ericbetz. “Ceres had kept its secrets well.” © 2016 Kalmbach Publishing Co. This material may not be reproduced in any 44 ASTRONOMY • JANUARYform without 2016 permission from the publisher. www.Astronomy.com White spots explained At first, scientists speculated the white spots could be excavated water ice, salt, or clay. And determining which they were turned out to be tougher than expected. “We didn’t like the ice explanation, but we felt we were being driven to that expla- nation by how bright the surface was,” Russell says. At nearly 3 AU from the Sun, Ceres, unlike distant Pluto, is bombarded by sun- light, and that would cause any surface ice to quickly turn to gas via sublimation. But then as Dawn flew over the white Ceres’ most intriguing features are the dwarf planet’s mysterious white spots, which astrono- spots in its survey orbit, the spectra instru- mers now say are salt deposits. ment shut itself down. When that happens, all the data are dumped. Astronomers Ceres’ lone mountain vaults some 4 miles (6 kilo- would have to wait to find out. meters) above the surrounding surface, making “The question is whether Ceres is active Irrefutable evidence finally came as it taller than even Denali, North America’s high- like Pluto, or whether Ceres was once more Dawn descended into its science orbit and est summit. Occator Crater spans 50 miles (80 kilometers) from rim to rim and is home to Ceres’ brightest spots. active like Pluto and it lost its surface vola- sent back better images. Dawn’s photos After months of intense speculation, Dawn scientists now believe they understand what causes them. tiles because it’s closer to the Sun,” says showed that the white spots are actually far Dawn mission scientist Vishnu Reddy of bigger than expected. That meant salt, regions together like an aquifer,” Russell the Planetary Science Institute in Tucson. which reflects less light than water ice, was says. “Maybe you can’t get from one place to An active protoplanet? In fact, the resemblance between Ceres Reddy and a team of astronomers think the only likely solution. And when NASA another, but the chemistry is the same.” As Dawn neared Ceres in early 2015, and newly revealed Pluto is so strong that they may already have found some clues. In finally got spectral data, it confirmed salt’s He thinks spectra will eventually show something truly unexpected emerged in Dawn team members have been left scram- early 2014, the European Space Agency chemical fingerprints. The white material that the salt covering Ceres’ mountain is the its imagery — two weird white spots. The bling for answers. pointed its Herschel Space Observatory at has now been detected covering peaks and same stuff that covers the craters. bright areas, which shine almost like a cat’s Michael Bland is on the Dawn team and Ceres and caught water vapor streaming crater rims across the dwarf planet. The salt forms in the world’s interior, eyes when seen from afar, have remained an astronomer at the United States from two small regions. Reddy says that the “Definitely [the white spots] can’t be ice,” and depending on the acidity of water below the fossil planet’s most intriguing features. Geological Survey (USGS). He says he areas are now known to coincide with the Russell says. “We’ve got enough spectra the surface, models indicate that this salt Astronomers believe that unraveling their expected Ceres to have a smoother surface white spots. from them to see they don’t have the absorp- could be one most earthlings are familiar mystery could explain what’s happened to with fewer pristine craters. Instead, that Dust rains onto everything in the aster- tion bands that we would expect ice to have.” with: magnesium sulfate, also known as Collisions are common in the asteroid belt, and Ceres since its growth was stunted all those description better fits Pluto. oid belt, turning surfaces a darker shade of Epsom salt. The popular bath salt is found Ceres has the craters to prove it. What’s most sur- billions of years ago. “Pluto looks a lot like what I expected gray. So, the white spots are younger than Extraterrestrial bath salts? across our planet and on other worlds too. prising is that the dwarf planet has remained so Vesta’s relative abundance of radio- Ceres to look like, and Ceres looks like how the rest of the surface. But just how young That also better aligns with what astrono- intact throughout our solar system’s history. active aluminum-26 (Al-26), known from I expected Pluto to look,” Bland says. “It’s is anyone’s guess. mers are seeing elsewhere on the Texas-sized The great pyramid of Ceres meteorites commonly found on Earth and like someone switched them on us.” Astronomers don’t know how much dust body. While scientists believe Ceres’ interior Salt isn’t the only revelation at Ceres. The traced back to the asteroid, tells astrono- And while high-resolution data has only falls onto the world. If the white spots are is packed with water ice and even possibly dwarf planet hosts a lone mountain that And the peak is made from the same mers that the asteroid formed in the solar just begun streaming home from the Dawn truly young, it’s possible that the Herschel a liquid ocean, the surface is dry. However, vaults more than 21,000 feet (6,400 meters) material as the rest of the dwarf planet — system’s earliest days. Vesta was blasted by spacecraft, astronomers must now try to telescope caught some sort of icy eruption that doesn’t mean there’s never been ice at off the surface, a height greater than even not some alien substance. the supernova shock wave, and the radio- explain how oddball Ceres has evolved. from Ceres’ subsurface. the surface or even in the white spots. Denali, North America’s highest peak. The next best idea was that the moun- active isotopes generated heat in the plan- “Water vapor could temporarily freeze “The team is totally baffled by the tain is actually a volcano.
Load more

Recommended publications
  • Exomoon Habitability Constrained by Illumination and Tidal Heating
    submitted to Astrobiology: April 6, 2012 accepted by Astrobiology: September 8, 2012 published in Astrobiology: January 24, 2013 this updated draft: October 30, 2013 doi:10.1089/ast.2012.0859 Exomoon habitability constrained by illumination and tidal heating René HellerI , Rory BarnesII,III I Leibniz-Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany, [email protected] II Astronomy Department, University of Washington, Box 951580, Seattle, WA 98195, [email protected] III NASA Astrobiology Institute – Virtual Planetary Laboratory Lead Team, USA Abstract The detection of moons orbiting extrasolar planets (“exomoons”) has now become feasible. Once they are discovered in the circumstellar habitable zone, questions about their habitability will emerge. Exomoons are likely to be tidally locked to their planet and hence experience days much shorter than their orbital period around the star and have seasons, all of which works in favor of habitability. These satellites can receive more illumination per area than their host planets, as the planet reflects stellar light and emits thermal photons. On the contrary, eclipses can significantly alter local climates on exomoons by reducing stellar illumination. In addition to radiative heating, tidal heating can be very large on exomoons, possibly even large enough for sterilization. We identify combinations of physical and orbital parameters for which radiative and tidal heating are strong enough to trigger a runaway greenhouse. By analogy with the circumstellar habitable zone, these constraints define a circumplanetary “habitable edge”. We apply our model to hypothetical moons around the recently discovered exoplanet Kepler-22b and the giant planet candidate KOI211.01 and describe, for the first time, the orbits of habitable exomoons.
    [Show full text]
  • OCEANOGRAPHY an Additional 1.4 Tg of Carbon Per Year Atmospheric CO2 Concentrations from Ice Loss and Ocean Life Over This Period
    research highlights OCEANOGRAPHY an additional 1.4 Tg of carbon per year atmospheric CO2 concentrations from Ice loss and ocean life over this period. A rise in phytoplankton Antarctic ice cores. They found that Glob. Biogeochem. Cycles http://doi.org/p27 (2013) productivity in the surface waters of the two younger periods of enhanced the Laptev, East Siberian, Chukchi and mixing coincided with a steep increase in Beaufort seas was responsible for the atmospheric CO2 levels, and the oldest with increase in carbon uptake. In contrast, net a small, temporary rise. carbon uptake declined in the Barents Sea, The team concluded that enhanced where a warming-induced outgassing of vertical mixing in these intervals brought surface-water CO2 countered the rise in CO2-rich waters from the deep ocean to the primary production. surface, allowing CO2 to escape from these The findings suggest that the continued upwelled waters to the atmosphere. AN decline of Arctic sea ice cover could be accompanied by a rise in the oceanic uptake PLANETARY SCIENCE of carbon dioxide, although uncertainties Weighing Phobos in the response of physical, chemical and Icarus http://doi.org/p26 (2013) biological processes to sea ice loss hinder reliable predictions at this stage. AA PALAEOCEANOGRAPHY Southern upwelling Nature Commun. 4, 2758 (2013). At the end of the last glacial period about 20,000 years ago, atmospheric CO2 concentrations rose in several steps. Radiocarbon measurements from a marine sediment core suggest that the upwelling of © FRANS LANTING STUDIO / ALAMY © FRANS LANTING STUDIO carbon-rich waters in the Southern Ocean contributed to the CO2 rise.
    [Show full text]
  • THE EARTH's GRAVITY OUTLINE the Earth's Gravitational Field
    GEOPHYSICS (08/430/0012) THE EARTH'S GRAVITY OUTLINE The Earth's gravitational field 2 Newton's law of gravitation: Fgrav = GMm=r ; Gravitational field = gravitational acceleration g; gravitational potential, equipotential surfaces. g for a non–rotating spherically symmetric Earth; Effects of rotation and ellipticity – variation with latitude, the reference ellipsoid and International Gravity Formula; Effects of elevation and topography, intervening rock, density inhomogeneities, tides. The geoid: equipotential mean–sea–level surface on which g = IGF value. Gravity surveys Measurement: gravity units, gravimeters, survey procedures; the geoid; satellite altimetry. Gravity corrections – latitude, elevation, Bouguer, terrain, drift; Interpretation of gravity anomalies: regional–residual separation; regional variations and deep (crust, mantle) structure; local variations and shallow density anomalies; Examples of Bouguer gravity anomalies. Isostasy Mechanism: level of compensation; Pratt and Airy models; mountain roots; Isostasy and free–air gravity, examples of isostatic balance and isostatic anomalies. Background reading: Fowler §5.1–5.6; Lowrie §2.2–2.6; Kearey & Vine §2.11. GEOPHYSICS (08/430/0012) THE EARTH'S GRAVITY FIELD Newton's law of gravitation is: ¯ GMm F = r2 11 2 2 1 3 2 where the Gravitational Constant G = 6:673 10− Nm kg− (kg− m s− ). ¢ The field strength of the Earth's gravitational field is defined as the gravitational force acting on unit mass. From Newton's third¯ law of mechanics, F = ma, it follows that gravitational force per unit mass = gravitational acceleration g. g is approximately 9:8m/s2 at the surface of the Earth. A related concept is gravitational potential: the gravitational potential V at a point P is the work done against gravity in ¯ P bringing unit mass from infinity to P.
    [Show full text]
  • 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.
    [Show full text]
  • 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.
    [Show full text]
  • Spectra As Windows Into Exoplanet Atmospheres
    SPECIAL FEATURE: PERSPECTIVE PERSPECTIVE SPECIAL FEATURE: Spectra as windows into exoplanet atmospheres Adam S. Burrows1 Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 Edited by Neta A. Bahcall, Princeton University, Princeton, NJ, and approved December 2, 2013 (received for review April 11, 2013) Understanding a planet’s atmosphere is a necessary condition for understanding not only the planet itself, but also its formation, structure, evolution, and habitability. This requirement puts a premium on obtaining spectra and developing credible interpretative tools with which to retrieve vital planetary information. However, for exoplanets, these twin goals are far from being realized. In this paper, I provide a personal perspective on exoplanet theory and remote sensing via photometry and low-resolution spectroscopy. Although not a review in any sense, this paper highlights the limitations in our knowledge of compositions, thermal profiles, and the effects of stellar irradiation, focusing on, but not restricted to, transiting giant planets. I suggest that the true function of the recent past of exoplanet atmospheric research has been not to constrain planet properties for all time, but to train a new generation of scientists who, by rapid trial and error, are fast establishing a solid future foundation for a robust science of exoplanets. planetary science | characterization The study of exoplanets has increased expo- by no means commensurate with the effort exoplanetology, and this expectation is in part nentially since 1995, a trend that in the short expended. true. The solar system has been a great, per- term shows no signs of abating. Astronomers An important aspect of exoplanets that haps necessary, teacher.
    [Show full text]
  • Relevance of Tidal Heating on Large Tnos
    Relevance of Tidal Heating on Large TNOs a, b a,c d a Prabal Saxena ∗, Joe Renaud , Wade G. Henning , Martin Jutzi , Terry Hurford aNASA/Goddard Space Flight Center, 8800 Greenbelt Rd, Greenbelt, MD 20771, USA bDepartment of Physics & Astronomy, George Mason University 4400 University Drive, Fairfax, VA 22030, USA cDepartment of Astronomy, University of Maryland Physical Sciences Complex, College Park, MD 20742 dPhysics Institute: Space Research & Planetary Sciences, University of Bern Sidlerstrasse 5, 3012 Bern, Switzerland Abstract We examine the relevance of tidal heating for large Trans-Neptunian Objects, with a focus on its potential to melt and maintain layers of subsurface liquid water. Depending on their past orbital evolution, tidal heating may be an important part of the heat budget for a number of discovered and hypothetical TNO systems and may enable formation of, and increased access to, subsurface liquid water. Tidal heating induced by the process of despinning is found to be particularly able to compete with heating due to radionuclide decay in a number of different scenarios. In cases where radiogenic heating alone may establish subsurface conditions for liquid water, we focus on the extent by which tidal activity lifts the depth of such conditions closer to the surface. While it is common for strong tidal heating and long lived tides to be mutually exclusive, we find this is not always the case, and highlight when these two traits occur together. Keywords: TNO, Tidal Heating, Pluto, Subsurface Water, Cryovolcanism 1. Introduction arXiv:1706.04682v1 [astro-ph.EP] 14 Jun 2017 It appears highly likely that numerous bodies outside the Earth possess global subsurface oceans - these include Europa, Ganymede, Callisto, Enceladus (Pappalardo et al., 1999; Khu- rana et al., 1998; Thomas et al., 2016; Saur et al., 2015), and now Pluto (Nimmo et al., 2016).
    [Show full text]
  • Ometries Driven by Tidal Heating in the Ice Versus the Core
    Differing Enceladean ocean circulation and ice shell ge- ometries driven by tidal heating in the ice versus the core Wanying Kang1∗, Suyash Bire1, Jean-Michel Campin1, Christophe Sotin2, Christopher German3, Andreas Thurnherr4 and John Marshall1 1Earth, Atmospheric and Planetary Science Department, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 2Jet Propulsion Laboratory, Caltech, 4800 Oak Grove Drive, Pasadena, CA, 91109, USA 3Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA 4Division of Ocean and Climate Physics, Lamont-Doherty Earth Observatory, Palisades, New York 10964, USA Beneath the icy shell encasing Enceladus, a small icy moon of Saturn, a global ocean of liquid water ejects geyser-like plumes into space through fissures in the ice, making it an attractive place to investigate habitability and to search for extraterrestrial life. The existence of an ocean on Enceladus has been attributed to the heat generated in dissipative processes associated with deformation by tidal forcing. However, it remains unclear whether that heat is mostly generated in its ice shell or silicate core. Answering this question is crucial if we are to unravel patterns of ocean circulation and tracer transport that will impact both the habitability of Enceladus and our ability to interpret putative evidence of any habitability and/or life. Using a nonhydrostatic ocean circulation model, we describe and contrast the differing circulation patterns and implied ice shell geometries to be expected as a result of 1 heating in the ice shell above and heating in the core below Enceladus’ ocean layer. If heat is generated primarily in the silicate core we would predict enhanced melting rates at the equator.
    [Show full text]
  • 1 on the Origin of the Pluto System Robin M. Canup Southwest Research Institute Kaitlin M. Kratter University of Arizona Marc Ne
    On the Origin of the Pluto System Robin M. Canup Southwest Research Institute Kaitlin M. Kratter University of Arizona Marc Neveu NASA Goddard Space Flight Center / University of Maryland The goal of this chapter is to review hypotheses for the origin of the Pluto system in light of observational constraints that have been considerably refined over the 85-year interval between the discovery of Pluto and its exploration by spacecraft. We focus on the giant impact hypothesis currently understood as the likeliest origin for the Pluto-Charon binary, and devote particular attention to new models of planet formation and migration in the outer Solar System. We discuss the origins conundrum posed by the system’s four small moons. We also elaborate on implications of these scenarios for the dynamical environment of the early transneptunian disk, the likelihood of finding a Pluto collisional family, and the origin of other binary systems in the Kuiper belt. Finally, we highlight outstanding open issues regarding the origin of the Pluto system and suggest areas of future progress. 1. INTRODUCTION For six decades following its discovery, Pluto was the only known Sun-orbiting world in the dynamical vicinity of Neptune. An early origin concept postulated that Neptune originally had two large moons – Pluto and Neptune’s current moon, Triton – and that a dynamical event had both reversed the sense of Triton’s orbit relative to Neptune’s rotation and ejected Pluto onto its current heliocentric orbit (Lyttleton, 1936). This scenario remained in contention following the discovery of Charon, as it was then established that Pluto’s mass was similar to that of a large giant planet moon (Christy and Harrington, 1978).
    [Show full text]
  • A 4565 Myr Old Andesite from an Extinct Chondritic Protoplanet
    A 4565 Myr old andesite from an extinct chondritic protoplanet. Jean-Alix Barrata*, Marc Chaussidonb, Akira Yamaguchic, Pierre Beckd, Johan Villeneuvee, David J. Byrnee, Michael W. Broadleye, Bernard Martye a Univ Brest, Institut Universitaire Européen de la Mer (IUEM), UMR 6539, Place Nicolas Copernic, F- 29280 Plouzané, France ;b Université de Paris, Institut de pHysique du globe de Paris, CNRS, F-75005 Paris;c National Institute of Polar ResearcH, Tokyo, 190-8518, Japan ;dUniversite Grenoble Alpes, CNRS, Institut de Planetologie et d’Astrophysique de Grenoble (IPAG), Saint-Martin d’Heres, France;e Université de Lorraine, CNRS, CRPG, F-54000 Nancy, France. *Corresponding autHor Jean-Alix Barrat Email: [email protected] Abstract The age of iron meteorites implies that accretion of protoplanets began during the first millions of years of the solar system. Due to the Heat generated by 26Al decay, many early protoplanets were fully differentiated, with an igneous crust produced during the cooling of a magma ocean, and the segregation at depth of a metallic core. The formation and nature of the primordial crust generated during the early stages of melting is poorly understood, due in part to the scarcity of available samples. The newly discovered meteorite Erg CHecH 002 (EC 002) originates from one sucH primitive igneous crust, and has an andesite bulk composition. It derives from the partial melting of a non-carbonaceous chondritic reservoir, witH no depletion in alkalis relative to the sun’s photosphere, and at a high melting rate of around 25%. Moreover, EC 002 is to date, the oldest known piece of an igneous crust witH a 26Al-26Mg crystallization age of 4565.0 Myr.
    [Show full text]
  • Astronomy Scope and Sequence
    Astronomy Scope and Sequence Grading Period Unit Title Learning Targets Throughout the B.(1) Scientific processes. The student, for at least 40% of instructional time, conducts School Year laboratory and field investigations using safe, environmentally appropriate, and ethical practices. The student is expected to: (A) demonstrate safe practices during laboratory and field investigations, including chemical, electrical, and fire safety, and safe handling of live and preserved organisms; and (B) demonstrate an understanding of the use and conservation of resources and the proper disposal or recycling of materials. B.(2) Scientific processes. The student uses scientific methods during laboratory and field investigations. The student is expected to: (A) know the definition of science and understand that it has limitations, as specified in subsection (b)(2) of this section; (B) know that scientific hypotheses are tentative and testable statements that must be capable of being supported or not supported by observational evidence. Hypotheses of durable explanatory power which have been tested over a wide variety of conditions are incorporated into theories; (C) know that scientific theories are based on natural and physical phenomena and are capable of being tested by multiple independent researchers. Unlike hypotheses, scientific theories are well-established and highly-reliable explanations, but they may be subject to change as new areas of science and new technologies are developed; (D) distinguish between scientific hypotheses and scientific
    [Show full text]
  • The Transition from Primary to Secondary Atmospheres on Rocky Exoplanets
    50th Lunar and Planetary Science Conference 2019 (LPI Contrib. No. 2132) 1855.pdf THE TRANSITION FROM PRIMARY TO SECONDARY ATMOSPHERES ON ROCKY EXOPLANETS. M. N. Barnett1 and E. S. Kite1, 1The University of Chicago, Department of Geophysical Sciences. ([email protected]) Introduction: How massive are rocky-exoplanet hydrodynamic escape is illustrated below in Figure 1. atmospheres? For how long do they persist? These ques- tions are compelling in part because an atmosphere is necessary for surface life. Magma oceans on rocky ex- oplanets are significant reservoirs of volatiles, and could potentially assist a planet in maintaining its secondary atmosphere [1,2]. We are modeling the atmospheric evolution of R ≲ 2 REarth exoplanets by combining a magma ocean source model with hydrodynamic escape. This work will go be- yond [2] as we consider generalized volatile outgassing, various starting planetary models (varying distance from the star, and the mass of initial “primary” atmos- phere accreted from the nebula), atmospheric condi- tions, and magma ocean conditions, as well as incorpo- rating solid rock outgassing after magma ocean solidifi- cation. Through this, we aim to predict the mass and lon- Figure 1: Key processes of our magma ocean and hydrody- gevity of secondary atmospheres for various sized rocky namic escape model are shown above. The green circles exoplanets around different stellar type stars and a range marked with a V indicate volatiles that are outgassed from the of orbital periods. We also aim to identify which planet solidifying magma and accumulate in the atmosphere. These volatiles are lost from the exoplanet’s atmosphere through hy- sizes, orbital separations, and stellar host star types are drodynamic escape aided by outflow of hydrogen, which is de- most conducive to maintaining a planet’s secondary at- rived from the nebula.
    [Show full text]