DOCSLIB.ORG

Physical Characteristics

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Physical Characteristics Physical Characteristics Encyclopedia—moon The study of the moon's surface increased with the invention of the telescope by Galileo in 1610 and culminated in 1969 when the first human actually set foot on the moon's surface. The physical characteristics and surface of the moon thus have been studied telescopically, photographically, and more recently by instruments carried by manned and unmanned spacecraft (see space exploration). The moon's diameter is about 2,160 mi (3,476 km) at the moon's equator, somewhat more than 1/4 the earth's diameter. The moon has about 1/81 the mass of the earth and is 3/5 as dense. On the moon's surface the force of gravitation is about 1/6 that on earth. It has been established that the moon completely lacks an atmosphere and, despite some tantalizing hints that there might be ice under the surface dust in shaded portions of Shackleton Crater (near the moon's south pole), there is no definite evidence of water. The surface temperature rises above 100°C (212°F) at lunar noon and sinks below -155°C (-247°F) at night. The gross surface features of the moon are visible to the unaided eye and were first studied telescopically in 1610 by Galileo. Surface Features The lunar surface is divided into the mountainous highlands and the large, roughly circular plains called maria (sing. mare; from Lat.,=sea) by early astronomers, who erroneously believed them to be bodies of water. The smooth floors of the maria, varying from flat to gently undulating, are covered by a thin layer of powdered rock that darkens them and accounts for the moon's low albedo (only 7% of the incident sunlight is reflected back, the rest being absorbed). The brighter regions on the moon are the mountainous highlands, where the terrain is rough and strewn with rocky rubble. The lunar mountain ranges, with heights up to 25,000 ft (7800 m), are comparable to the highest mountains on earth but in general are not very steep. The highlands are densely scarred by thousands of craters—shallow circular depressions, usually ringed by well- defined walls and often possessing a central peak. Craters range in diameter from a few feet to many miles, and in some regions there are so many that they overlap or several smaller craters lie within a large crater. Craters are also found on the maria, although there are nowhere near as many as in the lunar highlands. Other prominent surface features include the rilles and rays. Rilles are sinuous, canyonlike clefts found near the edges of mountain ranges. Rays are bright streaks radiating outward from certain craters, such as Tycho. Mare and highland rocks differ in both appearance and chemical content. For example, mare rocks are richer in iron and poorer in aluminum than highland rocks. The maria consist largely of basalt, i.e., igneous rock formed from magma. In the highlands the majority of the rocks are breccias—conglomerates formed from basaltic rock and often studded with small, green, glassy spheres. These spheres probably were formed as the spray of molten rock, originally melted by the heat of meteorite impact, recongealed in midflight. The exposure ages of some rocks (the time their surfaces have been exposed to the action of cosmic rays that produce radioactive isotopes) are as short as 50 million years, much shorter than their crystallization ages. These rocks may have been shifted in position by meteorite impact or seismic activity (moonquakes). However, present lunar seismic activity is very low, corroborating the image of the moon as an essentially static, nonevolving world. Internal Structure Diffraction of seismic waves provided the first clear-cut evidence for a lunar crust, mantle, and core analogous to those of the earth. The lunar crust is about 45 mi (70 km) thick, making the moon a rigid solid to a greater depth than the earth. The inner core has a radius of about 600 mi (1,000 km), about 2/3 of the radius of the moon itself. The internal temperature decreases from 830°C (1,530°F) at the center to 170°C (340°F) near the surface. The heat traveling outward near the lunar surface is about half that of the earth but still twice that predicted by current theory. This heat flow is directly related to the rate of internal energy production, so that the internal temperature profile provides information about long-lived radio isotopes and the moon's thermal evolution. The heat-flow measurements indicate that the moon's radioactive content is higher than that of the earth. The moon's magnetic field is a million times weaker than that of the earth, but it varies by a factor of 20 from point to point on the surface. Certain rocks retain a high magnetization, indicating that they crystallized in the presence of magnetic fields much higher than those presently existing on the moon. Mascons are large concentrations of unusually high density that are located below certain of the circular maria. The mascons may have been created by the implantation of very dense, iron-rich meteorites, whose impact formed the mare basins themselves. Formation and Evolution The moon probably formed by the cold accretion of small particles about 4.6 billion years ago at the same time that the rest of the solar system formed; thus, it is now believed that the moon was never in an entirely molten state. The crust, showing pronounced chemical differentiation, formed early. Subsequent impact of very large meteorites depressed the mare basins, at the same time thrusting up the surrounding crust to form the highlands. The mare basins later filled with lava flow, which in turn was covered by a thin layer of lunar “soil”—fine rock dust pulverized by the very slow mechanisms of lunar erosion (thermal cycling, solar wind, and micrometeorites). The craters were probably also formed by meteorite bombardment rather than by internal volcanic action as once believed. The rays surrounding the craters are material ejected during the impacts that formed the craters. The moon's rock types are correlated with its major geological periods. The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2007, Columbia University Press. All rights reserved. Cite Print Email HotWords Bookmark Add bookmark Add to del.icio.us Digg It! Add to Reddit.
Load more

Recommended publications
  • Chapter 12 the Moon and Mercury: Comparing Airless Worlds The
    11/4/2015 The Moon: The View from Earth From Earth, we always see the same side of the moon. Moon rotates around its axis in the same time that it takes to orbit Chapter 12 around Earth: The Moon and Mercury: Tidal coupling: Earth’s gravitation has Comparing Airless Worlds produced tidal bulges on the moon; Tidal forces have slowed rotation down to same period as orbital period Lunar Surface Features Highlands and Lowlands Two dramatically Sinuous rilles = different kinds of terrain: remains of ancient • Highlands: lava flows Mountainous terrain, scarred by craters May have been lava • Lowlands: ~ 3 km lower than highlands; smooth tubes which later surfaces: collapsed due to Maria (pl. of mare): meteorite bombardment. Basins flooded by Apollo 15 lava flows landing site The Highlands Impact Cratering Saturated with craters Impact craters on the moon can be seen easily even with small telescopes. Older craters partially … or flooded by Ejecta from the impact can be seen as obliterated by more lava flows bright rays originating from young recent impacts craters 1 11/4/2015 History of Impact Cratering Missions to the Moon Rate of impacts due to Major challenges: interplanetary Need to carry enough fuel for: bombardment decreased • in-flight corrections, rapidly after the formation of the solar system. • descent to surface, • re-launch from the surface, • return trip to Earth; Most craters seen on the need to carry enough food and other moon’s (and Mercury’s) life support for ~ 1 week for all surface were formed astronauts on board. Lunar module (LM) of within the first ~ ½ billion Solution: Apollo 12 on descent to the years.
    [Show full text]
  • X-Ray Computed Tomography of Tranquility Base Moon Rock
    X-ray Computed Tomography of Tranquility Base Moon Rock Dr. Justin S. Jones / Code 541 Dr. Jim Garvin / Code 600 Collaborators: Mike Viens/540, Ryan Kent/541, and Bruno Munoz/541 GSFC X-Ray CT System (Code 541 NDE Laboratory) Technique Background: • X-ray Computed Tomography (CT) is very similar Filtered Back- to Medical “CAT” scans Projection • An x-ray source creates a “cone beam” which enables geometric magnification • A series of 2D radiographs are taken at precise angle steps as the part rotates • Feldkamp filtered back-projection algorithm is applied to image “projections” to create 3D reconstructed “volume” Main Components: • 7-axis motion/manipulator system, up to 100lb capacity on rotation stage X-ray Source • Detector: Dexela 7529 CMOS with CsI scintillator – 75 µm pitch, 3888 x 3072 pixel array X-ray Detector • X-ray Source: Yxlon FXE-225.99 Dual Head Microfocus: 225kV • Installed in radiation shielded room Sample Stage (arbitrary • North Star Imaging and VG Studio Max software sample shown) • Reconstruction PC with 4 Tesla GPU computing North Star Imaging, custom X5000CT 2 GSFC CT Examples - Composites Impact Damage in Structural Experimental “Topological Composite Core” Composite Structure 3 GSFC CT Examples – Metallic Parts JWST: ISIM Structure 3D Welded Joint ISS: Cracked magnet in Europa: Additively EMU FPS Rotor Manufactured “Venturi” Assembly with stress relief crack 4 GSFC CT Examples – Circuit Boards/Components Circuit Board Interior Wiring Plane Full Circuit Board HV801 Diode Terminals 5 GSFC CT Examples – Reverse Engineering / 3D Reproduction JWST: CT Scan of Transition Link Assembly (fuse wire, ~1cm) 3D Model “Surfacing” to export as STL file for CAD/FEA/3D printer 3D printed replica of actual TLA (lower) at 10x scale 6 Apollo 11 Mission Background The following text was sourced, with minor edits, from the NASA site: http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.d o?sc=1969-059C • ‘The Lunar Module landed at 20:17:40 UT (4:17:40 p.m.
    [Show full text]
  • Geology of the Moon
    Geology of the moon William Joyce The moon is a little more accessible than other bodies in the solar system and this talk aimed to explain what moon rock reveals about the geology of the moon, which is an igneous cumulate complex. After some facts about the moon it looked at early ideas of the nature and origin of the moon, observations from earth, a look at both sides of the moon, major surface types – maria, highlands – craters and fieldwork near and on the moon. It finished with modern ideas on how the moon formed and some thoughts on impacting asteroids and volcanic eruptions. Facts The moon’s mass is 7.35x1022kg, 1.25% that of the earth. Its radius is 1,737km, 27.25% of the earth’s and its surface area 3.79x107km2, 7% of the earth’s. Its density is 60% of earth’s at 3.3g/cm3 and its gravity is 16.5% of earth’s at 1.62m/sec2. Its day is 27.322 earth days and temperatures range from +130oC to -130oC. As the only long-term natural companion of earth, the moon is a fairly large planetary body in its own right and has a complex geological history. 1t is 384,400km distant from earth, the equivalent of 60 earth radii. Early ideas Galileo Galilei was one of the first to make observations of the moon using a 20X telescope and published drawings of it in his Sidereii nunclus (1610). Thomas Harriot used a 6X telescope and produced the first drawings of the moon in 1609, before Galileo, and produced a map of the moon.
    [Show full text]
  • Little Learners' Activity Guide
    LUNAR RECONNAISSANCE ORBITER CAMERA Little Learners’ Activity Guide Learn about the Moon with puzzles, coloring, and fun facts! Mare Imbrium Mare Serenitatis Mare Tranquillitatis Oceanus Procellarum Mare Humorum Tycho Crater Visit us online at lroc.sese.asu.edu Online resources Additional information and content, including supplemental learning activities, can be accessed at the following online locations: 1. Little Learners’ Activity Guide: lroc.sese.asu.edu/littlelearners 2. LROC website: lroc.sese.asu.edu 3. Resources for teachers: lroc.sese.asu.edu/teach 4. Learn about the Moon’s history: lroc.sese.asu.edu/learn 5. LROC Lunar Quickmap 3D: quickmap.lroc.asu.edu Copyright 2018, Lunar Reconnaissance Orbiter Camera i Lunar Reconnaissance Orbiter Camera Fun Facts for Beginners • The Moon is 363,301 kilometers (225,745 miles) from the Earth. • The surface area of the Moon is almost as large as the continent of Africa. • It takes 27 days for the Moon to orbit around the Earth. • The farside is the side of the Moon we cannot see from Earth. • South Pole Aitken is the largest impact basin on the lunar farside. • Impact basins are formed as the result of impacts from asteroids or comets and are larger than craters. • Regolith is a layer of loose dust, dirt, soil, and broken rock deposits that cover solid rock. • The two main types of rock that make up the Moon’s crust are anorthosite and basalt. • A person weighing 120 lbs on Earth weighs 20 lbs on the Moon because gravity on the Moon is 1/6 as strong as on Earth.
    [Show full text]
  • Earth-Moon System
    ©JSR 2013/2018 Astronomy: Earth-Moon system Earth-Moon System Earth at night To see even the bright Moon properly you need clear skies and I can't resist taking the opportunity of beginning with NASA’s spectacular Earth-at-night picture - or how the Earth would appear without cloud cover. It's a picture that is not only of astronomical interest, but one that says a lot about the world's demography and economy. This section of the course, taking two to three lectures, covers the Earth-Moon system. Moon slide There are many features of the Earth-Moon system that are relevant to the study of the Universe at large. • It is held together by universal gravitation, whose basic law is simple but whose effects are not. • The Moon has craters, like many other objects in our solar system and presumably throughout the Universe. How were they formed and what do they tell us? • Measuring size and distance is a fundamental issue in astronomy. We have to start from homebase. The surer we are of distances in the solar system, the surer we are of measuring the much larger distances between stars and between galaxies. The Moon is the first permanent body beyond the Earth. The Earth-Moon system is the obvious first solar system distance to find. • The Earth-Moon system provides the fascinating spectacle of both lunar and solar eclipses. These have influenced societies, ancient and modern, and provided valuable insights into the nature of the Sun in particular. • There is a tendency to think of heavenly objects as points, because they are so far away.
    [Show full text]
  • The Moon Gateway to the Solar System
    THE MOON GATEWAY TO THE SOLAR SYSTEM G. Jeffrey Taylor, PhD WHEN ASTRONAUTS dug into the Moon’s surface during the Apollo program, they were doing more than digging up dry, dark sediment. They were time travelers. The rocks and sediment returned by Apollo contain vital clues to how Earth and the Moon formed, the nature and timing of early melting, the intensity of impact bombardment and its variation with time, and even the history of the Sun. Most of this information, crucial parts of the story of planet Earth, cannot be learned by studying rocks on Earth because our planet is so geologi-cally active that it has erased much of the record. The clues have been lost in billions of years of mountain building, volcanism, weath-ering, and erosion. Colliding tectonic plates The Moon, front and back The top right photograph is a telescopic image of the Earth-facing half of the Moon obtained at Lick Observatory in California. The one below right was taken during the Apollo 16 mission and shows mostly the farside, except for the dark areas on the left, which can be seen, though barely, from Earth. The two major types of terrain are clearly visible. The highlands, which are especially well displayed in the photograph of the farside, are light-colored and heavily cratered. The maria are darker and smoother; they formed when lava flows filled depressions. One of the mysteries about the Moon is why fewer maria occur on the farside than nearside. Note how many craters stand shoulder to shoulder on the farside.
    [Show full text]
  • Goodwill Moon Rock Rev B.Pages
    !Full product specification Goodwill Rock Lucky Moon Rock 70017 THE UNIVERSE IN THE PALM OF YOUR HANDS Product Name!Lucky Moon Rock 70017! ! Family Member! Moon Rock! ! Product Code! MR-70017! ! ! Schmitt standing next to a giant boulder during the Apollo Overview! !! 17 mission. Credit: NASA, Public domain Moon rock refers to rocks found on the Earth’s moon. Moon rock has been brought back to Earth by the US Apollo and Soviet Union Luna missions for scientists to study. The six manned Apollo missions brought back the most moon rock with a total of 2,415 samples weighing altogether 382 kg (842 lb). A variety of tools were used to gather the rocks and included: !hammers, scoops, tongs, rakes and core tubes.! The Goodwill Moon Rock (officially labelled sample 70017) was picked up by astronauts Eugene Cernan and Harrison Schmitt on the last of the Apollo Program moonwalks. They dedicated this special find to the young people of Earth. Back on Earth, President Nixon ordered that this rock be broken into fragments to share with the world. The pieces were mounted onto wooden plagues and presented to 135 foreign heads of state and the 50 US states.! ! Physical Properties! Composition ! The most common type of moon rock is igneous, meaning it is a rock formed through the cooling and solidification of magma or lava. There are four types of Moon rock:! • dark basalt (formed from rapidly cooling molten rock fem massive lava flow)! • anorthosite (when lava cools more slowly)! • breccias (fragments of different rocks, fused together by meteor impacts)! ! • lunar soil (glass like blobs, possibly created by the heat and pressure from a meteor impact)! Chemicals! Moon rock typically contains:! • refractory elements (eg: Calcium, Aluminium, Titanium) which have a high melting point! ! • silicon and oxygen! Precious metals such as Titanium are valuable and widely used here on Earth.
    [Show full text]
  • Magnificent, Mysterious Moon
    Adapted From AAC Newsletter FirstLight (2002 Oct & 2004 Apr/May) Magnificent, Mysterious Moon Howard L. Cohen Usually the bane of amateur and professional astronomers alike, the Moon is the most exquisite, detailed and educational object on the sky! “The Moon was but a Chin of Gold A Night or two ago — And now she turns Her perfect Face Upon the World below —” ~ Emily Dickinson ometime ago a colleague of mine stated that once you’ve seen the Moon, there is no sense having a second look. This is like saying once you’ve seen the Grand SCanyon, there is no sense coming back. If this is your thinking too, you need not read any further. Gerald North in his popular book, Observing the Moon, wrote that, “Interest in the Moon periodically ebbs and flows, like the tides it causes in our oceans.” Certainly interest in the Moon peaked during the Apollo landings more than thirty years ago and it has been on the wane ever since. Today, with many amateur astronomers proud owners of large reflecting telescopes, deep sky observing seems more fashionable. And professional astronomers usually hold star formation, exploding stars, black holes and galactic encounters among the more “fashionable” fields of study. Indeed, when moonlight prevails, astronomers often stow their telescopes and retreat indoors. The First Quarter Moon. Magnificent even in small telescopes. (Photo by author.) Still, our nearest celestial neighbor has attracted attention since earliest times and has influenced our culture in ways unknown to most people. Now ignorance and myths of the Moon prevail including the perception that, if you have seen a moon rock (or crater), you’ve seen it all.
    [Show full text]
  • Sampling South Pole-Aitken Basin to Determine the Age of the Impact Event and Test the Cataclysm Hypothesis
    Lunar Surface Science Workshop 2020 (LPI Contrib. No. 2241) 5091.pdf SAMPLING SOUTH POLE-AITKEN BASIN TO DETERMINE THE AGE OF THE IMPACT EVENT AND TEST THE CATACLYSM HYPOTHESIS. B. L. Jolliff1, C. K. Shearer2, N. E. Petro3, and B. A. Cohen3. 1Depart- ment of Earth & Planetary Sciences, Washington University in St. Louis, One Brookings Dr., St. Louis, MO 63130; 2University of New Mexico, Albuquerque, NM; 3Goddard Space Flight Center, Greenbelt, MD. ([email protected]) Summary: Regolith and rock samples collected at size [6] and excavating materials from great depth, po- landing sites near the south pole, including near Shack- tentially including crust and mantle materials. Its effects leton crater, will contain materials ejected by the impact on the Moon were global, forming a Moon-wide strati- that formed the giant South Pole-Aitken (SPA) basin graphic event. Determining the age of SPA will bracket [1]. Shackleton crater occurs on an SPA basin massif the ages of other ancient, Pre-Nectarian basins on the and the impact that formed it excavated and mixed SPA Moon as well the origin of the apparent episode of ig- material into the local regolith. Rock materials collected neous activity around 4.35 Ga [7-10]. Materials from near Shackleton will be suitable for petrographic, geo- SPA basin hold a record of the process of very large im- chemical, and chronologic analyses of SPA material. pact-basin formation [11] and will serve as ground truth Based on the known diversity of rock fragments in for remote sensing of SPA basin materials. Volcanic Apollo regolith samples, regolith sieved on the Moon rocks that occur in the SPA interior will contribute to will yield rock fragments in the several mm to cm size our understanding of basin materials and chronology, range that are ideal for studies needed to identify and and mantle heterogeneity.
    [Show full text]
  • The New Moon Race: Lunar Agriculture
    Project Number: JMW LUNA The New Moon Race: Lunar Agriculture An Interactive Qualifying Project Report submitted to the Faculty of the WORCESTER POLYTECHNIC INSTITUTE in partial fulfillment of the requirements for the Degree of Bachelor Science By ________________________ Peter Conerly Date: April 28, 2009 Approved: ________________________ Professor John M. Wilkes, Major Advisor 1 Abstract A lunar base is valuable economically as a foothold with relatively easy access to all of space. The burden of such a base will be providing it with resources. If a base can grow food for itself then it will become much less of a burden. Many factors surrounding lunar agriculture have been studied although plants have never been grown on the moon. This report examines the problem and proposed a strategy for productive agriculture on the moon. 2 Table of Contents: Abstract ………………………………………………………………………………………………….……….……….……………..2 Table of Contents………………………………………………………………………………………………….….…….………..3 Table of Figures………………………………………………………………………………………………….…….…….………..4 1: Introduction..……………………………………………………………………………………………………..….………………5 2: Literature Review.…………………………………………………………………………………………….….……………….6 2.1 IQP: Sustaining Agriculture on the Moon…………………………………………………...…..……….6 2.2 IQP: Proposal for the Development of an Economically Viable Lunar Base……..…….…7 3: Lunar Conditions.…………………………………………………………………………………………..…..….………………8 4: Agriculture Strategy.……………………………………………………………………………………..…….………………12 4.1: Growing Techniques…………………………………………………………………………..……….…………12 4.2:
    [Show full text]
  • China Shoots the Moon
    Volume 18 | Issue 23 | Number 3 | Article ID 5520 | Dec 01, 2020 The Asia-Pacific Journal | Japan Focus China Shoots the Moon Philip J. Cunningham China is taking aim at the moon, establishing itself as a space power to be reckoned with. While currently playing catch-up behind the space accomplishments of the US and Russia, it is rapidly gaining ground as a result of an ambitious Chinese space program coinciding with domestic squabbling in the US, budgetary shortfalls in Russia, and lack of focused political will on the part of both space pioneers. November 23, 2020 launch of China’s Chang'e-5 from Wenchang Satellite With the freshly-launched Chang’e 5 probe, Launch Center in Hainan locked into a moon orbit as of November 28, for the first time in forty years an attempt is being made to collect rocks on the moon and bring them back to earth for study. Abstract: With China’s Chang’e 5 rocket launch, which landed on the moon on The US Advance in Space and its December 1, the long US-Russian domination Subsequent Decline of space has a major challenger. The issues extend beyond national pride to a global The heyday of moon exploration by the US and leadership initiative in rocketry whose the USSR in the 1960s and 1970s coincided implications extend to military, economic and with a deadly serious space race that was diverse scientific applications at a time of effectively war by other means for the two mounting US-China rivalry in all spheres. reigning superpowers.
    [Show full text]
  • Denying the Apollo Moon Landings: Conspiracy and Questioning in Modern American History
    Denying the Apollo Moon Landings: Conspiracy and Questioning in Modern American History Roger D. Launius* Smithsonian Institution, Washington, DC 20650 I. Abstract Almost from the point of the first Apollo missions, a small group of Americans denied that it had taken place at all. It had, they argued, been faked in Hollywood by the federal government for purposes ranging—depending on the particular Apollo landing denier—from embezzlement of the public treasury to complex conspiracy theories involving international intrigue and murderous criminality. They tapped into a rich vein of distrust of government, populist critiques of society, and questions about the fundamentals of epistemology and knowledge creation. At the time of the first landings, opinion polls showed that overall less than five percent, among some communities larger percentages, ―doubted the moon voyage had taken place.‖1 For example, Andrew Chaikin commented in his massive history of the Apollo Moon expeditions that at the time of the Apollo 8 circumlunar flight in December 1968 some people thought it was not real; instead it was ―all a hoax perpetrated by the government.‖ Bill Anders, an astronaut on the mission, thought live television would help convince skeptics since watching ―three men floating inside a spaceship was as close to proof as they might get.‖2 He could not have been more wrong. Fueled by conspiracy theorists of all stripes, this number has grown over time. In a 2004 poll, while overall numbers remained about the same, among Americans between 18 and 24 years old ―27% expressed doubts that NASA went to the Moon,‖ according to pollster Mary Lynne Dittmar.
    [Show full text]