DOCSLIB.ORG

Summary of Lunar Stratigraphy- Telescopic Observations

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Summary of Lunar Stratigraphy- Telescopic Observations •; LIBRARY. .1. Summary of Lunar Stratigraphy- 1 Telescopic Observations --.· By DON E. W~LHELMS ., CONTRIBUTIONS TO ASTROGEOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 599-F Prepared on behalf of the National Aeronautics and Space A dminz"stration \ UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1970 UNITED STATES DEPARTMENT OF THE INTERIOR WALTER J. HICKEL, Secretar:v Y;'I GEOLOGICAL SURVEY William T. Pecora, Director Library of Congress catalog-card No. 77-608123 For sale by the Superintendent of Documents, U.S. Government Printing . , .. ~Office, .Washington, D.C.. 20402- Price 60 cents (paper cover) ). CONTENTS Page Page F1 ~bstract ----------------------------------------- Lunar stratigraphic column-Continued Introduction -------------------------------------­ 2 Imbrian System-Continued Previous work-------------------------------- 3 Terra units of the Theophilus quadrangle F29 ~cknowledgments ----------------------------- 6 nfare material (formerly Procellarum Group) 29 ~pplication of stratigraphic principles to the moon __ 6 Nomenclature -----------------------­ 30 Properties and sequence of lunar material units-­ 6 nfare materials with topographic relief _ 32 Lunar time-stratigraphic and geologic-time units _ 9 ~penninian and ~rchimedian Series -------- 32 Separation of observation and interpretation ___ _ 9 Imbrian or Eratosthenian Systems -----------­ 33 Types of geologic units -------------------­ 11 Dark terra-mantling units ---------------­ 33 nfap conventions ------------------------- 11 . Units with intrinsic relief ---------------- 33 Lunar stratigraphic column ---------------------- 12 Eratosthenian and Copernican Systems -------­ 36 13 General observations -------------------------­ Crater materials ------------------------­ 36 15 Pre-Imbrian units ---------------------------­ nfantling materials ---------------------­ 37 Pre-Imbrian and (or) Imbrian units ---------- 22 Plains-forming materials -----------------­ 37 ..,.. 23 Imbrian System ------------------------------ Units with intrinsic relief ---------------- 37 Definition and general features -----------­ 23 39 Fra nfauro Formation -------------------­ 23 Slope material --------------------------- 39 Definition ---------------------------- 25 nfiscellaneous units --------------------------­ 39 nfembers ----------------------------- 25 ~bandoned names ---------------------------­ 40 Interpretation ------------------------ 27 Crater material subunits ---------------------- Cayley and ~pennine Bench ~ormations ___ _ 27 Summary and-· conclusions ..,..,., __ _,,__,..; __ ..:...:_~...;.:. __ .:... __ .:.. __ _ 42 45 ··( Crater materials ------------------------­ 28 References cited ---------------------------------­ Materials near the Orientale basin --------- 28 Preliminary lunar geologic maps ------------------ 47 ILLUSTRATIONS Page FIGURE 1. Index map showing status of mapping at the 1:1,000,000 scale as of late 1967-------------------------- F2 2. Photomosaic of part of the lunar near-side showing areas covered by illustrations in this report_ _______ _ 4 3. Photograph of the craters Copernicus and Eratosthenes and vicinity under low-sun illumination _________ _ 8 4. Photograph and geologic sketch map of the vicinity of the crater ~rchimedes ___________ _: _____________ _ 10 5. Rectified photograph of nfare Imbrium and its multiringed basin _____________________________________ _ 14 6. Photograph of nfare IIumorum ______________________ ~---------------------------------------------- 19 7. Lunar ~stronautical Chart of IIyginus rille-------------------------------------------------------- 20 8-14. Photographs of: 8. Central part of moon showing "Imbrian sculpture" -------~------------------------------------ 21 9. The ~pennine nfountains and terra peninsula extending southward _____________________________ _ 24 10. The type area of. the Fra Mauro Formation __________________________________________________ _ 26 11. Flow lobes in Mare Imbrium----------------------------------------------------------------- 31 12. The craters Copernicus and Eratosthenes and vicinity under near-full-moon illumination__________ _ 34 13. The ~ristarchus plateau and IIarbinger Mountains ------------------------------------------- 35 14. Part of the crater Theophilus and the Theophilus Formation ---------------------------------- 38 15. Example of map explanation box for crater material subunits --------------------------------------- 41 TABLES Page TABLE 1. Composite lunar stratigraphic columnar section showing most units discussed in text ---------------- F16 2. Formally defined lunar stratigraphic names ---------------------------------------------------------- 39 3. Stratigraphic names that have appeared in Geological Survey publications but have not been defined formally 40 iii CONTRIBUTIONS TO ASTROGEOLOGY SUMMARY OF LUNAR STRATIGRAPHY-TELESCOPIC OBSERVATIONS By DON E. WILHELMS ABSTRACT pre-Imbrian basins, but greater degradation hinders their The geology of much of the moon has been mapped from recognition. the earth by means of telescopic photographs and observa­ Sufficient time elapsed between the formation of each mar~ tions. This mapping is based on the premise that the lunar basin and the completion of its flooding by the dark smooth crust is composed of material units that can be defined by material called mare material for extensive units to form. physical properties and ranked in order of relative age by Those units in or near the Imbrium and Orientale basins are application of the principles of stratigraphy. Units are of Imbrian age, whereas those in the pre-Imbrian basins may ranked locally by their superposition and transection relations be either pre-Imbrian or Imbrian in age. The most common and both locally and regionally by subordinate criteria such units are crater materials and light plains-forming materials. as density of superposed craters and degree of topographic Crater materials include those of Archimedes in the Imbrium y.· freshness. basin and of Gassendi in the Humorum basin. Light plains­ A moonwide stratigraphic column of material units has forming materials of Imbrian age include the Apennine been divided into approximate and tentative time-strati­ Bench Formation on the shelf south of Archimedes and the graphic ·units, whose type areas are near the craters Coper­ Cayley Formation in troughs surrounding the Imbrium basin. nicus, Eratosthenes, and Archimedes. The oldest time-strati­ Most light plains-forming materials are confined to depres­ graphic unit is the pre-lmbrian (not a formal system), sions or low plateaus. Other light materials of probable followed by the lmbrian, Eratosthenian, and Copernican Imbrian age form undulating or rolling topography and Systems. elevated plateaus. Pre-Imbrian materials have a subdued topography and are The top of the mare material between the craters Eratos­ highly cratered. Most are associated with craters and circular thenes and Archimedes has been used to define the top of the multiringed mare basins. Many pre-Imbrian craters originally Imbrian System. Most mare material is Imbrian in age but may have resembled the young crater Copernicus but are now some is post-Imbrian. The youngest mare materials ar~ the modified. The formation of each multiringed mare basin was darkest and least cratered; the oldest are almost as light and a major event which obliterated the earlier geologic record as heavily cratered as the light plains-forming materials. over a large area and started a new stratigraphic sequence. Indeed, mare and light plains materials may be composition­ On the basis of density of superposed craters and general ally similar, though different in age. Mare materials were freshness of appearance, the sequence of formation of some once called the Procellarian System and when this name was pre-Imbrian multiringed basins is believed to be, from oldest dropped, the Procellarum Group. The latter name as well as to youngest: Fecunditatis, Serenitatis, Nectaris, Humorum, the two series of the Imbrian System, the Apenninian and Crisium (or Crisium-Humorum). Other less distinct basins Archimedian, should be dropped. are also pre-Imbrian in age. Materials whose age relative to Imbrian mare material is Deposits called the Fra Mauro Formation that partly doubtful have been designated "Imbrian or Eratosthenian." surround another fresher appearing mare basin, the Imbrium They include crater materials, dark terra-mantling materials, basin, are used to define the base of the Imbrian System. The and materials that form domes, cones, sinuous rilles, and Fra Mauro apparently forms a blanket that grades in texture prominent stringy ridges. The dark mantling units occur and thickness away from the basin, and otherwise resembles mainly at the margins of maria and may be partly inter­ the ejecta of craters such as Copernicus that are believed to bedded with mare materials. have been produced by impact. Accordingly the Fra Mauro The two youngest lunar time-stratigraphic systems the Eratosthenian and Copernican, have been defined on the basis is believed to be ejecta from the impact that formed the of the physical properties of crater materials. Materials of Imbrium basin. Structures radial to and concentric with the rayless craters that are superposed on Imbrian mare material basin also apparently were formed at the same time as the are assigned an Eratosthenian age; some superposed on terra basin. The Fra Mauro and the structures divide the materials are also doubtless Eratosthenian but are not telescopically
Load more

Recommended publications
  • Geoscience and a Lunar Base
    " t N_iSA Conference Pubhcatmn 3070 " i J Geoscience and a Lunar Base A Comprehensive Plan for Lunar Explora, tion unclas HI/VI 02907_4 at ,unar | !' / | .... ._-.;} / [ | -- --_,,,_-_ |,, |, • • |,_nrrr|l , .l -- - -- - ....... = F _: .......... s_ dd]T_- ! JL --_ - - _ '- "_r: °-__.......... / _r NASA Conference Publication 3070 Geoscience and a Lunar Base A Comprehensive Plan for Lunar Exploration Edited by G. Jeffrey Taylor Institute of Meteoritics University of New Mexico Albuquerque, New Mexico Paul D. Spudis U.S. Geological Survey Branch of Astrogeology Flagstaff, Arizona Proceedings of a workshop sponsored by the National Aeronautics and Space Administration, Washington, D.C., and held at the Lunar and Planetary Institute Houston, Texas August 25-26, 1988 IW_A National Aeronautics and Space Administration Office of Management Scientific and Technical Information Division 1990 PREFACE This report was produced at the request of Dr. Michael B. Duke, Director of the Solar System Exploration Division of the NASA Johnson Space Center. At a meeting of the Lunar and Planetary Sample Team (LAPST), Dr. Duke (at the time also Science Director of the Office of Exploration, NASA Headquarters) suggested that future lunar geoscience activities had not been planned systematically and that geoscience goals for the lunar base program were not articulated well. LAPST is a panel that advises NASA on lunar sample allocations and also serves as an advocate for lunar science within the planetary science community. LAPST took it upon itself to organize some formal geoscience planning for a lunar base by creating a document that outlines the types of missions and activities that are needed to understand the Moon and its geologic history.
    [Show full text]
  • No. 40. the System of Lunar Craters, Quadrant Ii Alice P
    NO. 40. THE SYSTEM OF LUNAR CRATERS, QUADRANT II by D. W. G. ARTHUR, ALICE P. AGNIERAY, RUTH A. HORVATH ,tl l C.A. WOOD AND C. R. CHAPMAN \_9 (_ /_) March 14, 1964 ABSTRACT The designation, diameter, position, central-peak information, and state of completeness arc listed for each discernible crater in the second lunar quadrant with a diameter exceeding 3.5 km. The catalog contains more than 2,000 items and is illustrated by a map in 11 sections. his Communication is the second part of The However, since we also have suppressed many Greek System of Lunar Craters, which is a catalog in letters used by these authorities, there was need for four parts of all craters recognizable with reasonable some care in the incorporation of new letters to certainty on photographs and having diameters avoid confusion. Accordingly, the Greek letters greater than 3.5 kilometers. Thus it is a continua- added by us are always different from those that tion of Comm. LPL No. 30 of September 1963. The have been suppressed. Observers who wish may use format is the same except for some minor changes the omitted symbols of Blagg and Miiller without to improve clarity and legibility. The information in fear of ambiguity. the text of Comm. LPL No. 30 therefore applies to The photographic coverage of the second quad- this Communication also. rant is by no means uniform in quality, and certain Some of the minor changes mentioned above phases are not well represented. Thus for small cra- have been introduced because of the particular ters in certain longitudes there are no good determi- nature of the second lunar quadrant, most of which nations of the diameters, and our values are little is covered by the dark areas Mare Imbrium and better than rough estimates.
    [Show full text]
  • Glossary Glossary
    Glossary Glossary Albedo A measure of an object’s reflectivity. A pure white reflecting surface has an albedo of 1.0 (100%). A pitch-black, nonreflecting surface has an albedo of 0.0. The Moon is a fairly dark object with a combined albedo of 0.07 (reflecting 7% of the sunlight that falls upon it). The albedo range of the lunar maria is between 0.05 and 0.08. The brighter highlands have an albedo range from 0.09 to 0.15. Anorthosite Rocks rich in the mineral feldspar, making up much of the Moon’s bright highland regions. Aperture The diameter of a telescope’s objective lens or primary mirror. Apogee The point in the Moon’s orbit where it is furthest from the Earth. At apogee, the Moon can reach a maximum distance of 406,700 km from the Earth. Apollo The manned lunar program of the United States. Between July 1969 and December 1972, six Apollo missions landed on the Moon, allowing a total of 12 astronauts to explore its surface. Asteroid A minor planet. A large solid body of rock in orbit around the Sun. Banded crater A crater that displays dusky linear tracts on its inner walls and/or floor. 250 Basalt A dark, fine-grained volcanic rock, low in silicon, with a low viscosity. Basaltic material fills many of the Moon’s major basins, especially on the near side. Glossary Basin A very large circular impact structure (usually comprising multiple concentric rings) that usually displays some degree of flooding with lava. The largest and most conspicuous lava- flooded basins on the Moon are found on the near side, and most are filled to their outer edges with mare basalts.
    [Show full text]
  • January 2019 Cardanus & Krafft
    A PUBLICATION OF THE LUNAR SECTION OF THE A.L.P.O. EDITED BY: Wayne Bailey [email protected] 17 Autumn Lane, Sewell, NJ 08080 RECENT BACK ISSUES: http://moon.scopesandscapes.com/tlo_back.html FEATURE OF THE MONTH – JANUARY 2019 CARDANUS & KRAFFT Sketch and text by Robert H. Hays, Jr. - Worth, Illinois, USA September 24, 2018 04:40-05:04 UT, 15 cm refl, 170x, seeing 7/10, transparence 6/6. I drew these craters and vicinity on the night of Sept. 23/24, 2018. The moon was about 22 hours before full. This area is in far western Oceanus Procellarum, and was favorably placed for observation that night. Cardanus is the southern one of this pair and is of moderate depth. Krafft to the north is practically identical in size, and is perhaps slightly deeper. Neither crater has a central peak. Several small craters are near and within Krafft. The crater just outside the southeast rim of Krafft is Krafft E, and Krafft C is nearby within Krafft. The small pit to the west is Krafft K, and Krafft D is between Krafft and Cardanus. Krafft C, D and E are similar sized, but K is smaller than these. A triangular-shaped swelling protrudes from the north side of Krafft. The tiny pit, even smaller than Krafft K, east of Cardanus is Cardanus E. There is a dusky area along the southwest side of Cardanus. Two short dark strips in this area may be part of the broken ring Cardanus R as shown on the. Lunar Quadrant map.
    [Show full text]
  • General Index
    General Index Italicized page numbers indicate figures and tables. Color plates are in- cussed; full listings of authors’ works as cited in this volume may be dicated as “pl.” Color plates 1– 40 are in part 1 and plates 41–80 are found in the bibliographical index. in part 2. Authors are listed only when their ideas or works are dis- Aa, Pieter van der (1659–1733), 1338 of military cartography, 971 934 –39; Genoa, 864 –65; Low Coun- Aa River, pl.61, 1523 of nautical charts, 1069, 1424 tries, 1257 Aachen, 1241 printing’s impact on, 607–8 of Dutch hamlets, 1264 Abate, Agostino, 857–58, 864 –65 role of sources in, 66 –67 ecclesiastical subdivisions in, 1090, 1091 Abbeys. See also Cartularies; Monasteries of Russian maps, 1873 of forests, 50 maps: property, 50–51; water system, 43 standards of, 7 German maps in context of, 1224, 1225 plans: juridical uses of, pl.61, 1523–24, studies of, 505–8, 1258 n.53 map consciousness in, 636, 661–62 1525; Wildmore Fen (in psalter), 43– 44 of surveys, 505–8, 708, 1435–36 maps in: cadastral (See Cadastral maps); Abbreviations, 1897, 1899 of town models, 489 central Italy, 909–15; characteristics of, Abreu, Lisuarte de, 1019 Acequia Imperial de Aragón, 507 874 –75, 880 –82; coloring of, 1499, Abruzzi River, 547, 570 Acerra, 951 1588; East-Central Europe, 1806, 1808; Absolutism, 831, 833, 835–36 Ackerman, James S., 427 n.2 England, 50 –51, 1595, 1599, 1603, See also Sovereigns and monarchs Aconcio, Jacopo (d. 1566), 1611 1615, 1629, 1720; France, 1497–1500, Abstraction Acosta, José de (1539–1600), 1235 1501; humanism linked to, 909–10; in- in bird’s-eye views, 688 Acquaviva, Andrea Matteo (d.
    [Show full text]
  • Bills Paid by Payee Second Quarter Fiscal Year 20/21
    BILLS PAID BY PAYEE SECOND QUARTER FISCAL YEAR 20/21 A complete detailed record is available at the Elko County Comptroller's Office. Office Hours: Monday-Friday 8:00A.M. until 5:00P.M. 540 Court St. Suite 101 Elko, NV 89801 Office Phone (775)753-7073*Disclaimer-The original and any duplicate or copy of each receipt, bill,check,warrant,voucher or other similar document that supports a transaction, the amount of which is shown in the total of this report, along with the name of the person whom such allowance is made and the purpose of the allowance, is a public record that is available for inspection and copying by any person pursuant to the provisions of chapter 239 of NRS. VENDOR CHECK ARGO COMPANY, INC 821.98 A ARNOLD BECK CONSTRUCTION 1,599.40 AT&T 3,697.06 5TH GEAR POWER SPORTS 41.74 AT&T MOBILITY 42.24 A PLUS URGENT CARE 766 AUTO GRAPHICS 400 A PLUS URGENT CARE ELKO 846.33 B A-1 RADIATOR REPAIR INC. 1,079.00 BARBARA J HOFHEINS 121.9 ACKERMAN MATTHEW 1388.93 BARBARA JO MAPLE 762.5 ADVANCE AUTO CARE 629.89 BARRY RENTAL 86.03 ADVANCED RADIOLOGY 1195.5 BEI CAPELI 5,000.00 AIRGAS 541.3 BERTOLINI VALVES INC 1,859.12 AIRPORT SHELL 9 BETTY HICKS 177.56 ALCOHOL MONITORING SYSTEMS INC 791 BLAINE ROBINSON & NIKIERA CAST 1,132.00 ALERTUS TECHNOLOGIES LLC 4,950.00 BLOHM JEWELERS INC 5,000.00 ALICIA GUAMAN 58 BLUE 360 MEDIA LLC 70.75 ALLIED UNIVERAL SECURITY SERVI 37,229.50 BOARD OF REGENTS 14300.04 ALLUSIVE IMAGES 5,000.00 BOB BARKER COMPANY 4418.55 ALYSSA K DANN 120 BONANZA PRODUCE 320.23 AMANDA JEAN GIRMAUDO 160 BOSS TANKS 5,024.00 AMBER DAWN
    [Show full text]
  • 37845R CS3 Book Hatfield's Diaries.Indd
    “H.M.A.S. PERTH” 1939 -1941 From the diaries of P.O. George Hatfield Published in Sydney Australia in 2009 Publishing layout and Cover Design by George Hatfield Jnr. Printed by Springwood Printing Co. Faulconbridge NSW 2776 1 2 Foreword Of all the ships that have flown the ensign of the Royal Australian Navy, there has never been one quite like the first HMAS Perth, a cruiser of the Second World War. In her short life of just less than three years as an Australian warship she sailed all the world’s great oceans, from the icy wastes of the North Atlantic to the steamy heat of the Indian Ocean and the far blue horizons of the Pacific. She survived a hurricane in the Caribbean and months of Italian and German bombing in the Mediterranean. One bomb hit her and nearly sank her. She fought the Italians at the Battle of Matapan in March, 1941, which was the last great fleet action of the British Royal Navy, and she was present in June that year off Syria when the three Australian services - Army, RAN and RAAF - fought together for the first time. Eventually, she was sunk in a heroic battle against an overwhelming Japanese force in the Java Sea off Indonesia in 1942. Fast and powerful and modern for her times, Perth was a light cruiser of some 7,000 tonnes, with a main armament of eight 6- inch guns, and a top speed of about 34 knots. She had a crew of about 650 men, give or take, most of them young men in their twenties.
    [Show full text]
  • Martian Crater Morphology
    ANALYSIS OF THE DEPTH-DIAMETER RELATIONSHIP OF MARTIAN CRATERS A Capstone Experience Thesis Presented by Jared Howenstine Completion Date: May 2006 Approved By: Professor M. Darby Dyar, Astronomy Professor Christopher Condit, Geology Professor Judith Young, Astronomy Abstract Title: Analysis of the Depth-Diameter Relationship of Martian Craters Author: Jared Howenstine, Astronomy Approved By: Judith Young, Astronomy Approved By: M. Darby Dyar, Astronomy Approved By: Christopher Condit, Geology CE Type: Departmental Honors Project Using a gridded version of maritan topography with the computer program Gridview, this project studied the depth-diameter relationship of martian impact craters. The work encompasses 361 profiles of impacts with diameters larger than 15 kilometers and is a continuation of work that was started at the Lunar and Planetary Institute in Houston, Texas under the guidance of Dr. Walter S. Keifer. Using the most ‘pristine,’ or deepest craters in the data a depth-diameter relationship was determined: d = 0.610D 0.327 , where d is the depth of the crater and D is the diameter of the crater, both in kilometers. This relationship can then be used to estimate the theoretical depth of any impact radius, and therefore can be used to estimate the pristine shape of the crater. With a depth-diameter ratio for a particular crater, the measured depth can then be compared to this theoretical value and an estimate of the amount of material within the crater, or fill, can then be calculated. The data includes 140 named impact craters, 3 basins, and 218 other impacts. The named data encompasses all named impact structures of greater than 100 kilometers in diameter.
    [Show full text]
  • Exploration of the Moon
    Exploration of the Moon The physical exploration of the Moon began when Luna 2, a space probe launched by the Soviet Union, made an impact on the surface of the Moon on September 14, 1959. Prior to that the only available means of exploration had been observation from Earth. The invention of the optical telescope brought about the first leap in the quality of lunar observations. Galileo Galilei is generally credited as the first person to use a telescope for astronomical purposes; having made his own telescope in 1609, the mountains and craters on the lunar surface were among his first observations using it. NASA's Apollo program was the first, and to date only, mission to successfully land humans on the Moon, which it did six times. The first landing took place in 1969, when astronauts placed scientific instruments and returnedlunar samples to Earth. Apollo 12 Lunar Module Intrepid prepares to descend towards the surface of the Moon. NASA photo. Contents Early history Space race Recent exploration Plans Past and future lunar missions See also References External links Early history The ancient Greek philosopher Anaxagoras (d. 428 BC) reasoned that the Sun and Moon were both giant spherical rocks, and that the latter reflected the light of the former. His non-religious view of the heavens was one cause for his imprisonment and eventual exile.[1] In his little book On the Face in the Moon's Orb, Plutarch suggested that the Moon had deep recesses in which the light of the Sun did not reach and that the spots are nothing but the shadows of rivers or deep chasms.
    [Show full text]
  • Sky and Telescope
    SkyandTelescope.com The Lunar 100 By Charles A. Wood Just about every telescope user is familiar with French comet hunter Charles Messier's catalog of fuzzy objects. Messier's 18th-century listing of 109 galaxies, clusters, and nebulae contains some of the largest, brightest, and most visually interesting deep-sky treasures visible from the Northern Hemisphere. Little wonder that observing all the M objects is regarded as a virtual rite of passage for amateur astronomers. But the night sky offers an object that is larger, brighter, and more visually captivating than anything on Messier's list: the Moon. Yet many backyard astronomers never go beyond the astro-tourist stage to acquire the knowledge and understanding necessary to really appreciate what they're looking at, and how magnificent and amazing it truly is. Perhaps this is because after they identify a few of the Moon's most conspicuous features, many amateurs don't know where Many Lunar 100 selections are plainly visible in this image of the full Moon, while others require to look next. a more detailed view, different illumination, or favorable libration. North is up. S&T: Gary The Lunar 100 list is an attempt to provide Moon lovers with Seronik something akin to what deep-sky observers enjoy with the Messier catalog: a selection of telescopic sights to ignite interest and enhance understanding. Presented here is a selection of the Moon's 100 most interesting regions, craters, basins, mountains, rilles, and domes. I challenge observers to find and observe them all and, more important, to consider what each feature tells us about lunar and Earth history.
    [Show full text]
  • B. Apollo 16 Regional Geologic Setting
    B. APOLLO 16REGIONAL GEOLOGIC SETTING By CARROLL ANN HODGES CONTENTS Page Geography 6 Geologic description of Cayley plains and Descartes mountains 6 Relation in time and space to basins and craters 8 ILLUSTRATIONS Page FIGURE 1. Composite photograph of the lunar near side showing geographic features and multiring basins 7 2. Photographic mosaic of Apollo 16 landing site and vicinity 8 GEOGRAPHY Soderblom and Boyce,1972). The type area of the Cayley Formation is east of the crater Cayley, north of Apollo 16 landed at approximately 15”30’ E., 9” S. on the landing site (Morris and Wilhelms, 1967); the the relatively level Cayley plains, adjacent to the rug- name was extended to the apparently similar plains ged Descartes mountains (Milton, 1972; Hodges, material at the Apollo 16 site (Milton, 1972; Hodges, 1972a). Approximately 70 km east is the west-facing 1972a). These materials were presumed to be represen- escarpment of the Kant plateau, part of the uplifted tative of the widespread photogeologic unit, Imbrian third ring of the Nectaris basin and topographically light plains, which covers about 5 percent of the lunar the highest area on the lunar near side. With respect to highlands surface (Wilhelms and McCauley, 1971; the centers of the three best-developed multiringed Howard and others, 1974). Characteristics include rel- basins, the site is about 600 km west of Nectaris, 1,600 atively level surfaces, intermediate albedo, and nearly km southeast of Imbrium, and 3,500 km east-northeast identical crater size-frequency distributions. of Orientale. The nearest mare materials are in The plains were first interpreted as smooth facies of Tranquillitatis, about 300 km north (fig.1).
    [Show full text]
  • Science Concept 5: Lunar Volcanism Provides a Window Into the Thermal and Compositional Evolution of the Moon
    Science Concept 5: Lunar Volcanism Provides a Window into the Thermal and Compositional Evolution of the Moon Science Concept 5: Lunar volcanism provides a window into the thermal and compositional evolution of the Moon Science Goals: a. Determine the origin and variability of lunar basalts. b. Determine the age of the youngest and oldest mare basalts. c. Determine the compositional range and extent of lunar pyroclastic deposits. d. Determine the flux of lunar volcanism and its evolution through space and time. INTRODUCTION Features of Lunar Volcanism The most prominent volcanic features on the lunar surface are the low albedo mare regions, which cover approximately 17% of the lunar surface (Fig. 5.1). Mare regions are generally considered to be made up of flood basalts, which are the product of highly voluminous basaltic volcanism. On the Moon, such flood basalts typically fill topographically-low impact basins up to 2000 m below the global mean elevation (Wilhelms, 1987). The mare regions are asymmetrically distributed on the lunar surface and cover about 33% of the nearside and only ~3% of the far-side (Wilhelms, 1987). Other volcanic surface features include pyroclastic deposits, domes, and rilles. These features occur on a much smaller scale than the mare flood basalts, but are no less important in understanding lunar volcanism and the internal evolution of the Moon. Table 5.1 outlines different types of volcanic features and their interpreted formational processes. TABLE 5.1 Lunar Volcanic Features Volcanic Feature Interpreted Process
    [Show full text]