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General Disclaimer One Or More of the Following Statements May Affect General Disclaimer One or more of the Following Statements may affect this Document This document has been reproduced from the best copy furnished by the organizational source. It is being released in the interest of making available as much information as possible. This document may contain data, which exceeds the sheet parameters. It was furnished in this condition by the organizational source and is the best copy available. This document may contain tone-on-tone or color graphs, charts and/or pictures, which have been reproduced in black and white. This document is paginated as submitted by the original source. Portions of this document are not fully legible due to the historical nature of some of the material. However, it is the best reproduction available from the original submission. Produced by the NASA Center for Aerospace Information (CASI) ." I NA IONAL AENUNAU I Ic ; AND :,DACE ADMINISTRATION 'fHE NOW FRONTILI{ LINKING EARTH AND PLANETS (NASA-C'- 14 2 ) U ,5 ll PLAT. (J-t Prop il:ilon ib.) p Fi g -p 9.25 ,:SC:L 01B ''",c; 63/141 '" ^ entis and Mercury as Planets N ,^t ^ 9lOjj^^ w h j r- G S JET PROPULSION LABORATORY ISSUE NUMBER TWO CALIFORNIA INSTITUTE OF TECHNOLOGY PASADENA, CALIFORNIA PUBLIC EDUCATIONAL SERVICES OFFICE EVOLUTION OF THE PLANETARY into Earth's atmosphere to break water vapor SYSTEM into o x ygen and hydrogen. This is importam because the hydrogen would bubble off into Planets of the solar system probably formed , pace like steam from a saucepan arid grad four to five billion years ago when hosts of ually Earth would have lost its oceans in this ,mall rocky particles and clouds of gases way -ollected together by their own gravity. Gravity appears to be a universal property of A phutographic mosaic of the Earth, taken natter, as a result of which every particle, by Mariner 10, is shown in Figure 1. -io matter how small, attracts every other. Thus, left to themselves in space, individual THE CHARAC fERISTICS OF :)articles lend a gas consists of particles. VENUS nolecules) tend to collect together into large Masses. Venus is very similar to Earth in site and mass its rhanieter rs 7,520 miles compared So after the Sun condensed front pri- with Earth's 7,920, its mass and density are tieval nebula, planets of different sites and slightl', less than those of Earth. Physically )robably different composition originated the two plari:;ts -ire almost twins, but they from concentrations of matter present at seem to have groan up quite differently. various distances from the Sun. Arid electric and magnetic fields in the gas forced these Venus, too, is Earth's nearest neighbor in 'ondensing planets into o. pits around the space after the Moon. Its closest approach is central Sun and spun them on their own axes 26 million m' ompared with 34 million like tops. miles for Mars. Figure 1. A mosaic view of the Earth taken by Mariner 10 on its way to Venus and The larger craters ore Mi-s, the Moon, and But a telescope reveals virtually no details on Venus are thought to be gouged by filling the bright disc of the planet. Some obser• Mercury. Such pictures were used by the engineers and scientists to test the space- bodies during the final stages of planetary vers Have recorded faint arid elusive markings, craft's cameras in space. These pictures were accretion. as the process of falling together is visible in the near ultraviolet, ill-defined dark termed. Smaller ones represent a continuing shadows and aright patches seemingly be- taken when Mariner 10 was 120,000 miles front but much lower rate of bombardment by iraviitrJ v^ry much as cloud systerns might solar system debris. behave. quantities of heat that might have been the The absence of surface features or persis- While Mariner 10, now on its way to Venus, cause of extensive volcanism to generate the tent cloud features made it difficult to deter- is not designed to find out anything directly dense atmosphere of Venus. mine the period of rotation of Venus on its about life on Venus, .he scientific informa- axis. Wildly varying estimates were made, tion about conditions on Venus may be im. Venus has been the target for several earlier ranging from a 24 hour day like that of Earth portant to biologists seeking understanding space missions: two successful flybys were to a day equal to the Venusian year. The of why Earth spawned lite and Venus did made by earlier Mariners, and Soviet Veneta question was riot answered until recently not. It was life in the pr imitive atmosphere spacecraft flew by, orbited, and landed cap- Men radio waves penetrated the thick clouds of Earth which helped to produce the sules on the surface. These probes confirmed of the brilliant planet. Surprisingly, it was oxygen-rich atmosphere that in turn keeps a a high surface to iperature of around 4750C found that Venus rotates in 243 days in the lid on the oc-any and stops them leaking and a pressure at the base of Venus' atmos opposite diraction to that of the Earth. This off into space. Oxygen, converted to ozone phere about equal to that at a depth of 400 is slightly longer than the Venus year-the it high altitude by the Sun's rays, prevents fathoms in Earth's oceans. Genera„y Venus time the planet takes to revolve around the solar ultraviolet from penetrating low enough is a hot dry planet with only slight traces of Sun, which is 225 Earth days. Because of water vapor in its atmosphere of 95 per- the rotation and revolution in opposite di- cent carbon dioxide. There are also traces of Cover The planet Venus as it has been rections, the day on Venus is only 127 Earth oxygen, nitrogen, and inert gases, it is ohs.?rved from Earth through the technique days. But these figures pose the question of believed. of radar mapping, in which a radar signal is how Venus might have slowed down from bounced off the surface of the planet. The rotating as the other planets do and started The clouds of Venus, which, according to re- three light areas marked with Greek letters to rotate in the opposite direction. One of cent spectroscopic observations, may have a (a, 13, and h) are rough sections that may be several theories is that Venus captured a large topmost layer of concentrated sulfuric acrd mountains, but could also be craters or Moon like body moving in the opposite di- droplets, are about 18 to 25 miles thick, and bouldor field's. The mapping was done by rection to Venus' spin and that this body their tops may be about 90 miles above the the Jet Propulsion Laboratory (JPL), using crashed onto the surface of Venus. The surface, compared with Earth's highest clouds the NASA/JPL deep space antennas at Gold- impact would have stopped Venus from rota- of six miles or so. Below the Venus clouds stone, California. ting and would also have released tremendous is a clear atmosphere, while the cloud em- 1 selves probabl y consist of stacked layers of atmosphere build ap such high pressures? One theory suggests that water rs flapped in different composition, for example, carbon How could bodies plunge throerfll this dense volurninous polar cap', of Venus, another, dioxide ice at some levels and water ice at ahnospheie to produce craters detected by that all the water was lost because water ;ethers. riidar? vapor could rise in the atmosphere of Venus and be broken down by sunlight into oxygen Cloud features seen in ultraviolet light appear Answers to these and other questions about and hydrogen. The hydrogen !riled off into to move around the planet in only four days. Venus will help us understand how planets space. But what happened to the oxygen ? It There are also some large scale ulr and-down evo ve and why there is an Eden like Earth does not aplwar to be left in the atnwsphere. pulsations of the cloud layers. while nearby planets are so inhospitable. Understandinghow the atmosphere of Venus On the other hand, the major differences An •iteresting theoretical aspect of the dense became, or stayed, inimical to life may help among the terrestrial plane. s may have arisen but clear atmosphere below the clouds of us prevent our own atmosphere front to;;ause these planets former; at different dis- Venus is that if a student could stanc r on the wrong too, either from natural or man- tances from the Sun aril thus consisted of surface and look around, he would appear to made causes. An Important question today different rrlaterials in the first inst,.nre. For be standing in the bottom of a vast bowl. is whether pollution might tugger drastic example, Mercury might have formed from Looking into the distance in each direction, change s in Earth's atmosphere which could materials rich in iron, whereas Venus formed he would see a blurred, ruddy red landscape change our planet into another Venus. ;rom silicate-rich materials. Arid Earth may F curving upwards towards the cloud layers as have accreted in a region in wfuch there were though he were inside a hollow planet: the At the distance of Venus from the Sun itt water containing substances while Venus did atmosphere, acting like a grant lens, v )uld temperature would ue expected r j be abcat not. Calculations have shown that the pri- bend the light rays upwards in an eftrct GOoC on the average if it we a an aide-, meval nebula mryht have separated in this similar to a mirage appearing on a hot road body.
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