THE PLANETS ASTR 105G
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This 0 page Class Notes was uploaded by Reina Conn DVM on Sunday November 1, 2015. The Class Notes belongs to ASTR 105G at New Mexico State University taught by Jason Jackiewicz in Fall. Since its upload, it has received 28 views. For similar materials see /class/233213/astr-105g-new-mexico-state-university in Astronomy at New Mexico State University.
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Date Created: 11/01/15
Lecture 20 Atmospheres of Terrestrial Planets ASTR 105C The Planets April 7 2009 Announcements 1 2 3 4 5 HOMEWORK 9 DUE Thursday Exam next Tuesday Chapter 53 Chapter 9 Review session Monday night 7pm Today s stuff will not be on this exam It will be on the nal exam Last week s quiz Last time We compared the geological features of the inner planets Went over in detail the characteristics of Earth s features and how they are formed 1 Atmospheric Science 11 Basic Concepts Motivation Refer to Figure 1 for planet comparisons of atmospheres Importance of Atmospheres for Planets A layer of thin gas that surrounds a planet moon etc Typically cool enough to contain molecules 02 H20 C02 Create pressure due to the motion of molecules decreases with altitude Pressure determines how water exists solid liquid or gas very important Atmospheres absorb scatter re ect light a temperature Give climate and weather Heat a planet by the greenhouse effect Lecture 20 April 7 2009 2 6 Figure 1 Comparison of terrestrial atmospheres Lewm 217 Am 7 217179 9 5 Flgure 2 How the greenhouse effect works here on Earth Greenhouse Effect 7 Energ Exchange Source ol Flgure 2 nthnumbnesamemgmsemnsehml How Does it Work by Earth lt then gets reemltted by the Earth as lnlrared because ol temperature ln an atmosphere lled Wlth water or carbon dloxlde or methane molecules the lnlrared radlatlon gets absorbed lt then gets emltued In any dlrectlon lncludlng down to reheat the surlaoe n any the lower atmosphere Wlthout any greenhouse gases present the Earth would be about 0 degrees Fahrenhelt How Light lnueram with Atmospheres lnlrared hght gets absorbed by greenhouse gases vlslble hght is transparent but gets mlnlmalh scattered Ultrawolet hght can break molecules such as water vapor and orone or Lecture 20 April 7 2009 4 6 o X rays ionize most atoms or molecules a ionosphere Strati cation of the Atmosphere Source of Figure 3 httpWW i lami W 121T14 W Mn N L Dagelhtml Voting question Why is the sky blue A The peak intensity of the Sun s light is in the bluish range B Sunlight gets re ected from the oceans7 which are blue C Air molecules like oxygen and nitrogen are bluish in color D Blue light gets scattered by the molecules in the Earth s atmosphere 0 The answer is D Surface 0 Gets warmed by visible light passing through the atmosphere and reaching the ground 0 Some light gets scattered7 otherwise the sky would look black 0 Our sky scatters blue light the most Troposphere o This is what we are used to and it gets warmed by infrared light 0 Top 10 miles or so 0 Gets colder with altitude1 0 High density 0 This is where storms are born due to heating and convective motions Stratosphere 0 Not heated by Earth s infrared radiation not dense enough 0 Ozone absorbs ultraviolet light and heats these regions 0 No convection here because the heat is on the top not the bottom2 0 Since Earth is the only inner planet with an oxygen atmosphere7 it is alone in having a stratosphere 1httpw mm u d u M 1 m A A mimrim 2h IVW quot mm u d u M m A r 4 m inc Lecture 20 April 7 2009 5 6 Emsphere 119 km m nu mg m Thermosphere 150 km MG km 130 Em 129m 5 3 3 5 W ri A 511 mu m Figure 3 The layers of the atmosphere of the Earth Planets With atmospheres may have similar strati cation Note the temperature pro le With altitude Lecture 20 April 7 2009 6 6 Thermosphere o The topmost layer with any appreciable density 0 The gases here absorb X rays since these are the rst gases the X rays see c This heating can be quite effective3 0 Like a hot oven 0 The thermosphere also gets partially ionized by X rays and this is where the aurora can exist in the ionosphere Exosphere 0 Very high up 1000 km4 0 Very low density Magnetosphere o The solar wind is a steady stream of charged particles from the Sun 0 Objects with no magnetic eld are penetrated by these particles Venus Mars Mercury Moon 0 Objects with strong enough magnetic elds divert the particles5 0 Some get in near the poles and spiral along the eld lines 0 See Figure 1011 6 0 Aurora 0 See how special we are Basic Atmospheric Structure of Inner Planets 0 Forget the Moon and Mercury 0 Earth Venus and Mars have a troposphere o All 3 have a warm thermosphere 0 Earth is only one with a stratosphere because of ozone For next time 1 We will talk about weather on the indiVidual terrestrial planets 3httpw mm u d M 1 m A A Humans 4httpuploadwikimediaorgWildpediaCommons 778 Earl Atmospheresvg 5httpuploadwikimediaorgWilripediacommonsffMagnetospherelenditionjpg 6http WWWknowledgerushComWikiimageee7 Earth7 satmospherejpg
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