Astro 100 Chapter 10.pptx - Astronomy 100 Jaquelin Erazo...

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Jaquelin ErazoCollege of Staten IslandAstronomy 100
Chapter 10 – Earthlike Planets:Venus and Mars
10.1 – The Nearest Planets: OverviewMars and Venus are among the brightest objects in the nightskyThe average distance of Mars from the Sun is 227 millionkilometers (1.52 AU)Venus’ orbit is very nearly circulardistance of 108 million kilometers (0.72 AU) from the Sun.Like Mercury, Venus sometimes appears as an “evening star”and sometimes as a “morning star”Venus approaches Earth more closely than does any otherplanet: at its nearest, it is only 40 million kilometers from usThe closest Mars ever gets to Earth is about 56 millionkilometers
10.1 – The Nearest Planets: Overview(Appearance)Venus appears very brightGalileo discovered that Venus displays a fullrange of phasesused this as an argument to show that Venus mustcircle the Sun and not Earth
Venus as Photographed by the Pioneer VenusOrbiterThis ultraviolet image shows an upper-atmosphere cloudstructure that would be invisible at visible wavelengths. Notethat there is not even a glimpse of the planet’s surface.(credit: modification of work by NASA)
10.1 – The Nearest Planets: Overview(Appearance)In contrast, Mars is distinctly reddue to the presence of iron oxides in its soilThis color may account for its association with war (andblood) in the legends of early culturesThe best resolution obtainable from telescopes on theground is about 100 km, or about the same as whatwe can see on the Moon with the unaided eyeno hint of topographic structure can be detected: nomountains, no valleys, not even impact cratersOn the other hand, bright polar ice caps can be seen easily,together with dusky surface markings that sometimeschange in outline and intensity from season to season
Mars as Seen from Earth’s SurfaceThese are among the best Earth-based photos of Mars, takenin 1988 when the planet was exceptionally close to Earth. Thepolar caps and dark surface markings are evident, but nottopographic features. (credit: modification of work by SteveLarson, Lunar and Planetary Laboratory, University of Arizona)
10.1 – The Nearest Planets: Overview(Appearance)20thcentury: some astronomers believed thatthey saw evidence of an intelligent civilization onMarsThe controversy began in 1877, when Italianastronomer Giovanni Schiaparelli (1835–1910)announced that he could see long, faint, straightlines on Mars that he calledcanale, or channelsIn English-speaking countries, the term wasmistakenly translated as “canals,” implying anartificial origin
10.1 – The Nearest Planets: Overview(Appearance)Even before Schiaparelli’s observations, astronomershad watched the bright polar caps change size withthe seasons and had seen variations in the darksurface features

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Term
Fall
Professor
Robbins
Tags
Mars Global Surveyor

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