Unformatted text preview: the geologic forces that depressed the Northern Hemisphere far below the level of the south, in which case they have nothing whatever to do with Martian water. Furthermore, Mars Global Surveyor data released in 2003 seem to indicate that the Martian surface contains too few carbonate rock layers—layers containing compounds of carbon and oxygen―that should have been formed in abundance in an ancient ocean. Their absence supports the picture of a cold, dry Mars that never experienced the extended mild period required to form lakes and oceans. However, more recent data imply that at least some parts of the planet did in fact experience long periods in the past during which liquid water existed on the surface.
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9. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. ○But detractors argue that geological activity may be responsible for the water associated with the terraces.
○But detractors argue that the terraces may have been formed by geological activity rather than by the presence of water. ○But detractors argue that the terraces may be related to geological forces in the Northern Hemisphere of Mars, rather than to Martian water in the south. ○But detractors argue that geological forces depressed the Northern Hemisphere so far below the level of the south that the terraces could not have been formed by water.
10. According to paragraph 4, what do the 2003 Global Surveyor data suggest About Mars? ○Ancient oceans on Mars contained only small amounts of carbon.
○The climate of Mars may not have been suitable for the formation of large bodies of water.
○Liquid water may have existed on some parts of Mars’ surface for long periods of time.
○The ancient oceans that formed on Mars dried up during periods of cold, dry weather.
Paragraph 5: Aside from some smallscale gullies (channels) found since2000, which are inconclusive, astronomers have no direct evidence for liquid water anywhere on the surface of Mars today, and the amount of water vapor in the Martian atmosphere is tiny. Yet even setting aside the unproven hints of ancient oceans, the extent of the past. Where did all the water go? The answer may be that virtually all the water on Mars is now locked in the permafrost layer under the surface, with more contained in the planet’s polar caps.
11. The word hints in the passage is closest in meaning to ○clues
Paragraph 2: Outflow channels are probably relics of catastrophic flooding on Mars long ago. ■They appear only in equatorial regions and generally do not form extensive interconnected networks. ■Instead, they are probably the paths taken by huge volumes of water draining from the southern highlands into the northern plains. ■The onrushing...
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This note was uploaded on 09/17/2013 for the course LANGUAGE 13DL208 taught by Professor Wang during the Fall '13 term at East China Normal University.
- Fall '13