专八英语考前自测冲刺题：改错（二）

会计考友

Mars has provoked much speculation on the possibili- (1)
ties of life beyond Earth than any planet in the Solar System. (2) __
The presence of water is a prerequisite for the existing of life. (3) __
5 n  [- ~; p3 j/ pTherefore, "follow the water" has been NASA' s chief guide-
line for the exploration of a red planet. Although Mars experi- (4)
ences seasons like on Earth and has polar caps which com- (5) __
5 S5 b7 y' a3 X4 A% E! S& Gposed of carbon dioxide and water ice, today it is bone-dry and
) d  A" F4 F, H, Q* X6 Z9 C; Rfrigidly cold. But evidence is rapidly accumulating Mars was (6) __
6 z) D1 G$ c' Q0 G3 donce much wetter, with a more clement climate. This evidence
& H' K& D6 D% y6 W) vcomes from orbiting satellites and from data collected by rov-
ing landers.
      Since 1970s, space probes to Mars have revealed numer- (7) __
/ u3 |; ]8 `8 |* K4 g. tous features apparent carved by flowing water, such as wind-
Lng, branched valleys resembling dried-out streambeds and gi-
" A3 R+ s$ c+ _5 Z# ]. Q2 }! }2 zant outflow channels gouged by catastrophic floods. Recent
high-resolution imagery from the Mars Global Surveyor Mars
0 X' c, H5 J8 N" W& h. WOrbiter Camera and the Mars Odyssey THEMIS reveal nu- (8) __
merous examples of branched valleys that form tightly-packed,
integrated drainage systems. These channels origins at topo- (9) __
graphic high points; the valleys widen "downstream", some
/ ~- f& O. E: m: H4 j; neven displaying inner valleys. The valley networks exhibit
) `: T. M; B# |& G! c% ]5 bmorphometric characteristics, including network densities,
comparative to those of terrestrial drainage basins. These fea- (10) __
tures were most likely produced by rainfall, during wetter,
warmer periods in the past.