Mars has provoked much speculation on the possibilities of __1__
life on Earth than any other planet in the Solar System. __2__
The presence of water is a prerequisite for the existing of life. __3__
Therefore, “follow the water” has been NASA’s chief guideline
for the exploration of a red planet. Although Mars experiences __4__
seasons like on Earth and as polar caps which composed __5__
of carbon dioxide and water ice, today it is bone-dry and frigidly
cold. But evidence is rapidly accumulating that Mars is once __6__
much wetter, with a more clement climate.
This evidence comes from orbiting satellites and from data collected
by roving landers.
Since the 1970s, space probes of Mars have revealed __7__
numerous features apparent craved by flowing water, such as
winding, branched valleys resembling driedout streambeds
and giant outflow channels gouged by catastrophic floods.
Recent high-resolution imagery from the Mars Odyssey Themis
reveal numerous examples of branched valleys that from __8__
tightly-packed integrated drainage system. These channels
origins at topographic high points; the valleys widen “downstream”, __9__
some even displaying inner valleys. The valley networks densities,
comparative to those of terrestrial drainage basins. __10__
These features were most likely produced by rainfall, during wetter, warmer periods in the past.

答案：
1、much—more 或much后加more 句法錯誤，后半部分出現(xiàn)了than，前半部分用比較級
2、on---beyond 詞匯錯誤，“地球以外的生命”不因該用on。
3、existing—existence 此行混淆，“生命的存在”應用existence。
4、a---the
5、which去掉或which后加are，句法錯誤。
6、is---was 句法錯誤，時態(tài)錯誤。雖然主句的時態(tài)是現(xiàn)在進行時，但是從句中有時間狀語once，所以用過去時。
7、of-----to 詞匯錯誤，probe與to，into搭配。
8、reveal---reveals 主謂不一致。
9、origins-----originates 詞性混淆。Origin是名詞意思是“起源，由來”，動詞形式為originate意思是“引起，起源”
10、comparative---comparable詞匯錯誤。句意為：谷地網(wǎng)絡呈現(xiàn)變種度量特征，包括與陸地流域盆地相似的網(wǎng)狀密度。應用可比較的comparable。