文章来源:未知 文章作者:meng 发布时间:2010-06-28 01:45 字体: [ ]  进入论坛

Conditions favourable1 to life may once have existed all over Mars. Detailed2 studies of minerals found inside craters3(火山口) show that liquid water was widespread, not only in the southern highlands, but also beneath the northern plains. ESA's Mars Express and NASA's Mars Reconnaissance(侦查,勘探) Orbiter have discovered hydrated(含水的) silicate4 minerals(硅酸盐矿物) in the northern lowlands of Mars, a clear indication that water once flowed there.

The spacecraft have previously5 discovered thousands of small outcrops in the southern hemisphere where rock minerals have been altered by water. Many of these exist in the form of hydrated clay(粘土) minerals known as phyllosilicates(层状硅酸盐) , and indicate that the planet's southern hemisphere was once much warmer and wetter than it is today.

However, until this week, no sites with hydrated silicate minerals had been found in the northern lowlands, where thick blankets of lava7(火山岩浆) and sediments8 up to several kilometres thick hamper9 efforts to probe the underlying10 bedrock.

The first hints that there may be hydrated silicates6 beneath the northern plains were provided by Mars Express' OMEGA sensor11. However, the outcrops were small and more detailed observations were required to confirm their presence. The OMEGA team sifted12 higher resolution data from a sensor on NASA's orbiter.

Their search concentrated on 91 sizeable impact craters where incoming asteroids13(小行星) had punched down several kilometres, exposing ancient crustal(地壳的) material. As reported this week in the journal Science, at least nine craters were found to contain phyllosilicates or other hydrated silicates.

These minerals, which formed in wet environments on the surface or underground, were identical to those found in the southern hemisphere.

"We can now say that the planet was altered on a global scale by liquid water more than 4 billion years ago," says John Carter, University of Paris, the report's lead author.

With the small sample of widely scattered14 sites, it is difficult to draw conclusions about the type of environment all that time ago. However, the nature and locations of the minerals provide some clues.

"They are rich in iron and magnesium15(镁) , but less in aluminium16. Together with the close proximity17 of olivine, which is easily modified by water, this indicates that the exposure to water lasted only tens to hundreds of millions of years," says Jean-Pierre Bibring, the OMEGA Principal Investigator18 from the University of Paris.

Although Mars' potential habitability did not last long, remarkably19 its record is still preserved in phyllosilicate-rich spots.

A number of scientists have suggested that a shallow ocean subsequently covered the lava-coated northern plains. However, no evidence in support of this is provided by the new results.

"Our studies do not find any signs of the lava plains in the north being altered by water," says Dr Bibring.

On a positive note, the new results may suggest sites for future landers because evidence for water during the early history of Mars suggests that conditions may have been favourable for the evolution of primitive20(原始的,远古的) life.

"These results reveal the history of Mars derived21 from the planet's mineralogy(矿物学) ," says Olivier Witasse, ESA Project Scientist for Mars Express. "It is another example of the fruitful cooperation between European and American scientists."


1 favourable favourable     
  • The company will lend you money on very favourable terms.这家公司将以非常优惠的条件借钱给你。
  • We found that most people are favourable to the idea.我们发现大多数人同意这个意见。
2 detailed xuNzms     
  • He had made a detailed study of the terrain.他对地形作了缜密的研究。
  • A detailed list of our publications is available on request.我们的出版物有一份详细的目录备索。
3 craters 1f8461e3895b38f51c992255a1c86823     
n.火山口( crater的名词复数 );弹坑等
  • Small meteorites have left impact craters all over the planet's surface. 这个行星的表面布满了小块陨石留下的撞击坑。 来自《简明英汉词典》
  • The battlefield was full of craters made by exploding shells. 战场上布满弹坑。 来自《现代英汉综合大词典》
4 silicate 4EXy2     
  • There are large amounts of aluminum silicate in the area.这个地区有大量的硅酸铝。
  • Silicate minerals are characteristically refractory and difficult to break down.硅酸盐矿物的特点是耐熔和难以分离。
5 previously bkzzzC     
  • The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
  • Let me digress for a moment and explain what had happened previously.让我岔开一会儿,解释原先发生了什么。
6 silicates 5fa96a51fc1f734c7fad1c2ffc3a862b     
n.硅酸盐( silicate的名词复数 )
  • Did equilibration take place before or after setting of chromite and silicates? 究竟平衡作用发生在铬铁矿和硅酸盐下沉之前,还是在其后? 来自辞典例句
  • The commercial product however, containing silica and silicates, has a positive effect. 然而含有硅石和硅酸盐的工业品都有肯定的效果。 来自辞典例句
7 lava v9Zz5     
  • The lava flowed down the sides of the volcano.熔岩沿火山坡面涌流而下。
  • His anger spilled out like lava.他的愤怒像火山爆发似的迸发出来。
8 sediments 8b3acb612b624abdf2c2881bc6928565     
沉淀物( sediment的名词复数 ); 沉积物
  • When deposited, 70-80% of the volume of muddy sediments may be water. 泥质沉积物沉积后,体积的70-80%是水。
  • Oligocene erosion had truncated the sediments draped over the dome. 覆盖于穹丘上的沉积岩为渐新世侵蚀所截削。
9 hamper oyGyk     
  • There are some apples in a picnic hamper.在野餐用的大篮子里有许多苹果。
  • The emergence of such problems seriously hamper the development of enterprises.这些问题的出现严重阻碍了企业的发展。
10 underlying 5fyz8c     
  • The underlying theme of the novel is very serious.小说隐含的主题是十分严肃的。
  • This word has its underlying meaning.这个单词有它潜在的含义。
11 sensor sz7we     
  • The temperature sensor is enclosed in a protective well.温度传感器密封在保护套管中。
  • He plugged the sensor into a outlet.他把传感器插进电源插座。
12 sifted 9e99ff7bb86944100bb6d7c842e48f39     
v.筛( sift的过去式和过去分词 );筛滤;细查;详审
  • She sifted through her papers to find the lost letter. 她仔细在文件中寻找那封丢失的信。 来自《简明英汉词典》
  • She sifted thistles through her thistle-sifter. 她用蓟筛筛蓟。 来自《简明英汉词典》
13 asteroids d02ebba086eb60b6155b94e12649ff84     
n.小行星( asteroid的名词复数 );海盘车,海星
  • Asteroids,also known as "minor planets",are numerous in the outer space. 小行星,亦称为“小型行星”,在外太空中不计其数。
  • Most stars probably have their quota of planets, meteorids, comets, and asteroids. 多数恒星也许还拥有若干行星、流星、彗星和小行星。
14 scattered 7jgzKF     
  • Gathering up his scattered papers,he pushed them into his case.他把散乱的文件收拾起来,塞进文件夹里。
15 magnesium bRiz8     
  • Magnesium is the nutrient element in plant growth.镁是植物生长的营养要素。
  • The water contains high amounts of magnesium.这水含有大量的镁。
16 aluminium uLjyc     
n.铝 (=aluminum)
  • Aluminium looks heavy but actually it is very light.铝看起来很重,实际上却很轻。
  • If necessary, we can use aluminium instead of steel.如果必要,我们可用铝代钢。
17 proximity 5RsxM     
  • Marriages in proximity of blood are forbidden by the law.法律规定禁止近亲结婚。
  • Their house is in close proximity to ours.他们的房子很接近我们的。
18 investigator zRQzo     
  • He was a special investigator for the FBI.他是联邦调查局的特别调查员。
  • The investigator was able to deduce the crime and find the criminal.调查者能够推出犯罪过程并锁定罪犯。
19 remarkably EkPzTW     
  • I thought she was remarkably restrained in the circumstances. 我认为她在那种情况下非常克制。
  • He made a remarkably swift recovery. 他康复得相当快。
20 primitive vSwz0     
  • It is a primitive instinct to flee a place of danger.逃离危险的地方是一种原始本能。
  • His book describes the march of the civilization of a primitive society.他的著作描述了一个原始社会的开化过程。
21 derived 6cddb7353e699051a384686b6b3ff1e2     
vi.起源;由来;衍生;导出v.得到( derive的过去式和过去分词 );(从…中)得到获得;源于;(从…中)提取
  • Many English words are derived from Latin and Greek. 英语很多词源出于拉丁文和希腊文。 来自《简明英汉词典》
  • He derived his enthusiasm for literature from his father. 他对文学的爱好是受他父亲的影响。 来自《简明英汉词典》
TAG标签: life water Mars