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U.S. Scientists Confirm Water on Mars NASA scientists said that Mars was covered once by vast lakes, flowing rivers and a variety of other wet environments that had the potential to support life. Laboratory tests aboard NASA's Phoenix Mars Lander have identified water in a soil sample. The lander's robotic arm delivered the sample Wednesday to an instrument that identifies vapors produced by the heating of samples. 'We have water,' said William Boynton of the University of Arizona, lead scientist for the Thermal and Evolved-Gas Analyzer, or TEGA. 'This is the first time Martian water has been touched and tasted. ' The robotic arm is a critical part of the Phoenix Mars mission. It is needed to trench into the icy layers of northern polar Mars and deliver samples to instruments that will analyze what Mars is made of, what its water is like, and whether it is or has ever been a possible habitat for life. The soil sample came from a trench approximately 2 inches deep. When the robotic arm first reached that depth, it hit a hard layer of frozen soil. Two attempts to deliver samples of icy soil on days when fresh material was exposed were foiled when the samples became stuck inside the scoop. Most of the material in Wednesday's sample had been exposed to the air for two days, letting some of the water in the sample vaporize away and making the soil easier to handle. 'Mars is giving us some surprises,' said Phoenix principal investigator Peter Smith of the University of Arizona. 'We're excited because surprises are where discoveries come from. One surprise is how the soil is behaving. The ice-rich layers stick to the scoop when poised in the sun above the deck, different from what we expected, from all the Mars simulation testing we've done so far. ' Since landing on May 25, Phoenix has been studying soil with. a chemistry lab, TEGA, a microscope, a conductivity probe and cameras. The science team is trying to determine whether the water ice ever thaws enough to be available for biology and if carbon-containing chemicals and other raw materials for life are present. The mission is examining the sky as well as the ground. A Canadian instrument is using a laser beam to study dust and clouds overhead. 'It's a 30-watt light bulb giving us a laser show on Mars,' said Victoria Hipkin of the Canadian Space Agency. A full-circle, color panorama of Phoenix's surroundings also has been completed by the spacecraft. 'The details and patterns we see in the ground show an ice-dominated terrain as far as the eye can see,' said Mark Lemmon of Texas A & M University, lead scientist for Phoenix's Surface Stereo Imager camera. 'They help us plan measurements we're making within reach of the robotic arm and interpret those measurements on a wider scale. ' What was discovered by NASA's Phoenix Mars Lander on Mars?
A.
Vast lakes.
B.
Flowing rivers.
C.
Water in a soil sample.
D.
Living things.
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【简答题】下列关于替代品的说法,正确的有( )。
【判断题】混凝土立方体抗压强度标准值就是混凝土的强度等级
A.
正确
B.
错误
【多选题】下列构件中,达到设计要求的混凝土立方体抗压强度标准值的75%后就可以拆模的是()
A.
跨度>2米且≤8米的板
B.
跨度>8米的梁
C.
跨度≤8米的梁
D.
跨度≤2米的悬臂构件
E.
跨度>2米的悬臂构件
【单选题】在突触的描述中,哪一项错误?()
A.
突触是神经元与神经元之间特化的细胞连接
B.
突触分电突触和化学性突触
C.
化学性由突触前成分、突触间隙、突触后成分组成
D.
突触小泡内含有神经递质的受体
【单选题】对于突触描述错误的是
A.
突触可分为电突触和化学突触两类。
B.
电突触是通过桥粒连接传递信息。
C.
突触是神经元间传递信息的特化连接结构
D.
电突触在任何哺乳动物中较少。
【单选题】dasdsa
A.
dsdsd
B.
adasdsadasdasd
C.
fdfdfdf
D.
vcxvxvxc
【单选题】fdfdfdf
A.
fdfdf
B.
dfdfdsfdsf
C.
fdfdfds
D.
fdfdsfdsfdsff
【单选题】以下关于光源光网络 PON 特点的描述中,错误的是
A.
无源光网络 PON 是一种点对多点的系统
B.
无源光接入网 ODN 典型的拓扑是网状结构
C.
目前发展最快的是 PON 与 Ethernet 相结合的 EPOS 技术
D.
IEEE 制定了下行速率提高到 10Gpbs 的 802.3av 10Gbps EPON 标准
【单选题】()是依法治国的主体和力量源泉,人民代表大会制度是保证人民当家作主的根本政治制度。
A.
知识分子
B.
群众
C.
人民
D.
党员干部
【单选题】以下关于接入技术特征的描述中,错误的是______。
A.
HFC技术通过有线电视网互连各个终端用户,再通过光纤结点宽带连接Internet
B.
ADSL MODEM利用频分复用的方法,将信道分为上行信道和下行信道
C.
宽带无源光网络是PON和ATM相结合的产物,接入距离可以达到20~30km
D.
IEEE 802.16标准的重点在于解决局域网范围的移动结点通信问题
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