美国航天局宣布火星表面发现了有液态水活动的证据 :3hjj.cn/155

名本

NASA confirms present-day salt water flows on Mars

It was a search hundreds of years old. On Monday, NASA announced what so many have sought for so long – a groundbreaking discovery by the Mars Reconnaissance Orbiter (MRO) of definitive evidence of recent salt water flows on Mars. The discovery confirms long-held suspicions and mounting evidence from MRO and places Mars into a category of a planet that until now only had one occupant – planets with current water flow activity.

Mars Reconnaissance Orbiter’s storied history:

MRO, one of two missions considered as part of the 2003 Mars launch window opportunity, was designed to be a permanent orbiting presence at Mars with a suite of instruments performing detailed, round-the-clock, yearly observation of the Martian surface.

In this way, MRO would be able to detect seasonal, yearly, and unanticipated for changes in the Martian terrain on a regular basis.

With an initial mission duration of two Earth years, one Martian year, from November 2006 to November 2008, MRO was launched from the Cape Canaveral Air Force Station, Florida, atop an Atlas V rocket on 12 August 2005.

After a seven and a half month journey from Earth, MRO arrived at Mars for orbital insertion operations on 10 March 2006.

A 27 minute engine burn slowed MRO from 2,900 to 1,900 m/s, allowing it to be captured by Mars’ gravity in a highly elliptical polar orbit with an initial orbital period of 35.5 hours.

MRO then spent the first five months of its tenure at Mars in an aerobraking orbit to continuously lower and circularize its orbit for shorter periods.

Aerobraking and orbit circularization maneuvers were completed on 30 August 2006 followed by two September firings of MRO’s thrusters to fine-tune its near-circular orbit to 250 x 316 km above the Martian surface with an orbital period of 112 minutes.

By 2009, radar measurements obtained from MRO allowed scientists to accurately measure the northern polar ice cap of Mars and determine its volume of water ice at 821,000 cubic km, approximately 30% of the Greenland ice sheet on Earth.

Furthermore in 2009, information from MRO led to the discovery that some craters on Mars had been recently excavated with relatively pure water ice.

Captured by the Compact Imaging Spectrometer onboard MRO, the new craters were found to have been formed by ice after it was exposed to the surface environments and sublimated away.

A total of five of these craters were identified in various locations around the planet via information from MRO.

Moreover, information gathered by MRO has suggested that features called Lobate Debris Aprons (LDAs) contain large amounts of water ice due to their convex topography and gentle slopes, suggesting flow away from the steep source cliff.

These LDAs were further shown to have surface lineation just as rock glaciers on Earth.

That, coupled by strong reflections from the top and base of the LDAs suggested – though it was never confirmed – that pure water ice made up part of the formation.

Additionally, MRO provided data triangulated between itself, the Mars Global Surveyor, and Mars Odyssey regarding widespread deposits of chloride minerals.

On Earth, places with chloride minerals have supported life in the past and have preserved traces of ancient life.

But MRO’s greatest find came on its 2,125th solar day of operation at Mars – 4 August 2011 – when NASA announced that MRO had detected what appeared to be evidence of flowing salty water on the surface of Mars.

The potential discovery was made when MRO photographed dark, finger-like features extending down the side of some Martian slopes.

The finger-like features were observed to have faded away in winter and returned the following spring – observations possible due to the nature of MRO’s constant observational campaigns.

In fact, it would be these exact finger-like structures and the study of additional data from MRO that would lead to today’s announcement of the confirmation that liquid salty water flows are indeed present on current-day Mars.

名本

Water on Mars:

The new findings from MRO provide the strongest evidence yet that liquid water flows intermittently on present-day Mars.

Using an imaging spectrometer on MRO, researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the red planet.

These darkish streaks appear to ebb and flow over time. They darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons.

They appear in several locations on Mars when temperatures are above minus 10 degrees Fahrenheit (minus 23 Celsius) and disappear at colder times.

“Our quest on Mars has been to ‘follow the water’ in our search for life in the universe, and now we have convincing science that validates what we’ve long suspected,” said John Grunsfeld, associate administrator of NASA’s Science Mission Directorate in Washington.

“This is a significant development, as it appears to confirm that water – albeit briny – is flowing today on the surface of Mars.”

These downhill flows, known as recurring slope lineae (RSL), have often been described as possibly related to liquid water.

The new findings of hydrated salts on the slopes point to what that relationship may be to these dark features. The hydrated salts would lower the freezing point of a liquid brine, just as salt on roads here on Earth causes ice and snow to melt more rapidly.

See Also

• Robotics Forum Section
• Mars Forum Section
• L2 Exploration Section
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“We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration,” said Lujendra Ojha, lead author of a report on these findings published Sept. 28 by Nature Geoscience.

“In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks.”

HiRISE observations now have documented RSL at dozens of sites on Mars. The new study pairs HiRISE observations with mineral mapping by MRO’s Compact Reconnaissance Imaging Spectrometer for Mars.

The spectrometer observations show signatures of hydrated salts at multiple RSL locations, but only when the dark features were relatively wide.

When the researchers looked at the same locations where RSL weren’t as extensive, they detected no hydrated salt.

Ojha and his co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate.

NASA’s Phoenix lander and Curiosity rover both found perchlorates in the planet’s soil, and some scientists believe that the Viking missions in the 1970s measured signatures of these salts.

However, this study of RSL detected perchlorates, now in hydrated form, in different areas than those explored by the landers. This also is the first time perchlorates have been identified from orbit.

“The ability of MRO to observe for multiple Mars years with a payload able to see the fine detail of these features has enabled findings such as these: first identifying the puzzling seasonal streaks and now making a big step towards explaining what they are,” said Rich Zurek, MRO project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

For Ojha, the new findings are more proof that the mysterious lines he first saw darkening Martian slopes five years ago are, indeed, present-day water.

*Click here for more Mars Articles*

“When most people talk about water on Mars, they’re usually talking about ancient water or frozen water. Now we know there’s more to the story. This is the first spectral detection that unambiguously supports our liquid water-formation hypotheses for RSL.”

The discovery is the latest of many breakthroughs by NASA’s Mars missions.

“It took multiple spacecraft over several years to solve this mystery, and now we know there is liquid water on the surface of this cold, desert planet,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program.

“It seems that the more we study Mars, the more we learn how life could be supported and where there are resources to support life in the future.”

While the historic nature of this discovery cannot be understated, the confirmed presence of present-day liquid flowing water on the surface of Mars continues to lend evidence to the hypothesis that Mars was once a habitable planet that could have harbored life.

Moreover, the discovery holds potentially significant implications for current-day life on Mars. For on Earth, where there’s liquid water, there’s life.

However, the more immediate consideration is how this discovery will influence future human missions to the red planet.

The presence of not only water ice at the Martian poles but flowing, briny water on other areas of the planet under certain conditions holds great significance for future human exploration and the use of in-situ resources that may be vital to any human exploration of Mars.

(Images: Via NASA, NASA JPL and L2 – including SLS renders from L2 artist Nathan Koga – The full gallery of Nathan’s (SpaceX Dragon to MCT, SLS, Commercial Crew and more) L2 images can be *found here*)

(To join L2, click here: http://www.nasaspaceflight.com/l2/)

September 28, 2015 by Chris Gebhardt   NASA confirms present-day salt water flows on Mars
http://www.nasaspaceflight.com/2 ... t-water-flows-mars/

名本

3hhh.cn/155 :美国航天局宣布火星表面发现了有液态水活动的证据 :3hjj.cn/155
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火星侦查卫星（Mars Reconnaissance Orbiter）拍摄的照片

名本

▲圖中左下角密集、狹窄而長約百米的黑色條紋為流動水存在火星表面的證據。

無論是美國國家航空暨太空總署 （NASA）或歐洲太空總署（ESA）都曾以研究指出「火星表面有以冰冠形式存在的水體」，但無法證實水在火星能以液態的形式存在，不過，從今天起，我們可能要重新形塑對火星的認知了！NASA 於美東時間 28 日上午 11 時 30 分（台灣時間 28 日晚間 11 時 30 分）召開記者會，宣布發現火星上確實有液態水存在的證據。

若經常追隨火星新發現的新聞就不難發現，這並不是第一次有研究指出火星存在液態水了。NASA 於今年 3 月公布的研究曾指出，火星在距今 43 億年前，表面曾存在體積比北極海還要大的海洋，當時覆蓋面積為北半球的一半，部分水深甚至超過 1.6 公里，另外，火星探測器「好奇號」（Curiosity）最近也發現了火星表面下曾存在液態水體。許多年以來，不少科學家爭相釋出有關「火星液態水」的研究，每一次的發現都讓人懷抱期待，但每每總是缺乏足夠的證據支持。

不過，NASA 這次公布的重大發現，為有史以來針對「火星表面存在液態水」的假說提供最直接的證據，而這項研究同時也證實了 NASA 長久以來關於「火星表面奇特的黑色條紋為流動液態水所形成」的猜測。這些黑色條紋為 NASA 的「火星偵察軌道器」（Mars Reconnasissance Orbiter，MRO）於 2010 年所發現，條紋寬度小於 16 英尺（約 4.96 公尺），會在較溫暖的季節裡擴大、在較寒冷的季節減少進而消失。

火星上的平均溫度為攝氏零下 80 度，但炎熱夏天在赤道附近時，火星溫度可達攝氏 70 度以上，而觀察隨季節變換而有所改變的黑色條紋後，科學家認為，水及鹽分或許與這些黑色條紋的形成有關。首位提出火星隨季節變換而有流動鹽水理論的阿特蘭大喬治亞技術學院科學家 Lujendra Ojha 與其團隊便推測，若環境條件夠溫暖，液態水裡可能充滿高氯酸鹽、形成鹽水溶液，而高氯酸鹽水的冰點比水還要低許多，讓其即使在冬季溫度可降至攝氏零下 125 度的火星環境下，仍然能維持液態水形式，而鹽水隨著季節變換的流動，在水分乾枯後，就能將鹽分留在所經的火星表面，形成所見的黑色條紋。

利用 MRO 的透過可見光紅外成像光譜儀，觀察不同光波長以得知該黑色條紋的礦物組成為何，科學家研究了火星表面季節性反覆出現的黑色條紋，研究結果發現，這些黑色條紋確實是由晶體結構中含有水分子的鹽水，在水分乾枯後，殘留火星表密所形成的。

不過，「關於這些水有多少、又是從哪來的」，從 Ojha 與其團隊眼裡看來，至今仍是個待解的謎團， 但 Ojha 認為這些水有 3 種可能的來源。一為在火星空氣特別潮濕時，由高氯酸鹽吸收大氣中的水分形成鹽水；二為火星內部冰層融化滲出，與鹽接觸後形成鹽水；第三個可能，則來自地下含水土層。

姑且不論水的來源為何，這次 NASA 所公布的重大發現，對於火星存在液態水可說是證據確鑿了，也大大增加了火星可能存在如微生物等生命體的可能性。

• NASA confirms that liquid water flows on Mars
  

作者 林 薏茹 | 發布日期 2015 年 09 月 29 日 距離發現生命體不遠了？NASA 找到火星有液態水的最佳證據
http://technews.tw/2015/09/29/nasa-confirms-the-best-ever-evidence-for-water-on-mars/

名本

火星Mars上有水?


今天NASA宣布：

New findings from NASA's Mars Reconnaissance Orbiter (MRO) provide the strongest evidence yet that liquid water flows intermittently on present-day Mars.
标题是‘最强有力证据’表明“今天的火星上有液体水间歇性流动”，来看看其中的几个单词：
reconnaissance， 侦查、勘测
orbiter，人造卫星，盘旋物
intermittent，间歇的
NASA，The National Aeronautics and Space Administration 美国国家航空航天管理局

火星Mars这个单词，来自于罗马神话里的战神Mars，因为火星表面多氧化铁Iron Oxide而显得‘血红’，而血总是跟战争有关的，所以以战神Mars的名字命名之。血红的Mars如下图，其实也没有那么红啦。

火星在太阳系里Solar System里是第二小，按比例相对地球大小如下图：

上图中，从左往右，分别是地球Earth、火星Mars、金星Venus、水星Mercury

与其他行星相对位置如下（大小是实际比例，距离不是实际比例）：

上图中，围绕太阳旋转的，从最近到最远分别是：Mercury水星、Venus金星、Earth地球、Mars火星、Jupiter木星、Saturn土星、Uranus天王星、Neptune海王星，从图中可以看出，火星与地球的大小及与太阳之间的距离相差都不大，这也是世界上的科学家都想在登上月球之后，最希望登上的星球。

从下图，可以看看更详细的地球与火星的比较数据，确实和地球差别不是和其他行星那么大，尤其是地表温度，你可以看看（看不清的话，可以点击放大看），如果有不理解的地方，可以留言问我：

注：最后一张图片来自NASA官网，其他图片来自Wikipedia。