Ancient lakes on Mars could have hosted life, say scientists
Ancients lakes that prove there could have been life on Mars have been discovered by British scientists.
By Louise Gray, Environment Correspondent
Published: 5:23PM GMT 04 Jan 2010
有片：
http://www.telegraph.co.uk/news/newsvideo/?bcpid=4464161001&bctid=60279266001
A forensic examination of satellite images revealed lakes up to 12.5 miles (20km) wide along Mars' equator - similar to those found in Alaska and Siberia.
一法醫式檢驗的衛星圖像顯示，沿火星赤道的湖泊寬12.5英里（20公里）-類似在阿拉斯加和西伯利亞發現的。
But importantly, the lakes were linked by small tributaries and rivers, suggesting water was moving which means they would have been able to support microbial life, scientists from Imperial College London found.
Previously scientists believed that the lakes were merely ice, the research published in the journal Geology reported.
但重要的是，湖泊聯繫住小支流和河流，顯示水在動，這意味著他們已經能夠支持微生物的生命，英國倫敦帝國學院的科學家發現。此前科學家們認為湖泊純然是冰，地質雜誌的研究報告發表中說。
The lakes have been dated back three billion years and were probably created following volcanic activity in the region around the equator, which was previously thought to be a dry and arid.
Researcher Sanjeev Gupta, of Imperial College London, said the findings shed new light on our understanding of life on Mars.
"Potentially life could have survived in these lakes, we would be talking about microbial life," he said.
"But these are a potential place to go and look for that life."
The lakes are now dry but the depressions on the surface of Mars which they created remain, Mr Gupta said.
Mr Gupta said the tributaries and rivers which can been seen on the satellite photographs were an important indicator of the potential for life.
"We had discovered these depressions that could be lakes but they could have just contained ice which turned into gas when it melted but these channels connecting the lakes prove that the water must have been standing," he said.
Researchers had previously thought that there was water - and possibly life on Mars - around 3.8 to 4 billion years ago.
But today's findings throw open a whole new area of research after proving that the possibility of life was over a longer period of time.
The Imperial College researchers used images from the Mars Reconnaissance Orbiter to analyse the lakes.
Researchers plan to now focus their study on other areas along the equator of Mars to discover how widespread these lakes were and if the findings show there was widespread habitats that could have supported life.
http://www.telegraph.co.uk/science/space/6932130/Ancient-lakes-on-Mars-could-have-hosted-life-say-scientists.html
火星上的古代湖床 被美國Nasa探測到
Mars' ancient lake beds spied by Nasa probe
By Jonathan Amos
Science correspondent, BBC News
Page last updated at 15:09 GMT, Monday, 4 January 2010
A channel connects two depressions in this MRO image
在這MRO影像中，一條通道連接兩個凹陷位
New images of Mars suggest the Red Planet had large lakes on its surface as recently as three billion years ago.
新的火星圖像表明，這個紅色星球表面有大型湖泊，最近在三十億年前。
The evidence comes from Nasa's Mars Reconnaissance Orbiter (MRO) which spied a series of depressions linked by what look like drainage channels.
這些證據來自美國Nasa的火星偵察軌道器（MRO），它偵察一系列看來是被排水通道聯繫在一起的凹陷位。
Scientists tell the journal Geology that the features bear the hallmarks of being produced by liquid water.
科學家告訴地質學雜誌，那特徵有生產液態水的證明。
But they appear to have formed much later in Mars' history than many thought possible, the researchers add. The team, from Imperial and University Colleges London, studied pictures of several flat-floored depressions located above Ares Vallis, a giant gorge running some 2,000km across Mars' equator.
The hollows are about 20km in diameter.
Scientists had previously ascribed their formation to the slumping of the ground as ice in the soil was lost to Mars' thin atmosphere almost four billion years ago in the process of sublimation (in which the ice turns directly from a solid into a vapour).
But the detail in the MRO pictures has allowed the Imperial-UCL team to trace a series of channels that connect the depressions.
The group says these channels could only be formed by running water, and not by ice turning directly into gas.
The scientists' ageing of the region, which on bodies like Mars is done by counting craters, suggests the features formed during the so-called Hesperian Epoch on the Red Planet.
"The exciting thing is that this occurred at a time when Mars is thought to have been cold and dry and [liquid] water wasn't stable at the surface," Dr Sanjeev Gupta from Imperial College London told BBC News.
The researchers propose that Mars may have experienced bouts of short-lived warming during this epoch that were caused perhaps by volcanic activity, meteorite impacts, or even shifts in the planet's orbit.
This could have provided both the warmth to melt ice in the soil and the pressure needed in the atmosphere to maintain liquid water on the surface.
"We don't really understand what caused this transient episode," Dr Gupta explained. "We have different hypotheses. Maybe local conditions generated an atmosphere creating a minor greenhouse effect that allowed these lakes to exist. We don't know how long they existed for, but it's exciting nonetheless that we see [evidence of] liquid water."
The conditions would have made it possible for the depressions to fill with meltwater and even overflow, cutting channels as the liquid ran from a higher basin to a lower one.
"This provides another environment - another place to go and look for microbial life," said Dr Gupta.
"This would be fossil life. This is somewhere we hadn't perhaps considered as a place to go."
http://news.bbc.co.uk/2/hi/science/nature/8439657.stm
沒有留言:
發佈留言