Fwd: Ancient fresh water lake on Mars could have sustained life

Sent from my iPad

Begin forwarded message:

From: "Gary Johnson" <gjohnson144@comcast.net>
Date: December 10, 2013 4:38:03 PM CST
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: Ancient fresh water lake on Mars could have sustained life

9-Dec-2013
Science

Ancient fresh water lake on Mars could have sustained life
Scientists have found evidence that there was once an ancient lake on Mars that may have been able to support life, in research published today in the journal Science.

Contact: Colin Smith
cd.smith@imperial.ac.uk
44-020-759-46712
Imperial College London

 

 

Ancient fresh water lake on Mars could have sustained life

by Colin Smith 09 December 2013

A drill hole in an ancient mudstone on Mars

Scientists have found evidence that there was once an ancient lake on Mars that may have been able to support life.

It is exciting to think that billions of years ago, ancient microbial life may have existed in the lake's calm waters, converting a rich array of elements into energy.

– Professor Sanjeev Gupta, Imperial College London

MSL team member and co-author of the paper

A team of researchers from NASA's Mars Science Laboratory (MSL) Curiosity rover mission, which includes a researcher from Imperial College London, have analysed a set of sedimentary rock outcrops at a site named Yellowknife Bay in Gale Crater, near the Martian equator. These mudstones have revealed that Gale Crater, a 150 km wide impact basin with a mountain at its centre, sustained at least one lake around 3.6 billion years ago.

The scientists believe that the lake may have lasted for tens if not hundreds of thousands of years.

The team's analysis showed that the lake was calm and likely had fresh water, containing key biological elements such as carbon, hydrogen, oxygen, nitrogen and sulphur. Such a lake would provide perfect conditions for simple microbial life such as chemolithoautotrophs to thrive in.

On Earth, chemolithoautotrophs are commonly found in caves and around hydrothermal vents. The microbes break down rocks and minerals for energy.

 

Professor Sanjeev Gupta

Mudstones generally form in calm conditions. They are created by very fine sediment grains settling layer-by-layer on each other, in still water.

 

Professor Sanjeev Gupta, a member of the MSL mission from the Department of Earth Science and Engineering at Imperial College London and a co-author on the papers, says: "It is important to note that we have not found signs of ancient life on Mars. What we have found is that Gale Crater was able to sustain a lake on its surface at least once in its ancient past that may have been favourable for microbial life, billions of years ago. This is a huge positive step for the exploration of Mars.

"It is exciting to think that billions of years ago, ancient microbial life may have existed in the lake's calm waters, converting a rich array of elements into energy. The next phase of the mission, where we will be exploring more rocky outcrops on the crater's surface, could hold the key whether life did exist on the red planet."

In previous studies, Professor Gupta and the MSL team have found evidence of water on Mars' surface in other rocks such as conglomerates. However, the new research provides the strongest evidence yet that Mars could have been habitable enough for life to take hold.

The team analysed the geology and chemistry of the mudstones by drilling into the rock using the MSL six-wheeled science laboratory, which is remotely operated by the MSL team from the Jet Propulsion Laboratory in Pasadena in the USA.

The next step will see the team using the rover to explore Gale Crater for further evidence of ancient lakes or other habitable environments in the thick pile of sedimentary rocks scattered across the crater's surface.

The research is published today in the journal Science.

 

===============================================================

 

 

 

Large freshwater lake on Mars could have been hospitable to life

The lake may have housed microbes, similar to those on Earth and provided a hospitable environment for them to thrive.

By Ananth Baliga   |   Dec. 9, 2013 at 1:13 PM   |   

 

Mars rover Curiosity's arm holds the tool turret above a target called "Wernecke" on the "John Klein" patch of pale-veined mudstone. The mudstone sample suggests the presence of a large freshwater lake in the Gale Crater, which may have been hospitable to life nearly 3.5 billion years ago. (NASA/JPL-Caltech)

| License Photo

Dec. 9 (UPI) -- A string of studies published Monday suggest that an ancient freshwater lake existed on Mars and could have been hospitable to life.

The studies published in the journal Science suggest that the lake, thought to have existed 3.5 billions years ago, lay in the Gale Crater floor, the same crater where the Mars Curiosity rover landed in 2012.

The lake may have existed for hundreds or thousands of years and its timeline is almost similar to when life started on Earth.

"You can actually begin to line up in time what the Earth was doing and what Mars was doing," Dr. John Grotzinger, a professor of geology at the California Institute of Technology, told The New York Times. "It's kind of cool."

According to Grotzinger, microbes, similar to some present on Earth, could have inhabited the lake and thrived in its environment. These microbes would have been similar to chemolithoautotrophs, which are found on Earth and live in caves, hydrothermal vents and deep underground.

The findings are derived from the analysis of two mudstones, called John Klein and Cumberland, drilled by Curiosity earlier this year. The clays appear to have been formed at the bottom of the lake and not swept down from the walls of the crater, suggesting the lake wasn't acidic. The structure and chemical makeup of the rocks were very similar, almost Earth-like.

In 2004, NASA's Opportunity rover found that various Martian locations were at one time soaking wet, and these were initially thought to have been suitable for life. But on detailed analysis researchers found that these locations were too salty and acidic.

The surface of Mars today is arid, cold and constantly bombarded by radiation, not at all suitable for life. But these findings suggest that at some point Mars could have been hospitable to life, and also closely matched the beginning of life on Earth.

 

© 2013 United Press International, Inc. All Rights Reserved. 

 

===============================================================

Curiosity findings prompt new search strategy for organics

12/09/2013 05:05 PM 

By WILLIAM HARWOOD
CBS News

Exploring an ancient lakebed on Mars -- a now-vanished fresh-water lake that increasingly confirms the past habitability of the red planet -- NASA's Curiosity rover is looking for areas where erosion may have uncovered pristine layers in which organic compounds -- and possibly remnant traces of life -- might still be found, scientists said Monday.

"Really what we're doing is turning the corner from a mission that is dedicated to the search for habitable environments to a mission that is now dedicated to the search for that subset of habitable environments which also preserves organic carbon," Principal Investigator John Grotzinger told reporters Monday. "That's the step we need to take as we explore for evidence of life on Mars."

In papers published Monday in the journal Science, the Curiosity team unveiled critical new findings, including measurements of the radiation environment at Mars, which does not have an active magnetic field to shield the surface from its harmful effects.

In this orbital view of Gale Crater, scientists have filled in an area where they believe water once stood in a long, thin lake pooling at the base of Mount Sharp, a towering mound of layered rock at the center of the crater. Based on the latest findings, rover scientists are refining their search strategy for locating organic compounds and, possibly, remnant traces of life. (Credit: NASA)

As it turns out, cosmic rays from deep space can penetrate the upper few feet of martian rocks and soil, breaking apart organic compounds and effectively erasing evidence of past life or the materials necessary for life as it is known on Earth.

To find that evidence, scientists are looking for places along Curiosity's planned route where wind erosion over many millions of years has uncovered underlying beds in the relatively recent past, before energetic cosmic rays have had time to destroy whatever organic compounds might be present.

"Our measurements show that the organics could be preserved at a depth of one meter, even life could possibly, if it existed, survive at a depth of roughly one meter on Mars," said Robert Wimmer-Schweingruber, a co-investigator with the Radiation Assessment Detector on Curiosity.

"It also shows us that as radiation penetrates into the soil ... it reaches the natural background at a depth of roughly three meters. In the top surface layers of four to five centimeters, which (Curiosity) can drill into, it would, with this radiation, reduce the preserved organics by a factor of roughly 1,000 over about 650 million years. So if you want to find organics, you need to find places where it hasn't been exposed for such a long time."

Scientists were able to date a lakebed rock Curiosity drilled into earlier by measuring how an isotope of potassium decayed into argon. The rock in question was formed 3.86 billion to 4.56 billion years ago. It was once buried under many feet of rock and soil, but the martian winds slowly eroded the upper strata, bringing it into reach of Curiosity's drill.

Ken Farley, a Curiosity researcher with the California Institute of Technology, said an analysis of the drill sample showed the erosion happened relatively recently, over the past 60 million to 100 million years, and that about three feet of strata is removed every million years or so.

The relatively recent uncovering of the lakebed clays "suggests that there will be some organic degradation, but perhaps not extensive organic degradation," Farley said. "But more importantly, we now have a model of where to look for the least cosmic ray irradiated rock we can get to. We simply drive to the downwind scarp and drill at the base of that scarp."

By drilling within three feet or so of a scarp, or ridge line, where the martian wind has uncovered lower layers, "we might get surface exposure ages, cosmic ray dosages, of only about a million years."

If so, Curiosity would have a much better chance of detecting complex organic compounds.

"Our hypothesis is that we can decrease the surface exposure age by drilling right up at those edges," Farley said. "And then we can test that hypothesis by obtaining the surface age date. That's our goal as we go forward here and we think the big step for the mission that takes us closer to the search for life on Mars is being able to reduce this risk of radiation, which is a very Mars-unique process."

This view of the Glenelg region of Gale Crater, shot by a camera aboard the Curiosity rover, shows the Sheepbed mudstone deposit at lower left where the rover drilled into a rock, collecting samples that indicate the deposit was formed at the bottom of an ancient lake, part of a once-habitable environment. (Credit: NASA)

Curiosity landed in Gale Crater in August 2012. Since then, it has been slowly making its way toward a towering mound of layered rock in the heart of the crater known as Mount Sharp, stopping along the way to investigate intriguing formations.

One such site is known as Yellowknife Bay, where Curiosity's power drill collected samples confirming a once-habitable environment. Scientists do not yet know the full extent of the lake they now believe existed there, but it likely stretched at least 30 miles around the base of Mount Sharp.

"Imagine something, an environment you might have had back on Earth about .... 10,000 years ago," Grotzinger said. "Cool, cold, maybe even ice available at the time. ... The size of these lakes would have been like the small finger lakes of upstate New York, something like that.

"The important thing we learned about the chemistry, with the clay minerals forming there, we have a moderate to neutral pH. Also we know from the absence of salt in the rock ... that lake didn't have a lot of dissolved salt in it. And finally, we have the kinds of chemicals and minerals that would have allowed simple micro-organisms to live in that environment."

In the absence of oxygen, such micro-organisms likely would have had to get by with a process known as chemolithotrophy, or "eating rock" as a summary in Science put it.

But finding actual fossils, or any remnants of ancient microbial life, assuming any are there to be found, will remain a major challenge.

"The key thing here is that ... if you go back into rocks that are billions of years old and ask what remnants of life there are, it is rare, rare, rare to find an actual microfossil," Grotzinger said. "It is a little bit less rare to find a large organic molecule. We call those chemofossils.

"And so, the trick is to make sure you have enough of the good minerals and as little as possible of the bad chemical compounds that will (alter) them. That's the game we're now weighing in on, in addition to quantifying radiation exposure."

© 2011 William Harwood/CBS News

===============================================================

Curiosity Discovers Ancient Mars Lake Could Support Life

by Ken Kremer on December 9, 2013

Outcrops in Yellowknife Bay are being exposed by wind driven erosion. These rocks record superimposed ancient lake and stream deposits that offered past environmental conditions favorable for microbial life. This image mosaic from the Mast Camera instrument on NASA's Curiosity Mars rover shows a series of sedimentary deposits in the Glenelg area of Gale Crater, from a perspective in Yellowknife Bay looking toward west-northwest. The "Cumberland" rock that the rover drilled for a sample of the Sheepbed mudstone deposit (at lower left in this scene) has been exposed at the surface for only about 80 million years. Credit: NASA/JPL-Caltech/MSSS

NASA's Curiosity rover has discovered evidence that an ancient Martian lake had the right chemical ingredients that could have sustained microbial life forms for long periods of time – and that these habitable conditions persisted on the Red Planet until a more recent epoch than previously thought.

Furthermore researchers have developed a novel technique allowing Curiosity to accurately date Martian rocks for the first time ever – rather than having to rely on educated guesses based on counting craters.

All that and more stems from science results just announced by members of the rover science team.

Researchers outlined their remarkable findings in a series of six new scientific papers published today (Dec. 9) in the highly respected journal Science and at talks held today at the Fall 2013 Annual Meeting of the American Geophysical Union (AGU) in San Francisco.

The Curiosity team also revealed that an investigation of natural Martian erosion processes could be used to direct the rover to spots with a higher likelihood of holding preserved evidence for the building blocks of past life – if it ever existed.

View of Yellowknife Bay Formation, with Drilling Sites
This mosaic of images from Curiosity's Mast Camera (Mastcam) shows geological members of the Yellowknife Bay formation, and the sites where Curiosity drilled into the lowest-lying member, called Sheepbed, at targets "John Klein" and "Cumberland." The scene has the Sheepbed mudstone in the foreground and rises up through Gillespie Lake member to the Point Lake outcrop. These rocks record superimposed ancient lake and stream deposits that offered past environmental conditions favorable for microbial life. Rocks here were exposed about 70 million years ago by removal of overlying layers due to erosion by the wind. Credit: NASA/JPL-Caltech/MSSS

The ancient fresh water lake at the Yellowknife Bay area inside the Gale Crater landing site explored earlier this year by Curiosity existed for periods spanning perhaps millions to tens of millions of years in length – before eventually evaporating completely after Mars lost its thick atmosphere.

Furthermore the lake may have existed until as recently as 3.7 Billion years ago, much later than researchers expected which means that life had a longer and better chance of gaining a foothold on the Red Planet before it was transformed into its current cold, arid state.

NASA's Mars rover Curiosity took this self-portrait, composed of more than 50 images using its robotic arm-mounted MAHLI camera, on Feb. 3. The image shows Curiosity at the John Klein drill site. A drill hole is visible at bottom left. Credit: NASA / JPL / MSSS / Marco Di Lorenzo / Ken Kremer- kenkremer.com

Researchers also announced that they are shifting the missions focus from searching for habitable environments to searching for organic molecules – the building blocks of all life as we know it.

Why the shift? Because the team believes they have found a way to increase the chance of finding organics preserved in the sedimentary rock layers.

"Really what we're doing is turning the corner from a mission that is dedicated to the search for habitable environments to a mission that is now dedicated to the search for that subset of habitable environments which also preserves organic carbon," Curiosity Principal Investigator John Grotzinger, of the California Institute of Technology in Pasadena, said at an AGU press conference today.

"That's the step we need to take as we explore for evidence of life on Mars."

Earlier this year, Curiosity drilled into a pair of sedimentary Martian mudstone rock outcrops at Yellowknife Bay known as "John Klein" and "Cumberland" – for the first time in history.

Grotzinger said the ancient lake at Yellowknife Bay was likely about 30 miles long and 3 miles wide.

Powdered samples deposited into the rovers miniaturized chemistry labs – SAM and CheMin – revealed the presence of significant levels of phyllosilicate clay minerals.

These clay minerals form in neutral pH water that is 'drinkable" and conducive to the formation of life.

"Curiosity discovered that the fine-grained sedimentary rocks preserve evidence of an environment that would have been suited to support a Martian biosphere founded on chemolithoautotrophy," according to one of the science papers co-authored by Grotzinger.

"This aqueous environment was characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species."

The rover has detected key elements required for life including carbon, hydrogen, oxygen, sulfur nitrogen and phosphorous.

The team is still looking for signatures of organic molecules.

Right now the researchers are driving Curiosity along a 6 mile path to the base of Mount Sharp -the primary mission destination – which they hope to reach sometime in Spring 2014.

But along the way they hope to stop at a spot where wind has eroded the sedimentary rocks just recently enough to expose an area that may still preserve evidence for organic molecules – since it hasn't been bombarded by destructive cosmic radiation for billions of years.      

===============================================================

 

Mars rover finds chemical ingredients for life to have thrived

Curiosity drills into an ancient lake to discover signs that Gale Crater was once wet and potentially Earth-like. 'It's a great leap forward,' one scientist says.

 

NASA's Curiosity rover, shown in a self-portrait on Mars, has discovered chemical signs in an ancient lake that could have been friendly to life. (NASA / December 9, 2013)

By Amina Khan

December 9, 2013, 9:07 p.m.

Billions of years ago, when early life was just taking hold on Earth, Mars was home to an ancient lake filled with the right chemical ingredients for life to thrive, scientists said Monday.

Drilling into dry rock, NASA's Curiosity rover has discovered signs that Gale Crater was once watery, perhaps ringed with ice and snow, and could potentially have hosted an entire Martian biosphere based on a type of microbe found in caves on Earth. Such primitive organisms, called chemolithoautotrophs, feed on chemicals found in rocks and make their own energy.

"Ancient Mars was more habitable than we imagined," said Caltech geologist John Grotzinger, lead scientist for the Curiosity mission. This wet, potentially Earth-like environment could have lasted for tens of millions of years, giving life a wide-open window to emerge.

The findings, described Monday at the American Geophysical Union meeting in San Francisco and detailed among half a dozen papers published in the journal Science, impressed scientists who were not involved with the mission.

"They're really quite amazing," said Malcolm Walters, an astrobiologist at the University of New South Wales in Australia who helped find some of the earliest microfossils on Earth. "Now we have enormous detail on the chemistry of sediments [on Mars]. It's a great leap forward."

Still missing is evidence of the type of organic matter that forms the basis for most life on Earth. Curiosity's search will now focus on that — and thanks to some clever manipulation of the rover's inner laboratory, scientists now know exactly where to look for it.

"I think it's a critical turning point in the mission, to accept a much more significant challenge," Grotzinger said.

Mars' geologic history is inscribed in its layers of sedimentary rock, and Curiosity set out to read it after landing in Gale Crater in August 2012. The rover's primary goal was to search for life-friendly environments at Mt. Sharp, the 3-mile-high mound whose clay-rich layers could reveal details about Gale's environment over the eons.

But rather than head straight to Mt. Sharp, the rover took a months-long detour to an intriguing spot called Yellowknife Bay. There, Curiosity drilled into two mudstone rocks, named John Klein and Cumberland.

It was a risk to turn away from the planned mission, and it paid off, Grotzinger said.

The rocks, dated to roughly 3.6 billion years ago, have turned up a smorgasbord of elements needed for life, including carbon, hydrogen, oxygen, sulfur, nitrogen and phosphorus. They also show signs of sulfates, sulfides and other compounds that would have been fuel for chemolithoautotrophs.

What's more, the water that transformed these rocks had a neutral pH and would have been drinkable, unlike the highly acidic water detected by NASA's rover Opportunity at Meridiani Planum, on the other side of the planet.

Most likely, the lake would have been "suitable for quite a wide range of microorganisms as opposed to just extremophiles" that can survive salty, acidic environments, said David Catling, a planetary scientist at the University of Washington who was not involved in the new studies.

Curiosity has not yet found any organic carbon, the type that's combined with hydrogen and is a mainstay of life on Earth. That may be partly because its inner lab cooks soil samples to analyze the gases they form, and the test ends up destroying some crucial information in the process.

Life could certainly evolve and thrive without organic carbon. In a past watery environment, chemolithoautotrophs would have done just fine with the ingredients already found on Mars. That said, scientists do want to find organic carbon because it would indicate that the planet once had a wider range of life-friendly habitats.

But scientists feared that the surface had been exposed to cosmic radiation for so long — perhaps hundreds of millions of years — that any traces within reach of Curiosity's drill were long gone.

It was "a pretty serious concern," said Kenneth Farley, a Caltech geochemist and lead author of one of the Science papers.

So Farley directed Curiosity to analyze several soil samples and found telltale gases — such as helium-3, neon-21 and argon-36 — that helped pin down the age of the Martian surface. It was about 78 million years old, much younger than scientists had expected. That meant the amount of cosmic radiation exposure was also lower than they expected.

This was a relief, but how was it possible? The team noticed a small cliff, called a scarp, located some distance away. The geologists soon realized that the edge of the scarp had once extended to the top of the rocks they were sampling; over time it eroded, leaving the rocks newly exposed to radiation.

And while they couldn't dig underneath the scarp, they could drill right by the base of it, where cosmic radiation exposure was still minimal.

If any organic carbon exists in Gale Crater, the foot of one of these scarps would be the best place to search for it, the scientists concluded.

The scientists plan to take this information and run with it — at least as fast as good judgment (and Curiosity's theoretical top speed of 1.57 inches per second on flat ground) will allow.

In about two months, Curiosity will take a detour to an outcrop called KMS-9, Grotzinger said Monday. Scientists are not sure whether it held a lake, but they hope to ride right up to a protected spot and deploy Curiosity's drill.

"You just never know what you'll encounter," said NASA scientist Douglas Ming, who led the organic carbon study. "One thing I've come to expect doing Mars research is to expect the unexpected."

amina.khan@latimes.com

Copyright © 2013, Los Angeles Times

===============================================================

 

NASA: Ancient Mars lake may have supported life

By ALICIA CHANG

 

.

View gallery

This Feb 3, 2013 image provided by NASA shows a self portrait of the Mars rover, Curiosity. NASA's Curiosity rover has uncovered signs of an ancient freshwater lake on Mars that may have teemed with microbes for tens of millions of years, far longer than scientists had imagined, new research suggests.(AP Photo/NASA)

LOS ANGELES (AP) — NASA's Curiosity rover has uncovered signs of an ancient freshwater lake on Mars, which scientists say could have been a perfect spot for tiny primitive organisms to flourish if they ever existed on the red planet.

The watering hole near the Martian equator existed about 3.5 billion years ago around the time when life evolved on Earth. Scientists say the Martian lake was neither salty nor acidic, and contained life-friendly nutrients.

"This just looks like a pretty darn ordinary Earth-like lake in terms of its chemistry," said project scientist John Grotzinger of the California Institute of Technology. "If you were desperate, you could have a drink of this stuff."

The lake, about the size of a small Finger Lake in upstate New York, likely was around for tens of thousands — perhaps hundreds of thousands — of years. Even when the lake dried up, scientists said microbes could have migrated underground, and existed for potentially tens of millions of years.

It's not known whether simple life forms ever took hold on Mars and Curiosity lacks the tools to search for any fossilized microbes. It can only analyze the chemical makeup of rocks and soil.

The findings were published online Monday in the journal Science and presented at the American Geophysical Union meeting in San Francisco.

"The new results definitely reinforce the idea that past life on Mars was possible," planetary scientist David Paige at the University of California, Los Angeles said in an email.

Paige, who is not part of the Curiosity team, added: "The question of whether life existed or exists on Mars today is still open."

Present-day Mars is dusty and harsh, with no signs of water on the surface. But the red planet wasn't always a radiation-scarred frozen desert.

Early in its history, Mars was more tropical, with streams and rivers. With water plentiful, scientists think it was a place where primitive life could have thrived by feeding on rocks and minerals similar to tiny organisms on Earth that hide in caves and underwater vents.

Around 3.5 billion years ago, Mars underwent a shift and raged with volcanic activity. NASA's older rovers Spirit and Opportunity found geologic evidence that water flowed during this time, but it was highly acidic and considered too caustic for life.

Scientists thought much of the planet had been awash in acidic water until Curiosity earlier this year found signs of an old streambed near its landing site with a neutral pH.

Analyzing a sedimentary rock known as a mudstone, the nuclear-powered rover found further evidence of favorable environmental conditions — an ancient lake that was theoretically drinkable, harboring some of the key ingredients for life including carbon, hydrogen, oxygen, sulfur, nitrogen and phosphorus.

A roving science laboratory, Curiosity touched down in a massive depression called Gale Crater near Mars' equator last year, toting high-tech instruments to drill into rocks, forecast the weather and track radiation.

Now that the $2.5 billion mission has accomplished a main goal — finding a habitable environment in the lake — attention has turned to the hunt for elusive carbon-based organic compounds that are fundamental to all living things.

Before setting off on that search last summer, the six-wheel rover used its instruments to determine the age of a rock — the first time this has been achieved on another planet or celestial body.

Another study released Monday showed that the rock was 4.2 billion years old — not entirely surprising since observations from space suggested the bedrock in the crater was this old. Scientists also calculated the rock has been exposed on the surface — and to galactic cosmic rays — for 78 million years.

This knowledge should help the team find rocks in the foothills of Mount Sharp in the crater's center that have not been too zapped by radiation, said mission scientist Ken Farley of Caltech.

Scientists hope Curiosity will reach the mountain by next June, just a few months shy of its second landing anniversary.

Copyright © 2013 The Associated Press. All rights reserved. 

 

===============================================================

 

 

NASA Mars rover finds evidence of life-friendly ancient lake

By Irene Klotz 

 

.

View gallery

A self-portrait of the Mars rover Curiosity is seen in this February 3, 2013 handout image courtesy of …

By Irene Klotz

SAN FRANCISCO (Reuters) - Scientists have found evidence of an ancient freshwater lake on Mars well suited to support microbial life, the researchers said Monday.

The lake, located inside Gale Crater where the rover landed in August 2012, likely covered an area 31 miles long and 3 miles wide, though its size varied over time.

Analysis of sedimentary deposits gathered by NASA's Mars rover Curiosity shows the lake existed for at least tens of thousands of years, and possibly longer, geologist John Grotzinger, with the California Institute of Technology in Pasadena, told reporters at the American Geophysical Union conference in San Francisco.

"We've come to appreciate that is a habitable system of environments that includes the lake, the associated streams and, at times when the lake was dry, the groundwater," he said.

Analysis of clays drilled out from two rock samples in the area known as Yellowknife Bay show the freshwater lake existed at a time when other parts of Mars were dried up or dotted with shallow, acidic, salty pools ill-suited for life.

In contrast, the lake in Gale Crater could have supported a simple class of rock-eating microbes, known as chemolithoautotrophs, which on Earth are commonly found in caves and hydrothermal vents on the ocean floor, Grotzinger said.

Scientists also reported that the clays, which form in the presence of water, were younger than expected, a finding that expands the window of time for when Mars may have been suited for life.

Previous studies from Mars orbiters, landers and rovers have provided increasing evidence for a warmer, wetter, more Earth-like Mars in the planet's past. Ancient rocks bear telltale chemical fingerprints of past interactions with water.

The planet's surface is riddled with geologic features carved by water, such as channels, dried up riverbeds, lake deltas and other sedimentary deposits.

New related studies on how much radiation blasts the planet set new boundaries for how long any organic carbon, which so far has not been found on Mars, could have been preserved inside rocks within about 2 inches of the surface, the depth of Curiosity's drill.

But finding rock samples with relatively short exposure times should not be a problem. An age-dating technique, used for the first time on Mars, reveals that winds are sand-blasting away the rock faces at Gale Crater.

One of the mudstones at Yellowknife Bay, for example, has been exposed to the destructive effects of cosmic rays for only about 70 million years, well within the period of time to detect organics, said Don Hassler with the Southwest Research Institute in Boulder, Colorado.

The Yellowknife Bay samples also showed hints of possible organics that may have been destroyed in the rover's laboratory oven due to highly oxidizing chemicals known as perchlorates, which so far seem to be ubiquitous in the Martian soil.

Scientists will continue to look for rocks that may have higher concentrations of organics or better chemical conditions for their preservation, Grotzinger said.

"A key hurdle that we need to overcome is understanding how those organics may have been preserved over time, from the time they entered the rock to the time that we actually detect them," said Curiosity scientist Jennifer Eigenbrode with NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Curiosity currently is en route to a three-mile high mound of layered rock rising form the floor of Gale Crater, a formation known as Mount Sharp.

Based on the new information gleaned from the Yellowknife Bay samples, scientists are developing a new strategy to look for organics there.

Even if life never started on Mars, organic material presumably would have been deposited on the surface by crashing comets and asteroids.

(Editing by Kevin Gray and Doina Chiacu

 

Copyright © 2013 Reuters Limited. All rights reserved. 

 

===============================================================

 

Ancient Mars Lake Could Have Supported Life, Curiosity Rover Shows

by Mike Wall, Senior Writer   |   December 09, 2013 12:01pm ET

Mastcam mosaic of the Yellowknife Bay formation. This is a view from the base of an exposed section up through Sheepbed, Gillespie Lake, and basal Glenelg members. Locations of drill holes and Alpha Particle X-Ray Spectrometer (A PXS) measurements are shown. Image released Dec. 9, 2013. Credit: Science/AAAS View full size image

NASA's Curiosity rover has found evidence of an ancient Martian lake that could have supported life as we know it for long stretches — perhaps millions of years.

This long and skinny freshwater lake likely existed about 3.7 billion years ago, researchers said, suggesting that habitable environments were present on Mars more recently than previously thought.

"Quite honestly, it just looks very Earth-like," said Curiosity lead scientist John Grotzinger, of the California Institute of Technology in Pasadena. [Ancient Mars Could Have Supported Life (Photos)]

"You've got an alluvial fan, which is being fed by streams that originate in mountains, that accumulates a body of water," Grotzinger told SPACE.com. "That probably was not unlike what happened during the last glacial maximum in the Western U.S."

Habitable Mars

The lake once covered a small portion of the 96-mile-wide (154 kilometers) Gale Crater, which the 1-ton Curiosity rover has been exploring since touching down on the Red Planet in August 2012.

Do you think life exists on Mars today?

The main task of Curiosity's $2.5 billion mission is to determine whether Gale Crater could ever have supported microbial life. The rover team achieved that goal months ago, announcing in March that a spot near Curiosity's landing site called Yellowknife Bay was indeed habitable billions of years ago.

The new results, which are reported today (Dec. 9) in six separate papers in the journal Science, confirm and extend Curiosity's landmark discovery, painting a more complete picture of the Yellowknife Bay area long ago.

This picture emerged from Curiosity's analysis of fine-grained sedimentary rocks called mudstones, which generally form in calm, still water. The rover obtained powdered samples of these rocks by drilling into Yellowknife Bay outcrops.

The mudstones contain clay minerals that formed in the sediments of an ancient freshwater lake, researchers said. Curiosity also spotted some of the key chemical ingredients for life in the samples, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon.

The lake could have potentially supported a class of microbes called chemolithoautotrophs, which obtain energy by breaking down rocks and minerals. Here on Earth, chemolithoautotrophs are commonly found in habitats beyond the reach of sunlight, such as caves and hydrothermal vents on the ocean floor.

"It is exciting to think that billions of years ago, ancient microbial life may have existed in the lake's calm waters, converting a rich array of elements into energy," Sanjeev Gupta of Imperial College London, co-author of one of the new papers, said in a statement.

An icy Martian lake?

The shallow ancient lake may have been about 30 miles long by 3 miles wide (50 by 5 kilometers), Grotzinger said. Based on the thickness of the sedimentary deposits, the research team estimates that the lake existed for at least tens of thousands of years — and perhaps much longer, albeit on a possibly on-and-off basis.

Taking into account the broader geological context, "you could wind up with an assemblage of rocks that represent streams, lakes and ancient groundwater systems — so for times when the lake might have been dry, the groundwater's still there. This could have gone on for millions or tens of millions of years," Grotzinger said.

The lack of weathering on Gale Crater's rim suggests that the area was cold when the lake existed, he added, raising the possibility that a layer of ice covered the lake on a permanent or occasional basis. But such conditions wouldn't be much of a deterrent to hardy microbes.

"These are entirely viable habitable environments for chemolithoautotrophs," Grotzinger said.

Researchers still don't know if the Gale Crater lake hosted organisms of any kind; Curiosity was not designed to hunt for signs of life on Mars. But if chemolithoautotrophs did indeed dominate the lake, it would put an alien twist on a superficially familiar environment.

"You can imagine that, if life evolved on Mars and never got beyond the point of chemolithoautotrophy, then in the absence of competition from other types of microbes, these systems might have been dominated by that type of metabolic pathway," Grotzinger said. "And that's an un-Earth-like situation."

 

Copyright © 2013 TechMediaNetwork.com All rights reserved.

 

===============================================================