Restart shuttle: Fwd: Life on Mars? Scientist offers different take on Curiosity images

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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: January 9, 2015 at 11:00:56 AM CST
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Subject: FW: Life on Mars? Scientist offers different take on Curiosity images

Life on Mars? Scientist offers different take on Curiosity images
This mosaic of images from Curiosity's Mast Camera (Mastcam) shows a series of sedimentary deposits that include both the Gillespie Lake sandstone and the Sheepbed mudstone. A new paper in Astrobiology floats the idea that there may be signs of microbial mats in the Gillespie Lake sandstone. (NASA/JPL-Caltech/MSSS)

By Amina Khan

Do Curiosity's images reveal past life on Mars? Unlikely -- but it's worth looking for, NASA scientist says
Was there ever life on Mars? Without a human geologist roaming the surface, hammer in hand, it's devilishly difficult to find out, and current robotic explorers aren't really built to answer that question. But in a paper published in the journal Astrobiology, a scientist describes patterns in Martian rock that she says look uncannily like the fossil signatures from primitive microbial life on Earth.
In the paper, geobiologist Nora Noffke of Old Dominion University in Virginia analyzed Curiosity's Mast Camera images of a spot in Gale Crater called Gillespie Lake Member, where the rocks could be almost 3.7 billion years old. While examining the images that the rover snapped in 2012, Noffke began to notice patterns in the rock that reminded her of structures she studied on Earth.
As Noffke pointed out, scientists think that Mars and Earth may have looked fairly similar in their early history. One NASA video even depicts the now-dry, dusty planet as having puffy clouds and blue water about 4 billion years ago.
"If we have a very similar evolution of the planet Mars and Earth — so both planets have a very comparable early evolution with respect to climate, with respect to environment — it makes sense to go take a look at images that were obtained by the rovers," Noffke said.
Noffke says she has spent two decades studying microbial mats -- primitive microbes on Earth that live in sheet-like layers, which can be billions of years old and can leave telltale signatures in the rock. After analyzing the Martian formation, she compared the patterns she saw to those she has studied in the microbial mat fossil remnants on Earth.
A number of features jumped out: There were triangular protrusions along plateau edges that, on our home planet, often mark areas where microbial mats once hung over the edge like little drapes and eventually turned to stone. There were also spots that looked rather like a flattened tube; on Earth, these were caused by what Noffke called "roll-ups," where the currents in moving water flipped the edge of a microbial mat over, as if it were a rug's edge.
The geobiologist mainly analyzed five images over several weeks, examining and sketching "every square inch of the rock surface," she said. Not only did she see erosional pockets and remnants as well as desiccation cracks that resembled the fossil signature of microbial mats on Earth, she also found that these various features seemed to occur together, not in isolation.
But would the scientist really bet that the Martian structures were left by long-gone microbes?
"I would not put down too much money," Noffke said. As she pointed out in her paper, this is just a hypothesis – and there are many non-biological processes that could also potentially explain the structures she examined in Curiosity's images.
Ashwin Vasavada, who recently took over as project scientist for Curiosity, said the rover's scientists analyzed the Gillespie Lake Member earlier in the mission and did not reach the same conclusion.
"We were surprised that such a bold claim was out there in the scientific literature," the Jet Propulsion Laboratory scientist said. "It's interesting.… It's just that we don't think the evidence is quite as strong as what is described in the paper."
That's not to say that scientists shouldn't look for such signs of past life in the rock, Vasavada added.
"The premise of looking for microbially induced sedimentary structures is not a bad one at all," he said.
In fact, he added, the Curiosity scientists are also poring over images taken by the rover, looking for similar signs of past microbial life.
But given that the Gillespie formation was sandstone, it probably formed in a more active stream environment, which would not be the most conducive for preserving organics, he said.
"In this particular case, that bell didn't go off for us when we examined these rocks in excruciating detail," Vasavada said. "So we will continue to look for these same structures when we think the context is correct to have our eye out for them."
Copyright © 2015, Los Angeles Times

Mars Microbe Traces Spotted by Rover? Probably Not, Curiosity Team Says
by Mike Wall, Space.com Senior Writer | January 09, 2015 07:00am ET

Mars' Gillespie Lake outcrop on Mars — shown here in a photo taken by NASA's Curiosity rover — shows possible signs of ancient microbially induced sedimentary structures, according to a recent study. But Curiosity scientists say the features likely result from abiotic processes.
Credit: NASA View full size image
Intriguing features photographed by NASA's Mars rover Curiosity probably don't have a biological origin, mission team members say.
Outside researchers recently analyzed photos Curiosity took of an ancient sedimentary outcrop called Gillespie Lake, and noted some similarities to "microbially induced sedimentary structures" (MISS) here on Earth. Study author Nora Noffke, a geobiologist who is not a member of the Curiosity team, said the Gillespie Lake features could be consistent with a biological origin, but stressed repeatedly that it was just a hypothesis, and not proof of past Mars life.
Curiosity team members also noticed the Gillespie Lake structures (which include domes, cracks and pockets, among other shapes), said mission project scientist Ashwin Vasavada, of NASA's Jet Propulsion Laboratory in Pasadena, California. But the rover team arrived at a different interpretation. [The Search for Life on Mars: A Photo Timeline]
"We really didn't see anything that can't be explained by natural processes of transporting that sand in water, and the nature of the rocks suggested that it was just a fluvial sandstone," Vasavada told Space.com.
"We do have several members of our team who are always keen to look out for things that might be caused by biological processes, but there was no reason, we felt, to explore that [option] at that site," he added. "It came down to nothing exceptional, from our point of view, that wasn't just a consequence of erosion of this sandstone."
Vasavada also stressed that he and the rest of the Curiosity rover team welcome analyses by outside researchers such as Noffke.
An overlay of a sketch onto a photo taken by NASA's Mars rover Curiosity of the Gillespie Lake outcrop, showing intriguing structures on the rock bed surface. In a study in the journal Astrobiology, geobiologist Nora Noffke suggests that such structures could be signs of ancient microbial life on the Red Planet.
Credit: Noffke (2105). Courtesy of ASTROBIOLOGY, published by Mary Ann Liebert, Inc.
View full size image
If mission scientists had decided to study Gillespie Lake more closely, they could have taken up-close photos using Curiosity's Mars Hand Lens Imager, Vasavada said, or drilled the rock to deliver powder to the Sample Analysis at Mars (SAM) instrument, which is capable of detecting carbon-containing organic molecules.
The Curiosity team did decide to drill into a layer of fine-grained mudstone dubbed Sheepbed, which lies directly beneath Gillespie Lake within a broader region near the rover's landing site called Yellowknife Bay.
SAM's analysis of the Sheepbed mudstone, along with other Curiosity observations, allowed the rover team to determine that Yellowknife Bay could have supported microbial life in the ancient past. About 3.5 billion years ago, the area was part of a lake-stream system that may have been habitable for millions of years, mission scientists said.
SAM also detected organics in the Sheepbed sample, marking the first definitive detection of life's building blocks on Mars.
"We feel that choice paid off," Vasavada said of the focus on Sheepbed.
Curiosity landed inside Mars' huge Gale Crater in August 2012, then spent almost a year exploring the Yellowknife Bay area. It departed for Mount Sharp — which rises 3.4 miles (5.5 kilometers) into the Martian sky from Gale's Center — in July 2013 and reached the mountain's base last September.
Mount Sharp has been Curiosity's main science destination since before the rover's November 2011 launch. Mission team members want to drive Curiosity up through the mountain's foothills, reading a history of the Red Planet's changing environmental conditions in the rocks along the way.
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