NASA Mars Curiosity Rover: Potential signs of ancient life in Mars rover photos

A rock bed at the Gillespie Lake outcrop on Mars displays potential signs of ancient microbial sedimentary structures. 

Credit: NASA

A careful study of images taken by the NASA rover Curiosity has revealed intriguing similarities between ancient sedimentary rocks on Mars and structures shaped by microbes on Earth.

The findings suggest, but do not prove, that life may have existed earlier on the Red Planet.

The photos were taken as Curiosity drove through the Gillespie Lake outcrop in Yellowknife Bay, a dry lakebed that underwent seasonal flooding billions of years ago.

Mars and Earth shared a similar early history. The Red Planet was a much warmer and wetter world back then.

On Earth, carpet-like colonies of microbes trap and rearrange sediments in shallow bodies of water such as lakes and costal areas, forming distinctive features that fossilize over time.

These structures, known as microbially-induced sedimentary structures (or MISS), are found in shallow water settings all over the world and in ancient rocks spanning Earth's history.

Nora Noffke, a geobiologist at Old Dominion University in Virginia, has spent the past 20 years studying these microbial structures.

Last year, she reported the discovery of MISS that are 3.48 billion years old in the Western Australia's Dresser Formation, making them potentially the oldest signs of life on Earth.

In a paper published online last month in the journal Astrobiology (the print version comes out this week), Noffke details the striking morphological similarities between Martian sedimentary structures in the Gillespie Lake outcrop (which is at most 3.7 billion years old) and microbial structures on Earth.

The distinctive shapes include erosional remnants, pockets, domes, roll-ups, pits, chips and cracks, which on Earth can extend from a few centimeters to many kilometers.

Although Noffke makes a tantalizing case for possible signs of ancient life on Mars, her report is not a definitive proof that these structures were shaped by biology.

Getting such confirmation would involve returning rock samples to Earth and conducting additional microscopic analyses, a mission that isn't scheduled anytime in the near future.

"All I can say is, here's my hypothesis and here's all the evidence that I have," Noffke says, "although I do think that this evidence is a lot."

"The fact that she pointed out these structures is a great contribution to the field," says Penelope Boston, a geomicrobiologist at the New Mexico Institute of Mining and Technology.

"Along with the recent reports of methane and organics on Mars, her findings add an intriguing piece to the puzzle of a possible history for life on our neighboring planet."

A Careful Analysis
"I've seen many papers that say 'Look, here's a pile of dirt on Mars, and here's a pile of dirt on Earth,'" says Chris McKay, a planetary scientist at NASA's Ames Research Center and an associate editor of the journal Astrobiology. "And because they look the same, the same mechanism must have made each pile on the two planets.'"

McKay adds: "That's an easy argument to make, and it's typically not very convincing. However, Noffke's paper is the most carefully done analysis of the sort that I've seen, which is why it's the first of its kind published in Astrobiology."

Overlay of sketch on photograph from above to assist in the identification of the structures on the rock bed surface. 

Image credit: Noffke (2105). Credit: ASTROBIOLOGY, published by Mary Ann Liebert, Inc.

The images on which Noffke drew are publicly available on the Mars Science Laboratory page on NASA's website.

"In one image, I saw something that looked very familiar," Noffke recalls. "So I took a closer look, meaning I spent several weeks investigating certain images centimeter by centimeter, drawing sketches, and comparing them to data from terrestrial structures, and I've worked on these for 20 years, so I knew what to look for."

Noffke compared the rover pictures to images taken at several sites on Earth, including modern sediment surfaces in Mellum Island, Germany; Portsmouth Island, USA; and Carbla Point, Western Australia; as well as older fossils of microbial mats in Bahar Alouane, Tunisia; the Pongola Supergroup in Africa; and the Dresser Formation in Western Australia.

The photos showed striking morphological similarities between the terrestrial and Martian sedimentary structures.

The distribution patterns of the microbial structures on Earth vary depending on where they are found. Different types of structures are found together in different types of environments.

For instance, microbial mats that grow in rivers will create a different set of associations than those that grow in seasonally flooded environments.

The patterns found in the Gillespie Lake outcrop are consistent with the microbial structures found in similar environments on Earth.

What's more, the terrestrial structures change in a specific way over time. As the microbial mats form, grow, dry up, crack and re-grow, specific structures become associated with them.

Here again, Noffke found that the distribution pattern in Martian rocks correspond with microbial structures on Earth that have changed over time. Taken together, these clues strengthen her argument beyond simply pointing out the similarities in shape.

In her paper, she also describes alternative processes through which these could have formed. For instance, the chips, pits and cracks could be the product of erosion by salt, water, or wind.

"But if the Martian structures aren't of biological origin," Noffke says, "then the similarities in morphology, but also in distribution patterns with regards to MISS on Earth would be an extraordinary coincidence."

Potential MISS erosional remnant on Mars (top); edge of a microbial mat–overgrown erosional remnant on Portsmouth Island, USA (middle); erosional remnant of a modern MISS on Mellum Island, Germany (bottom). 

Credit: Mars: NASA; Earth: Nora Noffke

"At this point, all I'd like to do is point out these similarities," she adds. "Further evidence must be provided to verify this hypothesis."

More information: The paper is available online: online.liebertpub.com/doi/pdf/… 0.1089/ast.2014.1218

NASA Mars Curiosity Rover: Leaving Landing 'Safe Zone'

This image taken on June 27, 2014 by NASA's Mars Reconnaissance Orbiter shows NASA's Curiosity Mars rover on the rover's landing-ellipse boundary, which is superimposed on the image. 

The ellipse measures approximately 4 miles wide by 12 miles long.

Credit: NASA /JPL-Caltech /Univ. of Arizona

NASA's Curiosity Mars rover has entered a new realm on the Red Planet.

The 1-ton Curiosity rover has now cruised out of its landing ellipse, the area, about 4 miles wide by 12 miles long (7 by 20 kilometers), regarded as safe ground for its August 2012 touchdown within Mars' huge Gale Crater, NASA officials said.

Indeed, a photo taken by the space agency's Mars Reconnaissance Orbiter on June 27 shows Curiosity right on this boundary, which encloses a region of relatively flat and smooth terrain.



Curiosity landed with the aid of a rocket-powered sky crane, which lowered the six-wheeled robot down softly on cables before flying off to crash-land intentionally a safe distance away.

This system, which had never been used before at Mars, allowed Curiosity to land with much more precision than previous Red Planet missions had been able to achieve.

For example, NASA's twin Spirit and Opportunity rovers landed inside an ellipse measuring 93 miles by 12 miles (150 by 20 km) in January 2004, and the ellipse for the agency's two Viking landers, which touched down on Mars in 1976, spanned 174 miles by 62 miles (280 by 100 km).

Curiosity's $2.5 billion mission, officially known as the Mars Science Laboratory (MSL), seeks to determine if Mars has ever been capable of supporting microbial life.

The rover team has already achieved this goal, announcing last year that an area near Curiosity's landing site called Yellowknife Bay was a habitable lake-and-stream system billions of years ago.

NASA's Curiosity rover drills sandstone slab Windjana on Mars

This May 5, 2014, image from the Navigation Camera on NASA's Curiosity Mars rover shows two holes at top centre drilled into a sandstone target called "Windjana." 

The farther hole was created by the rover's drill while it collected rock-powder sample material from the interior of the rock. 

Credit: NASA/JPL-Caltech

Portions of rock powder collected by the hammering drill on NASA's Curiosity Mars rover from a slab of Martian sandstone "Windjana," will be delivered to the rover's internal instruments.

Rover team members at NASA's Jet Propulsion Laboratory, Pasadena, Calif., received confirmation early today (Tuesday) of Curiosity's third successful acquisition of a drilled rock sample, following the drilling Monday evening (PDT).

The fresh hole in the rock target "Windjana," visible in images from the rover, is 0.63 inch (1.6 centimeters) in diameter and about 2.6 inches (6.5 centimeters) deep.

The full-depth hole for sample collection is close to a shallower test hole drilled last week in the same rock, which gave researchers a preview of the interior material as tailings around the hole.

Jim Bell

"The drill tailings from this rock are darker-toned and less red than we saw at the two previous drill sites," said Jim Bell of Arizona State University, Tempe, deputy principal investigator for Curiosity's Mast Camera (Mastcam).

"This suggests that the detailed chemical and mineral analysis that will be coming from Curiosity's other instruments could reveal different materials than we've seen before. We can't wait to find out!"

The mission's two previous rock-drilling sites, at mudstone targets in the Yellowknife Bay area, yielded evidence last year of an ancient lakebed environment with key chemical elements and a chemical energy source that long ago provided conditions favourable for microbial life.

The rover's current location is at a waypoint called "The Kimberley," about 2.5 miles (4 kilometers) southwest of Yellowknife Bay, and along the route toward the mission's long-term destination on lower slopes of Mount Sharp.

Sample material from Windjana will be sieved, then delivered in coming days to onboard laboratories for determining the mineral and chemical composition: the Chemistry and Mineralogy instrument (CheMin) and the Sample Analysis at Mars instrument (SAM).

The analysis of the sample may continue as the rover drives on from The Kimberley toward Mount Sharp. One motive for the team's selection of Windjana for drilling is to analyze the cementing material that holds together sand-size grains in this sandstone.

NASA's Curiosity Mars Rover Inspects new Drill Site - Windjana

The team operating NASA's Curiosity Mars rover is telling the rover to use several tools this weekend to inspect a sandstone slab being evaluated as a possible drilling target.

If this target meets criteria set by engineers and scientists, it could become the mission's third drilled rock, and the first that is not mudstone.

The team calls it "Windjana," after a gorge in Western Australia.

The planned inspection, designed to aid a decision on whether to drill at Windjana, includes observations with the camera and X-ray spectrometer at the end of the rover's arm, use of a brush to remove dust from a patch on the rock, and readings of composition at various points on the rock with an instrument that fires laser shots from the rover's mast.

Curiosity's hammering drill collects powdered sample material from the interior of a rock, and then the rover prepares and delivers portions of the sample to onboard laboratory instruments.

The first two Martian rocks drilled and analyzed this way were mudstone slabs neighboring each other in Yellowknife Bay, about 2.5 miles (4 kilometers) northeast of the rover's current location at a waypoint called "the Kimberley."

Those two rocks yielded evidence of an ancient lakebed environment with key chemical elements and a chemical energy source that provided conditions billions of years ago favourable for microbial life.

From planned drilling at Windjana or some nearby location on sandstone at the Kimberley, Curiosity's science team hopes to analyze the cement that holds together the sand-size grains in the rock.

"We want to learn more about the wet process that turned sand deposits into sandstone here," said Curiosity Project Scientist John Grotzinger, of the California Institute of Technology in Pasadena.

"What was the composition of the fluids that bound the grains together?

That aqueous chemistry is part of the habitability story we're investigating."

The view is an excerpt from an April 11, 2014, observation by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. 

A larger scene from the same observation can be found here.

In the image's enhanced colour, Curiosity itself appears as the bright blue object at the two-o'clock position relative to the butte in the lower center of the scene.

That butte is called "Mount Remarkable" and stands about 16 feet (5 meters) high.

The rover subsequently drove to within its robotic arm's reach of Windjana. For scale, the distance between the parallel wheel tracks visible in the image is about 9 feet (2.7 meters).

NASA Mars Curiosity rover finds sandstone variations

Sandstone layers with varying resistance to erosion are evident in this Martian scene recorded by the Mast Camera on NASA's Curiosity Mars rover on Feb. 25, 2014, about one-quarter mile (about 400 meters) from a planned waypoint called "the Kimberley." 

Credit: NASA /JPL-Caltech /MSSS

Variations in the stuff that cements grains together in sandstone have shaped the landscape surrounding NASA's Curiosity Mars rover and could be a study topic at the mission's next science waypoint.

On a journey with many months yet to go toward prime destinations on the lower slope of Mount Sharp, Curiosity is approaching a site called "the Kimberley."

Scientists on the team picked this location last year as a likely place to pause for investigation.

Its informal name comes from a northwestern Australia region known as the Kimberley. The Martian site's geological appeal, based on images taken from orbit, is that four types of terrain with different rock textures intersect there.

Ashwin Vasavada

"The orbital images didn't tell us what those rocks are, but now that Curiosity is getting closer, we're seeing a preview," said Curiosity Deputy Project Scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory, Pasadena, Calif.

"The contrasting textures and durabilities of sandstones in this area are fascinating.

While superficially similar, the rocks likely formed and evolved quite differently from each other."

The rocks that the Curiosity mission has studied most intensively so far are finer-grain mudstone, rather than sandstone.

The rover found evidence for an ancient lakebed environment favorable for microbial life when it analyzed sample powder drilled from mudstone last year in an area called "Yellowknife Bay."

The rover team is eager to inspect sandstone at the planned waypoint, now just 282 feet (86 meters) south of the rover.

The pause for investigations at this site might include time for collecting rock-sample material with the rover's drill, for delivery to the laboratory instruments inside the vehicle.

NASA Curiosity Rover: Ancient Mars Lake Could Have Supported Life

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



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.

NASA Mars Curiosity Rover: Team Selects Cumberland as Second Drilling Target

This map shows the location of "Cumberland," the second rock-drilling target for NASA's Mars rover Curiosity.

It also Shows the rover's first drilling target, "John Klein," within the southwestern lobe of a shallow depression called "Yellowknife Bay." 

Cumberland, like John Klein, is a patch of flat-lying bedrock with pale veins and bumpy surface texture. 

The bumpiness is due to erosion-resistant nodules within the rock, which have been identified as concretions resulting from the action of mineral-laden water. 

Credit: NASA/JPL-Caltech/Univ. of Arizona

The team operating NASA's Curiosity Mars rover has selected a second target rock for drilling and sampling. The rover will set course to the drilling location in coming days.

This second drilling target, called "Cumberland," lies about nine feet (2.75 meters) west of the rock where Curiosity's drill first touched Martian stone in February.



Curiosity took the first rock sample ever collected on Mars from that rock, called "John Klein." The rover found evidence of an ancient environment favorable for microbial life.

Both rocks are flat, with pale veins and a bumpy surface. They are embedded in a layer of rock on the floor of a shallow depression called "Yellowknife Bay."

This second drilling is intended to confirm results from the first drilling, which indicated the chemistry of the first powdered sample from John Klein was much less oxidizing than that of a soil sample the rover scooped up before it began drilling.

Dawn Sumner

"We know there is some cross-contamination from the previous sample each time," said Dawn Sumner, a long-term planner for Curiosity's science team at the University of California at Davis.

"For the Cumberland sample, we expect to have most of that cross-contamination come from a similar rock, rather than from very different soil."

Although Cumberland and John Klein are very similar, Cumberland appears to have more of the erosion-resistant granules that cause the surface bumps.

The bumps are concretions, or clumps of minerals, which formed when water soaked the rock long ago.

Analysis of a sample containing more material from these concretions could provide information about the variability within the rock layer that includes both John Klein and Cumberland.

Mission engineers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., recently finished upgrading Curiosity's operating software following a four-week break.

NASA Mars Curiosity Rover Explores 'Yellowknife Bay'

The NASA Mars rover Curiosity used its left Navigation Camera (NavCam) to record this view of the step down into a shallow depression called "Yellowknife Bay." 

Image credit: NASA/JPL-Caltech

The NASA Mars rover Curiosity this week is driving within a shallow depression called "Yellowknife Bay," providing information to help researchers choose a rock to drill.

Using Curiosity's percussive drill to collect a sample from the interior of a rock, a feat never before attempted on Mars, is the mission's priority for early 2013.

After the powdered-rock sample is sieved and portioned by a sample-processing mechanism on the rover's arm, it will be analyzed by instruments inside Curiosity.

Yellowknife Bay is within a different type of terrain from what the rover has traversed since landing inside Mars' Gale Crater on Aug. 5, PDT (Aug. 6, UTC).

The terrain Curiosity has entered is one of three types that intersect at a location dubbed "Glenelg," chosen as an interim destination about two weeks after the landing.

MSL's percussive drill

Curiosity reached the lip of a 2-foot (half-meter) descent into Yellowknife Bay with a 46-foot (14-meter) drive on Dec. 11.

The next day, a drive of about 86 feet (26.1 meters) brought the rover well inside the basin.

Mast Camera (Mastcam)

The team has been employing the Mast Camera (Mastcam) and the laser-wielding Chemistry and Camera (ChemCam) for remote-sensing studies of rocks along the way.

On Dec. 14, Curiosity drove about 108 feet (32.8 meters) to reach rock targets of interest called "Costello" and "Flaherty."

Researchers used the Alpha Particle X-Ray Spectrometer (APXS) and Mars Hand Lens Imager (MAHLI) at the end of the rover's arm to examine the targets.

Mars Hand Lens Imager (MAHLI)

After finishing those studies, the rover drove again on Dec. 17, traveling about 18 feet (5.6 meters) farther into Yellowknife Bay.

That brings the mission's total driving distance to 0.42 mile (677 meters) since Curiosity's landing.

One additional drive is planned this week before the rover team gets a holiday break.

Curiosity will continue studying the Martian environment from its holiday location at the end point of that drive within Yellowknife Bay.

The mission's plans for most of 2013 center on driving toward the primary science destination, a 3-mile-high (5-kilometer) layered mound called Mount Sharp.

NASA's Mars Science Laboratory Project (MSL) is using Curiosity during a two-year prime mission to assess whether areas inside Gale Crater ever offered a habitable environment for microbes.

NASA Mars Curiosity Rover: MRO HiRise Traverse Map, Sol 130

This map traces where NASA's Mars rover Curiosity drove between landing at a site subsequently named "Bradbury Landing," and the position reached during the mission's 130th Martian day, or sol, (Dec. 17, 2012). 

The inset shows the most recent legs of the traverse in greater detail.

Credit: NASA /JPL-Caltech /Univ. of Arizona

The rover entered a shallow depression called "Yellowknife Bay" with a drive of about 86 feet (26.1 meters) on Sol 125 (Dec. 12). 

It subsequently drove about 108 feet (32.8 meters) on Sol 127 (Dec. 14) and about 18 feet (5.6 meters) on Sol 130.

Yellowknife Bay 

Yellowknife Bay is a potential location for selection of the first target rock for Curiosity's hammering drill. 

The ground in this basin is a different type of terrain from the terrain Curiosity crossed getting there from Bradbury Landing. 

Nighttime observations from orbit indicate that the ground in the basin retains daytime heating better than the terrain around Bradbury Landing does, a property called high thermal inertia.

Bradbury Landing

The mapped area is within Gale Crater and north of the mountain called Mount Sharp in the middle of the crater. 

After the first use of the drill, the rover's main science destination will be on the lower reaches of Mount Sharp. 

Broader-context images of the area

The base image from the map is from the High Resolution Imaging Science Experiment Camera (HiRISE) in NASA's Mars Reconnaissance Orbiter.