Ancient streambed found on surface of Mars

May 30, 2013
This set of images compares the Link outcrop of rocks on Mars (left) with similar rocks seen on Earth (right). Credit: NASA

Rounded pebbles on the surface of Mars indicate that a stream once flowed on the red planet, according to a new study by a team of scientists from NASA's Curiosity rover mission, including a University of California, Davis, geologist. The study will be published in the May 31 issue of the journal Science.

Rounded pebbles of this size are known to form only when transported through water over . They were discovered between the north rim of the planet's and the base of Mount Sharp, a mountain inside the crater.

The finding represents the first on-site evidence of sustained water flows on the landscape, and supports prospects that the planet could once have been able to host life.

As a co-investigator for NASA's Mars team, UC Davis geologist and study co-author Dawn Sumner played a key role in choosing Gale Crater as the landing site for Curiosity. Finding the rounded pebbles, which were deposited more than 2 billion years ago, was a matter of landing in the right place, she said.

"The main reason we chose Gale Crater as a landing site was to look at the layered rocks at the base of , about five miles away," she said. "We knew there was an alluvial fan in the landing area, a cone-shaped deposit of sediment that requires flowing water to form. These sorts of pebbles are likely because of that environment. So while we didn't choose Gale Crater for this purpose, we were hoping to find something like this."

The finding comes from Curiosity's exploration of the during its first 100 sols (102.7 days on Earth), or Martian days. During that time, the rover traveled about a quarter mile from its , examining multiple outcrops of pebble-rich slabs. Curiosity took high-resolution images of these pebbles at three locations known as Goulburn, Link and Hottah. The grain size, roundness and other characteristics of the pebbles led the researchers to conclude they had been transported by water.

Sumner said the discovery involves some of the most basic principles of geology.

The study area, which has been named 'Hottah', is by all accounts the remains of sediments from the bottom of an ancient stream, which had a relatively strong current. Credit: Malin Space Science Systems

"On the first day of my sedimentary class, I have the students measure grain size and the rounding," Sumner said. "It's simple, and it's important."

Sumner's work in South Africa and Australia studying signs of past microbial life in rocks and her work on living microbial communities in Antarctica helped land her the spot on the Laboratory team. NASA recognized her skills could be critical to the mission's goal: to determine whether there ever could have been life on Mars.

As part of the MSL team, Sumner helped coordinate the first scientific interpretations of what was seen during Curiosity's first few days on Mars, helps direct the rover, via computer, to shoot photographs of the planet, and continues to work on the mission from UC Davis. She will soon go on sabbatical to work on the mission at the Jet Propulsion Laboratory in Pasadena, Calif.

Explore further: The source of the sky's X-ray glow

More information: "Martian Fluvial Conglomerates at Gale Crater," by R.M.E. Williams et al. Science, 2013.

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User comments : 22

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5 / 5 (4) May 30, 2013
If life did evolve on Mars, would evidence of that life be found in surface samples or would it be found deeper underneath the surface? If underneath, how deep would we have to dig?
2.9 / 5 (10) May 30, 2013
Whar's my gold pan?
1.8 / 5 (5) May 30, 2013
Whatever happened to the infamous "blueberries" that were found all around the landing site of one of the rovers, and I believe also found near the other site as well?

Has Curiousity seen any of them?
2.1 / 5 (8) May 30, 2013
If life did evolve on Mars

If life did evolve on Mars, how come it didn't become multicellular or adapt to the surface environment (like it did here on Earth)?
2.8 / 5 (13) May 30, 2013
Whar's my gold pan?

If you think it was a long trek to the Klondike....
2.5 / 5 (13) May 30, 2013
Whatever happened to the infamous "blueberries" that were found all around the landing site of one of the rovers, and I believe also found near the other site as well?

Has Curiousity seen any of them?

Maybe the probe was hungry, not just filled with Curiosity.
2.7 / 5 (13) May 31, 2013
If life did evolve on Mars

If life did evolve on Mars, how come it didn't become multicellular or adapt to the surface environment (like it did here on Earth)?

We don't know it didn't. The odds are against it though, because the warm/damp times were relatively short, climate variations more extreme (no large moon to anchor Mars) and the variety of environments was likely less than Earths.
5 / 5 (2) May 31, 2013
If life did evolve on Mars

If life did evolve on Mars, how come it didn't become multicellular or adapt to the surface environment (like it did here on Earth)?

Life here didn't reach that point till 650 million years ago around. perhaps mars is not yet suitable for the emergence of more complex life? its possible that their will never be a chain of events leading to the possibility of complex life on mars. or its possible its already there but the ecosystems are deeper where we cant easily notice it.
5 / 5 (4) May 31, 2013
The nice thing is that 2 billion years ago, the upper limit, still leaves 2.5 billion years surface habitability.

@Gyrene: They are still looking for organics, whether as raw material for life or as trace fossils. But the surface has been heavily remodeled chemically due to the UV ionization (low pressure atmosphere), witnessed by the patchy redox states they have found.

OTOH, that patchiness shows that you don't have to dig deep before conditions becomes viable. Indeed, the bore holes shows the red (oxidized) rock shell is millimeters deep.
5 / 5 (4) May 31, 2013
@Sinister: Multicellularity has evolved independently at least 20 times on Earth. I think you mean _complex_ multicellulars, which only eukaryotes have done. (Again, independently a large number of times.)

According to Lane's energy theory on eukaryotes, it is the ancestral mitochondrial symbiont that gives us ~ 10^5 times the energy density of prokaryotes. These energy plants, hundreds in each cell, has a streamlined local genome just for energy production.

The higher energy density means higher protein turnover means supporting a vastly larger genome means complexity is an option.

But mitochondria metabolism use oxygen liberated from water through oxygenic photosynthesis. Mars never had an oxygen atmosphere, because its surface habitability was removed before cyanobacteria equivalents, the oxygen producers (still is, as plasmids in various algae and plants), could evolve.

5 / 5 (4) May 31, 2013

It took ~ 2 billion years on Earth, before cyanobacteria managed to establish a major oxygen cycle. The so called Great Oxygenation Event, as the atmosphere oxygenated.

It took another ~ 1 billion years before they, now having evolved multicellularity on their own prompted by the GOE biosphere change, also managed to establish a major nitrogen cycle. (Multicellular cyanobacteria diversify with nitrogen fixation cells.) That cycle removed dominant hydrogen sulfide anoxic conditions and oxygenated the oceans at last, opening the biosphere up for the spread of complex multicellulars.
2.3 / 5 (6) May 31, 2013

Fantastic comments. When you say 2.5 billion years of surface habitability, does that account for whatever time Mars needed to cool down to relatively sane and stable surface temperatures after formation?

On a tangent, presumably Mars would have had a head start versus Earth on "sane and stable" surface conditions compared with the Earth because of it's smaller size and diminished solar exposure, would it not? I wonder how much earlier.
2.7 / 5 (7) May 31, 2013
This is not definitive. I to wish there was water on Mars now or in the past. This like all other evidence of water can be explained by wind, sand and the voltage generated. This image can be explained by a rolling wind vortex created by wind+sand pressurizing as it interacts with the little out crop creating a higher pressure sand blaster on the pebbles near the out crop. Look at the rocks further away. They become more irregular the further away you get from the out crop. Further evidence is in the shape of the out crop. It is hollowed out along the area where most rounded pebbles appear. I understand this is a little less definitive since water can cause this. However with the other evidence only one conclusion can be asserted without further evidence. This is a wind+sand+pressure event.
2.3 / 5 (3) May 31, 2013
PoppaJ - I fully agree with you. It is not the water that creates pebble but the sand and water is only a medium that is crying the sand around. On MARS this well be done by wind.
But no worries this article is basically a COPY and PAST from other article published here couple months ago
Since there NASA starts to understand that wind is creating structures that were judged in the past to be created by water.
1 / 5 (1) Jun 02, 2013
Exactly how many times do we plan on proving the existence of past surface water on mars?

Edit- Until now, I was not aware that there were any doubters.
1.7 / 5 (3) Jun 03, 2013
Since all life on earth has one self replicating molecular ancestor, it was a singularity, thus not likely to happen elsewhere in the universe
3.5 / 5 (2) Jun 03, 2013
By that I mean it was more likely to happen in multiple places on earth (which it did not do) with some variation in the amino acid structure than just once on earth and just once or many times on Mars.
1.8 / 5 (5) Jun 03, 2013
would evidence of that life be found in surface samples or would it be found deeper underneath the surface?

That would depend on a number of things:
1) When did life develop (and how long ago did it die out)? The longer ago the deeper the evidence will be buried.
2) Did surface life develop or did it develop deep down and stay there? On Earth we've found very primitive life miles below the surface in mines. And it's not completely out of the question that life developd there and then moved up - rather than developing on the surface/in the oceans and then moving down.

If life did evolve on Mars, how come it didn't become multicellular or adapt to the surface environment

Maybe it died out before it got that far? Some environments are beyond life's capacity for adaptation.

Until now, I was not aware that there were any doubters

Rechecking ones' findings is never a bad thing.
1 / 5 (1) Jun 03, 2013

Until now, I was not aware that there were any doubters

Rechecking ones' findings is never a bad thing.

For this statement, you downvote me? is this science, or high school?
2.3 / 5 (6) Jun 03, 2013
Who are you referring to? It looks like me (since you included my answer) but I didn't downvote you.
1 / 5 (1) Jun 04, 2013
Well I tried to save your comment from oblivion too, but it looks like nothing has changed around here. No class,no etiquette, and voting still has nothing to do with contribution to the discussion.
2.2 / 5 (6) Jun 04, 2013
Well, there's people who think votes matter.

Then there's people who call themselves 'democractic' and think ballot stuffing is a way to win an argument (On scientific issues? Really?).

Then there's the really pathetic ones that go on voting rampages (yay! Maturity!).

Then there's the ones who feel the need to sockpupet-upvote themselves because they think that others will be impressed by their high vote (sorta like showing off their first potty-training success: "Look ma - look what I did all on my own!")

...Welcome to the internet: Where some people delight in showing how devoid of meaning their life really is that they think their votes (or 'likes' or what-have-you) matter for anything at all.
Someone posted this gem a while back:
On the internet you can be anything you want. It's strange that so many people choose to be stupid

So don't sweat it. Those who look at content don't care - and those are all that matter in this world.