Gullies on Mars show tantalizing signs of recent water activity

Mar 02, 2009
The gully system shows four distinct lobes. Credit: NASA/JPL/University of Arizona

(PhysOrg.com) -- Planetary geologists at Brown University have found a gully fan system on Mars that formed about 1.25 million years ago. The fan offers compelling evidence that it was formed by melt water that originated in nearby snow and ice deposits and may stand as the most recent period when water flowed on the planet.

Gullies are known to be young surface features on Mars. But scientists studying the planet have struggled with locating gullies they can conclusively date. In a paper that appears on the cover of the March issue of Geology, the Brown geologists were able to date the gully system and hypothesize what water was doing there.

The gully system shows four intervals where water-borne sediments were carried down the steep slopes of nearby alcoves and deposited in alluvial fans, said Samuel Schon, a Brown graduate student and the paper's lead author.

The gully system in the Promethei Terra region of Mars appears to have been carved by melt water and may be the most recent period when water was active on the planet. Credit: NASA/JPL/University of Arizona

"You never end up with a pond that you can put goldfish in," Schon said, "but you have transient melt water. You had ice that typically sublimates. But in these instances it melted, transported, and deposited sediment in the fan. It didn't last long, but it happened."

The finding comes on the heels of discoveries of water-bearing minerals such as opals and carbonates, the latter of which was announced by Brown graduate student Bethany Ehlmann in a paper in Science in December. Those discoveries build on evidence that Mars was occasionally wet far longer than many had believed, and that the planet may have hosted a warm, wet environment in some places during its long history.

However, the finding of a gully system, even an isolated one, that supported running water as recently as 1.25 million years ago greatly extends the time that water may have been active on Mars. It also adds to evidence of a recent ice age on the planet when polar ice is believed to have been transported towards the equator and settled in mid-latitude deposits, said James Head III, professor of geological sciences at Brown, who first approximated the span of the martian ice age in a Nature paper in 2003.

"We think there was recent water on Mars," said Head, who with Brown postdoctoral researcher Caleb Fassett is a contributing author on the paper. "This is a big step in the direction to proving that."

The gully system is located on the inside of a crater in Promethei Terra, an area of cratered highlands in the southern mid-latitudes. The eastern and western channels of the gully each run less than a kilometer from their alcove sources to the fan deposit.

Viewed from afar, the fan appears as one entity several hundred meters wide. But by zooming in with the HiRISE camera aboard the Mars Reconnaissance Orbiter, Schon was able to distinguish four individual lobes in the fan, and determine that each lobe was deposited separately. Moreover, Schon was able to identify the oldest lobe, because it was pockmarked with small craters, while the other lobes were unblemished, meaning they had to be younger.

Next came the task of trying to date the secondary craters in the fan. Schon linked the craters on the oldest lobe to a rayed crater more than 80 kilometers to the southwest. Using well-established techniques, Schon dated the rayed crater at about 1.25 million years, and so established a maximum age for the younger, superimposed lobes of the fan.

The team determined that ice and snow deposits formed in the alcoves at a time when Mars had a high obliquity (its most recent ice age) and ice was accumulating in the mid-latitude regions. Sometime around a half-million years ago, the planet's obliquity changed, and the ice in the mid-latitudes began to melt or, in most instances, changed directly to vapor. Mars has been in a low-obliquity cycle ever since, which explains why no exposed ice has been found beyond the poles.

The team tested other theories of what the water may have been doing in the gully system. The scientists ruled out groundwater bubbling to the surface, Schon said, because it seemed unlikely to have occurred multiple times in the planet's recent history. They also don't think the gullies were formed by dry mass wasting, a process by which a slope fails as in a rockslide. The best explanation, Schon said, was the melting of snow and ice deposits that created "modest" flows and formed the fan.

Source: Brown University

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User comments : 15

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tkjtkj
5 / 5 (3) Mar 02, 2009
"Using well-established techniques, Schon dated the rayed crater at about 1.25 million years,,,"

Perhaps a word or two about the method of dating would have been appropriate here, or at least some links!!! Surely they are not suggesting that the methods used are so 'well-known' as to
make ref's to them perfunctory!

tkjtkj@gmail.com
Modernmystic
1 / 5 (2) Mar 02, 2009
What's the point, we won't EVER get any conclusive proof that life exists or ever existed there...despite the fact that NASA sent a probe there not too long ago with that very mission.

half a billion dollars foiled by clumpy dirt....

pfft...
deatopmg
3.5 / 5 (4) Mar 02, 2009
More NASA fluff! The researchers did some nice investigative work but the organization is clearly muddying the waters by omission, obfuscation, and misdirection, like this report does. Water clearly (or muddily) flows on the surface - now. Maybe not in the massive flows reported above, but small spurts hear and there can be seen to have flowed in the minutes between released photographs.

Where there is liquid water....life may remain.
OckhamsRazor
2.3 / 5 (3) Mar 02, 2009
What's the point, we won't EVER get any conclusive proof that life exists or ever existed there...despite the fact that NASA sent a probe there not too long ago with that very mission.

half a billion dollars foiled by clumpy dirt....

pfft...


Holy cow...you are STILL whining about the dirt! Go and read up on something else and save yourself from these brain aneurisms. Clearly, Mars is not good for your health.

And what do you mean "won't ever"? Are you really that simple?
Modernmystic
2 / 5 (4) Mar 02, 2009
What's the point, we won't EVER get any conclusive proof that life exists or ever existed there...despite the fact that NASA sent a probe there not too long ago with that very mission.

half a billion dollars foiled by clumpy dirt....

pfft...


Holy cow...you are STILL whining about the dirt! Go and read up on something else and save yourself from these brain aneurisms. Clearly, Mars is not good for your health.

And what do you mean "won't ever"? Are you really that simple?


Holy cow...shill for NASA much? Do you sweep floors there or something?

And yes I'm STILL holding that idiotic agency accountable for a half billion dollars of wasted money over a mistake a THREE YEAR OLD could have foreseen.

FTR I'm not the one having aneurysms over this topic either. YOU are the one who incessantly whines about my opinion on the subject. YOU seem to be the one with some kind of point to prove here, not me.

I take great glee in posting on this particular subject and how NASA continues to piss tax dollars down the drain with wild abandon. It's so easy to do as well with as many boondoggles, moronic mistakes, and idiotic policy decisions over the past forty odd years.

Aneurysms? Well they say laughter is healthy...if that's the case NASA is as healthy for me as Monty Python.

Oh and I SHOULD amend my "won't ever" statement. We WILL NEVER get the evidence from a NASA mission. Maybe the ESA, or even the Chinese...but NOT that laughing stock pit of clueless bureaucrats we GENEROUSLY refer to as the National Aeronautics and Space Administration.
OckhamsRazor
2.3 / 5 (3) Mar 03, 2009
Your comments don't get to me, it just amazes me there are people out there with the short attention span and narrow mind that you seem proud to bare.

You behave like the studies and probes on Mars have done nothing, which is even more amusing. I think you stop reading these articles after the first sentence, which really just proves my point. Anyone with a brain can see how evidence of the presence of water on Mars is only the first step of finding signs of life.

If not literacy, maybe you should work on another helpful ability - it's called patience.
Modernmystic
2 / 5 (4) Mar 03, 2009
Your comments don't get to me,


Then why do you incessantly comment/reply to them.
Of course they get to you, you wouldn't do it otherwise. I suspect there are two reasons for this (though I could be wrong).

1. You work for NASA
2. You know deep down my comments are perfectly valid and NASA really needs a good shaking up, as in a HUGE house cleaning (we are in a recession after all...why should incompetent scientists get to keep their jobs when so many others have lost theirs).
OckhamsRazor
2.3 / 5 (3) Mar 03, 2009
Your comments don't get to me,


Then why do you incessantly comment/reply to them.
Of course they get to you, you wouldn't do it otherwise. I suspect there are two reasons for this (though I could be wrong).

1. You work for NASA
2. You know deep down my comments are perfectly valid and NASA really needs a good shaking up, as in a HUGE house cleaning (we are in a recession after all...why should incompetent scientists get to keep their jobs when so many others have lost theirs).


I'll let you pick your favourite. You're such an angry, angry man. Of course, there could be other reasons, but I'm happy for you to select which applies. If you're happy, I'm happy.

I just don't see why people think advances in knowledge of worlds other than our own should advance instantly - the very second we launch a new probe or uncover new technology to decipher the information we currently have on hand.

Until we physically have an outpost on Mars where scientists can live and study the planet directly, this is the best we can accomplish. And any knowledge is still knowledge. What happened with the Phoenix was glitchy, but still amazing. Previous creases in the flow of the mission will be ironed out in time, which increases the chances of the next mission being more successful.

In the meantime, how can you look at even newer evidence of water activity on a planet we've always seen as a barren wasteland, and not be impressed? I agree with you on NASA needing a shake up, but at least there are some people there earning their wages.
Modernmystic
2 / 5 (4) Mar 03, 2009
I'll let you pick your favorite.


OK I'll pick both.

You're such an angry, angry man.


Really? I don't remember ever meeting you, or your being inside my head. You, OTOH are apparently a horrible armchair psychologist.

What I AM is very intolerant and unforgiving of the last forty years of NASA administration. Space exploration (wow, remember when we actually used to do that) is very important to me. So are various questions with respect to cosmology.

With a few notable exceptions NASA has dropped the ball again, and again, and again on the important issues. If you interpret that as me being an angry, angry man then...well I guess opinions are like...well you know the rest.

If you're happy, I'm happy.


Interesting if true, I'd say from your past interactions with me nothing could be further from the truth...

I just don't see why people think advances in knowledge of worlds other than our own should advance instantly - the very second we launch a new probe or uncover new technology to decipher the information we currently have on hand.


And I don't see how after 30 odd years of sending probes to Mars someone could POSSIBLY consider someone impatient about the subject. Did you really use the word instantly....yep you sure did...

Until we physically have an outpost on Mars where scientists can live and study the planet directly, this is the best we can accomplish.


HA! So much for robotic exploration eh? I happen to agree, that is exactly why, since we've accomplished next to nothing, we should have been putting our resources into manned exploration in order to get some definitive answers.

And any knowledge is still knowledge. What happened with the Phoenix was glitchy, but still amazing. Previous creases in the flow of the mission will be ironed out in time, which increases the chances of the next mission being more successful.


Again, opinions, we all have em (yeah yeah me included). I think for half a bil we should have easily foreseen that particular "glitch".

In the meantime, how can you look at even newer evidence of water activity on a planet we've always seen as a barren wasteland, and not be impressed?


What am I supposed to be impressed with? We've known for some time that Mars very likely still has water in it. How many billions do we need to spend to reaffirm that over and over and over again?

I agree with you on NASA needing a shake up, but at least there are some people there earning their wages.


Oh I agree. The terrestrial planet finder (which may well ACTUALLY answer one of the most important scientific and philosophical questions of all time). The Hubble was worth it on the whole. Communications satellites, gps, weather, military are all worth the money (though most if not all could be handled commercially).

I started to list all the blatantly idiotic projects, but quite honestly I don't have the inclination or the time. I'm going to watch a movie with my son...
OckhamsRazor
2.3 / 5 (3) Mar 04, 2009
Ok bye bye. Your anti-NASA propaganda still isn't holding any water here, let alone on Mars, for any of the posts you make. I'm still waiting to see you do better, but rather than attack with fact you're just spitting your hatred all over this page and accomplishing far less by doing so than NASA did on the first day of Phoenix's soil-shaking.

This is me washing my hands of your tunnel-vision. Enjoy your movie with your son - maybe keeping your eyes fixated on Hollywood's by-products is what is making you so antsy about space exploration.
Jess
3.7 / 5 (3) Mar 07, 2009
the two of you do realize that you have almost entirely ignored the article and have devoted your little verbal spat to your own differing opinions, correct? NASA is as bad as every other US organization. (the term 'organization' in its most loose form, of course) saying that none of their accomplishments are good enough helps no one. take what they can give, because we won't be getting anything else.
Modernmystic
2.3 / 5 (3) Mar 07, 2009
the two of you do realize that you have almost entirely ignored the article and have devoted your little verbal spat to your own differing opinions, correct? NASA is as bad as every other US organization. (the term 'organization' in its most loose form, of course) saying that none of their accomplishments are good enough helps no one. take what they can give, because we won't be getting anything else.


Is there really a point in that puerile whine somewhere? Am I supposed to care what you think about how I post?

Kindly GET OVER yourself...mkkkay.
jonnyboy
1.3 / 5 (3) Mar 07, 2009
It's not just what Jess happens to think of you, it is what pretty much everyone thinks of your outlook, on every topic, that might make you want to either reevaluate your opinions or possibly seek professional help in dealing with your maladjustment to society.
Modernmystic
2.5 / 5 (2) Mar 07, 2009
It's not just what Jess happens to think of you, it is what pretty much everyone thinks of your outlook, on every topic, that might make you want to either reevaluate your opinions or possibly seek professional help in dealing with your maladjustment to society.



Yeah consensus makes people right. Let's take a vote on the law of gravity and see what happens...

Why that just makes sense on absolutely no level whatsoever, but thanks for your opinion all the same.

Oh, and looking at some of your posts, I wouldn't throw stones when suggesting someone seek professional help...you live in a BIG glass house buddy.
Egnite
not rated yet Mar 09, 2009
Everyone knows that nasa suck but that aside, if these Gullies were formed 1.25 million years ago, could it be possible that Mars has a similar iceage cycle to Earth and may someday defrost again?