If the water excavates the gullies deplacing the darker material underneath where are the vestiges of that material?
Mixed with the lighter one?

If you look at the ends of some of the gullies there are fan-shaped deposits of material and sediment that has come down the gully and then been spread out across the lower ground...

I assume it's being proposed that as the wet avalanches dry out the deposited materials become encrusted with light coloured salts.

I think this one is very interesting since it seems like the terrain where the gully formed is relatively flat. This tells me:

a. The flow was likely relatively persistent (i.e., probably not a short explosive burst)

b. Both the source and the gully look eminently roveable!

Looking through this image there are some lighter layers being disrupted by the mouvement (in blue).
Can they influence in the colour of the material deposited at the end of the flow?...
If you look there's a first stage where the rush excavates but then, finding one of this layers (a), maybe because it's force has lost strenght, is no longer capable of "breaking" it and it jumps over, running now only over the surface...Then this second stage white flow looks like is loosening power again untill finds another bright layer ( B ) and it ceases a short after this and there's no other under...

Original image

I just read Emily's article (the one that Alex cited above) and I have to say that it's raised some questions in my mind. The evidence cited for the white streaks as being from flowing water were: the light color, the fact that they moved around obstacles and the digitate nature of their terminus. Yet if you look at the image of the dark flows, which are considered to be dry dust flows, you can see two of the same features: a digitate terminus and flow around an obstacle. That leaves only the white color as distiguishing them from the dark, dust streaks. Perhaps the light streaks are just a different type of dry flow (we have seen white dust churned up by Spirit) or perhaps the dark streaks are a different type of aqueous flow.

Mike Malin addressed that as well. The slopes where these deposits are made are fairly gentle, a dry process would have trouble making it that far - was it 1 mile or so? They did computer simulations showing it's most plausible to be a liquid-driven process, liquids flow much more easily than dry stuff.

Ahh, thanks. I missed that part of the evidence.

Wow - my UMSF habit gets interrupted by work and life for a few days and look what I miss

What a great exit for MGS, good to see she "died with her boots on" (if indeed she's dead, of course)

Absolutely. Go to any old mining town in the western US like Butte, MT or Lead, SD & you'll find all kinds of hardy little critters enjoying themselves in extraordinarily toxic, acidic environments...

And if you go in the winter, the conditions will be remarkably similar to Mars (with -50F not being uncommon in Butte). There's also a very large crater there.

I was waiting to see how long it would take Nick Hoffmann to weigh in. Not surprisingly, I could have predicted this response.

Actually, and I may be wrong about this, my understanding of the current planetary protection plan is that we want to avoid sending missions to these gullies to ensure that they stay in pristine state. I would be very, very uncomfortable having MSL trundle up to one.

My understanding is much the same, what a pity... The really interesting targets, and we can't even send anything there... Oh well, I guess that's life...

Both of you may be right; I'll have to go back and re-read the latest PP guidelines for Mars. However, I thought that, for example, MSL-related restrictions were due mainly to possible crash scenarios with an RTG power source. I thought that a "go-to" traverse capability (i.e., landing at a safe distance and then roving to the area of interest) would permit visitation of biologically interesting sites, assuming the lander/rover was subjected to Viking-level sterilization.

Spacecraft fleet zeroing in on Martian water reserves
ESA News Release
7 December 2006

I looked at the Planetary Protection Guidelines posted on the MSL Marsoweb site and it states:

"1. Prepare the landing system to meet Viking post-sterilization cleanliness requirements (controlled cleaning and assembly as noted below, followed by a system-level dry heat microbial reduction step in accordance with NPR 8020.12C), with control of recontamination through launch and delivery to Mars:

Under this option no restrictions on landing sites or on horizontal or vertical mobility into martian special regions would be imposed on the MSL mission by my office.

John D. Rummel, Planetary Protection Officer"


From Planetary Protection Constraints, dated Aug. 23, 2005: http://marsoweb.nas.nasa.gov/landingsites/...ationLetter.pdf

http://marsoweb.nas.nasa.gov/landingsites/


So it looks like GoTo sites, like the gullies, would be acceptale

Thanks, aldo12xu. You saved me from having to wade through Rummel's paperwork.

That's quite a job title - I mean, think of the conversation at a BBQ: "so John, what do you do?"

It is, and now, I believe, it belongs to Dr. Catharine Conley, at least on an interim basis.

As I understand it, Rummel was recently named to replace Dr. Carl Pilcher as Senior Scientist for Astrobiology in SMD's Planetary Sciences Division. Pilcher is moving on to become Director of the NASA Astrobiology Institute (NAI).

You should listen to the interview of Rummel (last July) on Planetary Radio. Bob Zubrin still gets under his skin

A question this raises is how a top-notch exploration could be performed of one of these sites when it is active. What is the shortest possible reaction time?

Obviously, committing extravagant resources buys you something in ability to respond.

Detecting these events when they happen would be one part of the capacity. First, the frequency of the events at different candidate sites should be determined. Then, we could have some number of them on a "watchlist" that are monitored frequently. Imagine an orbiter that circled Mars every two hours, checking 12 suspect locations under its apomars at about 45 south.

Then you'd have a lander stashed in an orbit that would "follow" the orbiter, apomars for apomars, in making similar close approaches to the same locations at a "lag time" that allowed operations on Earth to proceed. Let's say the lag time was one sol.

When a positive observation of a gully flow was made, the lander could arrive one day later and settle right onto the gully path. Perhaps show up in time to see successive flows in successive sols.

In situ analysis alone would be the stuff of scientific gluttony, but a tremendous (and very pricey) combo would also settle a sample-return craft downslope (which would seem to ease engineering constraints if that means reducing the slope), allowing a minirover at the flow site to deliver the goodies to the sample return. More exploration of the areas *upslope* would also be interesting.

Clearly, this would be the ultimate "red meat" of solar system exploration: To deliver a sample of liquid water, or stuff that was immediately prior wet with liquid water, back to earthly labs offers an excellent opportunity to get a Big Answer on astrobiology and/or one heck of a giant leap into understanding where ELSE you might have to look in case the sample were (as I bet it would be, FWIW) sterile.

It would also be a hell of an expensive program, with many points of failure, and perhaps too subject to chance if these flows are too rare for the above architecture to produce a likely flow detection before the life of the orbiting elements gives out. Obviously, two-way planetary protection concerns would require superlative measures. And just doing this at all would cost a lot more than any generic sample return mission.

Still, if we don't do this, sooner or later, we've left a stone unturned. We have to do this, eventually.

I think when the MERs were launched we knew far too little about Mars to commit serious resources to lander missions. This event, IMO, changes that. Now we know something very big. We're not going to get a clearer "go ahead" signal than this.

Does somebody know the altitude of geo...oups Marsostationary orbit ? Could be a good place to look for changes with adequate cameras and software. Phobos could be a good place too.

I'll have to double check but I think it's ~17,000 km.

This was all over the news and immediately the suggestion was given that it might be a ‘dust-flow’ instead of ‘water-flow’ …

Stu, You’re so right… we have been waiting over 30 years for this …
By The Way where the artist impression from (is it by Pat Rawlings)?

My favorite photo for now is:
http://www.msss.com/mars_images/moc/2006/1...ater_mosaic.gif

Will it now be easier to decide where to land the first human crew ?

In fact, the "crater" is full of nasty acidic heavy-metal enriched water that supports an ecosystem:

http://www.mtech.edu/math_science/biology/...iodiversity.htm

...and, I'll personally vouch for the -50F winter temps...walking to school in that wasn't fun. Fortunately, it was only uphill one way...

That is correct. Pretty high up to get high-resolution images. Also, these events have been on slopes facing away from the Sun, which means that a equatorial vantage point would be less than ideal.

I forgot to post these yesterday but below are a few related stories:

news@Nature.com
Scientific American.com
Astronomy
Sky & Telescope

I see that Jim Bell had a nit to pick.

It depends the hour you take the pictures! You're Marsostationary not Sunstationary
But you're right it's very far

Thanks, aldo. I had a dim memory that there was a restriction for the special regions, but I wasn't sure what it was.

For those with regular online access to Science, the articles are now available for download.

After Mr. Bell correction some correction is needed...:



What I'm trying to say is that, on this particular image seems to me like this brighter layers have an important role on the tone of the flow...
What can that material be (other hypothesis than salt...)?

Here's Steve Squyre's comment on Life on Mars from his Open University Talk. I transcribed it from the audio file.

Steve (the other Steve, that is. )

-----

Steve Squyres Lecture at CEPSAR (Centre for Earth, Planetary, Space, & Astronomical Research), The Open University, 7 November 2006

Time: 65:12

Questions:

Stewart Hirst(?): After your 100– 1012 Sols on Mars are you more or less optimistic in finding evidence of life– or not you, but that evidence of life will be found on Mars?

SS: Oh, it’s hard to say. I think that what this has shown us is that early interpretations, going back as far as Mariner 9, that liquid water has been present below the surface and at the surface of Mars were correct. There has been water on Mars; that’s been believed since we first saw valleys in the Mariner 9 images and I think our data show that but you can go much more beyond just saying yeah, there was water on Mars.
Umm.
At these locations – particularly at the Opportunity site, which is, I guess, the more favorable of the two – Uh, as I said there are a number of things here that would be really I think very daunting for life. The acidity, the highly oxidizing character, the highly saline environment. Now you can go to very acidic, very oxidizing, very saline environments on Earth and they’re teaming with life, they’re teaming with microbes. You can find bugs that are perfectly happy at a PH of one: acidophiles. But those are organisms that developed first under more neutral, more normal if you will, conditions and then managed to find a way to evolve into that very challenging ecological niche. If you go to one of these acidophiles, and you measure the PH of their environment, the PH outside of their cell membrane is one and the PH inside is seven. OK and they have wonderful ion pumps across their cell membrane keeps them at a neutral PH inside. Umm. So while life can exist in that kind of environment, whether or not it can get started in that environment is another question.

Now one thing you’ve got to keep in mind is that these two places are just two little pin pricks on the surface of an incredibly diverse and complicated planet. For example, the Omega instrument on the Mars Express, the European Mars Express mission, French instrument, and also now the CRISM instrument on MRO have both detected philosyllicates, clay minerals, at some locations on Mars that may be indicative of more neutral PH at some point. Umm so there are no– It’s a complicated story that’s still evolving. There are a number of places where we see both morphological and mineralogical evidence for water on the surface of Mars. In terms of the habitability, yeah it was habitable but it was a challenge. I think we’ve still got a lot of work to do. I think what we need to do is send instruments like Colin [Pillinger]’s instrument package to the surface of Mars and look for organics and I think we need to bring some rocks back.

68:12

Instead of waiting for a site to become active and then dropping a probe/lander, I was thinking of the opposite. "Seed" gully sites with penetrators or Netlander-type packages, and then cue orbital assets when something (e.g., seismic activity, water vapor, etc.) is detected.

I've read the paper, which was interesting and, of course, provided the hard numbers and references in "Science-ese." I have to say, though, that most, if not all, of the information was provided via the MSSS web pages.

A little off-topic, but its worth noting that light-toned units on Mars often, but not always, exhibit different color properties than the surrounding terrains. Typically, they're redder. This has been a research interest of mine for a while, and presents an excuse to show a few pretty pictures.

Here are some THEMIS VIS examples from Aram, Aureum, and Iani Chaos, where the lighter-toned units are also "redder"--a quantity that is shown in the lower set of images as THEMIS VIS 540 nm band depth images. Anyway, these deposits are quite different from the gully light-toned material, but if that material has similar color properties to the above images, it would be indicative of an increased Fe3+ content.

Hate to say it, but I think it's gonna be a long time till we can conclusively answer the "L.O.M." question unless we get extremely lucky & identify a completely alien organism in a returned sample. (If hypothetical Martians are biochemically similar to Earth life, it will be much harder to distinguish them from contamination).

If there really isn't any life, it'll take centuries of in situ exploration to reach that conclusion definitively...

If the slopes are facing away from the equator and the probe is over the equator, then the hour won't matter.

Technically, the term "stationary" does stipulate that the orbiter be directly over the equator. It is possible to have an inclined orbit that is synchronized for longitude that will bob between latitudes X north and X south. But that wouldn't give you continuous viewing of any particular perspective, so I don't see the advantage this would have over a much lower orbit with higher resolution. It would give you periodic viewings of the same point.

My notion was to have a 2-hour orbit that would also give you periodic viewings of the same point(s), but MUCH closer up.

The pessimistic outlook for LOM re: this discovery would be that the same areas on Mars may not be getting anywhere near enough repeat soakings to entail a habitat. There are areas on Earth where various lifeforms lie dormant until flash rains come, but that surely requires some favorable ratio, however slight of wet-to-dry. For example, 10 minutes wet every ten thousand years probably would not do the trick. Mars could be awfully cruel in this way.

My hypothesis on why the sun-facing slopes don't have gullies is that there is a finite subsurface reservoir and the sun-facing slopes already had their gullies and exhausted their supply a long time ago. In essence, I'm positing that the sun-facing slopes are like short-period comets and the sun-hidden slopes are like long-period comets.

Here is a link to the conference on Google Video:

http://video.google.com/videoplay?docid=34...61245&hl=en

Next stop, Mars
By Adrienne So
Salon.com
December 8, 2006

NASA images, White Sands features support a wetter Mars
Andy Fell
Egghead Blog at UC Davis
December 7, 2006

Thanks, Tim. Is this figure from the paper "Evidence for aqueous deposition of hematite and sulfate-rich light-toned layered deposits in Aureum and Iani Chaos," which you and A. Deanne Rogers have submitted to JGR-Planets?

yep.

I had a couple of inquiries about Christensen's paper from people who don't have access to Nature. You can download it from Christensen's blibliography page - specifically, the 301 Kb PDF.

As for Malin and Edgett's paper, I believe that the full text to all papers in Science are freely available online after a year, so that particular paper should be accessible.

Oh shucks...I have access to some online journals, but Science is out of my reach. I have tried mostly every trick in my book to locate a copy of that file, but still came up short. Living 90+ miles from the nearest library that is likely to have a subscription is one of the problems I face while living on the edge of civilization. I so hoped I would be able to read it without a 12 month wait.

Oh well. I guess a drive to a large city is in my future.

The water stuff has grabbed everyone's attention, but the new calibration point for the recent cratering rate is also noteworthy.

It isn't. You can access most content older than 12 months (including Malin & Edgetts paper) for free, but you have to register as a user first. Details at:

http://www.sciencemag.org/about/access.dtl


tty

Sorry to add another bit to the water discussion, but I saw a version of this in a Christmas catalogue and couldn't quite resist the temptation.

Little Willie was a chemist.
Little Willie is no more.
For what he thought was H2O,
Was H2SO4.

Steve

Well,if you followed the press briefing towards the end of it,Mike Malin himself sort of hinted that mars scientists could be still getting it wrong as regards the geochemistry of the gully flows.So there you may have a point Steve!

I knew it as

"Johnny Brown whent to school
but now he is no more
For what he thought was H2O
Was really H2SO4"

Doug