http://www.nasa.gov/home/hqnews/2011/aug/H...Mars_Brief.html

Is it going to be about methane or new finding of calcium carbonate??

"NASA Announces News Briefing On Mars Orbiter Science Finding
Science Journal Has Embargoed Details Until 2 p.m. EDT on Aug. 4 "

Does anyone have any idea what discovery has been made???

Let me guess, they are going to announce that they've found the first solid evidence that intermediate amounts of liquid water once flowed on Mars.

There's a certain Monty Python aspect to it. "We've found middling quantities of tepid water!"

I'm sure the embargo will be busted before tomorrow, so all we have to do is wait...

Whose turn *is* it to breathlessly announce the 'discovery of water' on Mars? I've lost track of the score....

A glass of water on a well-known chocolate bar! That never gets old

Whatever it is, prepare for public underwhelment...but no doubt we will find it most interesting!

Here's a recent interview with Lisa Pratt:
http://newsinfo.iu.edu/web/page/normal/17323.html

Someone I'm working with at JPL was invited (but cannot) to be part of the chat during the conference. She works with gullies, so that's what she suspects is the topic of the announcement.

"NASA Spacecraft Data Suggest Water Flowing on Mars":

http://www.nasa.gov/mission_pages/MRO/news/mro20110804.html

Briefing started...

'Predictable and repeated evidence of water flowing on mars'

Does Gale have any of these features? If not....(?)

Didn't we see something similar at Santa María?
http://qt.exploratorium.edu/mars/opportuni...IEP1905L0M1.JPG

Cool! Though the fact that CRISM doesn't spectroscopically see any water associated with the dark features makes me somewhat skeptical. If they are made by water, why aren't they wet? I hope they keep scanning with CRISM in the hopes of catching one in the act- maybe it's a matter of looking at the right time of day.

Or maybe they are dust avalanches that happen to be triggered by summer winds, though in that case it's surprising that they advance downslope so slowly and gradually. Hmmm....

John

Yes, they will keep looking with Crism. Apparently the resolution hasn't been good enough for it yet.

That's weird CRISM does not see anything. They argue that flows are much smaller than the CRISM pixel scale (18m). That's true for a single flow, which width scales between 0.5 and 5m, but some HiRISE pictures show 60m*60m areas covered by this dark flows. So CRISM shoud see them. And a mixture of water and salt does not change anything : there is still a strong signature of water. I'm very skeptical...

At one step, during the conference we saw what they've called 3D animations. Were they Doug's?

Nope - nothing to do with me.

the water will boil off (evaporate) quickly under the low pressure. Suspect there would be some kind of evaporite (salt) left over. But for direct detection of water CRISM would almost need to catch it in the act.

Will need to see the Science paper for more details.

if there is water flowing downhill on mars today, what I wonder is how it gets back uphill. Condensation out of the atmosphere?

Possibly a naive question, but do any of the currently active orbiters have an instrument that can determine atmospheric humidity levels with high spatial resolution?

I'm sure there's not, but those would seem to be the root requirements for exactly the sort of gizmo you'd need to catch these things in the act & prove they're made by flowing mud.

Mars Climate Sounder onboard MRO can detect water vapor (and thus you can calculate humidity as it detects temperature also).

But it probably wouldn't work for this scenario. It's not ideal for detecting these values in the lowest layers in the atmosphere and whatever water comes out of these features probably won't significantly effect the water vapor concentration at higher altitudes.

Amusingly, it's similar images of water that make me wonder if the albedo changes simply have to do with the clumpiness of the dust in the streaks. There's activity in snowpack called either sloughing/sluffing. Basically by altering only the texture of the snow, it creates streaks like the ones found in the dust on Mars:


I guess this sort of thing is more common with SAR... but you can see it in plain old visible light. The whole slope is bright white snow. Up close the color of the sluffs is no different. They're just reflecting the sky back to the camera differently.

Like snow, the dust probably falls in dry and sparsely packed, and clumps up more when something starts it rolling.

I wonder if the streaks are just clumpier dust on airfall dust. They do need a trigger, though. That could be a tiny bit of water starting a basically dry sluff.

Wow. I'd call that a significant contribution to the discussion, Steve. Morphologically, at least, these streaks are astoundingly similar in appearance.

What would be the correlation to seasonal changes for the reflectivity of dust/soil? It seemed as if that was a major component to the liquid water hypothesis.

Whatever triggers the streaks is seasonal, sure. I'm open to the trigger being water.. Something changes the properties of one small section of dust, and a cascade starts. I just think a sluff of dry dust could also explain the apparent albedo change, if dry dust rolling downslope is simply clumpier than dust that fell from the atmosphere.

They slowly fade due to constant dust falling from the atmosphere. I think with any explanation for causing their appearance, that's the reason they disappear, right?

I actually don't think dry processes can explain it all. Sure, a few exfoliating pieces of gravel could drop onto dust slopes that are at their maximal steepness and start dry cascades... but it seems like there's way too much action going on, so of it triggered away from any rock faces. The real question in my mind seeing the apparent albedo change... is there necessarily a change in composition, or is it just a change in texture? It looks more wet... it may just be more rough. (Or ruff, if I stick with the phonetic version of slough.)

Intriguing and beautiful imagery...
http://hirise.lpl.arizona.edu/sim/science-2011-aug-4.php
http://www.nasa.gov/mission_pages/MRO/news/mro20110804.html

Of course i hope its water, but somehow wouldnt we expect dampened dust to be cohesive enough to clump together and change properties enough to over time alter the topography subtly but enough that we shoudl see some sort of evidence of that after repeated episodes over eons? With the analogous snow scenario posted above you wouldnt get any clumping or change of cohesion so that seems more persuasive. thanks for posting that.

I think the amount of water and the force of the water we are seeing is probably rather low and something similar to capillary action is causing the small amount of water to dampen the surface, so the effects are going to be quite subtle. Or maybe the long term effects of this have just been overlooked in the past?

There's a spectral processing technique called spectral mixture analysis (SMA) which has been used in many studies (including by yours truly) to determine the sub-pixel fractional area cover of different substances. If water covers a reasonable portion of the area of a pixel, SMA should be able to tease it out. I believe SMA has been used for Mars studies, but if not, it's a well known technique. If it's not been used in this case, this suggests that the CRISM investigators have used equally good spectral techniques for teasing out fractional coverage.

The lack of a water spectra suggests that (1) CRISM has been unlucky enough to look when water wasn't present, (2) there is so little water at any given time that it doesn't trigger a measurable spectral response, (3) water isn't involved.

One possibility for the source, if it is briny water, is overnight frost that is melted by contact with the salty bedrock, forming a brine. In that case, the time to try to "catch it in the act" might be the early morning hours.

There's also no reason why multiple CRISM images of these suspect locations cannot be stacked for improved resolution. Obviously the closer together in time the images in the sequence are captured, the better.

It was mentioned in the conference that they'd try super resolution eventually, don't remember who though.

Unfortunately, the MCS water detection capability has been compromised by less-than-ideal behavior of the "in band" water channels (i don't remember their filter names). As such, its capability remains theoretical. Hopefully, EMCS on ExoMars-TGO will be able to avoid this problem.

CRISM measures an integrated water column on a regular basis (i.e., Smith et al., 2009; http://adsabs.harvard.edu/abs/2009JGRE..11400D03S). However, one would really want to get the sporadic limb "scans" by CRISM to get a better sense of humidity levels in the atmosphere. These have been analyzed (and still are) by Smith et al., but only published in abstracts at the moment. Also, analogous to the issue pointed out by Drskywxlt for thermal sounding, the lower scale height is difficult to resolve in a meaningful way for water by CRISM (radiation field is "thermalized" by multiple scattering in the CRISM regime).

The best hope for orbital, vertically-resolved water vapor measurements would be sub-mm/microwave sounding, which are basically insensitive to the aerosol components in the atmosphere, at least in terms of confounding water line analyses.

I really like your photo of the snow sloughing features. I'm just starting a wikipedia article about martian dark slope streaks, and am wondering if I could use the photo there. If so, how should I credit it? Thanks.
Tom

It's from here, in context:
http://wowasatch.com/Journal%202008-09/May-09/may-3.html
Contact info here http://wowasatch.com/contact.html

I know of the photographer from his online presence. He'll often link to his own photos from online forums, but I'm not sure how he'd react to wikipedia. You can see he does reserve the copyrights.

Thank you.

Tom