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Aaaaaargh!

imipak, your post has really added some fuel to the fire; so let me ask this question:

If -- as now seems likely -- there was an Oceanus Borealis, do we really have the physics to account for its subsequent "sublimation" (I know this is not the correct word) into space; or is it not more likely that -- as I believe -- much or most of this ocean lies frozen still beneath the dust of the northern plains?

This research is quite interesting. But does not prove much as you guys have expertedly pointed out. The media are sure selling this discovery though...

However, what still strikes me as rather convincing evidence is the beautiful symmetry of the valley distribution. To say that they are random and so on would be rather unfair. Forgive me for being a little philosophical.

The likelihood that there was a lot of water on Mars at one time is old news (Mariner 9 at least) and certainly lots and lots of work has been done on the escape rate of water (see, for example, "Water loss and evolution of the upper atmosphere and exosphere over martian history", Valeille et al, in press at Icarus.) That paper concludes that "a conservative estimate of about 10 m of water is found to have escaped globally to space over the last ~3.5 Gyr."

I don't think that it's very controversial at all that there could be a lot of frozen water on Mars, so I'm a little confused by your implication that this is some big revelation and/or recent news. There is a long way between "has water" and "Earthlike".

Interesting news about ALH 84001,

http://www.newscientist.com/blogs/shortsha...il-life-in.html

Link to abstract,

http://www.sciencedirect.com/science?_ob=A...4478541063feb26

Interesting, sure. (I heard it first on Cumbrian Sky - thanks Stu.)

But probably best not discussed here.

Indeed - it's in direct breach of forum rules.

that rock again??
but if one thinks about it ...
It was "unmaned" on it's way here ,BUT it is NOT a spacecraft.

That's not why it's against forum rules.

I was checking some stuff from Mars Global Surveyor and then I came across this image: http://ida.wr.usgs.gov/fullres/divided/r09011/r0901196a.jpg

You could see the rest here: http://ida.wr.usgs.gov/html/r09011/r0901196.html
It's very strange!

Those are dust deposits left on the south polar ice from abrupt sublimation of subsurface CO2 deposits as spring approaches, Loiseri. 2006 BBC story.

Loiserl i had forgotten about that " pine tree" image

if one looks hard enough one can see many things in the images ,
i a diff. thread there is a pic of many "earth" things in a mer photo

Interesting paper in JGR: Arkani-Hamed, J. (2010), Possible crippling of the core dynamo of Mars by Borealis impact, J. Geophys. Res., 115, E12021, doi:10.1029/2010JE003602. Pay-for article abstract link: http://www.agu.org/pubs/crossref/2010/2010JE003602.shtml

According to the author, the whack that formed Vasitas Borealis may have also "quenched" the core. Did 120 Myr of no magnetosphere permanently alter Mars's evolutionary path?

ESA's Mars Express radar gives strong evidence for former Mars ocean

http://www.esa.int/esaMI/Mars_Express/SEMVINVX7YG_0.html

And some support for this theory comes from different instruments.
Here is evidence from Odyssey's GRS spectrometer - http://www.watergeek.net/geek/GRS_oceans_in_press.pdf

Emily's Blog
http://www.planetary.org/blog/article/00003365/
discusses this work (by Mouginot et al., in GRL) in nice detail. There is a
contour of dielectric constant that matches other estimates of the extent of
Oceanus Borealis : this must surely be the 'Mouginot Line'........

Aaargh!

That's almost Monty Python's grade!

Thanks, Ralph. I may require surgery to remove the wince from my face....

A relevant LPSC abstract on the stability of subsurface ice:
http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2260.pdf

I'll add a couple of comments about the abstract just posted. First, it shows that ice at 1m depth is stable down to latitude 40. That makes the story about the dielectric constant in the recent ESA press release (reported so clearly by Emily) a bit less tidy, I think. Second, they provide a graph on which there is really only one point of interest: for a single depth the critical latitude is 40 degrees. This leaves me with questions. How does the critical depth for ice survival vary with latitude? What is it at the equator?

Once upon a time we thought that there had been lakes in Valles Marineris. It was actually not that long ago, but around the time of the Viking lander/orbiter mission.

Then more lately when "our" rover Opportunity started to drive around in Meridiani Planum. It was at first thought to be a lake bottom or even might have been part of one inland ocean.

This idea had the problem with the local geography that could not really contain a lake, but also that nobody could find any shoreline for it. Add to that the finding that the water must have been quite sulfurous it would not have been any ordinary lake at all. Our planetary scientists then proposed a sort of marshland surrounded by desert as mr Squires have talked about in his updates about the mission.

A solution to this problem might be found in the text below which describe research that show how glaciers could have collected sulfur and ash from volcanic eruptions and so would have become quite acidic and resulted in the landforms, sediment layers etc, that we previously have thought formed by running water.

I have not been ready to embrace the cold Mars theory for a number of reasons, among them some sedimentary deposits and what appear to be river beds.

Now glaciers do the same work in creating valleys with flowing curving paths that look what we humans think of a riverbeds.
Many river valleys in my area were in fact first made by glaciers, it is only later that water have taken the same path.
One lingering mystery on Mars have been that we found no clays at first, we've found some now in later years, yet rivers that would have flown for a longer would have produced clays, but glaciers can indeed have this impact on landforms without producing much so also this fit with the observations.

Now that it turn out that these non-volcanic sediments are glacial in nature. And that water located under the icesheets that might have hydrated the minerals. I have finally started to cave in to the idea.
So to me this appear the cold and dry Mars scenario get increasingly more plausible. And we might very well have had one earthlike Mars, but only very early in the history for the planet.
(And this the reason I posted this, and with any apology if there's another thread started on this matter elsewhere.)


Mars Daily website

Aren't glacial valleys U-shaped while liquid rivers form V-shaped valleys? Basic physics are universal as far as I've heard.

That may be true but it doesn't tell us much here, with 3 billion years of talus formation obscuring the original shape.

Phil

Yes that is very true. And river like features might have been created in shorter time spans than what one might think.

Since the late Pliocene glacial period here on Earth glaciers and rivers have alternated in shaping the valleys of the arctic and sub arctic regions, in some cases creating new flows and breaking trough ridges as late as in the last 10.000 years.
So those valleys have been created in a very short time, and have either shape without conclusively telling which way it got started originally. And this might be a good analog for Mars, where some valleys have been carved by both water and ice.

@Explorer1: This finding by the Planetary science institute researchers do not rule out all formations as possible ancient lakes or river beds. There's no doubt there have been liquid water in some places like Nanedi Vallis, that have relatively few craters and so appear to have had a flow in a more resent age.
The question is of that valley were filled with water in one of the 'flash floods' described in some models, or that water did flow for a longer time under one ice sheet or even beneath a glacier. Stating "Sustained Water Flow?" with a question mark there.

The main point of that Mars daily item is that the layered deposits that have been found in many other areas might have been created by glaciers and not by pools or lakes of liquid water as previously thought.
Since the studies by the MER rover is of great interest for many on this forum I found it interesting that the text mentioned that such glaciers might be the explanation for the deposits found by Opportunity at Meridiani. I still wonder if that is consistent with the hints of karst topography that's been seen there though.