# What Caused Mars to Go Dry?



## j d worthington (Jan 28, 2007)

At this point, they seem fairly sure it wasn't the Sun:

Sun did not blow water off Mars, study finds - Yahoo! News



> WASHINGTON (Reuters) - Scientists trying to find out where all the water on Mars went ruled out one culprit on Thursday -- new measurements show the Sun did not blow it away.
> 
> They measured ions -- charged particles -- being blown off the planet by the solar wind, itself a stream of charged particles.
> 
> ...


 
There are other speculations (such as impact with a large object, etc.), but nothing definitive.

The story is from Reuters, titled "Sun did not blow water off Mars, study finds", datelined Thurs., Jan. 25, 2007. 

Does anyone else have any articles/information on this investigation?


----------



## mosaix (Jan 28, 2007)

Interesting stuff JD.

I thought, although I don't know why, that Mars couldn't keep it's water because the atmosphere was too thin. Come to think of it though, perhaps the atmosphere is thin _because_ there is no water!

Must look into this more!

Thanks for the info JD.


----------



## j d worthington (Jan 30, 2007)

Thought I'd add this to an existing thread rather than begin a new one:

Study: Surface of Mars Devoid of Life - Yahoo! News

The story is from LiveScience, by Ker Than, datelined Mon., Jan. 29, 2007, and is titled "Study: Surface of Mars Devoid of Life":



> The last refuge for Martian life, if it exists, might be deep below the planet's surface and beyond the reach of any currently planned missions, according to a new study.
> 
> 
> After mapping cosmic radiation levels at various depths on Mars, researchers have concluded that any life within the first several yards of the planet's surface would be killed by lethal doses of cosmic radiation.
> ...


----------



## Delvo (Jan 30, 2007)

The modern solar wind is too low, but I had thought it was pretty well accepted as the standard explanation, that the inner planets' original atmospheres were all blown away by T-Tauri wind, the "solar" wind during the sun's early T-Tauri stage. (Then the issue is how they acquired new atmospheres after that, and the basic answer is vulcanism, which Mars had little of because it was cooler than Earth or Venus.)


----------



## Carolyn Hill (Jan 31, 2007)

What caused Mars to go dry?

Prohibitionists.


----------



## j d worthington (Jan 31, 2007)

Brown Rat said:


> What caused Mars to go dry?
> 
> Prohibitionists.


 
OUCH!

Delvo... I would think that was put into consideration... but hasn't there also been some question about that model?


----------



## Nada (Apr 7, 2008)

Beside JOkes , the truth is simple: there is not enough data yet.

No mission has done a decent analysis of the subsoil, there is no idea how much water is trapped in the permafrost and no record of the climate changes on Mars in the recent past (up to 4-5 million years).

If you look at the papers, you won't find any good theory, or at least no theory is supported by enough strong data. Perhaps after exomars, with its drill and penetrometer (and seismometer), after the next two or three american missions we will know more.

Personally, and without substantial data, i vouch for the permafrost option (like Kim Stanley Robinson): the water is trapped in the soil and in subterranean acquifers, either as ice or hidrates (or clatrates) within the soil.

Readily available, provided there is enough energy to extract it from the regolith.
So one could say that Mars is cold, not dry


----------



## the smiling weirwood (Apr 8, 2008)

Mars: dry freeze? Interesting idea.


----------



## The Ace (Apr 8, 2008)

Oh no, it's the Kirkintilloch pubs all over again.  It wisnae me.


----------



## gully_foyle (Apr 8, 2008)

Perhaps it is a matter of perspective. Mars appears dry to an Earthling, but not to a martian. There is lots of evidence of Mars' wet past, but it still doesn't bear the hallmarks of a water world like good old Earth. So maybe it never was the cosmic snowball that we started off with, or it lost it's water long before it became geologically inert, and the evidence of the large oceans has been rubbed out. Mars does indeed have a tenuous atmosphere, a factor of its' lower gravity as well as lack of magnetic protection against the solar winds, so it is reasonable to assume that water vapour bubbled away into space. But there must be other factors at play as well. Our moon and its tidal effects must have a role. And why is Venus so much the opposite of Mars?


----------



## Drachir (Apr 8, 2008)

Low gravity anyone?  It is only one-quarter earth.  What is the critical level of gravitational pull needed to maintain an atmosphere?


----------



## Nada (Apr 9, 2008)

Gully, I think you are wrong. First of all, i get nervous everytime, outside a science FICTION discussion, i see "earthling" associated with "Martian": to the extent of our (i.e. Humanity's) knowledge, life on Mars can only be microbial, so no animal and no martian.
Then, Mars DOES show massive traces of Water: its northern emisphere was covered by an Ocean, for long periods of its history. Definitely for its first Gy (1GigaYear(Gy)=1 Billion years). This evidence is visible. Now. 
If you don't believe me, have a look to the mars pages of the german space agency: lots of beautiful images there.

DLR Mars Express - Home

You'll find plenty of images with clear evidence of oceans, rivers and such.
Today Mars has a tenuos atmosphere but it is NOT reasonable to "assume", as you do, that the water bubbled away. Have a look to the first post of the thread: that is exactly the point made by JDW: escape rate of ions does not justify the hypothesis (the whole discussion started from there).
The reason why the atmosphere is tenuos is another: there is no replenishment of the lost gases, since plate tectonics is absent and vulcanism is not as active as on Earth. The slow seeping of gases reduced the atmosphere to its present status. Keep in mind that the MASS of an ocean is many orders of magnitude more than the mass of an atmospheric shell: if the leakage is enough to reduce the atmospheric pressure, it is not enough to dissipate an ocean.

Regarding the "other effects" i agree with your principle, but I refrain to make a list: Planetology is a science that tries to extrapolate a data set of a single point: we just know, and imperfectly, one planet. It is impossible, without enough data, to assume what has happened 3 or 4 Billion years ago on a planet we have not yet analyzed.
As I said before, we need another 10 or 20 missions and perhaps some humans on Mars before being able to say something substantiate


----------



## Nada (Apr 9, 2008)

Drachir said:


> Low gravity anyone?  It is only one-quarter earth.  What is the critical level of gravitational pull needed to maintain an atmosphere?



Atmospheric pressure is NOT depending on gravity alone. Venus has the same surface gravity of Earth and a pressure at ground level of 80-100 atmospheres. Titan has a surface gravity of 0.14g (less than the moon) and an atmospheric pressure of ~1,5 atmospheres.
in the light of your helpful remark, can you explain that?

Gravity, composition, distance from the primary, characteristics of the primary, vulcanism, tectonics, presence of a biosphere, presence of liquid water (carbonates subtract carbon from the atmosphere and delay greenhouse effects), and a miriad of other factors play together to establish an equilibrium pressure.
There is NO "critical level" beyond which an effect is granted or negated.

And, by the way, Mars gravity is 0.38 of Earth's (10 seconds in google).


----------



## Drachir (Apr 10, 2008)

Thanks Nada.  Apparently their are mutliple factors to consider when attempting the determine whether or not a planet retains an atmosphere.  BTW myriad is just myriad.  It is never "a myriad of."  Very commonly misused word and I have even seen best-selling authors use it incorrectly.  Thus myriad factors not a myriad of factors.


----------



## Nada (Apr 10, 2008)

Thanks, this is what you get when you learn english as a second language: in my original one, you use "a myriad of". I just translated literaly 

I am seeing unexpected benefits of being here. I may actually learn Proper English!


----------



## Drachir (Apr 11, 2008)

Nada said:


> Thanks, this is what you get when you learn english as a second language: in my original one, you use "a myriad of". I just translated literaly
> 
> I am seeing unexpected benefits of being here. I may actually learn Proper English!


 
If you are even attempting words like myriad then your English is superlative.


----------



## Cayal (Apr 11, 2008)

Global Warming. I blame Global Warming for everything.


----------



## Nada (Apr 11, 2008)

Drachir said:


> If you are even attempting words like myriad then your English is superlative.



Well, it is a second language but it has also been used daily in the past 10 years. Anyway, I'm still quite far away from being a Joseph Conrad 

If you like "evolved" english, i can suggest you novels from A.A.Attanasio. It'S incredible how sophisticated he can be in his choice of words. I just finished his "Dark Shore" and i'm absolutely amazed by the quality of the language.

@cayal: global FREEZING in the case of Mars...


----------

