Early Mars: Not as much water as was thought?

[yevaud]

<i>University of Arkansas researcher studying the thermodynamics of the oldest present-day clays on Mars found a surprising result in his calculations. Although evidence suggests that liquid water once flowed on the planet's surface, the most common greenhouse gas that could have warmed the atmosphere enough for liquid water to exist appears to have been scarce.</i><br /><br />Full Story <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[paulanderson]

So how does that tie in with the information in the photo caption?<br /><br /><i>"This picture from NASA's Mars Global Surveyor could help settle a decades-long debate about whether the planet had long-lasting rivers instead of just brief, intense floods. The image of the delta-like fan shows eroded ancient deposits of transported sediment long since hardened into interweaving, curved ridges of layered rock. Scientists interpret some of the curves as traces of ancient "meanders" made in a sedimentary fan as flowing water changed its course over time. "Meanders are key, unequivocal evidence that some valleys on early Mars held persistent flows of water over considerable periods of time," said Dr. Michael Malin of Malin Space Science Systems, San Diego, which supplied and operates the spacecraft's Mars Orbiter Camera."</i><br /><br />See also:<br /><br />http://dailyheadlines.uark.edu/8488.htm

 

[yevaud]

One possibility is that the meanders are created through catastrophic outflows from subsurface pockets of liquid H2O or ice.<br /><br />I believe the actual point of their argument is more along the lines of it making it quite unlikely that any sort of life of higher organization could have developed. Primitive life - protozoa, and so on - sure, but no higher organisms. There just wasn't the time or conditions present. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[plutocrass]

c'mon, it's obvious that the 'deltas' are just places where the oxidized top soil rolled off a slope to reveal the reduced soil beneath.

 

[JonClarke]

Meanders are the result of gentle srteady flow of liquid, not castrophic outbursts. So regardless of the CO2-H2O debate, the meanders indicate gentling flowing conditions.<br /><br />The problem with CO2 producing the meanders is to have gently flowing CO2 requires much higher pressures than is needed for H20.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[yevaud]

Thank you, Sir.<br /><br />Actually (sorry, wasn't clear there), I was thinking along the lines of an outflow in a large area at some depth, perhaps caused by those rare geological moments that Mars appeared to have here and there. Creating something similar to a Sink or Sip-well kind of situation? E.g., a large area where the H20 would become liquid at depth, and be forced to the surface.<br /><br />Don't know, really. Not my forte. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[JonClarke]

Places "where the oxidized top soil rolled off a slope to reveal the reduced soil beneath" don't show the branching, dispersive channels, meanders, scroll bars, or cut-off loops we see in that image of delta in Holden N-E crater! Only sustained, gentle flow can do that.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[JonClarke]

Certainly underground flow of liquid is important on Mars - look at all the indurated fractures we see, the "Inca City" is perhaps the most spectacular examples. Under pressure it is quite possible that these liquids could include both H2O and CO2, or a solution of the two. Sapping by subsurface flow is postulated as a likely cause for one class of Martian channels, the so called valley networks (which are different to the massive outflow valleys or the dendritic runoff valleys.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>