Glass bowl on Mars

[Leovinus]

Thought experiment for you:<br /><br />We drop a lander on Mars. It deploys an upside-down glass bowl -- say it is the size of a punch bowl. We would expect a greenhouse effect to take place and the inside of the bowl would warm up. Given the much thinner atmosphere inside, how warm would it really get? Could we get liquid water inside? Remember that at lower pressures, the freezing and boiling points of water are different than 0 C and 100 C.<br /><br />If we could get liquid water inside after warming, could we then plant a seed and expect it to grow given the content of the Martian atmosphere? Also assume that when we watered it we applied fertilizer to give nutrients to the seed and plant. <div class="Discussion_UserSignature"> </div>

 

[Leovinus]

So you think it could get warm enough for liquid water at that low pressure? <div class="Discussion_UserSignature"> </div>

 

[silylene old]

yes, if the rim of the bowl is sealed to prevent loss of gas, and the soil is sealed so it does not lose gas pressure. Once the water vapor has reached equilibrium vapor pressure within the bowl, all excess water within should be present as a liquid (if the temp is above approx 0C). <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[Leovinus]

No. The bowl is not sealed. It is just plopped there on the surface. <div class="Discussion_UserSignature"> </div>

 

[silylene old]

If not sealed, then the gas pressure inside the bowl = atmospheric pressure. So at equilibrium, liquid water could exist only if the bowl was plopped down at the bottom of Hellas, where the atmospheric pressure is high enough to allow for liquid. But then the water gas vapor will escape since it isn't sealed, since the relative Martian humidity outside the bowl is far less than 100%, and in not too long all the water will be gone. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[Leovinus]

Oh well. <div class="Discussion_UserSignature"> </div>

 

[nexium]

The optimum shape may be like an upside down funnel without the neck. About 2 cubic meters above the surface and 4 cubic meters below the surface. Starting at 4 millibars, 20 millibars of mostly water vapor may be possible. Afternoon temperatures of about 68 degrees f = 20 degrees c inside may be typical at low elevations near the equator of Mars. Most plants require some oxygen, but a few kinds do not, or can tolerate very low oxygen pressure such as 10 millibars. A two meter path through the dry soil would allow some leakage, but the water in the soil might be sufficient to harvest one crop, after which the inverted funnel would need to be moved to a new location.<br /> The funnel needs to reduce the worst of the ultaviolet radiation. Yield will be small making the system impractical, unless it can be done mostly with materials avalable near the site. Neil

 

[paleo]

Radiation! How thick is your glass and does it protect mutiplying cells from nucleus destruction. One of the arguments against taking cautionary sterilization measures with landers etc. is any replicating DNA would be damaged if it became exposed to the Martian atmosphere.