How deep shall we drill to find a 20°C temperature?

[h2ouniverse]

Hi all,<br /><br />Here is a compilation, to be edited as per your comments, of the depth at which one can expect a quasi-constant Earth-like mild 20°C temperature.<br /><br />* Mercury: may be under the poles?<br />* Venus: ground too hot, value met in upper atmosphere at about 50km altitude<br />* Earth: few meters deep<br />* Moon: about 30-50km deep<br />* Mars: about 3km deep<br />* Ceres: about 80-150km deep<br />* Jupiter: upper atmosphere, variable altitude (strong vertical circulation)<br />* Io: (help Andrew)<br />* Europa: about 10km if underground ocean, much deeper otherwise<br />* Ganymede: 100km if underground ocean<br />* Callisto: 50 to 200km <br />* Saturn: upper atmosphere, variable altitude (strong vertical circulation)<br />* Enceladus: TBD<br />* Titan: about 50-200km (TBC)<br />* Uranus: about 250km below the 1bar reference altitude<br />* Nepune: similar to Uranus but less stable value (more vertical circiulation)<br />* All icy bodies about 1000km diameter, and a significant rocky core: at about 200km deep, or less if tidal heating (Dione? Tethys? Ariel?...)<br /><br />Please comment and help me to draw a reasonable list.<br /><br />= /> For almost all bodies, there is a region with mild temperatures. Prepare your shovels!<br /><br />Best regards.

 

[nexium]

If you are going to have people and equipment in the cavern, then you want about -39 degrees c = -39 degrees as the waste heat will warm the cavern to about 20 degrees c = 68 degrees f If you start at 20 degrees c, it will soon be too hot and you will need air conditioning which is difficult in a deep cavern. Heating is much easier. Each person is a 1000 watt heater. Neil

 

[h2ouniverse]

All the best! (less to drill)<br />But <br />1) we may too look for critters...<br />2) for many outer system bodies, -39°C should correspond to liquid water+ammonia. = /> more a giant submarine than a cavern if you really want to go and if you do not adapt yourself; NH3 tends to concentrate as an ice shelf of pure water forms outside, further decreasing the condensation temperature [can go down to 170K at 32% concentration]<br /><br />Warm regards.

 

[pyoko]

Venus: Temperature will drop the deeper you get. Worth drilling (only so far). <div class="Discussion_UserSignature"> <p> </p><p> </p><p><span style="color:#ff9900" class="Apple-style-span">-pyoko</span> <span style="color:#333333" class="Apple-style-span">the</span> <span style="color:#339966" class="Apple-style-span">duck </span></p><p><span style="color:#339966" class="Apple-style-span"><span style="color:#808080;font-style:italic" class="Apple-style-span">It is by will alone I set my mind in motion.</span></span></p> </div>

 

[h2ouniverse]

Pyoko:<br /><br />I am surprised. For most bodies, the average crust temperature tends to increase with depth.<br />Can you please give a link to a curve temperature=fn(depth)?

 

[nexium]

On Earth, in summar, caves are typically cooler than outside air. This partly due to evaporation of volitiles, but mostly it is a responce to the average annual temperature. Very deep caverns of Earth are typically warmer than 68 degrees f = 20 degrees c, even if it is very cold outside. This is because Earth and larger planets are hot inside. Venus and Mercury are likely hotter, inside on the average than Earth, because they are closer to the Sun. We can calculate, but we do not know all our assumptions are correct, so we may be surprised when we actually travel far below the surface of Earth and other bodies. I think the numbers by H2O look about correct. Mercury is likely hotter everywhere including the poles, except one to two meters below the surface of the center of the larger polar craters. Measurements have indicated very cold surfaces in craters where the sun never shines. This occurs because Mercury has essentially no tilt with respect to the plane of Mercury's orbit. Neil

 

[ashish27]

What actually are you up to Joel? <img src="/images/icons/smile.gif" />

 

[h2ouniverse]

That everything is at the same time very different from and very similar to what we know.<br />In other words, that we should never give up.

 

[l3p3r]

Great list thanks!!<br />Is there a spot in Saturn's atmosphere where you think the pressure and temperature would be ok for a human to be normally clothed (with breathing apparatus) and comfortable? <div class="Discussion_UserSignature"> </div>

 

[ashish27]

of course we should never give up. there may be life below the surface in solar system bodies, but how can we detect them? Iapetus comes to my mind, may be some lifeform is the cause of the growing dark patch on the surface

 

[alokmohan]

Subsoil lives are inportant.Why you require minus 39?

 

[h2ouniverse]

Mmm, if there is water on Iapetus, it should be very deep undergound. Provided that Iapetus is differentiated, AND has a core larger than say 800km<br /> (marginal at 750km for Ceres, but here far less solar flux so surface temperature is very low).<br /><br />On surface no chance for life as we know it. You have then to imagine exotic lifeforms.<br /><br />Regards

 

[h2ouniverse]

Ashish<br />In reply to<br />-------------<br />there may be life below the surface in solar system bodies, but how can we detect them? <br />-------------<br /><br />1) by drilling (ESA's Exomars mission to be launched in 2013, which will drill up to 2m)(or NASA's advanced projects for Europa drilling and submarine exploration)<br /><br />2) by leaving natural resurgence phenomena bring subsurface water to the surface, and then have surface collection and look for frozen fish (or frozen microbes). = /> E.g. on Titan, at the outlet of the big cryovolcano<br /><br />Best regards.<br />

 

[h2ouniverse]

Will Messenger IR-mapping detect areas close to poles at ambient (close to 20°C) temperatures? Craters floor should be at very cold negative temps. Few degrees of latitude from pole should be enough for >100°C temps.<br />Normally some terrains inbetween should have the right inclination vs sun rays so that the equilibrium temperature is close to 20°C.<br />

 

[siarad]

1kW I feel is too high I seem to recall something like 70 watt for diet of 2500 Calories. Too short of time to calculate it <img src="/images/icons/wink.gif" />

 

[thebigcat]

Let's not forget that a lower gravity field equals a reduced caloric need. <div class="Discussion_UserSignature"> </div>