<font color="yellow">I beleive weight is the most important factor, because the skiis provides their own pressure wich might keep CO2 liquid in itself(as the skiis/skates passes over), so I think it might be possible.</font><br /><br />*not possible*<br /><br />CO2 won't liquify on Mars under a ski. Why?<br /><br />1) Increasing the pressure would only help moreso to keep CO2 in the solid state. Look at the attached phase diagram. Imagine a temperature of -80C. Increasing the pressure will only help maintain the CO2 in a solid state. Same is true at 0C.<br /><br />2) Warming solid CO2 will only produce a gas (sublimation) at the pressures the CO2(s) would experience on Mars. The pressure under a ski is about 0.025 atmosphere (assuming a 75 kg person's weight is spread evenly over 2 skis). Keeping the pressure fixed at 0.025 atm, and increasing the temperature due to friction, you can see that solid CO2 would directly form gaseous CO2.<br /><br />But what could you do?<br />Notice that at a pressure between 6 atm to 10 atm, at a temp between -50 to -30C, that CO2(s) transitions to CO2(liq) by heating. So if you had an ice skate with artifically heated blades, and the pressure under the skate blades was about 6 atm, then you could skate on liq CO2 (as long as the blade did not warm above about -30C). <br /><br />A 75 kg person could skate using special skates that had blades about 6 cm2 in area each, in which the blades were warmed thermostatically between -50 to -30C, while the outdoor Martian temperature was below -50C. <font color="red">(you know, I should've patented this idea)</font><br /><br />Phase diagrams can be your friend!<br />(whoever said college thermodynamics wasn't useful?) <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>