From graph, taking the derivative of the best fit line gives an evaporation rate in g/min, which we convert to mm/hr. For instance in the graph below 0.033g/min = 0.367 mm/hr. This translates into a 27 hour lifetime for a 1cm thick block of ice.

The average evaporation rate for pure ice at -8ºC, in an atmospheric temperature of -1.1ºC, is 0.405 mm/hr.

Acknowledgements

Thank you to Jesse Buffington and Melissa Franzen for all their help with the chamber.

• Prepare sample by freezing water in graduated cylinder.

• Place thermocouple on surface of ice.• Fill chamber with CO2 gas, chill to 0°C, insert sample,

then pump down to 5.25 torr (6.11 mbar), Martian surface conditions.

• Record mass loss as a function of time.

Water Ice Evaporation in Simulated Water Ice Evaporation in Simulated Martian Martian Conditions Conditions

as a Function of Soil Depthas a Function of Soil DepthJennifer Hanley1,2, Jonathan Craig1, Julie Chittenden1, Dr. Derek Sears1

1. Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 727012. Department of Astronomy, Cornell University, Ithaca, NY 14853

Fundamental Science Future Research

• Continue adding soil to the ice in exponential fashion; obtain a trend of evaporation rates with increasing soil depths.

• Once a reliable curve is determined relating evaporation rate as a function of soil depth, the next step will be to determine if the water is surviving at a rate which would allow for it to melt.

• This will be established by placing a copper wire at the interface between the ice and soil.

• If the ice melts, then since water is conductive as ice is not, the resistance will drop markedly.

• Preliminary research indicates that this is a likely occurrence.

•The key point of determining the evaporation rate of ice on the surface of Mars is to learn more about its cycle through the three phases of liquid, ice and vapor.

•Revealing the equilibrium dynamics of the system is part of the solution to life on Mars.

•Right now we are measuring evaporation in the form of mass loss. In the future we wish to determine a depth whereat the evaporation is suppressed enough to allow the phase change to liquid.

The Implications of the Evaporation Rate

Procedure

y = 4E-05x2 - 0.033x + 42.28

R2 = 0.9998

40

41

42

43

0 20 40 60

Time (min)

Mas

s (g

)

Series1 Poly. (Series1)

• Ingersoll (1970) proposed a thermal convection analogy be applied to evaporation of water on Mars. • Farmer (1976) took this one step further and modeled evaporation rates under a layer of soil. He found that soil decreases

diffusion of water vapor into the atmosphere, thus suppressing evaporation rates.

• Under ideal circumstances on the surface of Mars, the lifetime of ice can be extended to the point where the water may melt.

• My project for the summer is to put these theories of evaporation rate as it is related to being covered with soil to test.

Results

References

Farmer, C.B.: Liquid Water on Mars. Icarus, vol. 28, 1976, pp. 279-289.

Ingersoll, A.P.: Mars: Occurrence of Liquid Water. Science, vol. 168, 1969, pp. 972-973.

Hecht, M.H.: Mestastability of Liquid Water on Mars. Icarus, vol. 156, 2002, pp. 373-386.

Placing a sample in the Andromeda Chamber.

31

31

)17.0(

)17.0(2

Grx

CD

g

CDE

Hecht (2002), Ingersoll (1970)