Conference on the Geophysical Detection of Subsurface Water on Mars (2001)
FUTURE EXPLORATIONS ON CHEMICAL COMPOSITIONS OF SEEPAGE WATER AND GROUND ICE ON MARS
DETECTED BY GAMMA-RAY SPECTROMETER, GC-MS, AND ION CHROMATOGRAPH. J.-S. Jean
1
and C.-H.
Yang
2
,
1
Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan, R.O.C., e-mail: jiinshuh@sparc4.cc.ncku.edu.tw
,
2
Department of Applied Geology, National Central University, Chungli, Taoyuan,
Taiwan, R.O.C., e-mail: yang@app.geo.ncu.edu.tw.
The 2001 Mars Odyssey’s gamma-ray spectrometer
(including neutron spectrometer) and THEMIS (Thermal emission imaging system) will find evidence for present near-surface water and locate hematites and carbonates from past water activity, which may prove the existence of liquid water on Mars. However, liquid water can exist only at water’s triple-point of the present-day martian vapor pressure of 6.1 mbar and the temperature of 273 K
[1]. Because average temperatures of Mars are below
273 K, liquid water is not likely to be found at the surface at such a low atmospheric pressure [2]. Even if liquid water exists, it easily evaporates as volatiles into the atmosphere and then into outer space due to the low gravity of Mars (~38% of Earth). The liquid water on the martian surface and water vapor in the atmosphere would have eventually disappeared from Mars.
As of January 2000, ~150 high-resolution images acquired by the Mars Global Surveyor Mars Orbiter
Camera showed ~120 locales as the results of fluid seepage and surface runoff , in which the one at the inner walls of southwestern Newton Crater (41.1
o
S, 159.8
o
W) was demonstrated as evidence for the presence of sources of liquid water at shallow depths beneath the martian surface [2]. However, in their work they did not specifically address the debate over whether liquid water or some other liquid is responsible for fluid erosional landforms on Mars. We consider in this study the recent groundwater seepage and surface runoff on Mars to be water containing certain antifreeze compounds or to be some other liquid, which can decrease evaporation and resist to freeze, such as brines with a salt base (e.g., sodium and calcium chlorides), brines with lowtemperature heat transfer (e.g., methylene chloride, trichloroethylene, trichlorofluoromethane, trichlorotrifluoromethane, dichlorofluoromethane, carbon tetrachloride, acetone, methanol, ethanol), brines with a glycol base (e.g., ethylene glycol, propylene glycol), isopropanol, glycerol, alkanes (e.g., pentane, hexane, heptane, octane), etc. The freezing points and boiling points of these antifreeze compounds are shown in Table 1. One of these compounds in Table 1 may possibly have mixed with or without water as aqueous antifreeze solutions on
Mars, thus facilitating to produce the erosion, transport, and deposition, and then to develop fluid erosional landforms (e.g., gullies, channels, valley networks, etc.).
Doran and Forman [3] proposed that the martian discharge is saline or hypersaline, which could reduce the freezing point and evaporation of liquid water. At such low atmospheric pressure (~6.1 mbar) as presently exists on Mars, the freezing temperatures of brines with a salt base can be at 209 K or –64 o
C [4]. Groundwater seepage, surface runoff, eroded gullies, and sedimentary formations were recently demonstrated by Malin and
Edgett [2, 5]. The erosion of the martian outflow channels and valley networks has been known in the literature. Water has been considered as one of the agents to form these features. However, whether it is in a pure
H
2
O form, or in other liquid form, or contains salts or some other antifreeze compounds is still something of enigma. It is crucial to identify these characters for human colonization in future. This study proposes an approach to detect chemical compositions on the seepage water and/or ground ice by gamma-ray spectrometer,
GC-MS (gas chromatograph-mass spectrometer), and ion chromatograph (Table 1) mounted with a lander for future Mars explorations.
References:
[1] Atkins P. W. (1986). Physical Chemistry, Oxford
University Press, London. [2] Malin M. C. and Edgett
K. S. (2000) Science, 288, 2330-2335. [3] Doran P. T.
and Forman S. L. (2000) Science, 290, 713-714. [4]
Knauth L. P. et al. (2000) Science, 290, 711-712. [5]
Malin M. C. and Edgett K. S. (2000) Science, 290, 1927-
1937.
7010.pdf

Conference on the Geophysical Detection of Subsurface Water on Mars (2001)
FUTURE EXPLORATIONS: J.-S. Jean and C.-H. Yang
Table 1. Properties of antifreeze compounds at 1 atmospheric pressure
Compounds Freezing or melting
Boiling
Point (K)
Methylene chloride point (K)
175.4
Trichloroethylene 200
313.1
359.7
Detection method
GC-MS
GC-MS
Trichlorofluoromethane
162 296.6
GC-MS
Trichlorotrifluoromethane
236.6
320.7
GC-MS
138 281.9
GC-MS Dichlorofluoromethane
Carbon tetrachloride
250 349.5
GC-MS
Acetone
Methanol
255 329.2
GC-MS
175.2
337.5
GC –MS or IC
155.7
351.3
GC-MS Ethanol or IC
Ethylene glycol 259.5
470.2
GC-MS
Propylene glycol 213
Pentane or IC
460.3
GC-MS or IC
143.3
309.1
GC-MS
Hexane
Heptane
Octane
Isopropanol
Glycerol
Sodium- and calcium- chloride solutions
178 341.7
GC-MS
182.4
371.4
GC-MS
216.2
398.7
GC-MS
187
291
355.4
563
GC-MS
GC-MS
IC
Water 273 373 Gammaray spectro-meter
Water is included for comparison. GC-MS: gas chromatograph-mass spectrometer; IC: ion chromatograph.
7010.pdf