On the possibility of liquid water on present‐day Mars

Abstract

Abstract. Using a validated general circulation model, we determine where and for how long the surface pressure and surface temperature on Mars meet the minimum requirements for the existence of liquid water in the present climate system: pressures and temperatures above the triple point of water but below the boiling point. We find that for pure liquid water, there are five "favorable" regions where these requirements are satisfied: between 0 ø and 30øN in the plains of Amazonis, Arabia, and Elysium; and in the Southern Hemisphere impact basins of Hellas and Argyre. The combined area of these regions represents 29% of the planet's surface area. In the Amazonis region these requirements are satisfied for a total integrated time of 37 sols each Martian year. In the Hellas basin the number of degree days above zero is 70, which is well above those experienced in the dry valley lake region of Antarctica. These regions are remarkably well correlated with the location of Amazonian paleolakes mapped by Cabrol and Grin [2000] but are poorly correlated with the seepage gullies found by Malin and Edgett [2000]. In both instances, obliquity variations may play a role. For brine solutions the favorable regions expand and could potentially include most of the planet for highly concentrated solutions. Whether liquid water ever forms in these regions depends on the availability of ice and heat and on the evaporation rate. The latter is poorly understood for low-pressure CO2 environments but is likely to be so high that melting occurs rarely, if at all. However, even rare events of liquid water formation would be significant since they would dominate the chemistry of the soil and would have biological implications as well. It is therefore worth reassessing the potential for liquid water formation on present day Mars, particularly in light of recent Mars Global Surveyor observations.

The Modern Near-Surface Martian Climate: A Review of In-situ Meteorological Data from Viking to Curiosity

“…Mars has large reservoirs of water as ice and vapor, but pure liquid water is unlikely to be present, even temporarily, on the surface of Mars because it would quickly evaporate in the regions where it neither freezes nor boils (Ingersoll 1970;Haberle et al 2001;Martínez and Renno 2013). However, the presence of water ice in the shallow subsurface midlatitude and polar regions Mitrofanov et al 2002;Byrne et al 2009), along with the detection of perchlorates in polar and equatorial soil Glavin et al 2013;Ming et al 2014) and of chloride-bearing deposits in the southern highlands at low and midlatitudes (Osterloo et al 2008), is important because they can melt this ice at Mars' present-day environmental conditions and produce liquid saline water (brine) (Clark 1978;Brass 1980;Clark and Van Hart 1981;Haberle et al 2001;Chevrier and Altheide 2008;Rennó et al 2009;McEwen et al 2011;Ojha et al 2015).…”

On laboratory simulation and the temperature dependence of the evaporation rate of brine on Mars

“…Haberle et al [2001] have pointed out that while pure water could exist over 29% of the planet for 37 sols each year, while a NaCl eutectic solution could remain liquid over most of the planet at some time of the year and up to 100 sols in some regions. The formation of eutectic solutions of CaCl 2 , with its much lower eutectic temperature, would greatly increase the extent and duration of liquid on Mars.…”

Scalloped terrains in the Peneus and Amphitrites Paterae region of Mars as observed by HiRISE

“…Moreover, this area may be able to support liquid water conditions for about 10% of the martian year when taking into account insolation and pressure factors (Lobitz et al, 2001); other estimates are lower, e.g., $2% (Haberle et al, 2001). However, while sufficient environmental conditions include the potential for the involvement of a solid-liquid phase change in morphological change on Mars during brief annual periods, it is difficult to prevent the depletion of an ice deposit by sublimation of ice directly into the gas phase, as temperatures rise, before the melting point can be reached (Hecht, 2002).…”