Extraterrestrial hydrogeology Victor R. Baker · James M. Dohm · Alberto G. Fairn · Ty P. A. Ferr · Justin C. Ferris · Hideaki Miyamoto · Dirk Schulze-Makuch Abstract Subsurface water processes are common for conditions delivered water to the northern plains. Water planetary bodies in the solar system and are highly was also cycled to the South Polar Region during changes probable for exoplanets (planets outside the solar system). in climate induced by endogenic activity and/or by For many solar system objects, the subsurface water exists changes in Mars’ orbital parameters. Venus very likely as ice. For Earth and Mars, subsurface saturated zones had a warm hydrosphere for hundreds of millions of have occurred throughout their planetary histories. Earth years, before the development of its current extremely hot is mostly clement with the recharge of most groundwater atmosphere and surface. Subsequently, Venus lost its reservoirs from ample precipitation during transient ice- hydrosphere as solar luminosity increased and a run-away and hot-house conditions, as recorded through the geo- moist greenhouse took effect. Subsurface oceans of water logic and fossilized records. On the other hand, Mars is or ammonia-water composition, induced by tidal forces mostly in an ice-house stage, which is interrupted by and radiogenic heating, probably occur on the larger endogenic-driven activity. This activity catastrophically satellites Europa, Ganymede, Callisto, Titan, and Triton. drives short-lived hydrological cycling and associated Tidal forces operating between some of the small bodies climatic perturbations. Regional aquifers in the Martian of the outer solar system could also promote the fusion of highlands that developed during past, more Earth-like ice and the stability of inner liquid-water oceans. Rsum Les processus de subsurface impliquant l’eau Received: 25 June 2004 / Accepted: 23 December 2004 Published online: 26 February 2005 sont communs pour les corps plantaires du systme so- laire et sont trs probables sur les exoplantes (plantes en Springer-Verlag 2005 dehors du systme solaire). Pour plusieurs objets du sys- tmes solaire, l’eau de subsurface est prsente sous forme de glace. Pour la Terre et Mars, les zones satures de V. R. Baker ()) · J. M. Dohm · T. P. A. Ferr Department of Hydrology and Water Resources, subsurface apparaissent à travers toute leur histoire pla- University of Arizona, ntaire. La Terre est particulirement clmente avec la Tucson, AZ, 85721, USA recharge des rservoirs, avec de amples prcipitations, des e-mail: [email protected] conditions glaciaires et de fortes chaleurs, comme l’at- V. R. Baker · H. Miyamoto teste les enregistrements gologiques et palontologiques. Lunar and Planetary Laboratory, D’un autre ct, Mars se trouve dans une phase essen- University of Arizona, tiellement glaciaire, qui est interrompue par des activits Tucson, AZ, USA contraintes par les phnomnes endogniques. Cette ac- A. G. Fairn tivit conduit de manire catastrophique à des cycles Centro de Biologa Molecular, hydrologiques et à des perturbations climatiques brutaux. Universidad Autnoma de Madrid, Les aquifres rgionaux dans les haute terres martiennes 28049, Cantoblanco, Madrid, Spain qui se sont forms dans des conditions similaires aux J. C. Ferris conditions terrestres, alimentent les plaines du Nord. Water Resources Research Center, L’eau a galement t dplace vers le Ple Sud martien University of Arizona, durant des changements marqus par une forte activit Tucson, AZ, 85721, USA endognique et une modification des paramtres de l’or- H. Miyamoto bite de Mars. Venus possdait vraisemblablement une Department of Geosystem Engineering, hydrosphre chaude durant des millions d’anne, avant le University of Tokyo, dveloppement de son atmosphre et sa surface particu- Tokyo, Japan lirement chaude. Par aprs Venus a perdit son hydro- D. Schulze-Makuch sphre alors que la luminosit solaire augmentait et Department of Geology, qu’une humidit lie à un effet de serre s’installait. Les Washington State University, ocans de subsurface d’eau ou d’eau ammoniacale, in- Pullman, WA, 99164, USA duits par les forces de mare et le chauffage radiognique, Hydrogeol J (2005) 13:51–68 DOI 10.1007/s10040-004-0433-2 52 Fig. 1 (Right) View of the solar system. Courtesy of the U.S. National Aeronautics and Space Administration/Jet Propulsion Laboratory-California Institute of Technology; revised from http://photojournal.wr.usgs.gov/ .(Left) Composite of images and airbrush shaded-relief maps of the larger bodies of the solar system. Courtesy of Rich Kozak and U.S. National Aeronautics and Space Administration apparaissent probablement sur les satellites les plus im- cuerpos pequeos del sistema solar externo podran portants (Europa, Ganymede, Callisto, Titan, Triton). Les tambin promover la fusin de hielo y la estabilidad de forces de mare entre les petits corps externes du systme lquido interno-aguas de los ocanos. solaire peuvent galement occasionner la fusion de glace et la stabilit des ocans internes d’eau liquide. Keywords Hydrogeology · Planets · Mars Resumen Los procesos hdricos subsuperficiales son comunes en cuerpos planetarios del sistema solar y son Introduction altamente probables para exoplanetas (planetas fuera del sistema solar). Para muchos cuerpos del sistema solar, el Recent space missions have revealed that Earth is not agua subsuperficial existe como hielo. Para la Tierra y alone in having had, or is currently having, a hydrological Marte han ocurrido zonas saturadas subsuperficiales a cycle. Moreover, there are manifestations of surprisingly travs de sus historias planetarias. La Tierra es princi- earth-like hydrological cycling on one planet: Mars. palmente generosa con la recarga de la mayora de re- While near-surface indications of water movement are servorios de aguas subterrneas a partir de amplia preci- evident, subsurface hydrologic processes have not been pitacin reconocida en condiciones transitorias calientes y directly imaged by many of the orbital sensors used in heladas, tal y como aparece en los registros fsiles y planetary exploration. Despite this lack of direct obser- geolgicos. Por otro lado, Marte se encuentra principal- vation of subsurface hydrologic processes, the field of mente en una etapa de cmara de hielo la cual es in- extraterrestrial hydrogeology is experiencing rapid terrumpida por actividad de tipo endognico. Esta acti- growth. As this field begins to emerge from its infancy, it vidad pone en funcionamiento catastrficamente ciclos is appropriate to provide a brief review of the current hidrolgicos de vida corta y perturbaciones climticas concepts of the existence, both past and present, of water asociadas. Acuferos regionales en las montaas de Marte on and beneath the surface of extraterrestrial bodies. The que se desarrollaron en el pasado en condiciones similares nascent science of extraterrestrial hydrogeology will face a la Tierra distribuyen agua a las planicies del norte. El many challenges in testing and expanding our concepts of agua ha sido transportada hacia el sur de la regin polar subsurface water distributions on distant bodies. It is durante cambios en el clima inducidos por actividad en- likely that in meeting these challenges, advances will be dognica y/o cambios en los parmetros orbitales de made in our understanding of the Solar System (Fig. 1) Marte. Venus muy probablemente tuvo una hidrsfera while honing our abilities to describe and predict hydro- caliente durante cientos de millones de aos, antes de que logic processes on Earth. se desarrollara su atmsfera y superficie actual extrema- damente caliente. Subsecuentemente, Venus perdi su hidrsfera a medida que la luminosidad solar aument y Mars un efecto de invernadero hfflmedo escapatorio se llev a cabo. Ocanos subsuperficiales de composicin agua o Present-day Mars has a mean atmospheric pressure at its amoniaco-agua, inducidos por fuerzas de marea y calen- surface of 600 Pa (6 mb). The atmosphere is composed of tamiento radiognico, probablemente ocurren en los sa- 95.3% carbon dioxide, 2.7% nitrogen, and 1.6% argon. tlites ms grandes como Europa, Ganimeda, Callisto, There are traces of other gases, notably water vapor. Titan y Triton. Las fuerzas de marea que operan entre los During the summer, water content in a vertical column of Hydrogeol J (2005) 13:51–68 DOI 10.1007/s10040-004-0433-2 53 Fig. 3 Phase diagram for water. Stability fields for the solid, liquid, and gas phases as shown. All the different solid phases of ice involve hydrogen bonding of water molecules to four neighboring water molecules (from Chaplin 2003). Notice that the triple point is located very close to Earth’s average temperature allowing all three Fig. 2 Mars Orbiter Laser Altimeter map (MOLA) showing phases to coexist under a wide variety of climatic conditions. Un- Tharsis and associated outflow channel systems, Circum-Chryse ique properties of water include: (1) very common compound in the and northwestern slope valleys (NSVs), the northeast and northwest universe with a molecular weight of 18.015 g/mol, (2) large range watersheds, respectively, and Valles Marineris, a canyon that would of liquidity (0–100C at 1 bar) with a critical temperature of 375C span the United Sates from roughly its western end to its eastern and a critical pressure of 215 bar extending the range of liquidity end. Courtesy of the MOLA Science Team and temperatures at which organisms can survive in water, (3) highest density of water is at a temperature of 4C, which prevents bottom