DOCSLIB.ORG

Methane Seepage on Mars: Where to Look and Why

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Methane Seepage on Mars: Where to Look and Why ASTROBIOLOGY Volume 17, Number xx, 2017 Review Article Mary Ann Liebert, Inc. DOI: 10.1089/ast.2017.1657 Methane Seepage on Mars: Where to Look and Why Dorothy Z. Oehler1 and Giuseppe Etiope2 Abstract Methane on Mars is a topic of special interest because of its potential association with microbial life. The variable detections of methane by the Curiosity rover, orbiters, and terrestrial telescopes, coupled with meth- ane’s short lifetime in the martian atmosphere, may imply an active gas source in the planet’s subsurface, with migration and surface emission processes similar to those known on Earth as ‘‘gas seepage.’’ Here, we review the variety of subsurface processes that could result in methane seepage on Mars. Such methane could originate from abiotic chemical reactions, thermogenic alteration of abiotic or biotic organic matter, and ancient or extant microbial metabolism. These processes can occur over a wide range of temperatures, in both sedimentary and igneous rocks, and together they enhance the possibility that significant amounts of methane could have formed on early Mars. Methane seepage to the surface would occur preferentially along faults and fractures, through focused macro-seeps and/or diffuse microseepage exhalations. Our work highlights the types of features on Mars that could be associated with methane release, including mud-volcano-like mounds in Acidalia or Utopia; proposed ancient springs in Gusev Crater, Arabia Terra, and Valles Marineris; and rims of large impact craters. These could have been locations of past macro-seeps and may still emit methane today. Microseepage could occur through faults along the dichotomy or fractures such as those at Nili Fossae, Cerberus Fossae, the Argyre impact, and those produced in serpentinized rocks. Martian microseepage would be extremely difficult to detect remotely yet could constitute a significant gas source. We emphasize that the most definitive detection of methane seepage from different release candidates would be best provided by measurements performed in the ground or at the ground-atmosphere interface by landers or rovers and that the technology for such detection is currently available. Key Words: Mars—Methane—Seepage—Clathrate—Fischer-Tropsch—Serpentinization. Astrobiology 17, xxx–xxx. 1. Introduction and by previous orbiter and Earth-based telescopic obser- vations (e.g., Mumma et al., 2009; Fonti and Marzo, 2010; he existence of methane (CH4) on Mars is a topic of Geminale et al., 2011; Webster et al., 2015, 2016; Roos- Tprimary interest in planetary exploration because of its Serote et al., 2016). Methane was also reported in martian potential link to microbial metabolic activity. Methane can be meteorites (e.g., Blamey et al., 2015). The fact that CH4 is generated by, and can provide energy (as an electron donor) estimated to have a relatively short lifetime in the martian to, microbial communities (e.g., Schulte et al., 2006). Me- atmosphere (about 300 years but potentially as short as thane, like other gases that can be produced in deep rocks, can 200 days or even a few hours near the surface; Lefe`vre and also be a proxy for dynamic geologic and subsurface fluid- Forget, 2009), coupled with its varying abundance, may circulation processes. imply an active gas source in the planet’s subsurface that Downloaded by California Institute Of Technology from online.liebertpub.com at 08/07/17. For personal use only. Spatially and temporally varying CH4, with concentra- periodically releases CH4 to the atmosphere. Methane could tions ranging from 0.2 to 60 ppbv, has been detected in the be generated in trace amounts above the martian surface martian atmosphere by the Curiosity rover in Gale Crater (possibly due to electrical discharges near iced ground 1Planetary Science Institute, Tucson, Arizona, USA. 2Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma 2, Roma, Italy, and Faculty of Environmental Science and Engineering, Babes-Bolyai University, Cluj-Napoca, Romania. ª Dorothy Z. Oehler and Giuseppe Etiope, 2017; Published by Mary Ann Liebert, Inc. This Open Access article is distributed under the terms of the Creative Commons Attribution Noncommercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited. 1 2 OEHLER AND ETIOPE [Robledo-Martinez et al., 2012] or UV irradiation [Section illustrations of key global features discussed; and Fig. 3, a 3.2.4]), but as is the case on Earth, larger amounts could be global map showing locations of figures in this paper. produced in the martian subsurface by a wide array of gas generation processes. Subsurface sources could be releasing 2. Gas Seepage Fundamentals either present-day methane or methane formed in the past 2.1. Definitions and mechanisms and subsequently stored in clathrates, zeolites, or reservoir- quality rocks trapped below sealing lithologies. The possi- In Earth sciences, the term ‘‘gas seepage’’ is used to bility of active subsurface sources of martian CH4 implies indicate a steady or episodic, slow or rapid flow of gas- the existence of a gas migration process known on Earth as eous hydrocarbons from subsurface sources to the surface ‘‘gas seepage.’’ Accordingly, in this paper, we concentrate (Etiope, 2015). In the petroleum geochemistry literature, the on the subsurface mechanisms that could account for mar- term ‘‘seepage’’ refers to hydrocarbon fluids, gas, and oil, tian CH4, including its generation, storage, and seepage to where gases are composed mainly of methane, with subor- the surface, as well as the likely physical manifestations of dinate amounts of heavier alkanes (ethane, propane, and that seepage on the surface of the planet. butane). These gases are formed in sedimentary rocks We address these processes in detail, as some readers may mainly through decomposition (microbial or thermogenic) be unfamiliar with the extensive body of knowledge of of organic matter. ‘‘Seepage’’ has also been used with ref- subsurface CH4 generation and migration from the petro- erence to exhalations of abiotic methane formed in igneous leum industry or the in-depth information on terrestrial (ultramafic) serpentinized rocks (e.g., Etiope, 2015; Etiope methane seeps accumulated from decades of studies. For et al., 2016), through inorganic reactions such as FTT example, because CH4 content is low in volcanic emissions, synthesis (e.g., Etiope and Sherwood Lollar, 2013). some have concluded that a geologic CH4 source would not Detailed description and classification of gas seepage be important for Mars (e.g., Krasnopolsky, 2005). Such processes on Earth, as well as their implications for resource conclusions neglect the array of geologic processes that exploration, atmospheric greenhouse gas budget, and the en- could produce CH4 on Mars. Similarly, clathrates occa- vironment, are reported in a wide body of literature (e.g., Link, sionally have been misconceived as potential origins for 1952; Hovland and Judd, 1988; Kopf, 2002; Etiope et al., martian methane. Yet clathrates are only a storage mecha- 2009; Etiope and Klusman, 2010; Etiope, 2015; Mazzini and nism for CH4, and the question of the derivation of that CH4 Etiope, 2017, and references therein). Terrestrial gas seepage remains. Here, we address the scope of potential CH4 gen- does not refer to geothermal or volcanic H2O- or CO2-rich gas eration processes for Mars, including some processes not manifestations (e.g., fumaroles, mofettes, and geysers) where generally recognized, and we clarify details of serpentini- hydrocarbons are a minor component. Accordingly, we do not zation and Fischer-Tropsch-type (FTT) reactions. We fur- use the term ‘‘seepage’’ for volcanic emissions, although we ther discuss criteria for trapping or storing subsurface CH4 discuss this form of degassing. Like terrestrial seepage, and on Mars as well as factors that could control CH4 seepage to according to the general theory of gas migration in geologic the martian surface, the types of surface manifestations that media (e.g., MacElvain, 1969; Malmqvist and Kristiansson, might reflect that seepage, and whether seepage could ac- 1985; Brown, 2000; Etiope and Martinelli, 2002), methane in count for the various CH4 detections on Mars. We conclude subsurface martian rocks should move preferably via advec- by combining all the above to identify sites or regions on tion, that is, in flow driven by pressure gradients and controlled Mars that may be prime candidates for methane release and by permeability (Darcy’s law). Diffusion, the slow motion of may be priority targets for orbital scans (such as by the gas molecules driven by concentration gradients (Fick’s law), ExoMars Trace Gas Orbiter) and for landed, ground-based is important only at small scales, in low-permeability porous analysis (using optimum seepage-detection methods) in fu- media and over long geologic time scales. Modeling studies ture missions. have also suggested that diffusion cannot explain the methane This work is divided into the following Sections: plumes and concentration variations observed on Mars (Ste- vens et al., 2015, 2017). On Earth, pressurized gas can occur in Section 2: Gas seepage fundamentals (definitions, both fine-grained rocks and in coarse-grained, reservoir rocks mechanisms, surface manifestations, and fluxes on Earth) (which are porous and permeable and sealed by impermeable Section 3: Methane generation mechanisms strata such as shales, permafrost, and salt). Reservoir rocks Section 4: Potential sites and timing of methane host gas produced in source rocks (or the ‘‘kitchen’’ as used in generation on Mars petroleum literature). Subsequent gas seepage can start from Section 5: Potential sites of methane accumulation either gas-rich, fine-grained source rocks or, more frequently, on Mars from pressurized reservoirs. Seepage occurs preferentially Section 6: Seepage pathways on Mars (from sites of Downloaded by California Institute Of Technology from online.liebertpub.com at 08/07/17. For personal use only. through permeable pathways, such as faults and fractures and generation or accumulation to the surface) in breaches in sealing lithologies.
Load more

Recommended publications
  • A Stringent Upper Limit of 20 Pptv for Methane on Mars and Constraints on Its Dispersion Outside Gale Crater F
    A&A 650, A140 (2021) Astronomy https://doi.org/10.1051/0004-6361/202140389 & © F. Montmessin et al. 2021 Astrophysics A stringent upper limit of 20 pptv for methane on Mars and constraints on its dispersion outside Gale crater F. Montmessin1 , O. I. Korablev2 , A. Trokhimovskiy2 , F. Lefèvre3 , A. A. Fedorova2 , L. Baggio1 , A. Irbah1 , G. Lacombe1, K. S. Olsen4 , A. S. Braude1 , D. A. Belyaev2 , J. Alday4 , F. Forget5 , F. Daerden6, J. Pla-Garcia7,8 , S. Rafkin8 , C. F. Wilson4, A. Patrakeev2, A. Shakun2, and J. L. Bertaux1 1 LATMOS/IPSL, UVSQ Université Paris-Saclay, Sorbonne Université, CNRS, Guyancourt, France e-mail: [email protected] 2 Space Research Institute (IKI) RAS, Moscow, Russia 3 LATMOS/IPSL, Sorbonne Université, UVSQ Université Paris-Saclay, CNRS, Paris, France 4 AOPP, Oxford University, Oxford, UK 5 Laboratoire de Météorologie Dynamique, Sorbonne Université, Paris, France 6 BIRA-IASB, Bruxelles, Belgium 7 Centro de Astrobiología (CSIC?INTA), Torrejón de Ardoz, Spain 8 Southwest Research Institute, Boulder, CO, USA Received 20 January 2021 / Accepted 23 April 2021 ABSTRACT Context. Reports on the detection of methane in the Martian atmosphere have motivated numerous studies aiming to confirm or explain its presence on a planet where it might imply a biogenic or more likely a geophysical origin. Aims. Our intent is to complement and improve on the previously reported detection attempts by the Atmospheric Chemistry Suite (ACS) on board the ExoMars Trace Gas Orbiter (TGO). This latter study reported the results of a campaign that was a few months in length, and was significantly hindered by a dusty period that impaired detection performances.
    [Show full text]
  • Observations of Mass Wasting Events in the Cerberus Fossae, Mars
    51st Lunar and Planetary Science Conference (2020) 2404.pdf OBSERVATIONS OF MASS WASTING EVENTS IN THE CERBERUS FOSSAE, MARS. C. M. Dundas1, I. J. Daubar, 1U.S. Geological Survey, Astrogeology Science Center, 2255 N. Gemini Dr., Flagstaff, AZ 86001 ([email protected]), 2Brown University. Introduction: The Cerberus Fossae are a set of ge- Rockfall tracks are observed at several locations. ologically-young, steep-sided fissures in the Elysium These include both simPle falls and large events break- region of Mars, which aPPear to have been the source of ing into many individual tracks (Fig. 2). floods of both water and lava [e.g., 1–4]. They have also been proposed as the site of recent seismically-triggered mass wasting [5–6]. The latter Possibility is of Particular interest because the fossae are in the same region as the InSight lander and may be tectonically active [7-8]. This abstract reports on observations of active mass move- ment in and near the Cerberus Fossae using before-and- after comparisons of images acquired by the High Res- olution Imaging Science Experiment (HiRISE) [9]. Observations: Thirty-six locations were analyzed, mostly covering the Cerberus Fossae but also including some nearby craters and massifs. SloPe activity of some form was observed at ten of these locations, although in some cases it is minor. The observed mass wasting near the fossae can be divided into three categories: slope streaks [cf. 10], sloPe lineae, and rockfalls. Slope lineae in the fossae were Previously described [11–12]. Recent observations confirm that some of the lineae in the Cer- berus Fossae grow incrementally (Fig.
    [Show full text]
  • The Mystery of Methane on Mars and Titan
    The Mystery of Methane on Mars & Titan By Sushil K. Atreya MARS has long been thought of as a possible abode of life. The discovery of methane in its atmosphere has rekindled those visions. The visible face of Mars looks nearly static, apart from a few wispy clouds (white). But the methane hints at a beehive of biological or geochemical activity underground. Of all the planets in the solar system other than Earth, own way, revealing either that we are not alone in the universe Mars has arguably the greatest potential for life, either extinct or that both Mars and Titan harbor large underground bodies or extant. It resembles Earth in so many ways: its formation of water together with unexpected levels of geochemical activ- process, its early climate history, its reservoirs of water, its vol- ity. Understanding the origin and fate of methane on these bod- canoes and other geologic processes. Microorganisms would fit ies will provide crucial clues to the processes that shape the right in. Another planetary body, Saturn’s largest moon Titan, formation, evolution and habitability of terrestrial worlds in also routinely comes up in discussions of extraterrestrial biology. this solar system and possibly in others. In its primordial past, Titan possessed conditions conducive to Methane (CH4) is abundant on the giant planets—Jupiter, the formation of molecular precursors of life, and some scientists Saturn, Uranus and Neptune—where it was the product of chem- believe it may have been alive then and might even be alive now. ical processing of primordial solar nebula material. On Earth, To add intrigue to these possibilities, astronomers studying though, methane is special.
    [Show full text]
  • Volcanism on Mars
    Author's personal copy Chapter 41 Volcanism on Mars James R. Zimbelman Center for Earth and Planetary Studies, National Air and Space Museum, Smithsonian Institution, Washington, DC, USA William Brent Garry and Jacob Elvin Bleacher Sciences and Exploration Directorate, Code 600, NASA Goddard Space Flight Center, Greenbelt, MD, USA David A. Crown Planetary Science Institute, Tucson, AZ, USA Chapter Outline 1. Introduction 717 7. Volcanic Plains 724 2. Background 718 8. Medusae Fossae Formation 725 3. Large Central Volcanoes 720 9. Compositional Constraints 726 4. Paterae and Tholi 721 10. Volcanic History of Mars 727 5. Hellas Highland Volcanoes 722 11. Future Studies 728 6. Small Constructs 723 Further Reading 728 GLOSSARY shield volcano A broad volcanic construct consisting of a multitude of individual lava flows. Flank slopes are typically w5, or less AMAZONIAN The youngest geologic time period on Mars identi- than half as steep as the flanks on a typical composite volcano. fied through geologic mapping of superposition relations and the SNC meteorites A group of igneous meteorites that originated on areal density of impact craters. Mars, as indicated by a relatively young age for most of these caldera An irregular collapse feature formed over the evacuated meteorites, but most importantly because gases trapped within magma chamber within a volcano, which includes the potential glassy parts of the meteorite are identical to the atmosphere of for a significant role for explosive volcanism. Mars. The abbreviation is derived from the names of the three central volcano Edifice created by the emplacement of volcanic meteorites that define major subdivisions identified within the materials from a centralized source vent rather than from along a group: S, Shergotty; N, Nakhla; C, Chassigny.
    [Show full text]
  • Evidence for Methane in Martian Meteorites
    Blamey, N. J. F., Parnell, J., McMahon, S., Mark, D. F., Tomkinson, T., Lee, M., Shivak, J., Izawa, M. R. M., Banerjee, N. R., & Flemming, R. L. (2015). Evidence for methane in Martian meteorites. Nature Communications, 6, [7399]. https://doi.org/10.1038/ncomms8399 Publisher's PDF, also known as Version of record License (if available): CC BY Link to published version (if available): 10.1038/ncomms8399 Link to publication record in Explore Bristol Research PDF-document This is the final published version of the article (version of record). It first appeared online via Nature Publishing Group at doi:10.1038/ncomms8399. Please refer to any applicable terms of use of the publisher. University of Bristol - Explore Bristol Research General rights This document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/red/research-policy/pure/user-guides/ebr-terms/ ARTICLE Received 19 Sep 2014 | Accepted 1 May 2015 | Published 16 Jun 2015 DOI: 10.1038/ncomms8399 OPEN Evidence for methane in Martian meteorites Nigel J.F. Blamey1,2, John Parnell2, Sean McMahon2, Darren F. Mark3, Tim Tomkinson3,4, Martin Lee4, Jared Shivak5, Matthew R.M. Izawa5, Neil R. Banerjee5 & Roberta L. Flemming5 The putative occurrence of methane in the Martian atmosphere has had a major influence on the exploration of Mars, especially by the implication of active biology. The occurrence has not been borne out by measurements of atmosphere by the MSL rover Curiosity but, as on Earth, methane on Mars is most likely in the subsurface of the crust.
    [Show full text]
  • Dikes of Distinct Composition Intruded Into Noachian-Aged Crust Exposed in the Walls of Valles Marineris Jessica Flahaut, John F
    Dikes of distinct composition intruded into Noachian-aged crust exposed in the walls of Valles Marineris Jessica Flahaut, John F. Mustard, Cathy Quantin, Harold Clenet, Pascal Allemand, Pierre Thomas To cite this version: Jessica Flahaut, John F. Mustard, Cathy Quantin, Harold Clenet, Pascal Allemand, et al.. Dikes of dis- tinct composition intruded into Noachian-aged crust exposed in the walls of Valles Marineris. Geophys- ical Research Letters, American Geophysical Union, 2011, 38, pp.L15202. 10.1029/2011GL048109. hal-00659784 HAL Id: hal-00659784 https://hal.archives-ouvertes.fr/hal-00659784 Submitted on 19 Jan 2012 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. GEOPHYSICAL RESEARCH LETTERS, VOL. 38, L15202, doi:10.1029/2011GL048109, 2011 Dikes of distinct composition intruded into Noachian‐aged crust exposed in the walls of Valles Marineris Jessica Flahaut,1 John F. Mustard,2 Cathy Quantin,1 Harold Clenet,1 Pascal Allemand,1 and Pierre Thomas1 Received 12 May 2011; revised 27 June 2011; accepted 30 June 2011; published 5 August 2011. [1] Valles Marineris represents the deepest natural incision and HiRISE (High Resolution Imaging Science Experiment) in the Martian upper crust.
    [Show full text]
  • Pre-Mission Insights on the Interior of Mars Suzanne E
    Pre-mission InSights on the Interior of Mars Suzanne E. Smrekar, Philippe Lognonné, Tilman Spohn, W. Bruce Banerdt, Doris Breuer, Ulrich Christensen, Véronique Dehant, Mélanie Drilleau, William Folkner, Nobuaki Fuji, et al. To cite this version: Suzanne E. Smrekar, Philippe Lognonné, Tilman Spohn, W. Bruce Banerdt, Doris Breuer, et al.. Pre-mission InSights on the Interior of Mars. Space Science Reviews, Springer Verlag, 2019, 215 (1), pp.1-72. 10.1007/s11214-018-0563-9. hal-01990798 HAL Id: hal-01990798 https://hal.archives-ouvertes.fr/hal-01990798 Submitted on 23 Jan 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Open Archive Toulouse Archive Ouverte (OATAO ) OATAO is an open access repository that collects the wor of some Toulouse researchers and ma es it freely available over the web where possible. This is an author's version published in: https://oatao.univ-toulouse.fr/21690 Official URL : https://doi.org/10.1007/s11214-018-0563-9 To cite this version : Smrekar, Suzanne E. and Lognonné, Philippe and Spohn, Tilman ,... [et al.]. Pre-mission InSights on the Interior of Mars. (2019) Space Science Reviews, 215 (1).
    [Show full text]
  • In Pdf Format
    lós 1877 Mik 88 ge N 18 e N i h 80° 80° 80° ll T 80° re ly a o ndae ma p k Pl m os U has ia n anum Boreu bal e C h o A al m re u c K e o re S O a B Bo l y m p i a U n d Planum Es co e ria a l H y n d s p e U 60° e 60° 60° r b o r e a e 60° l l o C MARS · Korolev a i PHOTOMAP d n a c S Lomono a sov i T a t n M 1:320 000 000 i t V s a Per V s n a s l i l epe a s l i t i t a s B o r e a R u 1 cm = 320 km lkin t i t a s B o r e a a A a A l v s l i F e c b a P u o ss i North a s North s Fo d V s a a F s i e i c a a t ssa l vi o l eo Fo i p l ko R e e r e a o an u s a p t il b s em Stokes M ic s T M T P l Kunowski U 40° on a a 40° 40° a n T 40° e n i O Va a t i a LY VI 19 ll ic KI 76 es a As N M curi N G– ra ras- s Planum Acidalia Colles ier 2 + te .
    [Show full text]
  • Life on Mars- Extracting the Signs for Future Human Habitation on The
    Muhammad Shadab Khan, Department of Aeronautical Engineering, Babu Banarasi Das National Institute of Technology and Management, Lucknow, India CONTENT- Introduction Life on Mars Signs of Life Found on Mars and Similarities with those signs on Earth Utilizing Life Support Resources present on Mars for human habitation INTRODUCTION 1- Rise of Global Warming and it’s alarming consequences which might cause complete loss of life on Earth– Search for an Earth like habitable body in the outer Space 2- Ongoing Exploration of Mars in search of Life on the Red Planet for future human habitation on the planet. 3- Mars is the planet which is very similar to Earth and it’s believed that Life had existed on Mars in the Past– Big support to our quest for life in the future 4- The life supporting features found on Mars are very similar to those found on Earth– Giving a sign of prospective life in the near future on Mars Life on Mars Life on Mars has been a subject of wide discussion from the very early beginning. There has been speculations about the existence of Life on the Red Planet in the Past But still about the presence of an Earth like habitable environment on Mars is a BIG QUESTION ? The first search for Life on Mars was carried out by NASA’s VIKING LANDER in 1976 Gas Chromatograph/Mass Spectrometer Instrument on the Lander detected the possible MICROBIAL LIFE in the soil sample . The question about MICROBIAL LIFE remains unresolved LIQUID WATER ON MARS The speculation about the presence of LIQUID WATER on Mars has been a subject of deep interest to the scientists from the very beginning As it’s believed in order to support LIFE, the need of WATER in LIQUID FORM is MUST.
    [Show full text]
  • Schultze-Makuch Methane Mars.Pdf
    International Journal of Astrobiology 7 (2): 117–141 (2008) Printed in the United Kingdom 117 doi:10.1017/S1473550408004175 f 2008 Cambridge University Press The case for life on Mars Dirk Schulze-Makuch1, Alberto G. Faire´n2 and Alfonso F. Davila2 1School of Earth and Environmental Sciences, Washington State University, Pullman, WA 99163, USA e-mail: [email protected] 2Space Science and Astrobiology Division, NASA Ames Research Center, USA Abstract: There have been several attempts to answer the question of whether there is, or has ever been, life on Mars. The boldest attempt was the only ever life detection experiment conducted on another planet: the Viking mission. The mission was a great success, but it failed to provide a clear answer to the question of life on Mars. More than 30 years after the Viking mission our understanding of the history and evolution of Mars has increased vastly to reveal a wetter Martian past and the occurrence of diverse environments that could have supported microbial life similar to that on Earth for extended periods of time. The discovery of Terran extremophilic microorganisms, adapted to environments previously though to be prohibitive for life, has greatly expanded the limits of habitability in our Solar System, and has opened new avenues for the search of life on Mars. Remnants of a possible early biosphere may be found in the Martian meteorite ALH84001. This claim is based on a collection of facts and observations consistent with biogenic origins, but individual links in the collective chain of evidence remain controversial. Recent evidence for contemporary liquid water on Mars and the detection of methane in the Martian atmosphere further enhance the case for life on Mars.
    [Show full text]
  • Spring 1989 5
    MIDDLE EAST LIBRARIANS ASSOCIATION NUMBER 47 SPRING, 1989 TAOLE OF CONTENTS Editor.. ., Note 2 ASSOClA'I ION NEWS Fr°"' ttHt President 3 Librarian of Congress responds to HELA GENERAL NEWS Future Conferences Electronic Addr11sses 7 ARTICLES h1la111 in Canada by Salwa Ferahian B Iraq-Iran Wart a Bibliographical Project by J. Anthony Gardner 14 Conte111porary Pt!r11ian Press in E1till! by Hasan Javadi and Abazar Sepehri lB A Lone Bibliographer at her PC by Priscilla H. Ro~rts 7.b Increa sing Productivity and Public Satisfaction with Middle East and Judaic Library Services through Use of a Personal Co111puter by Oona S. Straley and A111non Zipin 33 BOO!< REVIEW !!I.~irat al-ma•3rif Ta ~hayyu~ reviewed by Abaiar Sepehri :Sb POSITIONS AVAILABLE Princeton Univers ity 38 Sultan Daboos University 39 University of Chicago '10 lntifatlah Publication,,. Available Inside Back Cover l u raeli Fon!ign Relations Documents AvaUablll! Inside Back Cover MH n NIJIHi IU!IN U.U1'1 J410 MIDDLE EAST LIBRARIANS ASSOCIATION EDWARD A. JAJKO PresidP-nt 1989 Moover Ins ti tut ion MEAYLE GASTON Vice-Pr esident & NeH York University Progral'I Chair 1?89 JAMES WEINBERGER Secretary- P~inceta11 ~liver·sity ' Treasurer 1987- 1989 BRENDA E. BICKETT Editor 1900-1990 Georgetown University !:l('ll\ Not•• I• publislurd three ti,.es a year, in ,.inter, "'Pring, and fal I. It i• distributed to ...,,,.bers of the Association and to 11onll'l"'"h"'r ••lh"<: r l born1. M•.,hur•hl11 1h1e11 of US$10.00 for North Afllerican addresses or IJUtl:l.00 fut' •do:Jres!le!& outside North AMerica bring the ~and ..,.' ul:hotr- 111•il !r111•· Bub11criptions are USSl0.00 lUSSl:l.OO outside No rth l'IMlft Ar:al 1nu t.alwlldlit' year, or USS3.00 per issue for 111ost back 11u111hat •, l\ddr••• rnrr••JllHUletir• r11q,11nll11Q •11l111criptioms, dues, or "''"'"b"r""hip In fur111111tiun hll .J•lll!'!!t M• l11l11o·o•r 1 B•cr•tary-Treasurer MELA, l'rtnec•lun llf1iv•r•ily l lhr.,y, lluM 1'10, Princ:•ton, NJ 08:1'10 USA.
    [Show full text]
  • Paleoflooding in the Solar System: Comparison Among Mechanisms For
    Paleoflooding in the Solar System: comparison among mechanisms for flood generation on Earth, Mars, and Titan Devon Burr Earth and Planetary Sciences Department EPS 306 University of Tennessee Knoxville 1412 Circle Dr. Knoxville TN 39776-1410 USA [email protected] ABSTRACT Conditions allow surficial liquid flow on three bodies in the Solar System, Earth, Mars, and Titan. Evidence for surficial liquid flood flow has been observed on Earth and Mars. The mechanisms for generating flood flow vary according to the surficial conditions on each body. The most common flood-generating mechanism on Earth is wide-spread glaciation, which requires an atmospheric cycle of a volatile that can assume the solid phase. Volcanism is also a prevalent cause for terrestrial flooding, which other mechanisms producing smaller, though more frequent, floods. On Mars, the mechanism for flood generation has changed over the planet’s history. Surface storage of floodwater early in Mars’ history gave way to subsurface storage as Mars’ climate deteriorated. As on Earth, Mars’ flooding is an effect of the ability of the operative volatile to assume the solid phase, although on Mars, this has occurred in the subsurface. According to this paradigm, Titan conditions preclude extreme flooding because the operative volatile, which is methane, cannot assume the solid phase. Mechanisms that produce smaller but more frequent floods on Earth, namely extreme precipitation events, are likely the most important flood generators on Titan. 1. Introduction The historical flow of paleoflood science has risen and fallen largely in concert with prevailing scientific paradigms (Baker 1998). The paradigm in the 17 th century was catastrophism, the idea that geology is the product of sudden, short, violent events.
    [Show full text]