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January 31, 2008
January 30, 2008
Astrobiology Science News 30 January 2008
January 26, 2008
Astrobiology Science News 24 January 2008
January 25, 2008
Astrobiology Science News 25 January 2008
January 23, 2008
Astrobiology Science News 23 January 2008
January 22, 2008
Astrobiology Science News 22 January 2008
January 20, 2008
Future of Intelligence in the Cosmos Workshop Proceedings Available
This past summer, NAI participated in organizing a special weekend workshop held at NASA Ames Research Center entitled "The Future of Intelligence in the Cosmos." The workshop brought together internationally renown scientists and thinkers to explore potential scenarios for the evolution of intelligent civilizations in our galaxy. The talks were organized into sessions including The Fermi Paradox, Cultural Evolution, The Nature of Intelligence, and Technological Evolution, followed by several breakout sessions. The proceedings are now available for download at: http://event.arc.nasa.gov/main/home/reports/CP2007-214567_Langhoff.pdf
[Source: NAI newsletter]
2008 Research Experiences for Undergraduates
The SETI Institute is pleased to announce that applications are now open for the 2008 REU (Research Experiences for Undergraduates) program in Astrobiology. Undergraduate students in fields such as astronomy, biology, geology, chemistry, and physics are invited to apply to spend 10 weeks in the San Francisco Bay area working on a scientific research project in the field of astrobiology. Students receive a stipend, travel, and living expenses. Applications are due by February 1, 2008. For more information, visit http://www.seti.org/reu or contact Cynthia Phillips, phillips@seti.org, 650-810-0230.
Poster can be downloaded from: http://www.seti.org/pdfs/reuposter-2008.pdf
[Source: NAI newsletter]
New Astrobiology Book Published
Chris Impey from the University of Arizona is the author of the new book "The Living Cosmos: Our Search for Life in the Universe." Published by Random House in December, the book has been met with critical acclaim, especially in this review from the LA Times: http://www.latimes.com/features/books/la-et-book28dec28,1,1847735.story?ctrack=1&cset=true
[Source: NAI newsletter]
Online Course in Astrobiology for Teachers
Every semester, NAI sponsors an online course for teachers in astrobiology through the National Teacher Enhancement Network at Montana State University. Teachers login to the course at a time of day that best fits their schedule; it's necessary to connect at least 4 times a week, giving a commitment of 9-12 hours each week to stay current and successfully complete this 3 credit course. This semester's course runs from January 21 - May 2, 2008. For more information, go to: http://btc.montana.edu/courses/aspx/nten.aspx?TheID=162
[Source: NAI newsletter]
Astrobiology EPO, Undergrads, Grads, Postdocs
Upcoming Summer Astrobiology Workshops for Teachers
Astrobiology Summer Science Experience for Teachers (ASSET)
Application Deadline: February 15th
Workshop Dates: 27 July - 2 August, 2008
Workshop Location: San Francisco Bay Area
Website: http://www.seti.org/asset/
Astrobiology Laboratory Institute for Instructors (ALI'I)
Application Deadline: March 28th
Workshop Dates: 13-18 July, 2008
Workshop Location: Honolulu, HI
Website: http://www.ifa.hawaii.edu/UHNAI/epo/alii.htm
Earth's History: Interactions between Life and the Environment
Application Deadline: ongoing
Workshops Dates: 22-27 June, 2008
Workshop Location: Penn State University
Website: http://teachscience.psu.edu/earths_history.html
Evolution: How Important Is It to a Good Science Education
Application Deadline: ongoing
Workshops Dates: 13-18 July, 2008
Workshop Location: Penn State University
Website: http://teachscience.psu.edu/evolution.html
[Source: NAI newsletter]
Recently Published Research from the NAI
The following new papers have been published recently by NAI members. These and other recent NAI funded research are presented on the NAI website and collected in the NAI Research Highlights Archive - http://nai.arc.nasa.gov/research/. In this archive, you can link to the papers and any press materials that may have been generated about them.
If you have an upcoming or recent publication, please tell us about it as soon as possible. We will work with your institution to produce press releases, publicize the paper on the NAI website, and pre-populate your team's annual report with your publication. Please send any information to Daniella Scalice dscalice@mail.arc.nasa.gov
Follow the Energy
A decade of planetary exploration, focusing on a "follow the water" approach, has yielded a tantalizing array of astrobiologically compelling targets. But the growing list of water-bearing planets and moons has also underscored the need to develop additional metrics for habitability. Research from within the NASA Astrobiology Institute is developing a "follow the energy" approach to complement "follow the water." The new issue of Astrobiology compiles several papers on this approach, guest-edited by Tori Hoehler from NAI's Ames Team.
Red Dust in Planet-Forming Disk May Harbor Precursors to Life
Researchers from NAI's Carnegie Institution of Washington Team have found the first indications of highly complex organic molecules in the disk of red dust surrounding a distant star. The eight-million-year-old star, known as HR 4796A, is inferred to be in the late stages of planet formation, suggesting that the basic building blocks of life may be common in planetary systems. The paper appears in the Astrophysical Journal Letters; a copy of the paper can be found here.
[Source: NAI newsletter]
ISSOL Seeks Nominations for New Stanley L. Miller Award
In recognition of the pioneering role Stanley L. Miller played in our understanding of the origins of life, ISSOL, The International Astrobiology Society, shall present at each triennial meeting a Stanley L. Miller Award for outstanding contributions by a young scientist (under the age of 37) to origins of life research. The award is based on scientific merit without regard to nationality. The recipient will be honored during the awards banquet at the close of each triennial meeting. The next ISSOL meeting will be held in Florence from August 24-29, 2008 (http://www.dbag.unifi.it/issol2008/).
This is a formal call for nominations of outstanding young scientists eligible for the Stanley L. Miller Award. Nominations should be accompanied by a statement from the nominator of ~250 words describing the nominee's contributions to the field and a list of not more than ten (10) of the nominee's major publications. Please note that the original email stated that nominees must not be ISSOL members (as determined in the original by-laws of ISSOL 2003). The recently updated ISSOL by-laws state that nominees can be members of ISSOL.
Applications should be sent before April 1st, 2008 to the Miller Award Selection Committee Chair: Pascale Ehrenfreund (Email: p.ehrenfreund@chem.leidenuniv.nl).
The Miller Award Selection Committee: Pascale Ehrenfreund (Leiden University, Netherlands) Jack Szostak (Harvard Medical Center, USA) Jochen Brocks (Australian National University, Australia)
[Source: NAI newsletter]
University of Colorado Virtual Seminar
January 30th: "The New Worlds Observer: A Mission to Open Up Detailed Study of Planetary Systems"
NAI will be broadcasting this virtual seminar over the web at 2pm MST on Wednesday, January 30th. Webster Cash from UC Boulder will present. Please contact Marco Boldt for information on how to join. Marco.S.Boldt@nasa.gov
Abstract: The New Worlds Observer (NWO) is a concept for a major mission to be implemented in the coming decade with the goal of opening up detailed, direct studies of exo-planetary systems. The mission is based on the use of "Starshades", which are petal-shaped occulters about 50m in diameter, flying 70,000km from a conventional space telescope. This combination suppresses the light from the central star, revealing the planetary system in detail, free from scatter. NWO will be able to detect planets from the habitable zone outward and follow up discovery with high quality spectroscopy. It is the best approach to finding and identifying water planets and then studying the chemical balance of their atmospheres and surfaces. Photometric markers can indicate the presence of oceans and continents. And, even more exciting, spectroscopic biomarkers hold forth hope of finding indications of life outside our solar system.
[Source: NAI newsletter]
NAI Minority Institution Research Support (MIRS) Program
Application Deadline - March 7, 2008
The NAI-MIRS Program provides opportunities for researchers from qualified minority institutions to initiate joint partnerships with researchers in the field of astrobiology. The NAI-MIRS program provides summer sabbaticals, follow-up support, and travel opportunities for faculty and students from minority institutions. The application deadline for summer 2008 is March 7th. For more information, visit http://www.nai-mirs.org. [Source: NAI newsletter]
NAI Travel Scholarships Available for the International Conference on Polar and Alpine Microbiology
The NAI is pleased to sponsor travel scholarships for four graduate students (senior level) or postdoctoral fellows (with less than two years of postdoctoral training) to attend the Third International Polar and Alpine Microbiology Conference, to be held in Banff, Alberta, Canada, May 11-15, 2008. See the conference website for more details: http://www.polaralpinemicrobiology.com/. Each award will provide up to $2000 to defray the cost of economy airfare from US or Canadian cities and local travel, registration and up to four nights lodging at the workshop venue (shared room, if at all possible). Travel funds will be awarded on a competitive basis.
To apply, send 1) an application letter, of no more than one page, explaining how participation in this conference will benefit your research goals and how your research contributes to the goals of astrobiology; 2) a copy of your CV; 3) a letter of support from your research advisor; and 4) a copy of the abstract you intend to submit to the conference for either a poster or oral presentation. Note that applicants need not be formally affiliated with the NAI. The due date for receipt of the application materials is February 8, 2008, which coincides with the abstract submission deadline.
Please send application materials (and any questions) electronically or by mail to:
Jody W. Deming, Professor School of Oceanography and UW Astrobiology Program Box 357940 University of Washington Seattle, WA 98195 USA jdeming@u.washington.edu
[Source: NAI newsletter]
NAI Lewis and Clark Fund for Exploration and Field Research in Astrobiology
Application Deadline - February 15, 2008
The Lewis and Clark Fund for Exploration and Field Research in Astrobiology, a partnership between NAI and the American Philosophical Society (APS), is now accepting applications for astrobiological field studies for 2008. Graduate students, postdoctoral students, and junior scientists and scholars are eligible to apply for travel and related expenses, up to $5000. For more information, please see http://www.amphilsoc.org/grants/astrobiology.htm
[Source: NAI newsletter]
NAI Director's Seminar: The Effect of Protoplanetary Disk Dispersal on Planet Formation
Join us for the next NAI Director's Seminar on Monday, February 4th at 11am PST. The seminar, "The Effect of Protoplanetary Disk Dispersal on Planet Formation," will be given by David Hollenbach of NASA Ames Research Center. For information on how to join the seminar, go to: http://nai.arc.nasa.gov/seminars/seminar_detail.cfm?ID=117.
Abstract: One of the first questions facing astrobiologists is: "What is the likelihood of habitable planets or moons forming around stars in the universe?" During their formation from gas and dust orbiting young stars, planets compete with mechanisms that disperse the gas and dust: viscous accretion on the central star and dispersal into interstellar space by the effects of nearby stellar encounters, the winds from the central star, and the ultraviolet (UV) and X-ray photons from either the central star or nearby luminous stars. We show with theoretical models validated by astronomical observations how viscous accretion likely dominates the dispersal in the inner regions (< 1 AU) of protoplanetary disks, while UV-induced photoevaporation dominates in the outer regions. These dispersal mechanisms may prevent, truncate, or otherwise affect planet formation and the resultant planetary architecture. Planetary formation is most seriously affected around high mass stars and around low mass stars in clusters of stars with high mass star members. We review progress made on answering the above question and future prospects.
[Source: NAI newsletter]
NASA Astrobiology Institute Cooperative Agreement Notice Released (Cycle-5)
The NAI announces, through the release of this Cooperative Agreement Notice (CAN), an opportunity for the submission of team-based proposals for membership in the Institute. Proposals should clearly articulate an innovative, interdisciplinary, astrobiology research program, together with plans to advance the full scope of NAI objectives as defined in the Institute's Mission Statement. The Cooperative Agreement Notice can be accessed at: http://nspires.nasaprs.com
CAN Release Date: January 8, 2008 Notices of Intent Due: February 22, 2008
Proposals Due: April 11, 2008
[Source: NAI newsletter]
January 18, 2008
Astrobiology Science News 18 January 2008
January 17, 2008
Astrobiology Science News 17 January 2008
- DEPTHX Robot Dives Deep for Sinkhole Slime, Astrobiology Magazine
- Hexadecapole Approximation in Planetary Microlensing, astro-ph
- Impact of Orbital Eccentricity on the Detection of Transiting Extrasolar Planets, astro-ph
- On the observability of resonant structures in planetesimal disks due to planetary migration, astro-ph
NSF Dear Colleague Letter - Assembling the Tree of Life Solicitation
Dear Colleague, The National Science Foundation's Assembling the Tree of Life (AToL) solicitation has recently been renewed and updated (see the program solicitation, NSF 08-515; http://www.nsf.gov/publications/pub_summ.jsp?ods_key=nsf08515). As in the past, the AToL competition will support creative and innovative research to resolve evolutionary relationships for large groups of organisms. The program also supports research on theory and methods and tool development for these large scale phylogenetic investigations. With this letter we wish to draw your attention to several new and/or enhanced areas of interest. Proposals in the following areas are especially encouraged:
1. Proposals that seek to understand the role and importance of lateral gene transfer and reticulation in evolutionary history, as well as proposals to develop methods and theory that will address this important issue in phylogenetic research and phyloinformatics.
2. Proposals to develop tools to facilitate the efficient integration and management of the diverse types of data and extensive amounts of data that are generated by these large-scale phylogenetic studies.
3. Proposals that focus on major taxonomic groups not yet addressed in ongoing or completed AToL projects. Examples include but are not limited to: viruses and the various major groups of prokaryotes, protists, and lower invertebrates.
The deadline date for proposal submission to the AToL program is 14 March 2008. NSF FastLane requirements (www.fastlane.nsf.gov) apply to all proposals. Proposals must conform to all format requirements in the Grant Proposal Guide http://www.nsf.gov/publications/pub_summ.jsp?ods_key=papp; in addition there are special proposal requirements for this competition (see AToL solicitation http://www.nsf.gov/publications/pub_summ.jsp?ods_key=nsf08515). Investigators with questions about AToL proposals are encouraged to contact the AToL Working Group (BIO-atol@nsf.gov). A link to the list of previous AToL awards and abstracts can be found on the AToL web page (http://www.nsf.gov/ef).
January 16, 2008
Astrobiology Science News 16 January 2008
January 15, 2008
Astrobiology Science News 15 January 2008
January 11, 2008
Astrobiology Science News 11 January 2008
January 10, 2008
Astrobiology Science News 10 January 2008
January 9, 2008
NASA Research Announcement (NRA) NNJ08ZSA001N Ground-Based Studies in Space Radiobiology
The National Aeronautics and Space Administration (NASA) Lyndon B. Johnson Space Center (JSC) has released NASA Research Announcement (NRA) NNJ08ZSA001N, entitled "Ground-Based Studies in Space Radiobiology." This NRA solicits ground-based proposals for the Space Radiation Program Element (SRPE) components of the Human Research Program (HRP). Proposals are solicited by the SRPE in the area of Space Radiation Biology utilizing beams of high energy heavy ions simulating space radiation at the NASA Space Radiation Laboratory (NSRL), at Brookhaven National Laboratory (BNL) in Upton, New York.
The full text of the solicitation is available on the NASA Research Opportunities homepage at http://nspires.nasaprs.com under menu listing "Open Solicitations." Potential applicants are urged to access this site well in advance of the proposal due date to familiarize themselves with its structure and to register in the system. Proposals solicited through this NRA will use a two-step proposal process. Only Step-1 proposers determined to be relevant with respect to the Research Emphases outlined in Section (I)(F) of this NRA will be invited to submit full Step-2 proposals. Step-2 proposals must be compliant with respect to all sections of this NRA or they will be declined without review. Proposals must be submitted electronically. Step-1 proposals are due February 6, 2008.
This email is being sent on behalf of and is intended as an information announcement to researchers associated with the NASA Exploration Systems Mission Directorate (ESMD) Human Research Program (HRP).
Astrobiology Science News 9 January 2008
NASA offers Mission PI Training Course
NASA Science Mission Directorate to Sponsor NASA Academy of Program, Project, and Engineering Leadership (APPEL) Mission Principal Investigator Training Course
Beginning in 2008, the NASA Science Mission Directorate (SMD) will be sponsoring a series of offerings of a one-week Mission Principal Investigator (PI) Training Course to help mission PIs lead NASA science missions more effectively.
The Mission PI Training Course has been developed and will be delivered by the NASA Academy of Program, Project and Engineering Leadership (APPEL) under the direction of Dr. Edward Hoffman of the Office of the Chief Engineer. The course will cover material including the responsibilities of the PI, NASA policies and directives, project life cycles and reviews, project management and systems engineering, project assessment and control, NASA-provided services, and project-centered leadership fundamentals. The initial course offering is planned for June 15-20, 2008 at a soon to be announced location convenient to the Washington, DC area. The course will subsequently be offered three or more times per year.
Mission PIs have full responsibility for the scientific integrity and all other aspects of their missions including the execution of the mission investigation within the committed cost and schedule. Due to this level of responsibility, existing mission PIs will have a mandatory requirement to complete the course within three years of the initial course offering date, and PIs of missions subsequently selected to enter Phase B will have a mandatory requirement to complete the course within one year from their selection. The Mission PI Training Course requirement is in addition to, and not a substitute for, the experience requirements for the PIs of all mission proposals submitted in response to SMD Announcements of Opportunity.
Enrollment for the course will be limited to approximately 35 participants per class offering. NASA will cover the cost of the course including all food and lodging, but participants will be responsible for their own transportation to and from the course and for their salary during the weeklong course.
To receive consideration for the initial course offering, please send an email message with your electronic contact coordinates to katherine.thomas@asrcms.com with "Register: Mission PI Training Course" in the title. Aspiring mission PIs should also include a one-page summary of their relevant experience and describe their interest in becoming a mission PI. The email message must be received by January 31, 2008 in order to receive consideration for the initial course offering, and participants for the initial class will be selected from among those responding. Please forward any questions about the course to katherine.thomas@asrcms.com with "Question: Mission PI Training Course" in the title.
January 8, 2008
Proposal opportunity: NASA Astrobiology Institute
On January 8, 2008, the National Aeronautics and Space Administration (NASA) Science Mission Directorate (SMD) is releasing a Cooperative Agreement Notice (NNH08ZDA002C) soliciting new institutional members to the NASA Astrobiology Institute (NAI).
The NAI CAN (Cycle-5) is responsive to the recommendations of the recent NRC study (Assessment of the NASA Astrobiology Institute, 2007, http://www7.nationalacademies.org/ssb/). Proposers will be required to clearly articulate an innovative, interdisciplinary, astrobiology research program, together with plans to advance the full scope of NAI objectives as defined in the Institute's Mission Statement (see NAI website: http://nai.nasa.gov/). Proposers may also choose to focus their research on preparing for strategic mission objectives in astrobiology. NASA anticipates making $10-12M per year available for this selection, leading to at least 7 and possibly several more awards (approximately one-third of which will be focused on preparing for strategic mission objectives), each of 5 years duration.
Participation is open to all categories of organizations (domestic and non-U.S.), including industry, educational institutions, not-for-profit organizations, Federally Funded Research and Development Centers, NASA Centers, the Jet Propulsion Laboratory, and other Government agencies. Upon its release date, this Cooperative Agreement Notice will be available electronically from http://nspires.nasaprs.com/ (select "Solicitations" then select "Open Solicitations" then select "NNH08ZDA002C").
Notices of Intent (NOIs) are due February 22, 2008, and proposals are due April 11, 2008.
Obtain additional programmatic information from: Dr. Carl Pilcher, Director, NASA Astrobiology Insitute, Ames Research Center, Moffett Field, CA 94035; Tel: (650) 604-0022; email: can5@nasa.gov.
January 4, 2008
Astrobiology Science News 4 January 2008
January 3, 2008
NASA to Release Cooperative Agreement Notice for Membership in the NASA Astrobiology Institute
NASA intends to release a Cooperative Agreement Notice (CAN, Cycle-5) soliciting new institutional members to the NASA Astrobiology Institute (NAI). The CAN will be released early in 2008, and proposals will be due approximately 90 days later. NAI CAN Cycle-5 is responsive to the recommendations of the recent NRC study (Assessment of the NASA Astrobiology Institute, 2007, http://www7.nationalacademies.org/ssb/).
Proposals will be required to clearly articulate an innovative, interdisciplinary, astrobiology research program, together with plans to advance the full scope of NAI objectives as defined in the Institute's Mission Statement (see NAI website: ). NASA anticipates making $4-11M per year available for this selection, leading to 4-8 awards, each of 5 years duration. Participation in this solicitation is open to all categories of organizations, domestic and non-U.S., including industry, educational institutions, nonprofit organizations, NASA centers, and other Government agencies.
For further information please contact: Dr. Carl Pilcher, Director, NASA Astrobiology Institute, Mail Stop 247-6, Ames Research Center, National Aeronautics and Space Administration, Moffett Field, CA 94035-1000; Phone: 650-604-0022; E-mail: can5@nasa.gov.
January 2, 2008
Astrobiology Science News 2 January 2008
- Astronomy: Extrasolar planets, Nature
- A young massive planet in a star–disk system, Nature
- A "Follow the Energy" Approach for Astrobiology, Astrobiology
- An Energy Balance Concept for Habitability, Astrobiology
- Quantitative Habitability, Astrobiology
- Actinides and Life's Origins, Astrobiology
- Formate as an Energy Source for Microbial Metabolism in Chemosynthetic Zones of Hydrothermal Ecosystems, Astrobiology
- A Thermodynamic Analysis of Microbial Growth Experiments, Astrobiology
- Radiolytic Hydrogen and Microbial Respiration in Subsurface Sediments, Astrobiology
- Temporal Changes in Fluid Chemistry and Energy Profiles in the Vulcano Island Hydrothermal System, Astrobiology
- Geochemical Constraints on Sources of Metabolic Energy for Chemolithoautotrophy in Ultramafic-Hosted Deep-Sea Hydrothermal Systems, Astrobiology
- Hydrogeologic Controls on Episodic H2 Release from Precambrian Fractured Rocks--Energy for Deep Subsurface Life on Earth and Mars, Astrobiology
- Hydrothermal Systems in Small Ocean Planets, Astrobiology
- Energy, Chemical Disequilibrium, and Geological Constraints on Europa, Astrobiology
- Did Earthquakes Keep the Early Crust Habitable?, Astrobiology
A "Follow the Energy" Approach for Astrobiology
Astrobiology December 2007, 7(6): 819-823
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2007.0207
A key challenge in Astrobiology is to comprehend life and its interaction with the environment at a level sufficiently fundamental to embrace the alternative biochemistries that may be encountered in a search for life elsewhere (Baross et al., 2007).
Life on Earth presents us with a single (albeit highly diversified) biochemical model around which to build this comprehension. This model is extremely valuable in providing an empirical starting point for understanding metabolic potential and environmental tolerance, and as a continuing "reality check" on whatever generalized concepts of life may be developed. Reference to this single example, however, also carries the risk of narrowing our sense of possibility of leading us to define biochemistry, habitability, and biosignatures in terms so specific that they may exclude different forms of life.
The need for well-defined yet broadly applicable notions of habitability and biosignatures will become critical as astrobiological objectives are fac-tored increasingly into space missions.
The conception, parameterization, and instrumentation of these missions will require concrete determi- nations of where to look and what information to seek, and interpretation of the resultant data will require considerable plasticity in our conception of what constitutes evidence of life.
Did Earthquakes Keep the Early Crust Habitable?
Astrobiology December 2007, 7(6): 1023-1032
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2006.0091
The shallow habitable region of cratonal crust deforms with a strain rate on the order of 1019 s1. This is rapid enough that small seismic events are expected on one-kilometer spatial scales and one-million-year timescales. Rock faulting has the potential to release batches of biological substrate, such as dissolved H2, permitting transient blooms.
In addition, the steady-state deformation of the brittle crust causes numerous small faults to be permeable enough (on the order of 1015 m2) for water to flow on a kilometer scale over relatively short geological times (105 yr). Hence, active faults act as concentrated niches capable of episodically tapping resources in the bulk volume of the rock. Radiolysis and ferrous iron are potentially bases of sustainable hard-rock niches.
Energy, Chemical Disequilibrium, and Geological Constraints on Europa
Astrobiology December 2007, 7(6): 1006-1022
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2007.0156
Europa is a prime target for astrobiology. The presence of a global subsurface liquid water ocean and a composition likely to contain a suite of biogenic elements make it a compelling world in the search for a second origin of life. Critical to these factors, however, may be the availability of energy for biological processes on Europa.
We have examined the production and availability of oxidants and carbon-containing reductants on Europa to better understand the habitability of the subsurface ocean. Data from the Galileo Near-Infrared Mapping Spectrometer were used to constrain the surface abundance of CO2 to 0.036% by number relative to water. Laboratory results indicate that radiolytically processed CO2-rich ices yield CO and H2CO3; the reductants H2CO, CH3OH, and CH4 are at most minor species.
We analyzed chemical sources and sinks and concluded that the radiolytically processed surface of Europa could serve to maintain an oxidized ocean even if the surface oxidants (O2, H2O2, CO2, SO2, and SO4 2) are delivered only once every 0.5 Gyr. If delivery periods are comparable to the observed surface age (30-70 Myr), then Europa's ocean could reach O2 concentrations comparable to those found in terrestrial surface waters, even if 109 moles yr1 of hydrothermally delivered reductants consume most of the oxidant flux. Such an ocean would be energetically hospitable for terrestrial marine macrofauna. The availability of reductants could be the limiting factor for biologically useful chemical energy on Europa.
Hydrothermal Systems in Small Ocean Planets
Astrobiology December 2007, 7(6): 987-1005
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2007.0075
We examine means for driving hydrothermal activity in extraterrestrial oceans on planets and satellites of less than one Earth mass, with implications for sustaining a low level of biological activity over geological timescales. Assuming ocean planets have olivine-dominated lithospheres, a model for cooling-induced thermal cracking shows how variation in planet size and internal thermal energy may drive variation in the dominant type of hydrothermal system--for example, high or low temperature system or chemically driven system.
As radiogenic heating diminishes over time, progressive exposure of new rock continues to the current epoch. Where fluid-rock interactions propagate slowly into a deep brittle layer, thermal energy from serpentinization may be the primary cause of hydrothermal activity in small ocean planets. We show that the time-varying hydrostatic head of a tidally forced ice shell may drive hydrothermal fluid flow through the seafloor, which can generate moderate but potentially important heat through viscous interaction with the matrix of porous seafloor rock. Considering all presently known potential ocean planets--Mars, a number of icy satellites, Pluto, and other trans-neptunian objects--and applying Earth-like material properties and cooling rates, we find depths of circulation are more than an order of magnitude greater than in Earth.
In Europa and Enceladus, tidal flexing may drive hydrothermal circulation and, in Europa, may generate heat on the same order as present-day radiogenic heat flux at Earth's surface. In all objects, progressive serpentinization generates heat on a globally averaged basis at a fraction of a percent of present-day radiogenic heating and hydrogen is produced at rates between 109 and 1010 molecules cm2 s1.
Hydrogeologic Controls on Episodic H2 Release from Precambrian Fractured Rocks--Energy for Deep Subsurface Life on Earth and Mars
Astrobiology December 2007, 7(6): 971-986
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2006.0096
Dissolved H2 concentrations up to the mM range and H2 levels up to 9-58% by volume in the free gas phase are reported for groundwaters at sites in the Precambrian shields of Canada and Finland. Along with previously reported dissolved H2 concentrations up to 7.4 mM for groundwaters from the Witwatersrand Basin, South Africa, these findings indicate that deep Precambrian Shield fracture waters contain some of the highest levels of dissolved H2 ever reported and represent a potentially important energy-rich environment for subsurface microbial life. The
In Canada and Finland, several of the sites are in Archean greenstone belts characterized by ultramafic rocks that have under-gone serpentinization and may be ancient analogues for serpentinite-hosted gases recently reported at the Lost City Hydrothermal Field and other hydrothermal seafloor deposits. The hydrogeologically isolated nature of these fracture-controlled groundwater systems provides a mechanism whereby the products of water-rock interaction accumulate over geologic timescales, which produces correlations between high H2 levels, abiogenic hydrocarbon signatures, and the high salinities and highly altered
Radiolytic Hydrogen and Microbial Respiration in Subsurface Sediments
Astrobiology December 2007, 7(6): 951-970
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2007.0150
Radiolysis of water may provide a continuous flux of an electron donor (molecular hydrogen) to subsurface microbial communities. We assessed the significance of this process in anoxic marine sediments by comparing calculated radiolytic H2 production rates to estimates of net (organic-fueled) respiration at several Ocean Drilling Program (ODP) Leg 201 sites. Radiolytic H2 yield calculations are based on abundances of radioactive elements (uranium, thorium, and potassium), porosity, grain density, and a model of water radiolysis. Net respiration estimates are based on fluxes of dissolved electron acceptors and their products. Comparison of radiolytic H2 yields and respiration at multiple sites suggests that radiolysis gains importance as an electron donor source as net respiration and organic carbon content decrease.
Our results suggest that radiolytic production of H2 may fuel 10% of the metabolic respiration at the Leg 201 site where organic-fueled respiration is lowest (ODP Site 1231). In sediments with even lower rates of organic-fueled respiration, water radiolysis may be the principal source of electron donors. Marine sedimentary ecosystems may be useful models for non-photosynthetic ecosystems on early Earth and on other planets and moons, such as Mars and Europa.
Geochemical Constraints on Sources of Metabolic Energy for Chemolithoautotrophy in Ultramafic-Hosted Deep-Sea Hydrothermal Systems
Astrobiology December 2007, 7(6): 933-950
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2006.0119
Numerical models are employed to investigate sources of chemical energy for autotrophic microbial metabolism that develop during mixing of oxidized seawater with strongly reduced fluids discharged from ultramafic-hosted hydrothermal systems on the seafloor. Hydrothermal fluids in these systems are highly enriched in H2 and CH4 as a result of alteration of ultramafic rocks (serpentinization) in the subsurface. Based on the availability of chemical energy sources, inferences are made about the likely metabolic diversity, relative abundance, and spatial distribution of microorganisms within ultramafic-hosted systems.
Metabolic reactions involving H2 and CH4, particularly hydrogen oxidation, methanotrophy, sulfate reduction, and methanogenesis, represent the predominant sources of chemical energy during fluid mixing. Owing to chemical gradients that develop from fluid mixing, aerobic metabolisms are likely to predominate in low-temperature environments (<20-30*C), while anaerobes will dominate higher-temperature environments. Overall, aerobic metabolic reactions can supply up to 7 kJ of energy per kilogram of hydrothermal fluid, while anaerobic metabolic reactions can supply about 1 kJ, which is sufficient to support a maximum of 120 mg (dry weight) of primary biomass production by aerobic organisms and 20-30 mg biomass by anaerobes.
The results indicate that ultramafic-hosted systems are capable of supplying about twice as much chemical energy as analogous deep-sea hydrothermal systems hosted in basaltic rocks.
Temporal Changes in Fluid Chemistry and Energy Profiles in the Vulcano Island Hydrothermal System
Astrobiology December 2007, 7(6): 905-932
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2007.0128
In June 2003, the geochemical composition of geothermal fluids was determined at 9 sites in the Vulcano hydrothermal system, including sediment seeps, geothermal wells, and submarine vents. Compositional data were combined with standard state reaction properties to determine the overall Gibbs free energy (
Lithotrophic reactions in the H-O-N-S-C-Fe system were considered, and exergonic reactions yielded up to 120 kJ per mole of electrons transferred. The potential for heterotrophy was characterized by energy yields from the complete oxidation of 6 carboxylic acids-- formic, acetic, propanoic, lactic, pyruvic, and succinic--with the following redox pairs: O2/H2O, SO4 2/H2S, NO3 /NH4 +, S0/H2S, and Fe3O4/Fe2+. Heterotrophic reactions yielded 6-111 kJ/mol e. Energy yields from both lithotrophic and heterotrophic reactions were highly dependent on the terminal electron acceptor (TEA); reactions with O2 yielded the most energy, followed by those with NO3 , Fe(III), SO4 2, and S0. When only reactions with complete TEA reduction were included, the exergonic lithotrophic reactions followed a similar electron tower.
Spatial variability in
A Thermodynamic Analysis of Microbial Growth Experiments
Astrobiology December 2007, 7(6): 891-904
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2006.0118
The common thread of energy release suggests that diverse microbial metabolic processes can be compared through thermodynamic analyses. The resulting energy and power requirements can provide quantitative constraints on habitability. Because previous thermodynamic analyses have focused on the minimum amount of energy needed for the growth of a microorganism or community, the focus of this study is to gain a fuller understanding of the microbial response to highly habitable conditions.
This communication summarizes the results of a thermodynamic analysis of the energy and power consumed by microorganisms in experiments that were designed to optimize growth. Reports of microbial growth experiments taken from the literature were combined with speciation and standard state calculations to assess the overall Gibbs energy change during the experiments.
Results show that similar numbers of cells (109 to 1010 ) were produced in these experiments regardless of the duration of log phase growth (from <2 to >200 hours) or the total Gibbs energy change [from 1.3-29.6 kJ (mol electrons transferred)1]. As a result, optimal growth conditions appear to produce between 1010 and 1014 cells per watt of power consumed.
Formate as an Energy Source for Microbial Metabolism in Chemosynthetic Zones of Hydrothermal Ecosystems
Astrobiology December 2007, 7(6): 873-890
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2007.0127
Formate, a simple organic acid known to support chemotrophic hyperthermophiles, is found in hot springs of varying temperature and pH. However, it is not yet known how metabolic strategies that use formate could contribute to primary productivity in hydrothermal ecosystems. In an effort to provide a quantitative framework for assessing the role of formate metabolism, concentration data for dissolved formate and many other solutes in samples from Yellowstone hot springs were used, together with data for coexisting gas compositions, to evaluate the overall Gibbs energy for many reactions involving formate oxidation or reduction.
The result is the first rigorous thermodynamic assessment of reactions involving formate oxidation to bicarbonate and reduction to methane coupled with various forms of iron, nitrogen, sulfur, hydrogen, and oxygen for hydrothermal ecosystems.
We conclude that there are a limited number of reactions that can yield energy through formate reduction, in contrast to numerous formate oxidation reactions that can yield abundant energy for chemosynthetic microorganisms. Because the energy yields are so high, these results challenge the notion that hydrogen is the primary energy source of chemosynthetic microbes in hydrothermal ecosystems.
Actinides and Life's Origins
Astrobiology December 2007, 7(6): 852-872
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2006.0066
There are growing indications that life began in a radioactive beach environment. A geologic framework for the origin or support of life in a Hadean heavy mineral placer beach has been developed, based on the unique chemical properties of the lower-electronic actinides, which act as nuclear fissile and fertile fuels, radiolytic energy sources, oligomer catalysts, and coordinating ions (along with mineralogically associated lanthanides) for prototypical prebiotic homonuclear and dinuclear metalloenzymes.
A four-factor nuclear reactor model was constructed to estimate how much uranium would have been required to initiate a sustainable fission reaction within a placer beach sand 4.3 billion years ago. It was calculated that about 1-8 weight percent of the sand would have to have been uraninite, depending on the weight percent, uranium enrichment, and quantity of neutron poisons present within the remaining placer minerals.
Radiolysis experiments were conducted with various solvents with the use of uraniumand thorium-rich minerals (metatorbernite and monazite, respectively) as proxies for radioactive beach sand in contact with different carbon, hydrogen, oxygen, and nitrogen reactants. Radiation bombardment ranged in duration of exposure from 3 weeks to 6 months. Low levels of acetonitrile (estimated to be on the order of parts per billion in concentration) were conclusively identified in 2 setups and tentatively indicated in a 3rd by gas chromatography/mass spectrometry. These low levels have been interpreted within the context of a Hadean placer beach prebiotic framework to demonstrate the promise of investigating natural nuclear reactors as power production sites that might have assisted the origins of life on young rocky planets with a sufficiently differentiated crust/mantle structure.
Future investigations are recommended to better quantify the complex relationships between energy release, radioactive grain size, fissionability, reactant phase, phosphorus release, and possible abiotic production of sugars, amino acids, activated phosphorus, prototypical organometallic enzymes, and oligomer catalysts at a single putative beach site.
Quantitative Habitability
Astrobiology December 2007, 7(6): 839-851
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2007.0137 A framework is proposed for a quantitative approach to studying habitability. Considerations of environmental supply and organismal demand of energy lead to the conclusions that power units are most appropriate and that the units for habitability become watts per organism.
Extreme and plush environments are revealed to be on a habitability continuum, and extreme environments can be quantified as those where power supply only barely exceeds demand. Strategies for laboratory and field experiments are outlined that would quantify power supplies, power demands, and habitability. An example involving a comparison of various metabolisms pursued by halophiles is shown to be well on the way to a quantitative habitability analysis.
An Energy Balance Concept for Habitability
Astrobiology December 2007, 7(6): 824-838
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2006.0095
Habitability can be formulated as a balance between the biological demand for energy and the corresponding potential for meeting that demand by transduction of energy from the environment into biological process. The biological demand for energy is manifest in two requirements, analogous to the voltage and power requirements of an electrical device, which must both be met if life is to be supported.
These requirements exhibit discrete (non-zero) minima whose magnitude is set by the biochemistry in question, and they are increased in quantifiable fashion by (i) deviations from biochemically optimal physical and chemical conditions and (ii) energy-expending solutions to problems of resource limitation. The possible rate of energy transduction is constrained by (i) the availability of usable free energy sources in the environment, (ii) limitations on transport of those sources into the cell, (iii) upper limits on the rate at which energy can be stored, transported, and subsequently liberated by biochemical mechanisms (e.g., enzyme saturation effects), and (iv) upper limits imposed by an inability to use "power" and "voltage" at levels that cause material breakdown.
A system is habitable when the realized rate of energy transduction equals or exceeds the biological demand for energy. For systems in which water availability is considered a key aspect of habitability (e.g., Mars), the energy balance construct imposes additional, quantitative constraints that may help to prioritize targets in search-for-life missions. Because the biological need for energy is universal, the energy balance construct also helps to constrain habitability in systems (e.g., those envisioned to use solvents other than water) for which little constraint currently exists.
Astrobiology Science News 1 January 2008
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