Welcome to the NAI Newsletter! The Newsletter is a compendium of announcements, events, updates, and news items related to the NAI and its research. If you have news items or suggestions you can send them to the editor, Marco Boldt at: Marco.Boldt@nasa.gov.
Newsletter for January 4, 2007
- Director's Corner
- NAI Director's Seminar 1/29: Radiolysis of water as a source of bioavailable energy in the subsurface of Earth and Mars
- Science Mission Directorate Space Missions Briefing: Presentations and Podcasts Available
- Low Abundance Acidophilic Archea Revealed
- Snowball Earth and the Origin of Photosynthesis
- Found: A Hyperthermophilic Nitrogen Fixer
- Stardust Sample Analysis
Director's Corner
One of the most enjoyable responsibilities of being the NAI Director is staying on top of (or at least trying to!) all the great research done by NAI members and their colleagues. In just the last few months several major results were published by NAI members, in at least one case involving multiple NAI teams. Two of these studies were presented in Director’s seminars (high resolution podcasts available at http://nai.arc.nasa.gov/seminars/index.cfm) and a third will be in late January.
The first of the Director’s seminars was presented by NAI Postdoc Julie Huber. She reported on research by Mitch Sogin’s Marine Biological Laboratory NAI team that charted, for the first time, the underexplored “rare biosphere” of the deep oceans. It has been recognized for some time that the oceans harbor much more phylogenetic diversity than is present in the dominant microbial populations, and that this “genetic reservoir” may provide an enormous source of novel genetic information. Using a new high-throughput genetic sequencing technique, Mitch, Julie, and colleagues showed that there are thousands to tens of thousands of bacterial species present at abundances perhaps as low as a few per liter of seawater, in comparison to cumulative abundances of the dominant species of 108-109 per liter. The high degree of genetic diversity in this rare population indicates that it is old on evolutionary (and geologic) time scales.
One implication of these conclusions is that rare organisms could rapidly become dominant if a change in environmental conditions favored them over the then dominant population. Such changes in environmental conditions may have occurred globally in the geologic past, for example during “Snowball Earth” episodes when it appears that Earth was ice-covered to low latitudes, and can occur locally or regionally today in response to subsea volcanic eruptions, hurricanes, and other natural processes. The diversity and potential of this rare biosphere thus links the evolutionary timescales of interest to astrobiology with the much shorter timescales of interest to NASA’s Earth science program which focuses on understanding the Earth system’s response to natural or human-induced changes. Further, the techniques developed to characterize the rare biosphere are applicable to the detection of low abundance organisms on spacecraft we send to other planets to study habitable environments or search for evidence of life. This research thus illustrates how astrobiology can, and does, connect different aspects of NASA’s programs while advancing in fundamental ways our understanding of life on Earth.
A second discovery about Earth’s microbial ecosystems has direct implications for the potential of extraterrestrial environments to harbor life. The Indiana-Princeton-Tennessee NAI team (IPTAI) led by Lisa Pratt of Indiana University and T.C. Onstott of Princeton University has discovered an isolated microbial community nearly two miles underground that appears to derive all its energy from radioactive decay rather than directly or indirectly from sunlight. In this case radioactive decay leads to the decomposition of water into hydrogen and oxidants that convert naturally occurring sulfide minerals to sulfate. The dominant microbial species in this ecosystem then reduces the sulfate using the hydrogen as an electron donor, reforming water in the process. Isotopic noble gas analyses of the ecosystem’s bulk water indicate that it has been completely isolated from surface processes for millions to tens of millions of years.
The ecosystem thus appears able to maintain itself completely independently of sunlight. If indeed strictly geological processes such as radioactive decay and geochemical oxidation can sustain microbial communities indefinitely, then subsurface environments on Mars and other rocky planets could potentially sustain life even though they lack a surface photosynthetic biosphere. Lisa and TC will present this research in the next Director’s seminar on January 29 (see the announcement elsewhere in this newsletter).
Finally, another NAI Postdoc and an NAI-supported graduate student working with a more senior team member have demonstrated that extrasolar planetary systems with “hot Jupiters,” i.e., Jupiter-size planets close to their parent stars, may also contain terrestrial planets in the habitable zone where liquid water can exist on a planet’s surface. This conclusion is somewhat surprising because hot Jupiters most likely formed much farther from their parent stars, in the cold outer regions of a proto-planetary disk, and then migrated inward through the habitable zone to the orbit in which we observe them. Some earlier studies had indicated that this migration would prevent the formation of terrestrial planets.
Postdoc Sean Raymond, graduate student Avi Mandell, and Steinn Sigurdsson modeled terrestrial planet growth during and after giant planet migration. They found that, in general, terrestrial planets can form in the “wake” of an inward migrating giant planet, and that terrestrial planets can form in the habitable zone when the final giant planet orbit is inside ~0.5 AU. Further, if there is not an additional giant planet that remains at several AU to gravitationally scatter icy planetesimals from the outer regions of the disk, then those icy bodies arrive at the habitable zone planet in great number, leading potentially to the formation of an “ocean world.” This work, which involved the NAI teams at the University of Colorado, Pennsylvania State University, the NASA Goddard Space Flight Center, and the Virtual Planetary Laboratory, indicates that a third of the roughly 200 known extrasolar planetary systems may contain a habitable zone terrestrial planet. This study and others to follow will help us prepare to interpret data from NASA’s Kepler mission, scheduled to launch in 2008, which will study planetary system architectures with the goal of identifying systems with habitable zone terrestrial planets.
These studies illustrate just a few of the ways that astrobiology provides an overarching framework for much of NASA science. Other connections are being made between field research, laboratory studies, and space missions. Check our website frequently for other research highlights (http://nai.arc.nasa.gov), continue reading our electronic newsletter for the latest results (available through the website or by sending a request to mboldt@arc.nasa.gov to be added to the distribution list), and participate in our electronic seminars or download the podcasts afterward. There’s lots more to come!
NAI Director's Seminar 1/29: Radiolysis of water as a source of bioavailable energy in the subsurface of Earth and Mars
Speakers: Lisa Pratt (Indiana University) and T.C. Onstott (Princeton University)
Date/Time: Monday, January 29, 2007 11AM PST
Abstract:
An NAI research team has discovered an isolated community of bacteria nearly two miles underground that derives all of its energy from the decay of radioactive rocks rather than from sunlight. The finding suggests life might exist in similarly extreme conditions on other worlds. The self-sustaining bacterial community, which thrives in nutrient-rich groundwater found near a South African gold mine, has been isolated from the Earth's surface for several million years. It represents the first group of microbes known to depend exclusively on geologically produced hydrogen and sulfur compounds for nourishment. The extreme conditions under which the bacteria live bear a resemblance to those of early Earth, potentially offering insights into the nature of organisms that lived long before our planet had an oxygen atmosphere.
For more information and participation instructions, visit: http://nai.arc.nasa.gov/seminars/seminar_detail.cfm?ID=96
Science Mission Directorate Space Missions Briefing: Presentations and Podcasts Available
Presentations were given by videoconference and WebEx to the teams of the NASA Astrobiology Institute (NAI) on December 1, 2006. The presenters were senior officials of the Science Mission Directorate (SMD) at NASA Headquarters. The briefings cover the SMD Science Plan and the programs, particularly the flight programs, of the Planetary Science, Astrophysics, and Earth Science Divisions. Because of its scope and importance to astrobiology, a special presentation on the Mars Exploration Program was given as part of the Planetary Science Division programs.
Download the slides or view the podcasts here: http://nai.arc.nasa.gov/smdbriefing/
Recently Published Research from the NAI
Low Abundance Acidophilic Archea Revealed
Scientists from NAI's University of California, Berkeley Team report in this week's Science on their use of shotgun sequencing to uncover three novel archea present in all biofilms growing in pH 0.5 to 1.5 solutions within the Richmond Mine, California. Their results inform the problem of characterizing microbial communities and lineages which are difficult to cultivate.
Snowball Earth and the Origin of Photosynthesis
Using atmospheric chemical models of a Snowball Earth, scientists from NAI's Alumni Virtual Planetary Laboratory Team show that, during long and severe glacial intervals, a weak hydrological cycle coupled with photochemical reactions involving water vapor would give rise to the sustained production of hydrogen peroxide. The peroxide, upon release from melting ice into the oceans and atmosphere at the end of the snowball event, could mediate global oxidation events. Their results are published in the December 12th issue of PNAS.
Found: A Hyperthermophilic Nitrogen Fixer
Researchers from NAI's Carnegie Institution of Washington Team have published in Science their findings of a novel archaeon who's ability to fix nitrogen at 92 degrees Celcius has officially increased the upper limit of biological nitrogen fixation by 28 degrees Celcius. The hyperthermophilic methanogen was isolated from a hydrothermal vent. Thier findings could reveal a broader range of conditions for life in the subseafloor biosphere.
Stardust Sample Analysis
A special issue of Science (Dec 15) includes several papers reporting on various aspects of Stardust sample analysis including an organics survey, isotopic and elemental compositions, mineralogy and petrology, and infrared spectroscopy. Many NAI researchers contributed to this comprehensive analytical campaign, including members of NAI's Teams at the Carnegie Institution of Washington, NASA's Ames Research Center and Goddard Space Flight Center, and NAI's Alumni Team at the University of Washington.
Astrobiology EPO, Undergrads, Grads, Postdocs
2007 REU (Research Experiences for Undergraduates) Accepting Applications
The SETI Institute is pleased to announce that applications are now open for the 2007 REU (Research Experiences for Undergraduates) program in Astrobiology. Undergraduate students in fields such as astronomy, biology, geology, 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 2, 2007. For more information, visit http://www.seti.org/reu or contact Cynthia Phillips, phillips@seti.org, 650-810-0230.
A program poster can be downloaded from: http://www.seti.org/reuposter
Bioastronomy 2007: Molecules, Microbes, and Extraterrestrial Life
San Juan, Puerto Rico
July 16-20,2007
http://www.ifa.hawaii.edu/UHNAI/bioast07.htm
Early registration deadline: January 15, 2007
Abstract / travel support deadline: February 15, 2007
This meeting is the ninth meeting in a series of meetings that have been organized by the International Astronomical Union's Commission 51 on Bioastronomy. The series of Bioastronomy meetings have played an important role in integrating the broader interests and techniques of both astronomy and biology to understand the origin and evolution of our solar system, and of living systems in the universe. The theme of the 2007 meeting, "Molecules, Microbes and Extraterrestrial Life", deals with topics relevant both to solar system origins as well as to the origin of life.
