NASA Astrobiology Institute (NAI)

Titan First

Robert Shapiro (New York University) and Dirk Schulze-Makuch (Washington State University)

The Titan Saturn System Mission is planned to consist of a NASA orbiter, an ESA lander and a research balloon. Artist's image shows lander on one of Titan's hydrocarbon lakes with Saturn in the background.

We have written a paper “The Search for Alien Life in Our Solar System: Strategies and Priorities” which is now on line http://www.liebertonline.com/toc/ast/0/0 and will soon appear in Issue #4 (2009) of Astrobiology. We argue that Titan should be given the highest priority in the search for existing alien life in our Solar System, followed by Mars and Europa in that order. In setting priorities, we assume that economic constraints may limit existing space agencies to only one new multi-billion dollar planetary exploration mission, comparable to Galileo and Cassini, in the coming decades. We would be happy if our pessimism was unjustified, but still feel that prioritization is worthwhile as a precaution.

In considering our search for understanding of the origin of life, rather than the discovery of alien life, we hold that Titan is again an easy winner. Familiar life on Earth centers on the chemistry of carbon, and we are ignorant about the steps through which an unorganized chemical mixture of the type produced by abiotic organic chemistry can be converted by an energy flow into a metabolizing, reproducing system. We would benefit greatly by learning more about the detailed organic chemistry of our Solar System.

At present, our knowledge of unorganized abiotic mixtures comes almost entirely from meteorites. The study of such mixtures on planetary surfaces would enrich our knowledge of the starting materials from which carbon-based life may be constructed. If we were lucky, we might even encounter a mixture in which some degree of self-organization has taken place. This could occur through novel processes at low temperature, or during episodes in which the surface of Titan has been heated temporarily by a volcanic eruption or meteoric impact.

Titan is rich in organics, and the materials are available at the surface. The plumes and near-surface regions of Enceladus also offer organics, and their exploration could be bundled into a return mission to Titan. Only trace amounts of methane have been confirmed thus far on Mars, and they appear to originate from the deeper interior and thus may be difficult to access. The internal Europan ocean may support life, but it is rather inaccessible, and no carbon compounds have as yet been detected on the surface. Further exploration of Titan therefore deserves the strongest backing from the origin-of-life community.

Comment on Titan First

Andrew Pohorille (NASA-Ames)

Membranous vesicles that self-assemble in water from soap-like molecules extracted from the Murchison carbonaceous meteorite (courtesy of David Deamer). Besides water only very few other liquids have some capabilities to promote the formation of boundary structures.

In their recent, interesting paper, Robert Shapiro and Dirk Schulze-Makuch argue that Titan is the best target to search for indigenous alien life. The essence of their argument is that the environment on Titan is particularly conducive to rich organic, carbon-based chemistry. I agree that this, indeed, appears to be the case. Abundance of organic compounds, however, does not imply the existence of life or even a possibility of the emergence of life.

To become animated, organic matter has to separate itself from the environment and self-organize into functional structures capable of responding to environmental changes and self-reproduction. These processes are largely driven by non-covalent interactions. Folded proteins, membranes forming cell walls and the DNA double helix are examples of structures stabilized by such interactions. Non-covalent interactions might be either specific (enzyme-substrate interactions, selective ion transport) or nonspecific (lipid-lipid and lipid-protein interactions needed for membrane integrity, fusion and division). Their strength needs to be properly tuned. If they are too weak, there might be undesired response to natural fluctuations of physical and chemical parameters. If they are too strong it could impede kinetics and energetics of life processes.

Strength of non-covalent interactions depends critically on the solvent. Among different solvents, water plays a special role not only because it is the solvent for the only life that we know, but also because it exhibits a number of traits that in combination make it uniquely suited to promote self-organization of organic matter. For example, strong electrostatic interactions between polar or charged molecules are reduced in polar liquids, such as water, compared to those in the gas phase or non-polar liquids, such that they become well balanced with other non-covalent interactions. Furthermore, water exhibits a remarkable trait of promoting hydrophobic interactions between non-polar molecules or groups rich in hydrocarbons. In biology, these interactions are responsible, for example, for self-organization of cell walls, and protein folding and aggregation. Hydrophobic interactions provide a unique mechanism for separating polar and non-polar organic material that is critical to many functions of living systems.

Currently, there is no convincing evidence for the existence of water on Titan. There is also very little evidence that other solvents that might exist on Titan can promote the self-organizing processes leading to the emergence of life. Until one of those two possibilities is demonstrated we should exercise caution in advocating an expensive mission to search for life on Titan.

Membranous vesicles that self-assemble in water from soap-like molecules extracted from the Murchison carbonaceous meteorite (courtesy of David Deamer). Besides water only very few other liquids have some capabilities to promote the formation of boundary structures.

Program Solicitation in Sedimentary Geology and Paleobiology

The National Science Foundation (NSF) has released a program solicitation for research in sedimentary geology and paleobiology. The program focuses on numerous areas of research that are significant to the science of astrobiology. Among the topics of interest cited by the NSF are: the use of fossils, plants, animals and microbes to study how life has changed over geologic time; the science of dating and measuring time and rates of processes in the Earth’s sedimentary and biological fossil record; and studying the pre-Holocene climate systems of Earth. Proposals that seek to link multiple disciplines such as paleoclimatology, paleoenvironments and paleoecology are encouraged, as are those that integrate studies at national and international levels.

Studying how our planet and the biosphere are interconnected and how these connections have shaped the evolution of life are important goals of astrobiology. Studying the ancient climate of our planet can yield clues about how life establishes itself on terrestrial planets, and can ultimately help astrobiologists understand the potential for life in the Universe.

For submission guidelines and additional information on the Sedimentary Geology and Paleobiology program, see: http://www.nsf.gov/funding/pgm_summ.jsp?pims_id=13691

Source: [NSF]

NAI Team Seminars Recorded and Available Online

May 8, 2009 / Posted by: Marco Boldt

A series of virtual seminars highlighting the work of the NAI’s fourteen teams concluded on April 27, 2009. In successive seminars held two per week over a period of two months, each team presented their science, education and outreach and other activities. The seminars were open to all, and participants had the option of joining in by phone and web, or by videoconference. The seminars attracted audiences that ranged from ~50-80 people each, and were recorded and archived on the NAI website. The seminars may be downloaded as podcasts or viewed as web recordings that play in a browser.

Source: [Link]

Outer Space Oreos

May 7, 2009 / Written by: Michael Schirber

Scientists have previously exposed organisms and biomolecules to the many rigors of space, but those experiments only managed to take “before” and “after” pictures of their samples. A planned small satellite will monitor on a continuous basis the negative effects of space on biology. The upcoming O/OREOS mission will be the first demonstration flight of the ASTID small payloads initiative.

Source: [Astrobiology Magazine]

NAI Ames Research Center Team Launches New Website

May 4, 2009 / Posted by: Marco Boldt

The NAI Ames Research Center Team announces the launch of their new website at http://www.amesteam.arc.nasa.gov. The site contains news, highlights, a member directory, research overviews, E/PO information and more.

Darwin in a Test Tube

May 1, 2009 / Posted by: Aaron Gronstal

Scientists at the Scripps Research Institute have discovered a way to make molecules evolve and compete according to the laws of Darwinian evolution. Using RNA, the researchers were able to demonstrate that only the fittest molecules survived in the presence of a limited resource. When resources were plentiful, molecules would become increasingly specialized through generations of replication.

This fascinating work is helping astrobiologists better understand the processes that underlie evolution. Additionally, the results could shed some light on how primitive molecules on Earth first gave live to living organisms.

The work was funded through NASA’s Exobiology & Evolutionary Biology program.

Source: [Astrobiology Magazine]

Reflections of Chirality as a Possible Biomarker

April 30, 2009 / Posted by: Daniella Scalice

Scientists have come up with a novel way to detect life on other planets. Rather than try to measure the composition of atmospheres, they want to look at the chirality of light coming from the planet. “If the [planet’s] surface had just a collection of random chiral molecules, half would go left, half right,” says author T.A. Germer of the National Institute of Standards and Technology. “But life’s self-assembly means they all would go one way. It’s hard to imagine a planet’s surface exhibiting handedness without the presence of self assembly, which is an essential component of life.” And they have already built a working model: because chiral molecules reflect light in a way that indicates their handedness, the research team built a device to shine light on plant leaves and bacteria, and then detect the polarized reflections from the organisms’ chlorophyll from a short distance away. The device detected chirality from both sources. Their paper is published in a recent issue of the Journal of Quantitative Spectroscopy and Radiative Transfer.

Student Astronomers Earn Top Honors in State Science Fair

April 28, 2009 / Posted by: Daniella Scalice

NAI’s University of Hawai’i Team has conducted the Hawai’i Student-Teacher Astronomy Research (HI STAR) program for the past four years and counting, supporting middle and high school students to carry-out astronomy research projects under the mentorship of NAI scientists and other astronomers. Teams of 3-4 students and their science teacher come to UH for a week in the summer for background training, project selection, and mentor-matching. Through lectures, demos, and hands-on activities, the students learn astronomical concepts such as spectroscopy, image processing, and remote observation. Projects are selected, and students make plans with their mentors to conduct their research throughout the school year.

This year, three students who participated in HI STAR 2008 entered their projects into the 2009 Hawai’i State Science and Engineering Fair, and took home top honors. Ninth grader Travis Le garnered third place in the Senior Research category for his extra-solar planet project, “WASP 2-b Or Not Just 2-b.” And eighth graders Kira Fox and Gina Hyun took home second place in the Junior Research category for their asteroid project “1270 Datura.” Both projects earned other local awards as well, including The American Association of Physics Teacher’s Paul Hewitt Award, and awards from the NASA Pacific Regional Planetary Data Center, the American Public Works Association, and Sigma Xi. Travis will go on to enter his project in the INTEL International Science and Engineering Fair. He has earned a special invitation from the University of Hawai’i Institute for Astronomy to tour the Mauna Kea Observatory, but must wait until he is 16 years old to make the trip, and will tour the Haleakala Observatory in the meantime.

Reanimating Extinct Genes

April 27, 2009 / Written by: Michael Schirber

Can evolution be played over again in the lab? A group of researchers plans to insert an ancient gene in a modern day bacteria and see if this gene will mutate back to its current-day form. The results will give insight into how unique the evolutionary path may be.

Source: [Astrobiology Magazine]