Is Mars Alive?

Mark Allen, Barbara Sherwood Lollar, Bruce Runnegar, Dorothy Z. Oehler, James R. Lyons, Craig E. Manning, and Michael E. Summers

Mars long has been considered to be a cold, dead planet. However, recent reports of methane in the Martian atmosphere suggest that methane is being produced at present, since its calculated atmospheric lifetime of 400 years or less requires a constant re-supply. Possible subsurface sources for this re-supply are geological, or even microbiological, in nature. So, the question is: Is Mars alive, biologically or geologically speaking? There are several different processes on Earth--both biogenic and abiogenic--that form methane at rates that can contribute to a detectable atmospheric presence. Techniques used to characterize these various terrestrial sources can guide planning for future Martian investigations and missions.

Polar Crater Deposits as a Probe for Ancient Climate Change on Mars

John Armstrong

Dynamical studies of the Martian orbit suggest a planet that has undergone extreme orbital change. How has this affected the planet's climate? Is there a record of this orbit-induced climate change written in the geology that is expressed on the surface? If so, such a record would provide insight into Mars' climate history, and shed light on the types of habitats for life that may have existed in the past. We are exploring how the current seasonal polar caps interact with polar craters in an effort to identify modification that can be linked to the proximity of the polar cap. Ice deposits within the craters are evident in both thermal spectra and imagery from Mars orbiters. We have linked these ice deposits to morphological deposits that can be identified in other craters that are further from the pole. These deposits may act as a probe of the variations suggested by orbital calculations, as well as provide an indicator of the extent of the sub-surface ice table. We will present preliminary results from a sample of northern craters, and explain how this can be extended to southern craters, and possibly mid-latitude craters, in an effort to understand more fully the martian climate through time.

Methanogenesis in hypersaline environments: microbial ecology, rates, and isotopic composition

Brad Bebout

Methane is an important candidate biosignature gas, both for remote detection of life on extrasolar planets and for robotic and manned missions within our own solar system (where it may be possible to obtain the isotopic signature of the methane). The recent reports of hypersaline paleo-environments on Mars, as well as measurements of methane in that planet's atmosphere, have underscored the need to evaluate the importance of biological (as opposed to geological) methane production and consumption, including the isotopic signatures of these processes in hypersaline environments. We studied methane cycling in microbial mats (analogous to mats present on the early Earth at a period of time when Mars was experiencing similar environmental conditions) located in the Guerrero Negro hypersaline ecosystem, Baja California Sur, Mexico. We extracted methane from pore waters of microbial mats, and the isotopic signature of this methane was characteristic of biologically produced methane (ca. -70 per mil to -50 per mil). Bubbles of gas present in the evaporite deposits at higher salinities, where microbial mat growth was very much reduced, still contained relatively high concentrations of methane (generally a few percent by volume). The isotopic composition of this bubble methane, however, was quite enriched in 13C (ca. -35 to -25 per mil), and falls out of the range of values generally considered to be biogenic, unless oxidation has occurred. A molecular survey of methanogenic functional genes (methyl coenzyme M reductase) in this environment suggests methylotrophy (cleavage of methyl groups from organic compounds) as the dominiant methanogenic pathway, rather than hydrogenotrophy (reduction of carbon dioxide). These measurements demonstrate the potentially complicated task of determining biogenicity of methane within a single environment. Further work is needed to characterize the isotopic signature of biogenic methane acted upon by biological and chemical oxidation in these environments.

The Search for Life in the Universe

Robert Bonadurer

This stimulating new planetarium show will showcase the key role stars play in the evolution of planets and their suitability for life. Funded from an Educational Public Outreach (EPO) grant from the NASA FUSE telescope, The Planetarium at UT Arlington will produce Stellar Detectives: The Search for Life in the Universe. It will open in March 2007. The show will start with the best and only star and life planet relationship we know—the Sun and Earth. Then, the seven stellar classifications based on luminosity—OBAFGKM—will be introduced. Next, we'll explore possible interactions between extra solar planets and the various stars. More specifically, the show will be focus on the human and scientific story behind the FUSE research grant on "K stars and their impacts on exoplanetary environments." Our goal is to have planetarium visitors better understand the possibilities of life elsewhere in the universe. Stellar Detectives: The Search for Life in the Universe will be distributed to planetariums and science teachers nationwide.

Looking for "cosmic archaeology"; a search for Dyson Spheres

Richard Carrigan

Searching for stellar-scale archaeological artifacts like Dyson Spheres (DS) or Kardashev civilizations is an interesting alternative to conventional SETI searches since these artifacts do not posit the transmission of a signal. Dyson Spheres are hypothetical stars purposely shrouded by a thick swarm of broken-up planetary material to better utilize all of the solar energy. A number of searches have been carried out for both partial and fully shrouded DS. I have conducted a search using the IRAS data base. The search has now been extended by loosening the constraints and making use of the Calgary data collection of IRAS low resolution spectrometer data to look for fits to black body spectra. Several complications emerge when a more comprehensive search is undertaken. One problem is that less luminous objects will have poorer fits but may still be DS candidates. Likewise partial DS cannot be ruled out so that the presence of a visible or near infrared signature cannot eliminate an object as a type of DS. Another question is raised by the presence of various silicon features in the spectra since these might be left over in the creation of the DS. These loosening constraints let several different natural stellar source types through the search net. Results on the broadened search will be reported. Similar considerations may also challenge other searches like Kardashev searches. As noted by several investigators these factors may indicate that definitive searches will require more sophistication such as the use of better spectroscopy and radio astronomy. On the positive side there is increasing understanding of the spectroscopy of some of the natural source types so that future studies may be able to better separate natural and artificial objects.

Inquiries on habitability: the chemical environment of star forming regions

Marcela Ewert Sarmiento

The presence of a planet is a key parameter to define habitability. However, our understanding of habitability may be shaped by the hypothesis of an exogen delivery of prebiotic material. Such hypothesis postulates that volatiles and organic precursors for life on Earth did not necessarily arise on our planet but were brought -at least partially- by comets, early in Earth's history. In a similar way, extrasolar planetary systems might receive volatiles and organic material originated in their parental cloud. Hence, any approximation towards the characterization of habitable regions should take into account pre-stellar environments which might define the future chemical environment of planetary surfaces. As a first approach, current information on the chemical environment of star forming regions has been compiled, through the assembly of a database with reported molecular abundances of low and high mass star forming regions. A preliminary analysis of collected information is shown.

Habitable planet formation in binary star systems

Nader Haghighipour

Among the currently known extrasolar planet-hosting stars, the three systems of Gamma Cephei, GJ 86, and HD188753 contain a Jupiter-like planet and a stellar companion on a moderately close (<20 AU) orbit. Recent studies have shown that such binary-planetary systems, in addition to their giant planets, can also harbor terrestrial bodies (Haghighipour 2006). In this paper, we present the results of dynamical simulations of terrestrial planet formation in such binary-planetary systems and discuss conditions under which Earth-like planets, with substantial amount of water, can form in the habitable zones of their hosting stars. We consider a model that consists of a disk of Moon- to Mars-sized objects, extended from 0.5 to 4 AU, and a Jupiter-mass planet at a location exterior to the disk. We assume that the embryos beyond 2.5 AU contain water and explore the effects of the separation and orbital eccentricity of the binary companion on the formation and water content of terrestrial planets in the habitable zone of the primary star. Simulations indicate that it is indeed possible to form Earth-like planets in such environments. The results also indicate that, as shown by Chambers & Cassen (2002) and by Raymond, Quinn & Lunine (2004), the most important factor in the formation of terrestrial planets and their water contents is the orbital eccentricity of the system's Jupiter-mass object. The Jovian planet's eccentricity is excited by the binary companion, thereby exciting and often ejecting nearby embryos. We present the results of our simulations, and discuss the possibility of life in such dynamically complex systems.

Teaching Astrobiology: A Portfolio Approach

Chris Impey

As an interdisciplinary science, astrobiology presents a unique context in which to teach undergraduate non-science majors to critically think about science. This poster describes an innovative mode of assessment implemented in a large-lecture, undergraduate astrobiology course for non-science majors that strongly promotes students' abilities to evaluate scientific evidence, make scientific arguments, and gain a deeper appreciation for the subtleties associated with "the scientific method". A small team of scientists, science educators, and instructional technologists collaborated to implement a unique method of portfolio assessment in this class of over 100 students. Students in the class were not assessed using traditional materials, such as homework, quizzes, and exams, but were assessed based on a portfolio representing the students' best work. These portfolios consisted of a breadth of activities and assignments ranging from museum exhibits about astrobiology to analysis of real astrobiology data to detailed critiques of authentic scientific papers. In addition, students were allowed to personalize this part of the course by choosing portfolio pieces in a single discipline (e.g. biology, geology, astronomy). This poster discusses the challenges, rewards, and practicality of implementing this type of assessment in the large lecture environment.

The Terrestrial Planets Formation in the Solar-System Analogs

Ji Jianghui

We numerically studied the terrestrial planets formation in the Solar-Systems Analogs using MERCURY (Chambers 1999). The Solar-System Analogs are herein defined as a solar-system like planetary system, where the system consists of two wide-separated Jupiter-like planets (e.g., 47 UMa, Ji et al. 2005) move about the central star on nearly circular orbits with low inclinations, then low-mass terrestrial planets can be formed there, and life would be possibly evolved and developed. We further explored the terrestrial planets formation due to the current uncertainties of the eccentricities for two giant planets. In addition, we studied the evolution and formation of the planetesimals or planetary embryos in such systems to investigate the potential asteroidal structure and habitable zones. We showed that the secular resonances and mean motion resonances can play an important role in shaping the asteroidal structure. We acknowledge the financial support by National Natural Science Foundation of China (Grant No.10573040, 10233020, 10203005) and Foundation of Minor Planets of Purple Mountain Observatory.

Spectral Evolution Of An Earth-Like Planet

Lisa Kaltenegger (CfA), K. Jucks K.(CfA), Traub W. (JPL, CfA)

We have developed a characterization of the geological evolution of the Earth's atmosphere and surface in order to model the observable spectra of an Earth-like planet through its geological history. These calculations are designed to guide the interpretation of an observed spectrum of such a planet by future instruments that have the goal of observing extra-solar planets. Our models focus on the variations in important parameters that either imply habitability or are required for habitability. These parameters include H2O, CO2, CH4, O2, O3, N2O, and vegetation-like surface albedos. We chose six appropriate geological time periods to characterize which have a wide range in abundance for these molecules, ranging from a CO2 rich early atmosphere to a CO2/CH4-rich atmosphere around 2 billion years ago to a present-day atmosphere. We analyzed the spectra to quantify the strength of each important spectral feature in both the thermal infrared and visible spectral regions and the resolution required to unambiguously observe the features for each of the chosen time periods. Because of the wide range in abundance for these important molecules, we observe a wide range the strengths of the primary spectral features. We also see a wide range of spectral resolutions required for observing the different features. Molecules like H2O and O3 can be observed with relatively low resolution, while molecules like O2 and N2O require higher resolution. We also find that the inclusion of clouds in our models significantly affects both the strengths and resolutions required to observe molecular spectral features.

Titan: an "all-tropics" climate

Jonathan Mitchell

Titan, in many ways, is a close cousin to Earth. Like Earth, Titan's atmosphere is thick, and composed mostly of molecular nitrogen. Although Titan is much colder than Earth, with surface temperatures around 100 K, it appears to have a similarly active meteorology with intense methane storms which weather the surface. Titan's orbit around Saturn is inclined to the ecliptic, which gives its seasonal cycle comparable amplitude to Earth's. A further comparison can be made to the very young Earth, when it is thought methane may have existed in the atmosphere at higher abundances and provided an important thermostat that helped the Earth avoid a permanent, life- inhibiting freeze-out. But Titan is unique from Earth in many respects. It has about 1/3 the diameter of Earth, its diurnal cycle is 16 times longer, the solar forcing is ~100 times weaker, it's solid surface has much lower thermal inertia than the open oceans, and the seasonal cycle is 30 times longer; each of these physical parameters are known to be strong controls on the dynamics and seasonality of an atmosphere. Furthermore, the supply of methane from the surface is unconstrained by observations and methane condensation by convection is poorly understood; these mechanisms contribute strongly to thermodynamic controls on Titan's climate. These unique characteristics of Titan determine the interesting distribution and seasonality of its cloud features, which have only been observed in the summer hemisphere and primarily directly at the summer pole. Understanding the mechanisms that control the climate of Titan provide insight into what habitable worlds in different environments could be like. I will summarize our current understanding of the seasonal response of Titan's atmosphere, which can be best classified as a new category of planetary climate: an "all-tropics" climate.

Cosmic Vision 2015-2025: Search for Habitable Planets

Andreas Quirrenbach

Searching for habitable planets is one of the main goals of Cosmic Vision 2015-2025, the strategic plan for space science of the European Space Agency (ESA). In the middle of the next decade, GAIA will perform a complete census of giant planets in the Solar neighborhood. The NASA missions Kepler and SIM will likely have found the first twins of our Earth. Building on these missions, ESA intends to search for habitable planets, and to characterize their atmospheres spectroscopically. The DARWIN mission concept, a free-flying mid-infrared interferometer, is being developed to address these scientific goals. It will survey a sizeable sample of nearby stars (at least ~150) with a sensitivity and observing strategy adequate for detecting most Earth-like planets in their habitable zones. The detection of carbon dioxide, ozone, and water in a subset of these will be possible.

Habitable planetary systems (un)like our own: Which of the known extra-solar systems could harbor Earth-like planets?

Sean Raymond

Gas giant planets are far easier than terrestrial planets to detect around other stars, and are thought to form much more quickly than terrestrial planets. Thus, in systems with giant planets, the final stages of terrestrial planet formation are strongly affected by the giant planets' dynamical presence. Observations of giant planet orbits may therefore constrain the systems that can harbor potentially habitable, Earth—like planets. We combine two recent studies and establish rough inner and outer limits for the giant planet orbits that allow terrestrial planets of at least 0.3 Earth masses to form in the habitable zone (HZ). For a star like the Sun, potentially habitable planets can form in systems with relatively low—eccentricity giant planets inside 0.5 Astronomical Units (AU) or outside 2.5 AU. More than one third of the currently known giant planet systems could harbor a habitable planet.

The many faces of Earth

Enric Palle, P. Montañés-Rodríguez

Big Bear Solar Observatory, New Jersey Institute of Technology, Big Bear City, CA, 92314, USA

If we were to observe the Earth as an extrasolar planet, the portion of the planet reflecting starlight toward us would change depending on the viewpoint of our observatory. Here we have modeled the changes in the Earth.s albedo as a function of its phase angle, and in the direction of the observer.s. The reflectance models used here have been previously validated by simulating the Earth.s reflectance as seen from the Moon (the earthshine). Real cloud data from satellite observations is inputted for each day and allows us to characterize the hourly, diurnal, and seasonal variability that we might observed in earth-like extrasolar planets

Spectroscopy of the Earth observed as a distant planet

Pilar Montanes-Rodriguez, Enric Palle

Since the discovery of the first planet outside the solar system, the number of planet detections is increasing exponentially. Although we have not been capable of detecting and exploring planets like our own yet, challenging space missions are already being planned for the next decades, and the discovery of earth-like planets is only a matter of time. When the time arrives, one of our main concerns will be to determine their degree of similarity with our own planet, and to answer a more intriguing question for the humankind: if there is life on them. An indication of complex life is the vegetation's red edge. Using real cloud cover observations from satellite, we have unequivocally detected the vegetation's signature in the Earth's globally-integrated spectrum. The signature is stronger when large vegetated regions of the Earth are seen free of clouds. Our results show that, considering the real cloud cover present in our planet, previous estimates of the vegetation signal strength were over-optimistic.

None So Rare

Steinn Sigurdsson

Planets have been found in extreme systems; we have found planets where detection techniques have the requisite sensitivity. New theoretical modeling suggests that habitable terrestrial planets may be found in many of the already known "hot Jovian" systems, with protoplanetary cores surviving the migration phase and re-assembling into water rich terrestrial planets in the habitable zone outside the orbit of the giant planets.

Earths are likely to be common, not rare, and we should anticipate a very wide range of possible planetary systems and sites for life to start and evolve.

Ancient Earths: Glimpses Into Other Habitable Worlds

Linda Sohl

No investigation of the potential habitability of terrestrial planets can ignore the one planet we know to have been habitable through much of its lifespan: our own Earth. Careful consideration of Earth's history reveals that it has passed through multiple distinct phases of habitability, with each phase being an external expression of biological and environmental feedbacks, internal forcing mechanisms ( e.g., mantle outgassing of greenhouse gases), and external forcings (e.g., solar luminosity and spectral variability), all of which were evolving, although not necessarily in conjunction with each other, over geologic time. This review of the past shows a range of "alternate" habitable Earths, each with a distinctive combination of environmental conditions and dominant forms of life. In essence, we can follow the effects of the interplay between evolving life and evolving surface conditions on Earth. The distinction between phases of habitability extends to the spectral realm, an important consideration in the present and future searches for habitable worlds.

We plan to explore that concept of alternate habitable Earths by examining the paleoclimate of certain key intervals, from the earliest Earth and prebiotic conditions, up to the establishment of "modern" climates and biogeochemical cycles in the Paleozoic Era (circa 400 Ma). Our tool for simulating these paleoclimate intervals is a version of the NASA/GISS Global Climate Model (GCM), which is capable of reproducing the full range of climatic processes and feedbacks and includes explicit representations of both dynamical and hydrological physics. These simulations will not only provide us with a bridge to understanding some of the more extreme paleoclimates that existed earlier in Earth history, but also perhaps expand the range of habitable Earth-like planets we might expect to find elsewhere in the universe.

Spectroscopy of the Earth observed as a distant planet

W. B. Sparks(1,6), F. Chen(2,6), S. DasSarma(2,6) , T. Germer(3), J. H. Hough(4), T. Gledhill(4), N. Manset(5), I.N. Reid(1,6)

All life is made of molecules with a unique handedness that may offer a powerful remote sensing opportunity using polarization of light. Living organisms almost exclusively use L-amino acids and D-sugars. This homochirality may imprint itself on light interacting with organisms as circular polarization and hence offer a means to remotely sense living material. Development of a successful remote sensing capability for living matter would be tremendously important for exploration of the Solar System, for Mars and Europa orbiters and site selection on Mars and the outer Solar System moons. For TPF and life-finder investigations beyond our Solar System, remote sensing is a necessity and this approach may be our best hope for life detection.

Structure and Evolution of Nearby Stars with Planets. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog

Genya Takeda

We derive detailed theoretical models for 1074 nearby stars from the SPOCS (Spectroscopic Properties of Cool Stars) Catalog. The California and Carnegie Planet Search has obtained high-quality (R ~ 70000-90000, S/N ~ 3-500) echelle spectra of over 1000 nearby stars taken with the Hamilton spectrograph at Lick Observatory, the HIRES spectrograph at Keck, and UCLES at the Anglo Australian Observatory. A uniform analysis of the high-resolution spectra has yielded precise stellar parameters (effective temperature, surface gravity, stellar rotation, metallicity and individual elemental abundances for Fe, Ni, Si, Na, and Ti), enabling systematic error analyses and accurate theoretical stellar modeling. We have created a large database of theoretical stellar evolution tracks using the Yale Stellar Evolution Code (YREC) to match the observed parameters of the SPOCS stars. Our very dense grids of evolutionary tracks eliminate the need for interpolation between stellar evolutionary tracks and allow precise determinations of physical stellar parameters (mass, age, radius, size and mass of the convective zone, surface gravity, etc.). Combining our stellar models with the observed stellar atmospheric parameters and uncertainties, we compute the likelihood for each set of stellar model parameters separated by uniform time steps along the stellar evolutionary tracks. The computed likelihoods are used for a Bayesian analysis to derive posterior probability distribution functions for the physical stellar parameters of interest. We provide a catalog of physical parameters for 1074 stars that are based on a uniform set of high quality spectral observations, a uniform spectral reduction procedure, and a uniform set of stellar evolutionary models. We explore this catalog for various possible correlations between stellar and planetary properties, which may help constrain the formation and dynamical histories of other planetary systems.