Carbonaceous meteorites are relics of ancient parent bodies from the time of formation of our solar system, about 4.5 billion years ago. They contain many of the organic compounds (e.g. amino acids) that are considered the building blocks of life. Experiments that attempt to simulate the synthesis of amino acids from inorganic precursors results in racemates. However, we have observed that several of the common protein amino acids in carbonaceous meteorites are non-racemeic, exhibiting an L-enantiomer excess typical of life. Stable isotope analysis of the individual amino acid enantiomers confirms that this L-excess is extraterrestrial, rather than contamination subsequent to impact. It has generally been assumed that these amino acids were formed by abiotic processes and were initially racemic, with subsequent partial destruction of their respective D-enantiomers by abiotic processes. However, the alternative scenario, i.e. the L-excess being a relic of ancient life, is largely ignored. Here we address this possibility based on the distributions, stereochemistry and stable carbon and nitrogen isotope compositions of the amino acids in carbonaceous meteorites.
We have obtained x-ray spectral data and secondary/backscatter electron images of a suite of complex forms that we interpret as microfossils in several CI (Alais, Orgueil, and Tagish Lake) and CO3 (Rainbow and Dar al Gani 749) carbonaceous meteorites using the Field Emission and Environmental Scanning Electron Microscopes. Many of these embedded and lithified or carbonized forms are similar to photoautrophs (cyanobacteria or purple nonsulfur bacteria) or extinct phytoplankton (acritarchs and hystrichospheres) that are not considered likely post-arrival contaminants and therefore we interpret them as indigenous microfossils. We discuss the meteorites and provide images of several biogenic forms found embedded in freshly fractured meteorite matrix.
During the past few years, there has appeared much new and interesting data concerning the distribution of bacteriomorphic structures in both meteorites (carbonaceous chondrites) and in Earth rocks of different ages (Achaean to Recent). The bacterial forms studied are of very diverse morphologies including cocci, filaments, rod-shaped forms, etc. The biomorphic forms that are encountered in Earth rocks are practically indistinguishable from the biomorphic microstructures that are found in meteorites. Therefore, it has become necessary to compare and correlate bacteriomorphic structures from Earth rocks and from meteorites. In order to better understand this problem, we have initiated efforts to compile an Atlas of Bacteriomorphic Images.
Framboidal structures are common in both Earth rocks and in meteorites - carbonaceous chondrites. The main methods of formation of these structures are discussed. The role of biologic factors in formation of framboids is elevated. Comparison of crystal forms comprising framboids formed in laboratory conditions and in nature is provided. On the basis of investigations of framboidal structures the proposition that pyritoidal form of crystals is typical for the formation of biogenic framboidal structures.
Urazole (1,2,4-triazolidine-3,5-dione) (1), 4-methylurazole (12), and its carbon analog, 4,4-dimethylpyrazolidine-3,5-dione (18), react with 2-deoxy-D-ribose (2-deoxy-D-erythro-pentose; 6) in an aqueous solution at room temperature in a regioselective manner (a single substitution on a hydrazidic nitrogen, no reaction on the imide nitrogen) to give a mixture of four nucleosides. These are α and β pyranosides (p) and α and β furanosides (f). The α p forms in a stereoselective manner. A crystalline precipitate is formed in each of the above reactions, which is an exclusive enantiospecific product, 1R, 2R α p. 1 with 2-deoxy-L-ribose (10) gives a precipitate with the exclusive 1S, 2S α p stereochemistry. With 2-deoxy-D-glucose (2-deoxy-D-arabino-hexose; 7) the reaction with 1 is stereospecific, since only one isomer, β p, forms in the solution. Causes of enhanced reactivity of 1 with sugars were also studied. It was found that cyclic hydrazide analogs of 1, such as 12 and 18, are reactive, but open-chain analogs, 1,2,-diacetylhydrazine (21) and 1,2-dicarbethoxyhydrazine (22), are not. Although this reactivity assessment was done qualitatively and under restrictive reaction conditions, it still may be valuable for understanding α -effect of hydrazide nucleophiles. The prebiotic significance of our results is discussed.
The Triassic-Jurassic (TJ) mass extinction (~200 mya) event is one of the most severe in geologic history. It is also one of the most poorly understood. Few geologic sections containing the TJ boundary interval have been identified globally, and most of those are poorly preserved; the paucity of suitable stratigraphic sections has prevented corroborative geochemical studies of this interval. Recently, fullerene molecules (C60 to C200) have been shown to be present in the mass extinction boundary intervals of the Permian-Triassic (PT) event (~251.4 mya), as well as the well-known “dinosaur” extinction event of the Cretaceous-Tertiary (KT) (~65 mya). The presence of fullerenes in both these extinction intervals has been used to invoke an extraterrestrial impact cause for the extinctions. Preliminary results of laser desorption mass spectrometry (LDMS) of selected samples from the Kennecott Point TJ boundary section, Queen Charlotte Islands, British Columbia, suggest that fullerenes (C60 to ~C200) are present in the section, stratigraphically above the extinction interval (as defined by paleontological and isotopic data), but not actually within the interval itself. The presence of fullerenes may not be diagnostic of an impact event.
A filtered imager, the CONTOUR Forward Imager (CFI), was designed, fabricated, and qualified for the Comet Nucleus Tour (CONTOUR) Discovery class mission. The CONTOUR spacecraft was launched July 3, 2002, and failed during injection to heliocentric orbit on August 15, 2002. This paper provides an overview of the efforts to produce CFI.
The CFI imager was designed to perform optical navigation, comet nucleus imaging, and comet coma imaging. CFI was complemented in the CONTOUR payload by the CONTOUR Remote Imager and Spectrometer (CRISP). The emphasis in the CFI design was on high sensitivity at moderate to long ranges from the comet nucleus, while CRISP was designed for high-speed observations in close to the nucleus. A unique aspect of CFI was the requirement to image multiple comets after being exposed to high-velocity cometary dust on the
previous comet flybys (which damages and contaminates the forward looking optics). The first optical surface was replaceable between comet encounters, using a mirror "cube" mechanism, to alleviate the dust damage. Another challenging aspect of the design is that the spacecraft was thruster stabilized (no reaction wheels), placing limits on the available exposure time to accomplish the high sensitivity observations required.
CFI utilized ten filters covering from 300 to 920 nm to image onto a backthinned 1024 by 1024 element CCD. The Ritchie-Chrietien telescope provided a clear aperture of 62 mm, a full field of view of 2.5 degrees, and a pixel field of view of 43 microradians. CFI was designed and fabricated by a combined effort of the Johns Hopkins University Applied Physics Laboratory and SSG Precision Optronics. The CONTOUR mission was lost prior to CFI being powered on in flight.
The CONTOUR Remote Imager and Spectrometer (CRISP) was a multi-function optical instrument developed for the Comet Nucleus Tour Spacecraft (CONTOUR). CONTOUR was a NASA Discovery class mission launched on July 3, 2002. This paper describes the design, fabrication, and testing of CRISP. Unfortunately, the CONTOUR spacecraft was destroyed on August 15, 2002 during the firing of the solid rocket motor that injected it into heliocentric orbit. CRISP was designed to return high quality science data from the solid nucleus at the heart of a comet. To do this during close range (order 100 km) and high speed (order 30 km/sec) flybys, it had an autonomous nucleus acquisition and tracking system which included a one axis tracking mirror mechanism and the ability to control the rotation of the spacecraft through a closed loop interface to the guidance and control system. The track loop was closed using the same images obtained for scientific investigations. A filter imaging system was designed to obtain multispectral and broadband images at resolutions as good as 4 meters per pixel. A near IR imaging
spectrometer (or hyperspectral imager) was designed to obtain spectral signatures out to 2.5 micrometers with resolution of better than 100 meters spatially. Because of the high flyby speeds, CRISP was designed as a highly automated instrument with close coupling to the spacecraft, and was intended to obtain its best data in a very short period around closest approach. CRISP was accompanied in the CONTOUR science payload by CFI, the CONTOUR Forward Imager. CFI was optimized for highly sensitive observations at greater ranges. The two instruments provided highly complementary optical capabilities, while providing some degree of functional redundancy.
Landers and rovers are important to solar system exploration, and we are designing and analyzing a remote Raman system for a planetary mission. Raman spectroscopy is a common and powerful technique for materials analysis. We have developed a system that enables Raman spectroscopic measurements at distances of more than 50 meters. In order to design a flight instrument, we need to quantitatively understand the Raman efficiency of natural surfaces. We define remote Raman efficiency as the ratio of radiant exitance leaving a natural surface to the irradiance of the incident laser. The radiant exitance of a natural surface is the product of the sample radiance (minus background), the projected solid angle in steradians, and the spectral bandwidth of the spectrometer. The laser irradiance is the product of the energy of the laser (mJ/pulse) and the pulse rate (Hz), divided by the area of the laser spot. We have determined the remote Raman efficiency for several minerals and rocks: dolomite marble, dacite, milky quartz, anorthosite, calcite, biotite granite, magnesite, chert, gypsum (selenite), fibrous gypsum, and sandstone. By quantifying the remote Raman efficiency, we will be able to determine the number and quality of spectra that a remote Raman system can acquire on a planetary surface where available power is limited. Studies on hematite indicate that Raman shift (and thus remote Raman efficiency) depends on laser wavelength.
Life on Earth is characterized by a select group of low Z elements: C, H, N, O, P, K, S, Na, Cl. The presence of these elements and their ratios can provide indications of possible biogenicity and thus they may constitute valuable biomarkers that may help determine the best locations to seek more definitive evidence of life. We discuss the possible applications and significance of the inelastic neutron scattering induced gamma spectroscopy (INSGS) for future Astrobiology Missions to Mars or other solar System bodies. The general
requirements and capabilities of the proposed approach are presented.
Microbial biofuel cells generate electrical power through the collection of respiratory electrons, which are liberated by the metabolism of nutrients by microorganisms. In the context of in-situ detection of extraterrestrial life, the following question is raised: if microorganisms can be used to generate electrical power, under what circumstances can the generation of electrical power be used to indicate the presence of microbial life? Such an approach to the detection of microorganisms is susceptible to the same ambiguities as similar approaches in that local geochemistry may produce a signal that mimics the presence of life. Consideration is given to time -resolved signal observation to the discrimination of biochemistry and geochemistry and how this approach may be combined with alternate approaches to build a case for, or against, the presence of life. Construction and operation details of microbial biofuel cells, based on marine sediments, are discussed, as are considerations for space flight hardware.
Recent Odyssey data indicate water ice within centimeters or meters of the Martian surface over wide latitudes. A significant finding in itself, this has much broader applications. This paper applies water phase physics to Odyssey, Viking and Pathfinder data to make a case for the availability of liquid water at the planet’s surface. Liquid water, possibly in biologically significant quantities, is predicted at least diurnally over broad reaches of Mars, including the two Viking landing sites where the Labeled Release (LR) life detection experiment obtained positive signals. Moreover, the data argue strongly against any putative oxidant in the Martian soil that many have assumed was responsible for the LR positive responses. The recently published theory, that currently occurring changes in ravines observed on Mars are caused by flows of solid carbon dioxide rather than liquid water, are shown to be irrelevant to this interpretation of the Odyssey data. The paper concludes that the Odyssey data lend further strength to the author’s claim that the 1976 Viking LR results are of biological origin, and warrant his proposal to send a chiral LR experiment to Mars as an unambiguous way to end the controversy.
The search for life on Mars is an important goal of NASA and other space agencies. It is not known if chemical evolution on Mars produced the same or similar types of life as on Earth. If not, what would non-Earth biosignatures look like? If life has left its footprint on Mars, what chemical signatures can we recognize, and how can we prevent missing novel life signatures? Alternatively, chemical evolution on Mars may have produced complex chemical systems, which, however, did not lead to life. How can such systems be identified? We use as a model a complex inorganic-organic-biotic system on Earth, commonly called desert or rock varnish, which has been known to Darwin, and which is now also indicated on Mars. We describe unique complex chemical markers that are preserved in rock varnish on Earth. An intricate interaction between minerals, metals, and organic compounds is responsible for their preservation. We suggest some important types of organic compounds to look for in the Martian varnish, should it exist.
Key to the possibility of Martian biology is the availability of liquid water. The issue hinges on the physics of water under an atmosphere whose total pressure is only slightly higher than the triple point of water. The general consensus, that liquid water cannot exist on the Martian surface, was first challenged in 1998. This paper offers a more detailed analysis.
While orbital images from Mariner 9 onward have shown evidence of ancient water flows, recent Global Surveyor and Odyssey orbiters have produced images of apparently active erosion. The 1997 Pathfinder Lander measured surface atmospheric temperatures well above freezing, while temperatures one meter higher were as low as -40° C. The low vapor capacity of the atmosphere just above the surface acts as a lid, or barrier, to evaporation. This could allow ice to melt into liquid water instead of subliming to vapor. In 2000, in a demonstration made in a simulated Martian environment, water ice melted and remained liquid. However, many questions have been raised about the physics of this experiment. In this paper, numerical simulation provides values for the thermodynamic quantities controlling the phase of water. The binary diffusion coefficient of water vapor in CO2, and the law of binary gas diffusion are applied. Fluxes of water vapor under Martian conditions, including wind speeds, are calculated for various distances from surface ice sources. Evaporative heat loss is compared to the heat available from the sun. The paper provides the theoretical, if counterintuitive, basis for the existence of liquid water on the present Martian surface.
The color of published Viking and Pathfinder images varies greatly in hue, saturation and chromaticity. True color is important for interpretation of physical, chemical, geological and, possibly, biological information about Mars.
The weak link in the imaging process for both missions was the reliance on imaging color charts reflecting Martian ambient light. While the reflectivity of the charts is well known, the spectrum of their illumination on Mars is not. “Calibrated” images are usually reddish, attributed to atmospheric dust, but hues range widely because of the great uncertainty in the illumination spectrum. Solar black body radiation, the same on Mars as on Earth, is minimally modified by the atmosphere of either planet. For red dust to change the spectrum significantly, reflected light must exceed the transmitted light. Were this the case, shadows would be virtually eliminated. Viking images show prominent shadows. Also, Pathfinder’s solar cells, activated by blue light, would have failed under the predominately red spectrum generally attributed to Mars.
Accordingly, no consensus has emerged on the colors of the soil, rocks and sky of Mars. This paper proposes two techniques to eliminate color uncertainty from future images, and also to allow recalibration of past images: 1. Calibration of cameras at night through minimal atmospheric paths using light sources brought from Earth, which, used during the day, would permit calculation of red, green and blue intensities independent of scene illumination; 2. Use of hyperspectral imaging to measure the complete spectrum of each pixel.
This paper includes a calibration of a NASA Viking lander image based on its color chart as it appears on Earth. The more realistic Martian colors become far more interesting, showing blue skies, brownish soil and rocks, both with yellow, olive, and greenish areas.
Hydrothermal environments, whether terrestrial or marine, provide a window into potentially thriving ecosystems on other solar bodies. If such extraterrestrial biotopes do exist, they might be inhabited by extremophilic microorganisms, perhaps related to hyperthermophiles (optimal growth temperature > 80°C) previously characterized from geothermal sites on this planet. Study of the physiological and metabolic patterns in hyperthermophiles will shed light on
microbial lifestyles consistent with putative hydrothermal niches on other planets and moons.
For more than a century (since Winogradsky discovered lithautotrophic bacteria) there has been a dilemma in microbiology about life that first inhabited the Earth. Which types of life forms first appeared in the primordial oceans during the earliest geological period on Earth as the primary ancestors of modern biological diversity? How did a metabolism of ancestors evolve: from lithoautotrophic to lithoheterotrophic and organoheterotrophic or from organoheterotrophic to organautotrophic and lithomixotrophic types? At the present time, it is known that chemolithoheterotrophic and chemolithoautotrophic metabolizing bacteria are wide spread in different ecosystems. On Earth the acidic ecosystems are associated with geysers, volcanic fumaroles, hot springs, deep sea hydrothermal vents, caves, acid mine drainage and other technogenic ecosystems. Bioleaching played a significant roel on a global geological scale during the Earth's formation. This important feature of bacteria has been successfully applied in industry. The lithoautotrophs include Bacteria and Archaea belonging to diverse genera containing thermophilic and mesophilic species. In this paper we discuss the lithotrophic microbial acidophiles and present some data with a description of new acidophilic iron- and sulfur-oxidizing bacterium isolated from the Chena Hot Springs in Alaska. We also consider the possible relevance of microbial acidophiles to Venus, Io, and acidic inclusions in glaciers and icy moons.
Microbial extremophiles live on Earth wherever there is liquid water and a source of energy. Observations by ground-based observatories, space missions, and satellites have provided strong evidence that water ice exists today on comets, Europa, Callisto, and Ganymede and in the snow, permafrost, glaciers and polar ice caps of Mars. Studies of the cryoconite pools and ice bubble systems of Antarctica suggest that solar heating of dark rocks entrained in ice can cause localized
melting of ice providing ideal conditions for the growth of microbial communities with the creation of micro-environments where trapped metabolic gasses produce entrained isolated atmospheres as in the Antarctic ice-bubble systems. It is suggested that these considerations indicate that several groups of microorganisms should be capable of episodic growth within liquid water envelopes
surrounding dark rocks in cometary ices and the permafrost and polar caps of Mars. We discuss some of the types of microorganisms we have encountered within the permafrost and snow of Siberia, the cryoconite pools of Alaska, and frozen deep within the Antarctic ice sheet above Lake Vostok.
Desert varnish coatings are found on rock surfaces throughout arid regions of the world. Rock varnishes may exist on Mars, as suggested by some observations on both Viking and Mars Pathfinder landing sites. There has long been a debate as to whether varnish coatings are microbially mediated or deposited by inorganic processes. Dozens of bacteria have been cultured from the surface of varnish coatings and recently the molecular ecology of varnish coatings have been characterized using 16S rRNA techniques. Colonies of micro colonial fungus are associated with varnish coatings but it is unclear whether bacteria or fungus are directly involved in varnish formation. Another alternative is the incorporation of microbial components into varnish coatings either by complexation with metals or in association with clays. For instance polysaccharides found in bacterial cell walls contain linear polymers of sugars that may be preserved in arid conditions when complexed with usual varnish components such as calcium, aluminum, silicon, iron and manganese. Understanding the organic components of desert varnish may help to resolve the question of the mechanism of formation of rock coatings, biomineralization processes and bacterial fossils and how to detect past microbially activity on planets.
The presence of viable, but non-cultureable, bacteria on membranes through which strastopheric air samples were passed has been confirmed using viable fluorescent staining. The results are discussed in relation to the likely origin of the observed organisms.
Data acquired from various scientific disciplines in the past five years have converged to elevate the status of panspermia as one of the major contenders in theories of the origins of life on Earth. We review the trends that point towards a vindication of the idea that biomaterial from comets may be distributed widely throughout the universe and might even be reaching us in the present day.