Kathie L. Thomas-Keprta

NASA · Astromaterials Research and Exploration Directorate

While indigenous organic matter has been previously reported in the Mars meteorite Nakhla, little is known as to either its form or distribution. A notable feature of Nakhla is the prevalence of secondary phases associated with aqueous alteration. By analogy with the terrestrial environment, our objective was to determine whether Martian secondary...

Introduction: The success of selecting future Martian landing sites to discover extinct and/or extant extraterrestrial life is strongly dependent on the extent to which ancient and/or present habitable zones may have existed or presently exist on Mars. It has been suggested that early Mars could have been supportive for life since it was wet and wa...

We shocked calcite in an unconfined environment by launching small marble cylinders at 0.8–5.5 km s−1 into aluminum or copper plates, producing shock stresses between 5 and 79 GPa. The resulting 5–20 mm craters contained intimately mixed clastic and molten projectile residues over the entire pressure range, with melting commencing already at 5 GPa....

We separated the respirable dust and other size fractions from Apollo 14 bulk sample 14003,96 in a dry nitrogen environment. While our toxicology team performed in vivo and in vitro experiments with the respirable fraction, we studied the size distribution and shape, chemistry, mineralogy, spectroscopy, iron content and magnetic resonance of variou...

Carbonaceous matter on the surfaces of black pyroclastic beads, collected from Shorty crater during the Apollo 17 mission, represents the first identification of complex organic material associated with any lunar sample. We report the chemical, physical and isotopic properties of this organic matter that together support a pre-terrestrial origin. W...

Here we report the nature of mineral phases spatially associated with vesicles in a green glass bead from Apollo sample 15411,42.

We present results of the first coordinated in situ isotopic and chemical mapping of the Bells meteorite using a newly developed two-step laser mass spectrometer.

Impact cratering can destroy life from local to global scales and result in sudden turnovers of dominant genera and/or species. Here we report that it can also preserve components of the local biology present at the time of impact. We have investigated floral matter encapsulated within Cenozoic Era impact glasses produced by separate bolide impacts...

We have observed the presence of a previously undescribed microtopography on the surface of a lunar grain from Apollo regolith sample 12070,29.

Abstract We report the first observation of indigenous carbonaceous matter in the martian meteorite Yamato 000593. The carbonaceous phases are heterogeneously distributed within secondary iddingsite alteration veins and present in a range of morphologies including areas composed of carbon-rich spheroidal assemblages encased in multiple layers of id...

We separated the respirable dust and other size fractions from Apollo 14 bulk sample 14003,96 in a dry nitrogen environment. While our toxicology team performed in vivo and in vitro experiments with the respirable fraction, we studied the size distribution and shape, chemistry, mineralogy, spectroscopy, iron content and magnetic resonance of variou...

We have identified for the first time arguably indigenous complex organic matter on the surfaces of the 74220 pyroclastic beads, collected on the rim of Shorty crater during the Apollo 17 mission.

We report the identification of arguably indigenous organic matter present within surface deposits of Apollo 17 black glass grains.

We report the identification of arguably indigenous carbonaceous matter present on pristine surface coatings of Apollo 17 volcanic black glass beads.

Using a laser microprobe instrument equipped with a new vacuum ultraviolet laser ionization source we have been able to map in situ the distribution of organic matter in fresh fracture surfaces of carbonaceous chondrites.

We report for the first time the identification of arguably indigenous carbonaceous matter present within surface deposits of a black glass grain collected on the rim of Shorty Crater during the Apollo 17 mission.

Microprobe two-step laser mass spectrometry utilizing a novel vacuum UV photoionization source has been applied to mapping the spatial distribution of organic species in carbonaceous chondrite matrices at micron spatial resolutions.

Surface deposits on lunar pyroclastic glass spherules have been characterized using HRTEM. These deposits are dominated by Zn and S, but also include Mg and exhibit a rather complex stratigraphy.

Despite the high potential for oxidative stress stimulated by reduced iron, contemporary iron-depositing hot springs with circum-neutral pH are intensively populated with cyanobacteria. Therefore, studies of the physiology, diversity, and phylogeny of cyanobacteria inhabiting iron-depositing hot springs may provide insights into the contribution of...

Selected Martian meteorites contain reduced carbon phases associated with clay minerals. The sources of the reduced carbon within the meteorites appears to be associated with fluids which have caused preterrestrial alteration of primary silicates.

Siderophilic (iron-loving) cyanobacteria were shown to use phosphates for sequestration of their internal Fe pool. The analysis of the genomes of siderophilic cyanobacteria indicates putative links between physical and molecular biosignatures.

The first 600 My of martian history were ripe for life to develop. Standing bodies of water, precipitation and flowing surface and subsurface water and possibly abundant hydrothermal energy would favor the formation of early life.

We have used two-step laser mass spectrometry to map, in situ, the spatial distribution of organics in the matrices of the Tagish Lake and Bells carbonaceous chondrites.

The search for reduced carbon species on the martian surface has been enhanced with the identification of reduced carbon components within martian meteorites of different ages. Reduced carbon has been identified in materials ranging from 3.9 Ga to as young as 600,000 Ma.

Characterized by TEM and Raman, significant chemical and physical differences exist between the disks found in the fractures and pores spaces of peridotite xenoliths and basalts in Spitsbergen and the carbonates present in martian meteorite ALH 84001.

Siderophilic (iron-loving) cyanobacteria were shown to use phosphates for sequestration of internal Fe pool. The analysis of the genomes of siderophilic cyanobacteria indicates putative links between physical and molecular biosignatures.

We are investigating the origin and evolution of volcanic surface coatings on Apollo 15 green and Apollo 17 black glasses.

The search for organic carbon on Mars has been a major challenge. The first attempt was the Viking GC-MS in situ experiment which gave inconclusive results at two sites on Mars [1]. After the discovery that the SNC meteorites were from Mars [2], [3-5] reported C isotopic compositional information which suggested a reduced C component present in the...

The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global...

The Martian meteorite ALH84001 preserves evidence of interaction with aqueous fluids while on Mars in the form of microscopic carbonate disks. These carbonate disks are believed to have precipitated 3.9 Ga ago at beginning of the Noachian epoch on Mars during which both the oldest extant Martian surfaces were formed, and perhaps the earliest global...

Comparison of new TEM results with decomposition studies of sideritic carbonates conducted under a range of heating scenarios suggests that the magnetite nanocrystals in ALH 84001 carbonate disks are not the products of thermal decomposition.

Thermal decomposition of Roxbury siderite resulted in the formation of impure (Mg,Mn)-ferrites. These findings, which are supported by kinetic and thermodynamic equilibrium modeling studies, are in stark contrast to the chemically pure ALH 84001 magnetite.

For life to exist on a planet there must be water, carbon and energy sources along with a dynamic geologic past. Mars meets all of these requirements. Life is probably present beneath the surface of Mars today in regions associated with water.

Prior to 2.4 Ga, global oceans were likely significantly enriched in soluble iron (Rouxel, Bekker, Edwards, 2005), a condition that is not conducive to the growth of most contemporary mesophilic cyanobacteria (CB). Recent studies of the mechanisms of iron-deficiency stress in CB suggest that contemporary mesophilic freshwater and marine СB underwen...

The results on the bioweathering of analogs of lunar and martian soil analogs by siderophilic CB are described in the abstract. Obtained results seem to be applicable to ISRU needs on the Moon and Mars.

We are studying the surfaces of individual volcanic glass beads using state-of-the-art field emission SEM and TEM techniques, which have improved significantly since the glasses were first examined.

The martian meteorite Yamato 000593 contains possible evidence of biogenic activity as noted by the similarity of biogenic features reported by Fisk et al. (2006). A combination of micro-analytical techniques were used to support these observations.

"Why do we have such a longstanding fascination with Mars? Very simply put, it's about life. The search for life elsewhere in our Solar System has been a major driver for exploring Mars, pretty much since we began seriously looking at that planet."1 The major objective of this work is to describe signs of possible life, that is biosignatures, in ro...

The conditions on Mars during its first 600 Gy were suitable for biogenic activity to have occurred. Abundances of water, carbon, energy along with the operating geological processes fostered development of early life forms on Mars and they may be found beneath the surface today.

Indigenous reduced carbon has been observed in the Martian meteorite Nakhla. For the first time we have analyzed the in situ carbon by a suite of micro-analytical techniques in order to identify and characterize the reduced carbonaceous matter. Optical analysis of the Nakhla petrographic thin-section revealed the existence of a dark brown/red vein-...

New analyses of indigenous secondary material in the martian meteorite Nakhla reveal amorphous carbon-rich veins and dendrites. The texture and chemistry of this material resembles that of biogenically altered sub-ocean basaltic glasses.

Analysis of in situ carbonaceous matter in the Nakhla SNC meteorite has been carried out using a variety of techniques. Laser raman data shows the carbonaceous matter to be highly complex and static mass spectrometry has shown it to have an isotopic composition of –18 to –20‰ C.

Extended abstract of a paper presented at Microscopy and Microanalysis 2005 in Honolulu, Hawaii, USA, July 31--August 4, 2005.

Our aim is to understand the mechanism(s) of formation of carbonate assemblages in ALH84001. A prerequisite is that a detailed characterization of the chemical and physical properties of the carbonate be established. We present here analyses by transmission electron microscopy (TEM) of carbonate thin sections produced by both focused ion beam (FIB)...

Martian Meteorite ALH84001 contains four unusual features which have been interpreted as possible signatures of relic biogenic activity. After six years of intense study by the world's scientific community, the current status of the biogenic hypothesis is reviewed and shown to still be valid. Furthermore additional features have been observed in tw...

Up to ~25% of magnetites embedded in ALH84001 carbonate disks have morphological and chemical similarities to biogenic MV-1 magnetites. We have proposed that these Martian magnetites can be best explained as the diverse products of biogenic and inorganic processes that operated on early Mars.

Dated at approximately 3.9 billion years of age, carbonate disks, found within fractures of the host rock of Martian meteorite ALH84001, have been interpreted as secondary minerals that formed at low temperature in an aqueous medium. Heterogeneously distributed within these disks are magnetite nanocrystals that are of Martian origin. Approximately...

The properties that define habitability are commonly understood to include the following: Presence of water. Temperature range allowing some or all of the water to be liquid. A suitable physical volume or space permitting metabolism and growth. Presence of organic compounds or the building blocks to make them. Presence of an energy source suitable...

The Microarray Assay for Solar System Exploration (MASSE) is based on the use of immunological reactions to detect chemical compounds in samples of extraterrestrial material. In order for this technology to be useful for in situ studies on any given planet, molecules present within the material examined must be extracted and recognizable to the ant...

We report here the crystal morphologies of MV-1 and ALH84001 magnetites as calculated by back-projection using electron tomography. In the present study, we used a 300 keV TEM with a field emission gun (Tecnai F-30 from FEI Inc.), equipped with a 2048 x 2048 pixel CCD camera from Gatan Inc. to image magnetite crystals over tilt ranges of approx. +/...

Intracellular magnetite (Fe 3O4) crystals produced by magnetotactic bacteria strain MV-1 are in the single-domain size range, and are chemically pure. We have previously suggested that they exhibit an unusual crystal habit described as truncated hexa-octahedral. Such a crystal morphology has not been demonstrated for any inorganic population of mag...

Evidence of biogenic activity on Mars has profound scientific implications for our understanding of the origin of life on Earth and the presence and diversity of life within the Cosmos. Analysis of the Martian meteorite Allan Hills 84001 (ALH84001) revealed several lines of evidence that has led some investigators to suggest that microbial life exi...

Possible biosignatures in martian meteorites are evaluated to see if they can be explained by terrestrial contamination. PAHs, carbonate globules, and nano-size magnetites in ALH84001 are very unlikely to be terrestrial contamination. Additional information is contained in the original extended abstract.

FE-SEM and TEM studies of martian meteorites are focused on identifying and characterizing possible martian weathering products using SEM petrography. New data include unambiguous evidence that Ca-sulfate in the Nakhla meteorite is of martian origin. Additional information is contained in the original extended abstract.

No single process, either inorganic or biogenic, can explain all the magnetites in ALH84001 carbonates. We propose that their origins can best be explained as a product of multiple processes, one of which is Martian biogenic intracellularly produced magnetite. Additional information is contained in the original extended abstract.

Some Interplanetary Dust Particles (IDPs) have large isotope anomalies in H and N. To address the nature of the carrier phase, we are developing a procedure to spatially resolve the distribution of organic species on IDP thin sections utilizing fluorescent molecular probes. Additional information is contained in the original extended abstract.

Preliminary data suggest that biofabrics are preserved by Mn and Fe minerals (birnessite and hematite) in desert varnish. A martian hematite-rich deposit with indications of biological activity may prove to be a prime site for future sample return. Additional information is contained in the original extended abstract.

Silicified bacteria are the earliest evidence of life on Earth. If life evolved on Mars or Europa, its traces may have been silicified. Detailed knowledge on silicification therefore helps refine our search parameters for extraterrestrial life. Additional information is contained in the original extended abstract.

Evidence of microbial life on Earth has been found in siliceous rock formations throughout the geological and fossil record. To understand the mechanisms of silicification and thus improve our search patterns for evidence of fossil microbial life in rocks, a series of controlled laboratory experiments were designed to simulate the silicification of...

Evidence of life on Earth in form of silicified microorganisms is reported from throughout the geological record as early as 3.5 Ga ago to recent hot spring environments. Silicified microfossils are resistant to weathering which renders them readily preservable over long time spans. This is of particular interest in astropalaeontological research a...

The evidence from the martian meteorites shows that the subsurface environment of Mars was favorable (by earth microbial standards) for life throughout much of the past nearly 4GY. Currently, 25 martian meteorites are available in collections on Earth. These meteorites have formation ages ranging from 4.5GY to 165MY. Many show clear evidence for aq...

We have been studying the martian meteorite, Nakhla. This meteorite was an observed fall in June, 1911 near the village of El Nakhla, Egypt, and was collected soon thereafter. We have been studying subsamples from a British Museum specimen that had a nearly complete fusion crust before it was broken up recently in a clean bench at Johnson Space Cen...

The Dead Sea is located on the northern branch of the African-Levant Rift systems. The rift system, according to one model, was formed by a series of strike slip faults, initially forming approximately two million years ago. The Dead Sea is an evaporite basin that receives freshwater from springs and from the Jordan River. The Dead Sea is different...

McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemica...

Analyses both support and are in opposition to the hypothesis that the Martian meteorite ALH84001 contains evidence for possible biogenic activity on Mars. New observations in two additional Martian meteorites, Nakhla (1.3 Ga old) and Shergotty (300–165 Ma old) indicate possible biogenic features. Features in the three Martian meteorites compare fa...

Microbial fossilization processes in the Dead Sea is primarily associated with the calcium cation. The putative fossilized microbes do not represent the reported living microbial population. Additional information is contained in the original extended abstract.

A diversity of biogenic structures is described from Storr's Lake, Bahamas. Structures include four groups of coccoid structures, diatoms and probable cyanobacterial sheaths. Additional information is contained in the original extended abstract.

Textures of secondary minerals in cracks in Nakhla are described and illustrated with high resolution Scanning Electron Microscopy (SEM) and BSE. Some Nakhla textures resemble alteration textures of glass in seafloor basalts. Criteria for inorganic vs. biogenic alteration are discussed. Additional information is contained in the original extended a...

Evaporites in martian meteorites contain weathering or alteration features that may provide clues about the martian near-surface environment over time. Additional information is contained in the original extended abstract.

We outline the development of a new breed of robotic life detection instruments based on immunological reactions. Additional information is contained in the original extended abstract.

We suggest that the observation of truncated hexa-octahedral magnetites in ALH84001 are both consistent with, and in the absence of terrestrial inorganic analogs, likely formed by biogenic processes. Additional information is contained in the original extended abstract.

Using transmission electron microscopy (TEM), we have analyzed magnetite (Fe_3O_4) crystals acid-extracted from carbonate globules in Martian meteorite ALH84001. We studied 594 magnetites from ALH84001 and grouped them into three populations on the basis of morphology: 389 were irregularly shaped, 164 were elongated prisms, and 41 were whisker-like...

Physical evidence of life (physical biomarkers) from the deposits of carbonate hot springs were documented at the scale of microorganisms—submillimeter to submicrometer. The four moderate-temperature (57 to 72°C), neutral pH springs reported on in this study, support diverse communities of bacteria adapted to specific physical and chemical conditio...

The Shergotty martian meteorite contains weathering features and secondary minerals much like those in Nakhla, including secondary silicates, NaCl, and Ca-sulfate. It is likely that the weathering occurred on Mars.

Oxygen isotopic analysis of Martian samples shows two distinct O2 reservoirs throughout Martian history indicating late cometary additions of volatiles and a lack of plate tectonics.

Iron-bearing spherules in Archean Warrawoona rocks are composed of hematite and goethite. They are clearly syngenetic with the rock but their origin, whether biological or abiogenic, is not yet known.

Life in extreme environments exhibiting conditions similar to early Earth and Mars, such as Sulphur Spring, may harbor microbiota serving as both relics from the past as well as present day Martian analogues.