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Westall, Frances

Publications and source records attributed to Westall, Frances.

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Report of the Workshop for Life Detection in Samples from Mars

The question of whether there is or was life on Mars has been one of the most pivotal since Schiaparellis' telescopic observations of the red planet. With the advent of the space age, this question can be addressed directly by exploring the surface of Mars and by bringing samples to Earth for analysis. The latter, however, is not free of problems. Life can be found virtually everywhere on Earth. Hence the potential for contaminating the Mars samples and compromising their scientific integrity is not negligible. Conversely, if life is present in samples from Mars, this may represent a potential source of extraterrestrial biological contamination for Earth. A range of measures and policies, collectively termed 'planetary protection', are employed to minimise risks and thereby prevent undesirable consequences for the terrestrial biosphere. This report documents discussions and conclusions from a workshop held in 2012, which followed a public conference focused on current capabilities for performing life-detection studies on Mars samples. The workshop focused on the evaluation of Mars samples that would maximise scientific productivity and inform decision making in the context of planetary protection. Workshop participants developed a strong consensus that the same measurements could be employed to effectively inform both science and planetary protection, when applied in the context of two competing hypotheses: 1) that there is no detectable life in the samples; or 2) that there is martian life in the samples. Participants then outlined a sequence for sample processing and defined analytical methods that would test these hypotheses. They also identified critical developments to enable the analysis of samples from Mars.

Life Detection↗
NASA NTRS2003

Mars Hematite Site: Potential for Preservation of Microfossils

Defining locations where conditions may have been favorable for life is a key objective for the exploration of Mars. Of prime importance are sites where conditions may have been favorable for the preservation of evidence of pre-biotic or biotic processes. Areas displaying significant concentrations of the mineral hematite (alpha-Fe2O3) have been identified from orbit by thermal emission spectrometry. The largest such deposit, in Sinus Meridiani, is a strong candidate landing site for one of the twin Mars Exploration Rovers, scheduled to launch in 2003. The Martian hematite site may have significance in the search for evidence of extraterrestrial life. Since iron oxides can form as aqueous mineral precipitates, the potential exists for preserving microscopic evidence of life in ecosystems that deposit iron oxides. Terrestrial hematite deposits proposed as possible analogs for the hematite sites on Mars include massive (banded) iron formations, iron oxide hydrothermal deposits, iron-rich laterites and ferricrete soils, and rock varnish. We are engaged in a systematic effort to document the evidence of life preserved in iron oxide deposits from each of these environments.

Allen, Carlton C.↗
NASA NTRS2001

Astrobiology Investigations at a Martian Hematite Site

Christensen et al, using data from the Mars Global Surveyor Thermal Emission Spectrometer (TES), have identified gray crystalline hematite in a 350 km by 750 km region near Sinus Meridiani. The deposit corresponds closely to the low-albedo highlands unit 'sm', mapped as a wind-eroded, ancient, subaqueous sedimentary deposit. Christensen et al interpreted the Sinus Meridiani deposit to be 'an in-place, rock-stratigraphic sedimentary unit characterized by smooth, friable layers composed primarily of basaltic sediments with approximately 10 to 15 % crystalline gray hematite.' Christensen et al discussed five possible mechanisms for the formation of this deposit: direct precipitation from standing, oxygenated, Fe-rich water; precipitation from Fe-rich hydrothermal fluids; low-temperature dissolution and precipitation through mobile groundwater leaching; surface weathering and coatings; thermal oxidation of magnetite-rich lavas. Four of these mechanisms involve the interactions of rock with water, and thus have implications in the search for evidence of microbial life.

Allen, Carlton, C.↗
NASA NTRS2000

Beagle 2 and NASA's Mars 2003 Orbiter: A Unique Exobiology Opportunity with an Orbiter

With the exploration strategy for Mars undergoing reexamination, the opportunity exists for the incorporation of the 60 kg Beagle 2 lander, developed in the United Kingdom for inclusion on ESA's 2003 Mars Express mission, with NASA's Mars 2003 orbiter derived from the Mars Global Orbiter. The combination of Beagle 2 with a Mars orbiter would result in a unique mission which could obtain information on Mars' life, climate and resources both from orbit as well as on the surface of the planet. Beagle 2 has been developed in the LJK for ESA as a low-cost opportunity to study the exobiology of Mars and the spacecraft is in its final stages of manufacture. Only limited modifications to the Beagle 2 package would be required for inclusion on NASA's Mars 2003 orbiter. With the ESA Mars Express mission launch in 2003 and a potential NASA Mars orbiter in 2003, both Beagle 2 landers on Mars would offer a low-cost, decreased risk and increased science return opportunity for the exploration of Mars at two distinct geologically interesting sites.

Gibson, Everett K., Jr.↗
NASA NTRS2000

The Geologic History of Mars: An Astrobiology Perspective

Fourteen SNC meteorites contain information which must be incorporated with recent spaceflight data for developing Mars' geologic history. SNCs have crystallization ages of 4500 to 160 m.y. Tle oldest meteorite ALH84001 contains information on the Noachian period of Mars' history. There are no meteorites from the Hesperian period and the remaining 13 meteorites fall into two age groups within the Amazonian: The nakhlites around 1300 m.y. and the shergottites between 800-160 m.y. Oxygen isotopic analysis of Martian samples shows two distinct O2 reservoirs throughout Martian history indicating late additions of volatiles and a lack of plate tectonics prior to 3.9 Gy. Evidence for percolation of aqueous brines through impact-produced fractures in the rocky surface is contained in the 3.9 Gy-old ALH84001 carbonate deposits. These carbonates precipitated at approx. 100 C. At this time life had already evolved on Earth. Early Mars could have hosted life similar to the bacteria that inhabited early Earth. Potential microorganisms could have been transported into fractures by carbonate-bearing waters and their remains could have become incorporated into the precipitated carbonate. Since Mars had a weak magnetic field at this time, it can be hypothesized that some of the Martian microorganisms may have been similar to terrestrial magnetotactic bacteria. Over geologic time episodic cratering, and tectonic events have occurred on Mars along with the periodic release of subsurface waters which may have produced clays within SNC meteorites. The geochemical data contained within SNC meteorites complements previous observational data and the recent Mars Global Surveyor data to provide a geological and environmental history which spans almost the entire lifespan on Mars. One of the outstanding features of this model is the possible creation of an early (about 4 Gy) volatile reservoir distinct from the outgassed Mars volatiles, and the persistence of this reservoir throughout most, if not all of subsequent Mars' history. Within the framework of this history a potential scenario for a possible record of living organisms is provided by suggestive structures and organic signatures trapped within secondary mineral deposits and alteration features of some SNC meteorites. Tracing the differences in oxygen isotopic compositions within Martian components allows us to gain insight in the history of Mars.

Gibson, Everett K.↗
NASA NTRS2000

Scanning Electron Microscopy Investigation of a Sample Depth Profile Through the Martian Meteorite Nakhla

The ongoing scientific debate as to whether or not the Martian meteorite ALH84001 contained evidence of possible biogenic activities showed the need to establish consistent methods to ascertain the origin of such evidence. To distinguish between terrestrial organic material/microbial contaminants and possible indigenous microbiota within meteorites is therefore crucial. With this in mind a depth profile consisting of four samples from a new sample allocation of Martian meteorite Nakhla was investigated using scanning electron microscopy (SEM) and energy dispersive X-ray analysis. SEM imaging of freshly broken fractured chips revealed structures strongly recent terrestrial microorganisms, in some cases showing evidence of active growth. This conclusion was supported by EDX analysis, which showed the presence of carbon associated with these structures, we concluded that these structures represent recent terrestrial contaminants rather than structures indigenous to the meteorite. Page

Toporski, Jan↗
NASA NTRS1999

Biogenic Activity in Selected Martian Meteorites

Criteria are well established within the scientific community for the acceptance of evidence for biogenic activity within samples from the early Earth. The eight criteria are: (1) geologic context, (2) age and stratigraphic location, (3) cellular morphology, (4) colonies, (v) biominerals, (6) isotope patterns, (7) organic biosignatures, and (8) features indigenous to sample. In the case of samples from Mars, we must also apply the same criteria. For the martian meteorite ALH84001, we have presented evidence which indicates possible biogenic activity associated with the 3.94 b.y. old, fracture-bound carbonate deposits. Subsequent major criticism of our hypothesis concerned the fact that many of the biogenic features could have been introduced during the time the meteorite was in Antarctica, prior to its collection. We address the possibility of Antarctic contamination and compare our evidence with accepted criteria for establishing the presence of past life. Although, we are close to matching some of the required criteria (likely biominerals, organic biomarkers, bacterial appendages, microfossils and indigenous features), there are others (well-documented geologic context, and evidence for colonies) which have not yet been met. It is not yet possible to come to a definitive conclusion concerning life on early Mars, but it is hoped that continued research will provide more relevant information.

Gibson, Everett K., Jr.↗
NASA NTRS1998

Phosphate Biomineralization of Cambrian Microorganisms

As part of a long term study of biological markers (biomarkers), we are documenting a variety of features which reflect the previous presence of living organisms. As we study meteorites and samples returned from Mars, our main clue to recognizing possible microbial material may be the presence of biomarkers rather than the organisms themselves. One class of biomarkers consists of biominerals which have either been precipitated directly by microorganisms, or whose precipitation has been influenced by the organisms. Such microbe-mediated mineral formation may include important clues to the size, shape, and environment of the microorganisms. The process of fossilization or mineralization can cause major changes in morphologies and textures of the original organisms. The study of fossilized terrestrial organisms can help provide insight into the interpretation of mineral biomarkers. This paper describes the results of investigations of microfossils in Cambrian phosphate-rich rocks (phosphorites) that were found in Khubsugul, Northern Mongolia.

McKay, David S.↗
NASA NTRS1998

Instrumentation: Analytical Capabilities on Mars

Human exploration of Mars will consist of a series of long-term missions, with early missions focusing upon establishing the Mars base, and undertaking basic field reconnaissance. A capable laboratory on Mars is an essential element in the exploration strategy. Analytical equipment both in the field and in the laboratory serves to extend the senses of the crew and help them sharpen their sampling skills as they learn to recognize rocks in the field and understand their geologic context and significance. On-site sample analyses allow results to be incorporated into evolving surface exploration plans and strategies, which will be developing in real-time as we learn more about Mars. Early Mars missions will focus on reconnaissance EVAs to collect rock and soil samples, maximizing the amount of Mars material returned to Earth. Later missions will be increasingly devoted to both extensive field campaigns and laboratory analyses. The capabilities and equipment described below will be built up at the Mars base incrementally over many missions, with science payloads and investigative infrastructure being partitioned among launch opportunities. This discussion considers what we require to measure, observe, and explore on a new planetary territory. Alternatively, what do we need to know and how do we equip ourselves to provide ample capabilities to acquire these data? Suggestions follow describing specific instruments that we could use. Appendix 5 lists a strawman science instrument payload, and a feasibility study of equipment transportation into the field on pressurized or unpressurized rovers.

Westall, Frances↗