Mr. Barry E. DiGregorio Profile

Barry E. DiGregorio

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Publications (5)

Proceedings Article | 24 October 2012 Paper

Possible biological structures in the Tissint Mars Meteorite

Jamie Wallis, N. Chandra Wickramasinghe, Daryl Wallis, Nori Miyake, Max Wallis, Barry Di Gregorio, Richard Hoover

Proceedings Volume 8521, 85210R (2012) https://doi.org/10.1117/12.2013827

KEYWORDS: Mars, Iron, Scanning electron microscopy, Pyrite, Minerals, Particles, X-rays, Sensors, Carbon, Silicon

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Proceedings Article | 1 November 2004 Paper

Accretionary lapilli, tektites, or concretions: the ubiquitous spherules of Meridiani Planum

Barry DiGregorio

Proceedings Volume 5555, (2004) https://doi.org/10.1117/12.563673

KEYWORDS: Hematite, Mars, Liquids, Minerals, Spherical lenses, Sulfur, Spectroscopy, Iron, Particles, Magnesium

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One of the most enigmatic discoveries made by the NASA Mars Exploration Rover Opportunity (MER-B) at the Meridiani Planum landing site are the ubiquitous spherules referred to as "blueberries" by the science team. They cover the entire landing area and can be seen in every direction within view of the rover cameras. Subsequent analysis of a small grouping of the spherules laying on top of a rock outcrop by Mossbauer spectroscopy showed an intense hematite signature not found on the rock or in the surrounding basaltic soils. Spherules were also found attached to and embedded within sedimentary sulfate rock outcrops found at the landing area that have been determined by the MER science team as having been formed in an acidic liquid water environment. The appearance of most of the Meridiani spherules is strikingly similar to the morphology and size of terrestrial accretionary lapilli and show similarities to terrestrial tektites. Accretionary lapilli are spherical balls and fragments with a concentric layered structure that are formed by a variety of mechanisms including hydrovolcanic eruptions, geysers and large meteorite impacts in water. Tektites are glassy impact spherules that form as a result of large meteorite impacts and also seem apparent in some of the rover images. Tektites can be perfectly spherical or have teardrop and dumbbell shapes. A lack of a visible volcanic source capable of producing high volumes of accretionary lapilli as seen in the MER-B images, in combination with the strong spectral signature of hematite, that some of the spherules display, led the MER science team to favor a concretion hypothesis thus far. All of these types of spherules involve interaction of with surface water or ice to form. Problems exist in explaining how the Martian “concretions”, if that is indeed what they are, are of such uniform size and have such a wide distribution. Evidence from Martian orbit and on the surface indicate that the Meridiani Planum landing ellipse is located within an ancient 800 km diameter impact structure with another 140 km crater under the site. Estimated hydrothermal output from this size of an impact would be equivalent to 38 times Yellowstone over a 15,000 year time period. Life as we understand it is dependent on a source of liquid water, energy, and nutrients. Hydrothermal energy can originate from either internal volcanic sources or through the action of large bolide impact. A 25 km diameter fluidized ejecta (rampart) crater named Victoria is located 50 km to the southwest of the Opportunity rover landing site and might explain how the Meridiani Planum region is covered with such an enormous abundance of spherules.

Proceedings Article | 1 November 2004 Paper

A planetary quarantine laboratory on the moon

Barry DiGregorio

Proceedings Volume 5555, (2004) https://doi.org/10.1117/12.563700

KEYWORDS: Mars, Space operations, Microorganisms, Contamination, Soil contamination, Planets, Astrobiology, Solar system, Lawrencium, Earth's atmosphere

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In January of 2004 NASA was directed by the President of the United States to setting a goal to establish a permanent human tended scientific outpost on the Moon by 2015-2020. Discussions on what kind of facilities on the Moon would be most beneficial to science have already begun. One of the highest priority goals for the NASA Mars exploration program has been how to proceed with the return of Martian soil and rock samples directly to Earth for extensive laboratory analysis. However scientific debates exist on how to obtain pristine samples from Mars without introducing terrestrial contaminants and also for preventing the back contamination of the Earth’s biosphere by putative Martian microbes. In 1976, the Viking Labeled Release experiment provided peer-reviewed scientific evidence for possible microbial activity in the upper soil layers of Mars in two different locations on the planet. Although the LR evidence is not considered as absolute proof of life on Mars by many in the scientific community, the Viking LR data should be taken seriously as an important signpost that life, either as dormant endospores (which may have been revived on the addition of the LR nutrient solution), or found as a currently thriving microbial community, might pose a serious risk to the terrestrial biosphere in the event of a sample return spacecraft failure. Examples of spacecraft technological failures include most recently the British built Beagle 2 lander, the NASA Mars Climate Orbiter and Mars Polar Lander. These examples show there is no guarantee of a 100% foolproof spacecraft. In 2001 the Space Studies Board of the National Research Council published that the likelihood of life on Mars is low, "but it is not zero" and proposed the construction of a level-4 biohazard containment facility "like no other on the Earth". Since at this time we cannot guess whether any putative Martian organisms would be toxic or pathogenic to Earth life, every effort should be made to ensure that the terrestrial biosphere is not contaminated. Recent Mars Sample Return (MSR) scenarios have focused on a direct return to the surface of the Earth by means of a passive reentry capsule similar to the Stardust sample capsule but designed to use atmospheric friction and ablating to slow its decent instead of a parachute. This scenario offers less planetary protection than LEO examination by a specially trained scientific crew aboard the ISS or space shuttle. While a number of Mars Sample Return strategies have been published since the 1976 Viking mission, probably the most comprehensive concerning examination in LEO is the 1981 The Antaeus Report: Orbiting Quarantine Facility (NASA SP-454). Although the Antaeus Report demonstrated the feasibility of examining planetary samples in LEO it did not offer Earth's biosphere maximum protection against back contamination hazards due to possible catastrophic failure and reentry of the orbiting quarantine facility or space shuttle. A human tended Planetary Quarantine Laboratory as part of a scientific outpost on the Moon would offer 100% protection of Earth's biosphere against any toxic or pathogenic bioactive materials from Mars or any other solar system samples returned.

Proceedings Article | 26 February 2003 Paper

Dissolution cavities in Upper Ordovician sandstones from Lake Ontario: Analogs to vesiculated rocks on Mars?

Barry DiGregorio

Proceedings Volume 4859, (2003) https://doi.org/10.1117/12.457566

KEYWORDS: Mars, Organisms, Carbonates, Calcite, Calcium, Cameras, Space operations, Analog electronics, Astrobiology, Near field

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Fossiliferous sandstones of the Upper Ordovician (Lorraine Group) found along the Erie-Ontario Lowlands represent near-shore marine invertebrate communities which dominated the warm shallow sea that existed in this region 450 my ago. Subsequent glacial scouring and breakup of this ancient seabed during the Pleistocene resulted in its being buried under glacial sediments and soil. Then over a period of thousands of years, mild carbonic acid from rainwater mixed with humic acids from soil percolated through the sandstones and dissolved the entombed fossils leaving only dissolution cavities. This same process is how caves and karst features are formed. Rocks imaged by NASA’s Viking 2 lander in 1976 revealed ubiquitous “vesicles” that to this day remain enigmatic because the mineralogy of Martian rocks has not been adequately analyzed to date. Neither a sedimentary nor a volcanic origin for the rocks has been firmly established. Furthermore, proposed theories on the evolution of the Utopia Basin near the Viking 2 landing site include an ancient shallow ocean and glacial scouring. If Mars did indeed have an ocean at one point in its history, then the question must be asked “Did Martian lakes and oceans also have time enough for the development of life and ultimately to the multicellular stage that may have left traces of their existence as dissolution cavities? In this report, attention is drawn to the morphological similarities of biogenic dissolution cavities in terrestrial sandstones and in the near-field rocks at the Viking 2 landing site on Mars. The Beagle 2 astrobiology lander, part of the ESA’s Mars Express mission in 2003, will once again land in the northern plains of Mars not far from the shoreline of the proposed northern ocean basin. A comparison of the rocks from the Beagle 2 landing site to those at Viking 2 may shed further light on whether they are sedimentary or volcanic in origin, and, of greatest interest, whether the vesicles in the Martian rocks constitute analogs to the biologically formed dissolution cavities in the rocks of the Upper Ordovician on Lake Ontario.

Proceedings Article | 5 February 2002 Paper

Rock varnish as a habitat for extant life on Mars

Barry DiGregorio

Proceedings Volume 4495, (2002) https://doi.org/10.1117/12.454750

KEYWORDS: Mars, Iron, Ultraviolet radiation, Fiber optic gyroscopes, Manganese, Microorganisms, Bacteria, Oxides, Fungi, Atmospheric particles

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Many of the rocks on the surface of Mars that have been imaged by the Viking and Mars Pathfinder Landers display dark shiny surface coatings resembling Mn-rich terrestrial rock varnish. On our planet, these thin (5 um - 1 mm) coatings can be the result of a combination of various weathering processes combined with microbial precipitation of mineral oxides over a wide variety of geographical locations but most commonly in those with arid and semi-arid conditions. Terrestrial Mn-rich rock varnish is produced by a wide variety of microorganisms including epilithic and edolithic cyanobacteria, bacteria and microcolonial fungi. As these microorganisms absorb trace amounts of Mn and Fe from atmospheric dust, rain and fog, they slowly precipitate 'reddish' iron and 'brown to black' manganese oxides as well as magnetite particles. These microbial communities then produce secretions that cement the Mn/Fe mix together with clay particles in a process involving time periods of perhaps thousands of years for a thin 5 um layer. Mn-rich rock varnish has been found to form on the surfaces of undisturbed desert fragments and even sand grains. Both Mn and Fe would serve as a UV shield for any microflora residing beneath and within the layers of varnish thus protecting against high UV irradiation, dissication, and widely varying temperature extremes. Recent research on rock varnish has led to the discovery that some microbial communities that produce dark ferromanganese varnishes also precipitate biogenic magnetite. In view recent independent evidence put forth by D. McKay and E.I. Friedmann et al for indigenous biogenic magnetite-chains in ALH 84001 along with meteorological models showing the possibility for small quantities of liquid water on the surface of Mars in combination with data obtained from the Viking LR experiment 27 years ago, recommendations are made to elucidate on whether or not the shiny dark-coatings covering some Martian rocks have been produced by living or extinct microbial communities.

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