Haraldur Gunnlaugsson - Academia.edu (original) (raw)

Papers by Haraldur Gunnlaugsson

Research paper thumbnail of Mars og Marsaktiviteter - nye projekter under opsejling

Geologisknyt, 2006

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Research paper thumbnail of Mars og Marsaktiviteter - nye projekter under opsejling

GeologiskNyt, 2006

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Research paper thumbnail of Optical Properties of the Magnetic Dust on Mars

The abstract summarizes the results from a new analysis of the data from the Magnetic Properties ... more The abstract summarizes the results from a new analysis of the data from the Magnetic Properties Experiment on Mars Pathfinder, regarding the optical properties of the magnetic dust. Among the remarkable results of the Viking mission was the discovery that the Martian dust/soil is highly magnetic, in the sense that the dust is attracted by small hand magnets. Study of the properties of the magnetic dust is of importance, as it may contain invaluable clues on the surface processes that have shaped the planet, especially the role of water in these processes. The Mars Pathfinder lander carried two sets of the so-called Magnet Array (MA): an upper MA, placed on top of the electronics box, and a lower MA situated on the base petal between two of the solar-cell petals of the lander. Each MA consists of five "bulls eye" pattern magnets of various surface magnetic field strength. During the mission, these magnets collected magnetic dust particles suspended in the Martian atmosphere. Pictures were taken of the magnets at regular intervals using various optical filters, and these data were used for the analysis. Additional information is obtained in the original extended abstract.

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Research paper thumbnail of Magnetic Properties of the Dust on Mars

The abstract summarizes the results from a new analysis of the data from the Magnetic Properties ... more The abstract summarizes the results from a new analysis of the data from the Magnetic Properties Experiment on Mars Pathfinder regarding the magnetic properties of the dust. The Mars Pathfinder lander carried two sets of the socalled Magnet Array (MA): an upper MA, placed on top of the electronics box, and a lower MA situated on the base petal between

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Research paper thumbnail of Wind Mediated Oxidation of Pyrite: A Putative Mechanism for Sulfate Production on Mars

A reaction for sulfate formation from pyrite under conditions similar to the present martian envi... more A reaction for sulfate formation from pyrite under conditions similar to the present martian environment is reported.

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Research paper thumbnail of Wind Mediated Oxidation of Magnetite: A Putative Mechanism for Hematite Production on Mars

Experiments on magnetite (Fe3O4) to produce hematite (Fe2O3) under martian conditions are reporte... more Experiments on magnetite (Fe3O4) to produce hematite (Fe2O3) under martian conditions are reported. Water and atmospheric oxygen are not involved in oxidation. The findings represent a putative mechanism for the reddish color of Mars.

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Research paper thumbnail of The New Danish/ESA Mars Simulation Wind Tunnel at Aarhus University

This paper will present a new Mars wind tunnel that can work under simulated martian surface cond... more This paper will present a new Mars wind tunnel that can work under simulated martian surface conditions with a dusty atmosphere. It will be used for research projects, instrument development, testing and calibration.

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Research paper thumbnail of Mars Surface Simulations

Laboratory simulations of the Martian surface are of importance to broaden scientific understandi... more Laboratory simulations of the Martian surface are of importance to broaden scientific understanding of the physical processes, but also in order to develop the technology necessary for exploration of the planet. The Mars Simulation Laboratory at Aarhus University [1] has been involved in such simulations for around ten years and has developed several experimental facilities for carrying out science or instrument testing under conditions similar to those at the Martian surface, specifically low pressure, low temperature and importantly recreating the wind flow environment and dust suspension (reproducing the Martian dusty aerosol) using Mars analogue material [2]. The science involved in this simulation work has covered a broad spectrum including, erosion induced mineralogy/chemistry, particulate electrification, magnetic properties of Martian dust, biological survival, UV induced chemistry/mineralogy (using a solar simulator), adhesion/cohesion processes and the wind driven transpor...

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Research paper thumbnail of Wind Erosion

All planets/moons with an atmosphere can generate surface winds which can lead to the transport o... more All planets/moons with an atmosphere can generate surface winds which can lead to the transport of material and generate surface erosion, producing sand and sand form, forming dust and generating atmospheric dust aerosols. These processes actively restructure the planetary surface and can change its mineralogy. Although the physical processes are basic, there are wide variations in the transport/erosion rates, the spatial scales and the impact on climate. The work presented here covers various aspects of wind driven particulate transport specifically on Mars and Earth, from missions and laboratory work.

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Research paper thumbnail of Production of mineral aggregates in quartz tumbling experiments

Introduction Tumbling experiments with quartz sand with the purpose of tracing the effect of brok... more Introduction Tumbling experiments with quartz sand with the purpose of tracing the effect of broken bonds in mineral surfaces resulted in an unexpected production of aggregates. These aggregates are a few microns in diameter, spherical and resembling tiny white "snowballs." Particle comminution by aeolian and other natural weathering processes are known in soil science and is often seen as an increase of fine particles towards the top of soil profiles (Nørnberg, P. 1987, 1988, 2002, J.S. Wright 2007). When mineral grains collide in aeolian processes they break up along weakness zones in the crystal lattice. This mechanism causes broken bonds between atoms in the crystal lattice and results in reactive groups in the mineral surface. This mechanism provides the background for experiments to investigate the oxidation processes of magnetite on the planet Mars. The primary magnetic iron oxide phase on Mars is to day known to be magnetite and the colour of the dust on Mars is mo...

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Research paper thumbnail of Simulation of Martian surface conditions and dust transport

The suspended atmospheric dust which is also found deposited over most of the Martian globe plays... more The suspended atmospheric dust which is also found deposited over most of the Martian globe plays an important (possibly vital) role in shaping the surface environment. It affects the weather (solar flux), water transport and possibly also the electrical properties at the surface. The simulation facilities at Aarhus provide excellent tools for studying the properties of this Martian environment. Much can be learned from such simulations, supporting and often inspiring new investigations of the planet. Electrical charging of a Mars analogue dust is being studied within a wind tunnel simulation aerosol. Here electric fields are used to extract dust from suspension. Although preliminary the results indicate that a large fraction of the dust is charged to a high degree, sufficient to dominate adhesion/cohesion processes. A Mars analogue dust layer has been shown to be an excellent trap for moisture, causing increased humidity in the soil below. This allows the possibility for liquid wat...

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Research paper thumbnail of Characterization of barren, granitic soils from the Nubian Desert (SW Egypt) by 57Fe Mössbauer spectroscopy

Mineralogia, 2013

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Research paper thumbnail of Transformation of goethite/ferrihydrite to hematite and maghemite under temperate humid conditions in Denmark

ABSTRACT At a number of sandy soil sites in Mid Jutland, Denmark, with iron content of 1-2%, very... more ABSTRACT At a number of sandy soil sites in Mid Jutland, Denmark, with iron content of 1-2%, very red spots (Munsell colour: dusky red 10R 3/4) of a few square meters are found. These spots are most likely due to burning events. After the fire ashes raised pH. This dispersed silt and clay size soil particles which were then transported with seepage water down into lower soil horizons. These particles contain hematite and maghemite due to influence of the fire. However, a long-standing unresolved question is how hematite and maghemite can also be present along with goethite and ferrihydrite, in the same geographical region, and in extended areas with high iron content (8-40 %) in the topsoil. Hematite and particularly maghemite would normally not be expected to form under the temperate humid Danish climate, but be interpreted as the result of high temperature as found in tropical regions or as seen in soils exposed to fire. The high iron content most likely has its origin in pyrite dissolution in top of the groundwater zone in deeper Miocene deposits. From there Fe2+ is brought to the surface by the groundwater, and in wells oxidized by meeting the atmosphere and precipitated as two line ferrihydrite. This is later transformed into goethite. However, along with these two minerals hematite and maghemite are present in the topsoil around the well area. Forest fires would be a likely explanation to the hematite and maghemite. But a body of evidence argues against these sites having been exposed to fire. 1) The pH in the topsoil is 3.6 - 4.8 and thus not raised by ashes. 2) No charcoal is present. 3) There is no indication of fire outside the high iron content areas. 4) Goethite is present along with hematite and maghemite in microparticles, and the mineralogical zonation produced in a forest fire is not seen. The natural sites contain a uniform mixture of goethite/ferrihydrite, hematite and maghemite down to 20 cm depth. An experimental forest fire left charcoal and ashes at the topsoil, produced high pH, mineral zonation and decreased organic matter content, all of which is in contrast to the natural sites. In the freshly precipitated iron materials iron oxidizers as Gallionella sp. were found, but also iron reducing Geobachter sp.were present. Microbial activity might have influenced the mineral transformations.

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Research paper thumbnail of Mineralogical effects of an experimental forest fire on a goethite/ferrihydrite soil-an attempt to solve the presence of hematite and maghemite in topsoils in a temperate …

… 2010, held 2-7 May …, 2010

... conclusion from this work is that the mineralogy of these sites is not consistent with exposu... more ... conclusion from this work is that the mineralogy of these sites is not consistent with exposure to fire, but may rather result from long term transformation within a reducing environment, possibly involving microorganisms. References: Nørnberg, P., Vendelboe, AL, Gunnlaugsson ...

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Research paper thumbnail of Magnetic Properties Experiments Designed for Use with a Mössbauer Spectrometer and an APX Spectrometer on Mars

Lunar and …, 1994

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Research paper thumbnail of Salten Skov I: A Martian magnetic dust analogue

Planetary and Space Science, 2009

... Bell et al., 2000 JF Bell, HY McSween, JA Crisp, RV Morris, SL Murchie, NT Bridges, JR Johnso... more ... Bell et al., 2000 JF Bell, HY McSween, JA Crisp, RV Morris, SL Murchie, NT Bridges, JR Johnson, DT Britt, MP Golombek, HJ Moore, A. Ghosh, JL Bishop, RC Anderson, J. Brückner, T. Economou, JP Greenwood, HP Gunnlaugsson, RB Hargraves, SF Hviid, JM Knudsen, MB ...

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Research paper thumbnail of Analysis of the magnetic properties experiment data on Mars: results from Mars Pathfinder

Planetary and Space Science, 2000

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Research paper thumbnail of Mineral alteration induced by sand transport: A source for the reddish color of martian dust

Icarus, 2010

... The size distribution of quartz grains with selected diameters >125 μm (bl... more ... The size distribution of quartz grains with selected diameters >125 μm (blue curve) and after 212 ... Chemistry of rocks and soils in gusev crater from the alpha particle X-ray spectrometer ... KR Rasmussen, The effect of wind speed and bed slope on sand transport, Sedimentology 46 ...

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Research paper thumbnail of Titanium and the magnetic phase on Mars

Hyperfine Interactions, 1995

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Research paper thumbnail of Application of external magnetic field to characterize magnetic oxides in the carbonaceous chondrite Orgueil

Hyperfine Interactions, 1994

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Research paper thumbnail of Mars og Marsaktiviteter - nye projekter under opsejling

Geologisknyt, 2006

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Mars og Marsaktiviteter - nye projekter under opsejling

GeologiskNyt, 2006

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Optical Properties of the Magnetic Dust on Mars

The abstract summarizes the results from a new analysis of the data from the Magnetic Properties ... more The abstract summarizes the results from a new analysis of the data from the Magnetic Properties Experiment on Mars Pathfinder, regarding the optical properties of the magnetic dust. Among the remarkable results of the Viking mission was the discovery that the Martian dust/soil is highly magnetic, in the sense that the dust is attracted by small hand magnets. Study of the properties of the magnetic dust is of importance, as it may contain invaluable clues on the surface processes that have shaped the planet, especially the role of water in these processes. The Mars Pathfinder lander carried two sets of the so-called Magnet Array (MA): an upper MA, placed on top of the electronics box, and a lower MA situated on the base petal between two of the solar-cell petals of the lander. Each MA consists of five "bulls eye" pattern magnets of various surface magnetic field strength. During the mission, these magnets collected magnetic dust particles suspended in the Martian atmosphere. Pictures were taken of the magnets at regular intervals using various optical filters, and these data were used for the analysis. Additional information is obtained in the original extended abstract.

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Research paper thumbnail of Magnetic Properties of the Dust on Mars

The abstract summarizes the results from a new analysis of the data from the Magnetic Properties ... more The abstract summarizes the results from a new analysis of the data from the Magnetic Properties Experiment on Mars Pathfinder regarding the magnetic properties of the dust. The Mars Pathfinder lander carried two sets of the socalled Magnet Array (MA): an upper MA, placed on top of the electronics box, and a lower MA situated on the base petal between

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Research paper thumbnail of Wind Mediated Oxidation of Pyrite: A Putative Mechanism for Sulfate Production on Mars

A reaction for sulfate formation from pyrite under conditions similar to the present martian envi... more A reaction for sulfate formation from pyrite under conditions similar to the present martian environment is reported.

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Research paper thumbnail of Wind Mediated Oxidation of Magnetite: A Putative Mechanism for Hematite Production on Mars

Experiments on magnetite (Fe3O4) to produce hematite (Fe2O3) under martian conditions are reporte... more Experiments on magnetite (Fe3O4) to produce hematite (Fe2O3) under martian conditions are reported. Water and atmospheric oxygen are not involved in oxidation. The findings represent a putative mechanism for the reddish color of Mars.

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Research paper thumbnail of The New Danish/ESA Mars Simulation Wind Tunnel at Aarhus University

This paper will present a new Mars wind tunnel that can work under simulated martian surface cond... more This paper will present a new Mars wind tunnel that can work under simulated martian surface conditions with a dusty atmosphere. It will be used for research projects, instrument development, testing and calibration.

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Research paper thumbnail of Mars Surface Simulations

Laboratory simulations of the Martian surface are of importance to broaden scientific understandi... more Laboratory simulations of the Martian surface are of importance to broaden scientific understanding of the physical processes, but also in order to develop the technology necessary for exploration of the planet. The Mars Simulation Laboratory at Aarhus University [1] has been involved in such simulations for around ten years and has developed several experimental facilities for carrying out science or instrument testing under conditions similar to those at the Martian surface, specifically low pressure, low temperature and importantly recreating the wind flow environment and dust suspension (reproducing the Martian dusty aerosol) using Mars analogue material [2]. The science involved in this simulation work has covered a broad spectrum including, erosion induced mineralogy/chemistry, particulate electrification, magnetic properties of Martian dust, biological survival, UV induced chemistry/mineralogy (using a solar simulator), adhesion/cohesion processes and the wind driven transpor...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Wind Erosion

All planets/moons with an atmosphere can generate surface winds which can lead to the transport o... more All planets/moons with an atmosphere can generate surface winds which can lead to the transport of material and generate surface erosion, producing sand and sand form, forming dust and generating atmospheric dust aerosols. These processes actively restructure the planetary surface and can change its mineralogy. Although the physical processes are basic, there are wide variations in the transport/erosion rates, the spatial scales and the impact on climate. The work presented here covers various aspects of wind driven particulate transport specifically on Mars and Earth, from missions and laboratory work.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Production of mineral aggregates in quartz tumbling experiments

Introduction Tumbling experiments with quartz sand with the purpose of tracing the effect of brok... more Introduction Tumbling experiments with quartz sand with the purpose of tracing the effect of broken bonds in mineral surfaces resulted in an unexpected production of aggregates. These aggregates are a few microns in diameter, spherical and resembling tiny white "snowballs." Particle comminution by aeolian and other natural weathering processes are known in soil science and is often seen as an increase of fine particles towards the top of soil profiles (Nørnberg, P. 1987, 1988, 2002, J.S. Wright 2007). When mineral grains collide in aeolian processes they break up along weakness zones in the crystal lattice. This mechanism causes broken bonds between atoms in the crystal lattice and results in reactive groups in the mineral surface. This mechanism provides the background for experiments to investigate the oxidation processes of magnetite on the planet Mars. The primary magnetic iron oxide phase on Mars is to day known to be magnetite and the colour of the dust on Mars is mo...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Simulation of Martian surface conditions and dust transport

The suspended atmospheric dust which is also found deposited over most of the Martian globe plays... more The suspended atmospheric dust which is also found deposited over most of the Martian globe plays an important (possibly vital) role in shaping the surface environment. It affects the weather (solar flux), water transport and possibly also the electrical properties at the surface. The simulation facilities at Aarhus provide excellent tools for studying the properties of this Martian environment. Much can be learned from such simulations, supporting and often inspiring new investigations of the planet. Electrical charging of a Mars analogue dust is being studied within a wind tunnel simulation aerosol. Here electric fields are used to extract dust from suspension. Although preliminary the results indicate that a large fraction of the dust is charged to a high degree, sufficient to dominate adhesion/cohesion processes. A Mars analogue dust layer has been shown to be an excellent trap for moisture, causing increased humidity in the soil below. This allows the possibility for liquid wat...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Characterization of barren, granitic soils from the Nubian Desert (SW Egypt) by 57Fe Mössbauer spectroscopy

Mineralogia, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Transformation of goethite/ferrihydrite to hematite and maghemite under temperate humid conditions in Denmark

ABSTRACT At a number of sandy soil sites in Mid Jutland, Denmark, with iron content of 1-2%, very... more ABSTRACT At a number of sandy soil sites in Mid Jutland, Denmark, with iron content of 1-2%, very red spots (Munsell colour: dusky red 10R 3/4) of a few square meters are found. These spots are most likely due to burning events. After the fire ashes raised pH. This dispersed silt and clay size soil particles which were then transported with seepage water down into lower soil horizons. These particles contain hematite and maghemite due to influence of the fire. However, a long-standing unresolved question is how hematite and maghemite can also be present along with goethite and ferrihydrite, in the same geographical region, and in extended areas with high iron content (8-40 %) in the topsoil. Hematite and particularly maghemite would normally not be expected to form under the temperate humid Danish climate, but be interpreted as the result of high temperature as found in tropical regions or as seen in soils exposed to fire. The high iron content most likely has its origin in pyrite dissolution in top of the groundwater zone in deeper Miocene deposits. From there Fe2+ is brought to the surface by the groundwater, and in wells oxidized by meeting the atmosphere and precipitated as two line ferrihydrite. This is later transformed into goethite. However, along with these two minerals hematite and maghemite are present in the topsoil around the well area. Forest fires would be a likely explanation to the hematite and maghemite. But a body of evidence argues against these sites having been exposed to fire. 1) The pH in the topsoil is 3.6 - 4.8 and thus not raised by ashes. 2) No charcoal is present. 3) There is no indication of fire outside the high iron content areas. 4) Goethite is present along with hematite and maghemite in microparticles, and the mineralogical zonation produced in a forest fire is not seen. The natural sites contain a uniform mixture of goethite/ferrihydrite, hematite and maghemite down to 20 cm depth. An experimental forest fire left charcoal and ashes at the topsoil, produced high pH, mineral zonation and decreased organic matter content, all of which is in contrast to the natural sites. In the freshly precipitated iron materials iron oxidizers as Gallionella sp. were found, but also iron reducing Geobachter sp.were present. Microbial activity might have influenced the mineral transformations.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Mineralogical effects of an experimental forest fire on a goethite/ferrihydrite soil-an attempt to solve the presence of hematite and maghemite in topsoils in a temperate …

… 2010, held 2-7 May …, 2010

... conclusion from this work is that the mineralogy of these sites is not consistent with exposu... more ... conclusion from this work is that the mineralogy of these sites is not consistent with exposure to fire, but may rather result from long term transformation within a reducing environment, possibly involving microorganisms. References: Nørnberg, P., Vendelboe, AL, Gunnlaugsson ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Magnetic Properties Experiments Designed for Use with a Mössbauer Spectrometer and an APX Spectrometer on Mars

Lunar and …, 1994

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Salten Skov I: A Martian magnetic dust analogue

Planetary and Space Science, 2009

... Bell et al., 2000 JF Bell, HY McSween, JA Crisp, RV Morris, SL Murchie, NT Bridges, JR Johnso... more ... Bell et al., 2000 JF Bell, HY McSween, JA Crisp, RV Morris, SL Murchie, NT Bridges, JR Johnson, DT Britt, MP Golombek, HJ Moore, A. Ghosh, JL Bishop, RC Anderson, J. Brückner, T. Economou, JP Greenwood, HP Gunnlaugsson, RB Hargraves, SF Hviid, JM Knudsen, MB ...

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Research paper thumbnail of Analysis of the magnetic properties experiment data on Mars: results from Mars Pathfinder

Planetary and Space Science, 2000

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Research paper thumbnail of Mineral alteration induced by sand transport: A source for the reddish color of martian dust

Icarus, 2010

... The size distribution of quartz grains with selected diameters >125 μm (bl... more ... The size distribution of quartz grains with selected diameters >125 μm (blue curve) and after 212 ... Chemistry of rocks and soils in gusev crater from the alpha particle X-ray spectrometer ... KR Rasmussen, The effect of wind speed and bed slope on sand transport, Sedimentology 46 ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Titanium and the magnetic phase on Mars

Hyperfine Interactions, 1995

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Application of external magnetic field to characterize magnetic oxides in the carbonaceous chondrite Orgueil

Hyperfine Interactions, 1994

Bookmarks Related papers MentionsView impact