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Sökning: WFRF:(Johnsson Andreas 1977)

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1.
  • Bernhardt, H., et al. (författare)
  • Debris flow recurrence periods and multi-temporal observations of colluvial fan evolution in central Spitsbergen (Svalbard)
  • 2017
  • Ingår i: Geomorphology. - : Elsevier BV. - 0169-555X. ; 296, s. 132-141
  • Tidskriftsartikel (refereegranskat)abstract
    • Fan-shaped accumulations of debris flow deposits are common landforms in polar regions such as Svalbard. Although depositional processes in these environments are of high interest to climate as well as Mars-analog research, several parameters, e.g., debris flow recurrence periods, remain poorly constrained. Here, we present an investigation based on remote sensing as well as in situ data of a similar to 0.4 km(2) large colluvial fan in Hanaskogdalen, central Spitsbergen. We analyzed high resolution satellite and aerial images covering five decades from 1961 to 2014 and correlated them with lichenometric dating as well as meteorological data. Image analyses and lichenometry deliver consistent results and show that the recurrence period of large debris flows (>= 400 m(3)) is about 5 to 10 years, with smaller flows averaging at two per year in the period from 2008 to 2013. While this is up to two orders of magnitude shorter than previous estimates for Svalbard (80 to 500 years), we found the average volume of -220 m(3) per individual flow to be similar to previous estimates for the region. Image data also reveal that an avulsion took place between 1961 and 1976, when the active part of the fan moved from its eastern to its western portion. A case study of the effects of a light rain event (similar to 5 mm/day) in the rainy summer of 2013, which triggered a large debris flow, further shows that even light precipitation can trigger major flows. This is made possible by multiple light rain events or gradual snow melt pre-saturating the permafrost ground and has to be taken into account when predicting the likelihood of potentially hazardous mass wasting in polar regions. Furthermore, our findings imply a current net deposition rate on the colluvial fan of similar to 480 m(3)/year, which is slightly less than the integrated net deposition rate of 576 to 720 m(3)/year resulting from the current fan volume divided by the 12,500 to 10,000 years since the onset of fan build-up after the area's deglaciation. However, the actual deposition rate, which should increase in a warmer climate including more rain, cannot be constrained due to effects like ongoing toe-cutting of the debris fan and some flows only causing internal redistributions.
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2.
  • Carlsson, Ella, et al. (författare)
  • An evaluation of models for Martian gully formation using remote sensing and in situ measurments of Svalbard analogs.
  • 2008
  • Ingår i: Lunar and Planetary Science Conference 39. ; XXXIX:1852
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The newly discovered gully systems on Mars have been found on rather young geologi-cal surfaces such as dunes and polygons. This in combination with the general absence of superimposed impact craters suggests that the gullies are relatively young geological features. Their morphology indicates that they have been eroded by a liquid fluid, most probably water. A recent discovery suggests that gully formation is an ongoing process, which appears to occur even today. This is a paradox since water in current Martian atmospheric conditions cannot be found in a stable form on the surface due to the low pressure and temperature during normal conditions. Several formation mechanisms have been proposed for the Martian gullies such as liquid carbon dioxide reservoirs, shallow liquid water aquifer, melting ground ice, dry landslide, snow melt and deep liquid water aquifer. However, none of these models can alone explain all the gullies discovered on Mars. So far Martian gullies have only been studied from high orbit via satellites. Gullies found in Arctic climates on Earth could be an equitable analog for the Martian gullies and a com-parative analysis could help disclose the formation mechanisms of the Martian gullies as well as their eroding agent.
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3.
  • Carlsson, Ella, et al. (författare)
  • FIELD STUDIES OF GULLIES AND PINGOS ON SVALBARD – A MARTIAN ANALOG.
  • 2008
  • Ingår i: European Planetary Science Congress, 21-26 September 2008. ; 3
  • Konferensbidrag (refereegranskat)abstract
    • The gully systems on Mars have been found to superpose young geological surfaces such as dunes and thermal contraction polygons. This in combination with the general absence of superimposed impact craters suggest that the gullies are relatively recent geological formations. The observed gullies display a wide set of morphologies ranging from features seemingly formed by fluvial erosion to others pointing to dry landslide processes. A recent discovery suggests that this is an ongoing process, which appears to occur even today. Several formation mechanisms have been proposed for the Martian gullies, such as liquid carbon dioxide reservoirs, shallow liquid water aquifer, melting ground ice, dry landslide, snow melt and deep liquid water aquifer. However, none of these models can alone explain all the gullies discovered on Mars. So far Martian gullies have been studied only from orbit via remote sensing data. Hydrostatic pingos are perennial ice-cored mounds that may reach an elongated or circular radius of approximately 150 m. They are found in periglacial environments where they are formed by freezing processes in the continuous permafrost. The pingos go through different evolutionary stages as they mature, where the final stage leaves an annular rim left by the collapse of the summit. Images from the High Resolution Imaging Science Experiment (HiRISE) show small fractured mounds in the Martian mid-latitudes. Even though some differences are observed, the best terrestrial analogues for the observed mound morphology are pingos. Gullies and pingos found in Arctic climates on Earth could be an analog for the Martian ones. A comparative analysis might help to understand the formation mechanisms of the Martian pingos and gullies and their possible eroding agent.
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4.
  • de Vera, Jean Paul, et al. (författare)
  • EUROX (Europa Explorer): An astrobiology mission concept to the Jovian icy moon Europa.
  • 2008
  • Ingår i: Geophysical Research Abstracts. ; 10, EGU2008-A-01483, 2008
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The discovery of so-called extremophiles indicates how robust life is. That microbial life can resist extreme and harsh environmental conditions as e.g. very high and cold temperatures, desiccation, acidity, salinity and wide ranges of radiation spectra including UV and X-rays, suggests that micro organisms are capable of surviving and maintaining essential living functions, or often thriving, in conditions previously thought impossible. Recently it seems that only liquid water and an energy source are the core prerequisites for the development of life, greatly expanding the range of potential habitats for life both on Earth and in the solar system. In light of these discoveries, the definition of the “Habitable Zone” as the region where liquid water can exist at a planetary surface may need revision. Energy in the form of heat may be found on several volcanic worlds in our solar system, and subsurface liquid water may exist there, too. One likely candidate for such a reserve of water is the jovian icy moon Europa. Imaged by the Voyager and Galileo probes, this icy body appears to have a geologically young outer surface. Spectroscopic studies from Earth have confirmed that the European crust is composed of water ice. Long cracks across its surface may be suggestive of huge ice blocks rafting upon an underlying liquid layer. Darker non ice material also covers much of the surface and is spatially associated with the cracks. Recent modeling suggests that tidal forces imparted upon the moon by Jupiter may cause heating in the depth – raising the possibility of a liquid water ocean beneath Europa’s icy crust. Further on it is supposed that a weak induced magnetic field is present on the moon. This classifies Europa as an object of great scientific interest, warranting investigation for habitability and even the presence of life within the supposed ocean of the moon. The Europa Explorer (EUROX) mission complements other proposed missions to study Europa. EUROX will characterize the habitability potential of Europa, with the aim of understanding whether life could exist there or not. The mission will address the following key questions: (i) existence or non- existence of a liquid ocean beneath the surface, (ii) the nature of the non icy material visible upon the surface cracks, (iii) the physical characteristics of the ice crust, (iv) effects by local radiation on the surface chemistry, (v) the depth of radiation penetration in the ice and probably shielding effects by a magnetic field and (vi) the presence of organic compounds on or in the Europan ice crust. Our proposed mission will operate as a fully European and further on international mission, with the aim of providing the initial information required for later, larger missions to visit Europa. EUROX will involve both remote-sensing and in-situ research. Its mission architecture sees a single space craft deployed to Europa, launched by an Ariane 5. This vehicle will use conventional propulsion and a Venus-Earth-Earth flight path to travel to the jovian system in six years. Upon arrival at Europa, the space craft will commence remote observations of the icy moon, to determine the physical nature of the ice crust, and to investigate the presence of a subsurface liquid ocean. The orbiter will carry two independent vehicles (two penetrators) that will then separate, de-orbit, and penetrate the crust nearby or in the cracks to a depth of several meters. A suite of compact instruments will address the physical and chemical properties of the crust, as well as seeking organic compounds and pre-biotic material in the ice. The use of a laser communication system removes the need for a relay spacecraft in orbit around Jupiter, decreasing overall mission cost. Expected orbiter mission duration is on the order of two months, with each penetrator functioning for approximately 24 hours.
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5.
  • Ekelin, Svante, et al. (författare)
  • Real-Time Measurement of End-to-End Available Bandwidth using Kalman Filtering
  • 2006
  • Ingår i: 10th IEEE/IFIP Network Operations and Management Symposium, 2006. NOMS 2006.. - Piscataway, New Jersey, USA : IEEE Computer Society. - 1424401429 - 9781424401420 ; , s. 73-84
  • Konferensbidrag (refereegranskat)abstract
    • This paper presents a new method, BART (bandwidth available in real-time), for estimating the end-to-end available bandwidth over a network path. It estimates bandwidth quasi-continuously, in real-time. The method has also been implemented as a tool. It relies on self-induced congestion, and repeatedly samples the available bandwidth of the network path with sequences of probe packet pairs, sent at randomized rates. BART requires little computation in each iteration, is lightweight with respect to memory requirements, and adds only a small amount of probe traffic. The BART method uses Kalman filtering, which enables real-time estimation (a.k.a. tracking). It maintains a current estimate, which is incrementally improved with each new measurement of the inter-packet time separations in a sequence of probe packet pairs. The measurement model has a strong non-linearity, and would not at first sight be considered suitable for Kalman filtering, but we show how this non-linearity can be handled. BART may be tuned according to the specific needs of the measurement application, such as agility vs. stability of the estimate. We have tested an implementation of BART in a physical test network with carefully controlled cross traffic, with good accuracy and agreement. Test measurements have also been performed over the Internet. We compare the performance of BART with that of pathChirp, a state-of-the-art tool for measuring end-to-end available bandwidth in real-time
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6.
  • Gastineau, R., et al. (författare)
  • Small-scale lobate hillslope features on Mars: A comparative 3D morphological study with terrestrial solifluction lobes and zebra stripe lobes
  • 2020
  • Ingår i: Icarus. - : Elsevier BV. - 0019-1035. ; 342
  • Tidskriftsartikel (refereegranskat)abstract
    • Small-scale lobes (SSL) observed at the surface of Mars are thought to be the result of solifluction. Hence, their existence has important implications for our understanding of recent climate history, the distribution of thaw liquids and its geomorphic effects, as water is believed not to have been recently stable at the martian surface. These small-scale lobes are limited to sloping terrains and often occur alongside polygonal patterned ground attesting to the presence of ice in the environment. In this study, we perform a comparative 3D morphometric analysis of the lobes on Mars with terrestrial analogues. We use data from High Resolution Imaging Science Experiment (HiRISE) camera in order to create Digital Terrain Models (DTMs) on Mars at 1 m/pix. For the terrestrial analogues, we use DTMs and orthophotos from five periglacial environments with solifluction lobes and from one site with lobate features found in the Atacama Desert. The lobate features in the Atacama Desert are found within features called “zebra stripes”, which are apparently unique to the Atacama and are now generally accepted to be the result of seismic shaking. We show that SSL on Mars overlap morphometrically with terrestrial solifluction lobes, and are less similar to zebra stripe lobes. The majority of martian SSL occur below the angle of repose which demonstrates that a dry fall mechanism cannot be responsible for their formation and that lubrication of the subsurface is required. We found that martian SSL only occur on slopes greater than ~10°, a constraint not observed for terrestrial solifluction lobes nor zebra stripe lobes in Atacama. We hypothesise that this apparent constraint does not result from the lowered gravity on Mars, but instead from differing soil properties and/or thermal regime between Mars and Earth which affects the slope at which creep can initiate. We cannot rule out a role of CO2 sublimation in lobe-formation based on our terrestrial measurements. © 2019 Elsevier Inc.
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7.
  • Haas, Tjalling de, et al. (författare)
  • Earth-like aqueous debris-flow activity on Mars at high orbital obliquity in the last million years
  • 2015
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 6
  • Tidskriftsartikel (refereegranskat)abstract
    • Liquid water is currently extremely rare on Mars, but was more abundant during periods of high obliquity in the last few millions of years. This is testified by the widespread occurrence of mid-latitude gullies: small catchment-fan systems. However, there are no direct estimates of the amount and frequency of liquid water generation during these periods. Here we determine debris-flow size, frequency and associated water volumes in Istok crater, and show that debris flows occurred at Earth-like frequencies during high-obliquity periods in the last million years on Mars. Results further imply that local accumulations of snow/ice within gullies were much more voluminous than currently predicted; melting must have yielded centimetres of liquid water in catchments; and recent aqueous activity in some mid-latitude craters was much more frequent than previously anticipated.
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8.
  • Harris, M., et al. (författare)
  • The Kumbis and Nagatis Formations and the Helmeringhausen Gabbro: Oldest undeformed rocks of the Sinclair Supergroup in Namibia
  • 2020
  • Ingår i: Journal of African Earth Sciences. - : Elsevier BV. - 1464-343X. ; 165
  • Tidskriftsartikel (refereegranskat)abstract
    • The Mesoproterozoic rocks of the Kumbis and Nagatis Formations and Helmeringhausen Gabbro in Southern Namibia are now recognised as the oldest rocks in the sedimentary and volcanic Sinclair Supergroup. The stratigraphic subdivision and plate tectonic setting are still debated and reliable ages are sparse. This work investigates the relatively undeformed felsic and mafic lava of the Kumbis Formation, rhyolitic lava of the Nagatis Formation and the intrusive Helmeringhausen Gabbro. Microscopic and field investigation reveals no evidence of regional metamorphism in these units. Ion probe U-Pb zircon dating yields ages of 1374 +/- 7 Ma to 1358 +/- 5 Ma (2 sigma) for the Kumbis Formation, 1363 +/- 11 Ma for the Nagatis Formation and 1372 +/- 12 Ma for the Helmeringhausen Gabbro. These dates are in contrast to the published stratigraphy in which the Helmeringhausen Gabbro was regarded as much older than the Kumbis Formation and both were excluded from the Sinclair Supergroup, whereas the Nagatis Formation was considered to be younger and was included as the oldest unit of the Sinclair Supergroup. Lu-Hf data on zircon indicates different magma sources for the Kumbis and Nagatis Formations, implying that although they are time equivalent, they are not co-magmatic. The geochemical data suggests that the most felsic rocks contain large amounts of older crustal material, from which their apparent subduction signatures were inherited. The more mafic rocks also contain minor crustal components mixed with material derived from depleted mantle. The Helmeringhausen Gabbro is similar to coeval hybrid gabbros at Neuhof Valley 150 Km to the north and they are grouped in the intrusive Helmering Suite. Taking the regional context into account, these oldest rocks of the Sinclair Supergroup probably formed in a rift environment which split the Rehoboth Province apart at the beginning of the Mesoproterozoic Namaqua-Natal Wilson Cycle.
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9.
  • Hauber, Ernst, et al. (författare)
  • DEBRIS FLOW FANS AND PERMAFROST LANDFORMS ON SVALBARD (NORWAY): TERRESTRIAL ANALOGUES FOR MARTIAN MID-LATITUDE PERIGLACIAL LANDSCAPES.
  • 2010
  • Ingår i: 41st Lunar and Planetary Science Conference. ; :1922
  • Konferensbidrag (refereegranskat)abstract
    • Many young landforms on Mars that were probably formed by exogenic processes show a latitude- dependent geographic distribution. They include surface mantling, lobate debris aprons, lineated valley fill, and concentric crater fill, viscous flow features, gullies, and patterned ground. Collectively, these landforms are hypothesized to represent the surface records of Martian ice ages that were induced by astronomical forcing and associated climate changes. Previous studies often considered just one of the features in isolation (e.g., gullies), without taking into account the geomorphologic context. A more comprehensive investigation of the full assemblage of landforms (landscape analysis), however, has the potential to reduce the ambiguity in interpreting landforms (the problem of equifinality, e.g., in the case of pingos), and to reveal the evolution of the climatic environment in more detail. Here we present permafrost landforms of Svalbard (Norway) as useful terrestrial analogues for the suite of possible periglacial landforms that are typically found at mid-latitudes on Mars. We build on our previous investigations of gullies and fans, and include a number of classical periglacial landforms (patterned ground, rock glaciers, pingos) that all have close morphological analogues on Mars. Based on this comparison, we propose an evolutionary scenario which helps to understand the sequential formation of the Martian landforms into their present state.
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10.
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11.
  • Hauber, Ernst, et al. (författare)
  • Landscape evolution in Martian mid-latitude regions: Insights from analogous periglacial landforms in Svalbard.
  • 2011
  • Ingår i: Geological Society, London, Special Publications. ; 356, s. 111-131
  • Tidskriftsartikel (refereegranskat)abstract
    • Periglacial landforms on Spitsbergen (Svalbard, Norway) are morphologically similar to landforms on Mars that are probably related to the past and/or present existence of ice at or near the surface. Many of these landforms, such as gullies, debris-flow fans, polygonal terrain, fractured mounds and rock-glacier-like features, are observed in close spatial proximity in mid-latitude craters on Mars. On Svalbard, analogous landforms occur in strikingly similar proximity, which makes them useful study cases to infer the spatial and chronological evolution of Martian coldclimate surface processes. The analysis of the morphological inventory of analogous landforms on Svalbard and Mars allows the processes operating on Mars to be constrained. Different qualitative scenarios of landscape evolution on Mars help to better understand the action of periglacial processes on Mars in the recent past.
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12.
  • Hauber, Ernst, et al. (författare)
  • MORPHOMETRY OF ALLUVIAL FANS IN A POLAR DESERT (SVALBARD, NORWAY): IMPLICATIONS FOR INTERPRETING MARTIAN FANS.
  • 2009
  • Ingår i: 40th Lunar and Planetary Science Conference. ; :1648
  • Konferensbidrag (refereegranskat)abstract
    • Alluvial fan-like landforms have been identified on Mars. Since alluvial fans are recorders of processes that are sensitive to climatic conditions, the investigation of possible Martian fans can reveal information about the planet`s climate. In lieu of direct observations of active depositional processes on Martian fans, comparisons with terrestrial analogues can constrain models of Martian fan formation derived from remote sensing data. Since present-day Mars is cold and dry, alluvial fans formed in cold deserts should be considered as useful analogues. The probably closest climatic analogue to Mars on Earth are the Antarctic Dry Valleys , but polar deserts can also be found in the Arctic. We report on our field work in summer 2008 and a simultaneous flight campaign with an airborne version (HRSC-AX) of the High Resolution Stereo Camera (HRSC) onboard Mars Express. The results are compared with measurements of Martian fans, based on HRSC DEM.
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13.
  • Hauber, Ernst, et al. (författare)
  • Periglacial landscapes on Svalbard: Terrestrial analogs for cold-climate landforms on Mars
  • 2011
  • Ingår i: The Geological Society of America, Special Paper. - : Geological Society of America. ; 483
  • Tidskriftsartikel (refereegranskat)abstract
    • We present landforms on Svalbard (Norway) as terrestrial analogs for possible Martian periglacial surface features. While there are closer climatic analogs for Mars, e.g., the Antarctic Dry Valleys, Svalbard has unique advantages that make it a very useful study area. Svalbard is easily accessible and offers a periglacial landscape where many different landforms can be encountered in close spatial proximity. These landforms include thermal contraction cracks, slope stripes, rock glaciers, protalus ramparts, and pingos, all of which have close morphological analogs on Mars. The combination of remotesensing data, in particular images and digital elevation models, with field work is a promising approach in analog studies and facilitates acquisition of fi rst-hand experience with permafrost environments. Based on the morphological ambiguity of certain landforms such as pingos, we recommend that Martian cold-climate landforms should not be investigated in isolation, but as part of a landscape system in a geological context.
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14.
  • Hauber, Ernst, et al. (författare)
  • Svalbard (Norway) as a terrestrial analogue for Martian landforms: Results on
  • 2009
  • Ingår i: EPSC Abstracts. European Planetary Science Congress. ; 4, EPSC2009-772
  • Konferensbidrag (refereegranskat)abstract
    • Small alluvial fan-like landforms have been observed on Mars in association with recent gullies. Such fans are relatively small (km-scale) when compared to large alluvial fans on Mars, which can reach dimensions of tens of kilometers. The small fans are part of an erosion-transportsedimentation system (alcove-channel-apron). Morphologically very similar systems can be studied on Svalbard (Norway), which is a cold and dry polar desert and, therefore, a potentially useful terrestrial analogue for Mars` climate and climaterelated landforms. Here we give an update on our field work in summer 2008 and a simultaneous flight campaign with an airborne version (HRSCAX) of the High Resolution Stereo Camera (HRSC) onboard Mars Express. We also present very preliminary results from the field campaign in summer 2009.
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15.
  • Johnsson, Andreas, 1977 (författare)
  • Bokrecension: Framåt Mars! : Framåt Mars!. Ella Carlsson. Stockholm: Fahrenheit, 2006. 214 pp.
  • 2006
  • Ingår i: Populär Astronomi. Redaktör: Dr. Björn Stenholm. - 1650-7177. ; 7:2
  • Recension (övrigt vetenskapligt/konstnärligt)abstract
    • Så har den äntligen kommit, den första boken om planeten Mars skriven av en svensk marsforskare och sann rymdentusiast. Ella Carlsson är doktorand vid institutet för Rymdfysik där hon analyserar data från instrumentet Analyzer of Space Plasma and Energetic Atoms (ASPERA) som finns ombord på europeiska sonden Mars Express. Ellas forskning går ut på att fastställa hur solvinden inverkar på Mars atmosfär och hur mycket av atmosfären som har eroderats bort under planetens utveckling. Hennes forskning är mycket viktig då den lägger nya pusselbitar till frågan om var vattnet på Mars tagit vägen. Ella har vid sidan om sitt stora rymdintresse en gedigen bakgrund inom farkostteknik. Innan civilingenjörsstudierna inom rymdteknik, som kom att leda fram till den nuvarande forskarutbildningen, var hon verksam som officer inom svenska flygvapnet med bl.a. FN uppdrag i Bosnien. Ella har dessutom fått möjlighet att delta vid två spännande simuleringar av mars-vistelser på Mars Desert Research Station (MDRS) Utah-öknen i USA respektive på Flashline Mars Archtic Research Station (FMARS) på Devon Island i arktiska Kanada. Forskningen kring Mars är nu inne i ett spännande skede efter att en rad uppdrag till planeten rönt enorma framgångar. För närvarande rullar två robotbilar på ytan och fyra sonder cirkulerar i omlopp kring planeten där Mars Reconnaissance Orbiter satelliten är det senaste tillskottet. Dessa har påbörjat, och kommer att fortsätta generera en mängd nya data som idag sysselsätter många forskargrupper runt om i världen. Vår kunskap om Mars ökar snabbare idag än den någonsin gjort tidigare. Därför är en svensk bok tillägnad den senaste utforskningen av Mars ytterst önskvärd och välkommen.
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16.
  • Johnsson, Andreas, 1977 (författare)
  • Cold-climate landforms on Mars and Earth-analogues in Svalbard
  • 2012
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Periglacial landforms on Earth reflect cold-climate conditions and are intimately related to processes due to the presence of ground ice and perennially frozen ground, permafrost. The overall objective of this thesis is to investigate the potential of Svalbard as an analogue to Mars cold-climate landforms, and explore past and present processes and surface conditions on Mars by inference from morphological counterparts in Svalbard. Svalbard has unique advantages that make it a very useful study area. Svalbard is easily accessible and offers a periglacial landscape where many different landforms can be encountered in close spatial proximity. These landforms include thermal contraction cracks, slope stripes, rock glaciers, gullies, debris flows, solifluction lobes, protalus ramparts, and pingos, all of which are close morphological analogues to landforms on Mars. An approach of integrated landscape analysis, inferred from landform assemblages in Svalbard, is aimed to explore modeling landscape evolution on Mars. Key datasets include visual remote sensing data of similar resolution (20–25 cm/pxl) from Svalbard (High Resolution Stereo Camera–Airborne Extended [HRSC-AX]) and Mars (High Resolution Imaging Science Experiment [HiRISE]). Additional data are digital elevation models over both Svalbard and Mars and remote sensing data from Mars, such as Thermal Emission Imaging System (THEMIS) and Context Camera (CTX) images. Field work was done in combination with remote sensing to acquire ground-truth data. In Svalbard, fluvial and debris-flow processes are evident in the formation of gullies, but the morphological characteristics clearly show that the transport and sedimentation of eroded material are predominated by debris flows. Most investigated gullies on Mars lack clear evidence for debris-flow processes. The Martian gully fan morphology is more consistent with the deposition of small overlapping fans by multiple fluvial flow events. Clear evidence for debris flows on Mars was only found in two new locations, in addition to a few previously published examples. Detailed studies on debris-flow deposits in a young mid-latitude crater on Mars suggest the action of liquid water after Mars’ last ice age (0.4–2.1 Ma ago). It may represent the most recent morphological indication of water induced mass wasting on Mars. An investigation of small-scale lobes on Mars northern high-latitudes and their morphological counterparts in Svalbard (solifluction lobes) further suggests widespread thawing and the presence of transient liquid water in the recent past on Mars. Finally, different qualitative scenarios of landscape evolution on Mars to better understand the action of periglacial processes on Mars in the recent past are proposed. The results show that field work is a suitable approach in analogue studies and facilitates acquisition of first-hand experience with permafrost environments. Based on the morphological ambiguity of certain landforms, it is concluded that Martian cold-climate landforms should not be investigated in isolation, but as part of a landscape system in a geological and spatial context. Analogous landforms in Svalbard occur in strikingly similar proximity as on Mars, which makes them useful to infer the spatial and chronological evolution of Martian cold-climate surface processes. The analysis of the morphological inventory of analogous landforms and landform systems in Svalbard and on Mars give substantial information to constrain the processes operating on the surface of Mars
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17.
  • Johnsson, Andreas, 1977 (författare)
  • Debris flows of the mountain massif of Hjorthfjellet and Adventtoppen, Svalbard: Implications for gullies on mountains in the Argyre basin, Mars
  • 2008
  • Ingår i: European Planetary Science Congress, 21-26 september 2008. ; 3
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Martian gullies resemble terrestrial features formed by mass-wasting processes of a flowing mixture of clastic debris and water (debris flows). Their existence on Mars is interpreted to indicate liquid water in the recent past because of their pristine appearance, their stratigraphic relationships to young surface features, their lack of superimposed impact craters, and their distinct albedo relative to the surroundings, indicating limited dust cover. The global distribution of gullies is limited to mid- and high-latitudes poleward of 30° in both hemispheres, with the highest frequency in the 30°–50° latitude bands. Gullies occur preferentially on poleward-facing slopes. The most likely and physically most plausible medium to explain the gully morphology is liquid water. Two main theories exist for the water source. One holds that water was released from the subsurface. The other proposes that water is deposited as near-surface ice or snow from the atmosphere and is subsequently melted by insolation. Debris flows found in Arctic climates on Earth could be an equitable analog for the Martian gullies. A comparative analysis might help to understand their formation mechanisms and the latitude-dependent, but clustered distribution as well as their specific orientations. The comparative analysis in the Arctic environment of Svalbard will be carried out in July/August of 2008. First results of the analog study of gullies will be presented at the conference.
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18.
  • Johnsson, Andreas, 1977, et al. (författare)
  • Evidence for very recent melt-water and debris flow activity in gullies in a young mid-latitude crater on Mars
  • 2014
  • Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 235, s. 37-54
  • Tidskriftsartikel (refereegranskat)abstract
    • Terrestrial debris flows and their deposits are mainly studied and monitored because of their hazardous nature. On Mars they may serve as geomorphologic indicators of transient liquid water. We compared the morphology of debris flow-like deposits within a young (∼0.2 Ma) mid-latitude crater on Mars with debris flow fans on Svalbard as possible terrestrial analogues. It was our objective to constrain whether dry granular flow or processes related to water-saturation at or close to the surface were responsible for the formation of the deposits within the crater. We found that the morphological attributes of the deposits on Mars are very similar to debris flows in Svalbard and include overlapping terminal lobes, debris tongues and snouts, debris-flow fans, scoured channels with medial deposits (debris plugs), and clearly defined lateral deposits (levées). Furthermore, the interior crater walls display a range of landforms indicating aspect-dependent degradation, ranging from debris flow-dominated pole-facing slopes, to east-and-west-facing single channel gullies and north-facing talus cones (granular flow). Our findings suggest that the debris flows are not related to impact-induced heating and release of meltwater. We further suggest that degradation of a latitude dependent dust-ice mantling unit may only have played a minor role in this youthful terrain. Instead, we propose that the debris flows are mainly formed by melting of very recent snow deposits after the termination of the last Martian ice-age. As such they may represent some of the most recent geomorphological indicators of transient liquid water in the Martian mid-latitudes. The distinct north-south asymmetry in degradation further demonstrates that insolation-controlled slope processes are surprisingly efficient on Mars during the last <1 Myr.
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19.
  • Johnsson, Andreas, 1977, et al. (författare)
  • GEOLOGICALLY RECENT DEBRIS FLOWS IN A WELL-PRESERVED IMPACT CRATER, MARS: INSIGHTS FROM TERRESTRIAL ANALOGS IN SPITSBERGEN, SVALBARD.
  • 2011
  • Ingår i: 42nd Lunar and Planetary Science Conference. ; 42:2541
  • Konferensbidrag (refereegranskat)abstract
    • Gullies on Mars are known to display a range of different morphologies but typically include an alcove, channel and apron. Several processes have been invoked to explain their genesis ranging from grain flow, debris flow to fluvial erosion with alluvial deposition. Albeit there is a general consensus that the medium involved is water, more attention is now drawn towards the dominant depositional processes of the gully fan formation. The observed range of fan morphologies asks for several depositional mechanisms and likely vary at different sites due to regional and local differences in climate and colluvial source material. Studies indicate that the common mechanism is fluvial deposition in contrast to debris flow dominated fans which have only been documented at three sites. These sites formed debris deposits of apparently fine grained dusty mantle material. Here we report on unusual Martian debris flows in an unnamed southern hemisphere crater which is rich in coarse grained colluvial material that forms well preserved debris flows, debris plugs and levees. It also displays numerous fresh looking rock falls. This raises the following questions: Why does so well-developed debris flows occur here and not in other nearby craters? What role does the coarse colluvial material play in debris flow initiation and development? Here we describe the debris flow morphology and we compare the morphology of debris flow deposits in Svalbard as potential terrestrial analogs. Furthermore, we investigate the sieve-deposition model as an explanation for the unusual morphology of these debris deposits.
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20.
  • Johnsson, Andreas, 1977, et al. (författare)
  • LATITUDINAL SURVEY OF PERIGLACIAL LANDFORMS AND GULLIES IN EASTERN ARGYRE AND POLEWARDS ON MARS.
  • 2009
  • Ingår i: 40th Lunar and Planetary Science Conference. ; :2405
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • On Earth periglacial features consists of an arrange of landforms with ground ice affinities, which involves different formation processes. On Mars there are extensive areas of ground ice which display a range of landforms similar to those on Earth. These landforms are important in understanding late climate evolution, subsurface processes and surface atmosphere interaction on Mars. In our study we focus on patterned ground, thermokarst and gullies. Patterned ground can be divided in to non-active (annual frozen) layer features like thermal contraction polygons and sublimation polygons, and active layer (freeze and thaw) features like sorted nets and circles, striated soils and stripes. Previous investigations have mainly looked at the global distribution and seasonal changes in patterned ground. A recent study using high resolution HiRISE images hypothezise that active layer patterns of sorted circles occur on Mars which would have important implications for late climate evolution. We are currently performing a detailed investigation of the Argyre area 325º - 335º E and 30º S – 90º S using all available MOC, HiRISE, HRSC, THEMIS and MOLA data. The area was chosen due to a wide diversity of periglacial landforms, a large difference in elevation, and for the past glacial and hydrologic history of the Argyre basin. The focus of this ongoing work is to investigate the influence by changes in topography, ground conditions, geologic context and latitude on a local and regional level. One addressed question is of micro climate zonation and its implication for late climate evolution.
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21.
  • Johnsson, Andreas, 1977 (författare)
  • Mars undersöks via Svalbard
  • 2009
  • Ingår i: Geologiskt Forum. - 1104-4721. ; 16:64, s. 13-16
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Kan vi lära oss något om vår grannplanet Mars genom att studera karga miljöer, exempelvis uppe i Arktis? Den frågan ställde sig en grupp forskare som fältarbetade på Svalbard i somras. Deras uppgift var att studera bäckraviner. Läs Andreas Johnssons berättelse om vatten på Mars och Svalbardforskningen.
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22.
  • Johnsson, Andreas, 1977- (författare)
  • Modeling, Implementation and Evaluation of IP Network Bandwidth Measurement Methods
  • 2007
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Internet has gained much popularity among the public since the mid 1990's and is now an integrated part of our society. A large range of high-speedbroadband providers and the development of new and more efficient Internet applications increase the possibilities to watch movies and live TV, use IP-telephony and share files over the Internet. Such applications demand high data transmission rates, which in turn consume network bandwidth. Since several users must share the common bandwidth capacity on the Internet, there will be locations in the network where the demand is higher than the capacity. This causes network congestion, which has negative impact on both the data transmission rate and transmission quality.This thesis is about methods for measuring the available bandwidth of a network path between two computers. The available bandwidth can be interpreted as the maximum transfer rate possible without causing congestion. By deploying the methods studied in this thesis the available bandwidth can be measured without previous knowledge of the network topology. When an estimate of the available bandwidth is obtained, the transfer rate when sending messages between computers can be set to the measured value in order to avoid congestion.In the thesis an active end-to-end available bandwidth measurement method called "Bandwidth Available in Real Time" (BART for short) is evaluated. BART measures the available bandwidth by injecting probe packets into the network at a given rate and then analysing how this rate has changed on the receiving side. A Kalman filter is used to update the current estimate of the available bandwidth using the new measurement sample.The focus of the thesis is on how methods, such as BART, function in wireless 802.11 networks, which are very popular in work as well as in home environments. Wireless networks have a different construction compared to many other types of networks and this can affect the accuracy of the measurement methods discussed in this thesis. The effects must be analyzed and understood in order to obtain accurate available bandwidth estimates. Since wireless links are often parts of the network path between a sender and a receiver on the Internet, it is important to study how these links affect the estimates of the available bandwidth.
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23.
  • Johnsson, Andreas, 1977 (författare)
  • Periglacial landforms on Mars as indicators of a changing climate – morphologic evidence from the southern water ice margin
  • 2006
  • Ingår i: Astrobiology Conference 'Origin and Distribution of Life in the Universe - a Nordic Perspective'. Stockholm, Sweden, 2006.
  • Konferensbidrag (refereegranskat)abstract
    • Data from the Mars Global Surveyor and Mars Odyssey missions have significantly added to the family of morphologies with ground-ice affinities. From the high resolution images acquired by Mars Orbiter Camera a new array of small scale patterned ground have been detected which range in size and shape. A continuous meters-thick deposit interpreted to be ice rich is observed at latitudes above 60º at both hemispheres, but which has undergone degradation at lower latitudes and is absent in the equatorial regions (within ±30º). The Odyssey’s neutron spectrometer made direct measurements of hydrogen which shows the presence of high water-ice abundance (>60% by volume) in the surface soils in the northern and southern latitudes above 60º. This observation is consistent with theoretical modelling of ice stability under current martian surface conditions. We have done a comprehensive inventory of patterned ground features along the southern polar water-ice margin. These features range in size from 25-300 m, they display a variety of shapes forming nets, stripes and polygons and they show strong latitudinal gradients above 50º S. Fusing these data together with a previous investigation on degraded surface deposits we may analyse the gradual change in surface morphology due to a decreasing gradient of near surface ice towards lower latitudes. The range of morphologies interpreted to be ice-rich are thus strongly supported by direct measurements of water-ice for those observed at latitudes >60º S and for those at lower latitudes for conditions in the past when ice was stable to lower latitudes. This pattern of landforms provides an excellent research environment to investigate periglacial features formed in a very cold environment with long term climate change.
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24.
  • Johnsson, Andreas, 1977, et al. (författare)
  • Periglacial mass-wasting landforms on Mars suggestive of transient liquid water in the recent past: Insights from solifluction lobes on Svalbard
  • 2012
  • Ingår i: ICARUS. - 0019-1035. ; 218:1, s. 489-505
  • Tidskriftsartikel (refereegranskat)abstract
    • On Earth, periglacial solifluction is a slow mass-wasting process related to freeze–thaw activity. We compare the morphology of small-scale lobate features on Mars to solifluction lobes in Svalbard to constrain their processes of formation. The analysis is based on high-resolution satellite imagery of Mars (HiRISE, 25 cm/pxl), aerial images of Svalbard with a similar spatial resolution (HRSC–AX, 20 cm/pxl) acquired through an air campaign in summer 2008, and ground truth obtained during two summer expeditions in 2009 and 2011 on Svalbard. We present a detailed study of two crater environments on Mars displaying two types of lobate forms, characterized as sorted (clast-banked) and non-sorted lobes. On both Svalbard and Mars such lobes typically occur as clusters of overlapping risers (lobe fronts), pointing to differential velocities in the soil. The martian small-scale lobes have well-defined arcuate risers and lobe treads (surface). Lobe widths range between 14 and 127 m and tread lengths between 13 and 105 m. Riser height is estimated to be approximately 1–5 m. The lobes on Mars share the plan view morphology of solifluction lobes on Svalbard and their morphometry is within the range of values of terrestrial solifluction lobes. The lobes are distinct from permafrost-creep landforms such as rock glaciers. We show the results of a survey of 53 HiRISE images covering latitudes between 59N and 81N. Similar to Svalbard, the studied lobate features on Mars occur in close spatial proximity to gullies and thermal contraction polygons. The widespread distribution of the lobate forms in the northern hemisphere and their close association to ground-ice and gullies are best explained by mass-wasting processes related to frost creep, gelifluction and/or plug-like flow. This suggests a protracted process (thousand to several thousands of years) of freeze–thaw activity at the northern high latitudes on Mars. Age constraints on lobe deposits and superposition relationships with gullies and polygons imply a process involving liquid water within the last few million years.
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25.
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26.
  • Johnsson, Andreas, 1977, et al. (författare)
  • POSSIBLE FREEZE AND THAW LANDFROMS ON HIGH-LATITUDE SLOPES ON MARS: INSIGHTS FROM TERRESTRIAL ANALOGS IN SPITSBERGEN, SVALBARD.
  • 2011
  • Ingår i: 42nd Lunar and Planetary Science Conference. ; 42:2758
  • Konferensbidrag (refereegranskat)abstract
    • Solifluction lobes are common slope features in Polar Regions on Earth where freeze and thaw processes occur. Mars is currently a cold and barren planet with its water resources locked up in ice caps, glaciers and ice-enriched permafrost. However, features resembling solifluction lobes have been observed on high-latitude slopes on Mars and in most, but not all, cases in close proximity to gullies. Lobes are found on steep inner crater walls and in planform they show striking resemblance to terrestrial solifluction lobes. These observations may point to a late phase in Mars history with transient melt water in local environments. In our study we have examined solifluction lobes on slopes in Svalbard in order to compare to the Martian lobate landforms. Specific questions we address are: how widely distributed are these lobate landforms on Mars and how do they relate to known ground-ice related landforms?
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27.
  • Johnsson, Andreas, 1977, et al. (författare)
  • POSSIBLE FREEZE/THAW LANDFORMS ON MARTIAN SLOPES: USING SVALBARD ADVENT VALLEY AS AN ANALOGUE TO MARS.
  • 2010
  • Ingår i: Third European Conference on Permafrost. - 9788248100102 ; 2010, s. 58-58
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Stripes and gelifluction lobes are common slope features in polar regions on Earth where freeze and thaw processes occur. Mars is currently a cold and barren planet with its water resources locked up as ice caps and ice-rich permafrost. However, features resembling stripes and gelifluction lobes have been observed on high-latitude slopes on Mars and in most, but not all, cases in close proximity to gullies. Stripe width typically ranges from ~50 cm to 1.5 m, and their orientation is consistently down slope, although it can not be excluded that it sometimes slightly deviates from the steepest topographic gradient. Lobes are found on steep inner crater walls and display similar dimensions as terrestrial gelifluction lobes. These observations may point to a late phase in Mars history with transient melt water in local niches. In our study we have examined sorted and non-sorted stripes as well as gelifluction lobes on slopes in Svalbard in order to test the working hypothesis of a freeze and thaw origin of the Martian landforms.
  •  
28.
  • Johnsson, Andreas, 1977, et al. (författare)
  • PRISTINE DEBRIS FLOWS IN A WELL-PRESERVED IMPACT CRATER IN THE AONIA REGION, MARS.
  • 2010
  • Ingår i: EPSC Abstracts 2010. ; 5:EPSC2010-641
  • Konferensbidrag (refereegranskat)abstract
    • Gullies on Mars are known to display a range of different morphologies but typically include an alcove, channel and apron. Several processes have been invoked to explain their genesis ranging from dry granular flows, debris flows to fluvial erosion with alluvial deposition. Albeit there is a general consensus that the medium involved is water, more attention is now drawn towards the dominant depositional processes of the gully fan formation. The observed range of fan morphologies asks for several depositional mechanisms and likely vary at different sites due to regional and local differences in climate and colluvial source material. Studies indicate that the common mechanism is fluvial deposition in contrast to debris flow dominated fans which have only been documented at three sites. These sites formed debris deposits of apparently fine grained dusty mantle material. Here we report on unusual Martian debris flows in an unnamed southern hemisphere crater which is rich in coarse grained colluvial material that forms well preserved debris flows, debris plugs and levees. It also displays numerous fresh looking rock falls. This raises the following questions: Why do so well-developed debris flows occur here and not in other nearby craters? What role does the coarse colluvial material play in debris flow initiation and development? Here we describe the debris flow morphology and we investigate the sieve-deposition model as an explanation for the unusual morphology of these debris deposits.
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29.
  • Johnsson, Andreas, 1977, et al. (författare)
  • Slow Periglacial Mass Wasting (Solifluction) on Mars
  • 2018
  • Ingår i: Dynamic Mars 1st Edition - Recent and Current Landscape Evolution of the Red Planet. - Cambridge, MA 02139, United States : Elsevier. - 9780128130193
  • Bokkapitel (refereegranskat)
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30.
  • Johnsson, Andreas, 1977, et al. (författare)
  • Small scale polygonal patterns along the southern water ice margin on Mars.
  • 2008
  • Ingår i: Lunar and Planetary Science Conference 39. ; XXXIX:1753
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • From the high resolution images acquired by Mars Orbiter Camera an array of small scale polygon patterns have been detected which range in size and shape. They occur in a continuous meters-thick deposit interpreted to be ice rich which is observed at latitudes above 60º at both hemispheres, but which has undergone degradation at lower latitudes and is absent in the equatorial regions (within ±30º). Also, the Mars Odyssey’s Neutron spectrometer measurements of hydrogen emissions shows the presence of high water-ice abundance (>60% by volume) in the surface soils in the northern and southern latitudes above 60º [3]. The polygons interpreted to be forming in ice-rich terrain are thus strongly supported by indirect measurements of water-ice for those observed at latitudes higher than 60º S and for those at lower latitudes the morphology indicate a past when ice was stable to lower latitudes. We have performed a comprehensive investigation of polygons along the latitudes of 30º S – 80º S on the southern hemisphere of Mars to highlight the change in morphology with latitude due to the presence or absence to subsurface water ice. The hypothesis is that the surface morphology would reflect the proposed subsurface ice content, similar to periglacial landscapes on Earth, which is both theorised and measured indirectly by Mars Odysseys Neutron spectrometer. The idea is also to differentiate the genesis of polygons and link them to different processes and time of formation. As an addition we includ cryocarst data which reflect the absence of near surface ice (m to tens of m). These previously unpublished results are the outcome of a master thesis project. This work focus on the latitudinal distribution of polygons in relation to the cryocarst terrain.
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31.
  • Johnsson, Andreas, 1977, et al. (författare)
  • Small scale polygonal patterns along the southern water ice margin on Mars.
  • 2008
  • Ingår i: EPSC Abstracts. European Planetary Science Congress. ; 3, EPSC2008-A-00379
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • From the high resolution images acquired by Mars Orbiter Camera an array of small scale polygonal patterns have been detected which range in size and shape. They occur in a continuous meters-thick deposit interpreted to be ice rich which is observed at latitudes above 60º at both hemispheres, but which has undergone degradation at lower latitudes and is absent in the equatorial regions (within ±30º). Also, the Mars Odyssey’s Neutron spectrometer measurements of hydrogen emissions shows the presence of high water-ice abundance (>60% by volume) in the surface soils in the northern and southern latitudes above 60º. The polygons interpreted to be forming in ice-rich terrain are thus strongly supported by indirect measurements of waterice for those observed at latitudes higher than 60º S and for those at lower latitudes the morphology indicate a past when ice was stable to lower latitudes. We have performed a comprehensive investigation of polygonal patterns along the latitudes of 30º S – 80º S on the southern hemisphere of Mars to highlight the change in morphology with latitude due to the presence or absence to subsurface water ice. The hypothesis is that the surface morphology would reflect the proposed subsurface ice content, similar to periglacial landscapes on Earth, which is both theorised and measured indirectly by Mars Odysseys Neutron spectrometer. The idea is also to differentiate the genesis of polygons and link them to different processes and time of formation. As an addition we include dissected terrain data which reflect the absence of near surface ice due to sublimation. These previously unpublished results are the outcome of a master thesis project.
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32.
  • Johnsson, Andreas, 1977, et al. (författare)
  • THE ORIGIN OF STRIPE-LIKE PATTERNS ON MARTIAN GULLY SLOPES; USING SVALBARD ADVENT VALLEY AS A MARS ANALOGUE.
  • 2010
  • Ingår i: 41st Lunar and Planetary Science Conference. ; :1665
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Stripes are a common slope features in polar regions on Earth were active layer processes (freezing/thawing and gelifluction) occur. Their origin is most likely polygenic and closely related to frost crack plygons and sorted circles with the addition of a gravitational component. Stripes are either sorted or unsorted. Features resembling stripes have been observed on slopes on Mars with or without association with polygons. Due to the current temperature and pressure regime on Mars soil moisture and active layer processes are not likely to occur. However, in recent HiRISE images stripelike patterns can be observed in proximity to gullies . Stripe width typically ranges from ~50 cm to 1.5 m, and their orientation is consistently down slope, although it can not be excluded that it sometimes slightly deviates from the steepest topographic gradient. In our study we have examined sorted and nonsorted stripes on slopes in Svalbard in order to test the working hypothesis of an cryoturbation origin for the martian stripe-like patterns. In doing so we compare their morphological characteristics, settings, and slope to those on Mars.
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33.
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34.
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35.
  • Oberst, J., et al. (författare)
  • Planetary polar explorer – the case for a next-generation remote sensing mission to low Mars orbit
  • 2022
  • Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 54, s. 695-711
  • Tidskriftsartikel (refereegranskat)abstract
    • We propose the exploration of polar areas on Mars by a next-generation orbiter mission. In particular, we aim at studying the seasonal and regional variations in snow-deposits, which – in combination with measurements of temporal variations in rotation and gravity field – will improve models of the global planetary CO2 cycle. A monitoring of polar scarps for rock falls and avalanche events may provide insights into the dynamics of ice sheets. The mapping of the complex layering of polar deposits, believed to contain an important record of climate history, may help us understand the early climate collapse on the planet. Hence, we propose an innovative next-generation exploration mission in polar circular Low Mars Orbit, which will be of interest to scientists and challenging to engineers alike. Schemes will be developed to overcome atmosphere drag forces acting upon the spacecraft by an electric propulsion system. Based on the experience of missions of similar type in Earth orbit we believe that a two-year mission in circular orbit is possible at altitudes as low as 150 km. Such a mission opens new opportunities for novel remote sensing approaches, not requiring excessive telescope equipment or power. We anticipate precision altimetry, powerful radars, high-resolution imaging, and magnetic field mapping. © 2022, The Author(s).
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36.
  • Orgel, Csilla, et al. (författare)
  • Gridmapping the Northern Plains of Mars: A New Overview of Recent Water‐ and Ice‐Related Landforms in Acidalia Planitia.
  • 2019
  • Ingår i: Journal of Geophysical Research - Planets. - 2169-9100. ; 124:2, s. 454-82
  • Tidskriftsartikel (refereegranskat)abstract
    • We used a grid‐mapping technique to analyze the distribution of 13 water‐ and ice‐related landforms in Acidalia Planitia as part of a joint effort to study the three main basins in the northern lowlands of Mars, that is, Acidalia, Utopia, and Arcadia Planitiae. The landforms were mapped at full Context Camera resolution along a 300‐km‐wide strip from 20°N to 84°N. We identified four landform assemblages: (1) Geologically recent polar cap (massive ice), which superposes the latitude‐dependent mantle (LDM) (LA1); (2) ice‐related landforms, such as LDM, textured terrain, small‐scale polygons, scalloped terrain, large‐scale viscous flow features, and gullies, which have an overlapping distribution (LA2); (3) surface features possibly related to water and subsurface sediment mobilization (LA3; kilometer‐scale polygons, large pitted mounds, small pitted mounds, thumbprint terrain); and (4) irregularly shaped pits with raised rims on equator‐facing slopes. Pits are likely the result of an energetic release of volatiles (H2O, CO2, and CH4), rather than impact‐, volcanism‐, or wind‐related processes. LDM occurs ubiquitously from 44°N to 78°N in Acidalia Planitia. Various observations suggest an origin of air fall deposition of LDM, which contains less ice in the uppermost tens of meters in Acidalia Planitia than in Arcadia and Utopia Planitiae. However, LDM may be thicker and more extended in the past in Acidalia Planitia. The transition between LDM‐free terrain and LDM is situated further north than in Utopia and Arcadia Planitiae, suggesting different past and/or present climatic conditions among the main basins in the northern lowlands.
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37.
  • Pallarès, David, 1975, et al. (författare)
  • Interpretation of dynamics of pressure measurements
  • 2006
  • Ingår i: Proceedings of the 19th FBC Conference. ; 2
  • Konferensbidrag (refereegranskat)abstract
    • This work investigates how wall-sampled pressure measurements are to be interpreted withrespect to dynamics of industrial fluidized bed units. Such units have large cross sectionswith many bubbles passing the bed more or less simultaneously and, consequently, wallmeasurements will reflect superimposed dynamics from these bubbles and interpretation ofpressure signals is therefore not straight forward. In addition, variations in release of volatilesmay also cause pressure fluctuations. The work applies pressure measurements in a coldfluidized bed unit (over the cross section of the riser) as well as in a 12 MW CFB boiler (inthe bottom bed, the freeboard and the air feed system). The dynamics of the release ofvolatiles were studied by means of zirconia-cell probes.The results show that the coupling between in-bed and wall pressure fluctuations in thedense bottom bed depends strongly on fluidization regime and that variations in release ofvolatiles can give rise to large pressure fluctuations, however, on a different time scale thanthat of the in-bed fluid dynamics. In the freeboard there was, as expected, a strong couplingbetween in-bed and wall pressure fluctuations.
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38.
  • Raack, J., et al. (författare)
  • Present-day gully activity in Sisyphi Cavi, Mars - Flow-like features and block movements
  • 2020
  • Ingår i: Icarus. - : Elsevier BV. - 0019-1035. ; 350
  • Tidskriftsartikel (refereegranskat)abstract
    • The continuously increasing number of multi-temporal high-resolution images from the surface of Mars offers the possibility for detailed studies of present-day surface activity. In this study we investigated all gullies in the Sisyphi Cavi region (355 degrees E, 71 degrees S) of the south polar region of Mars. This region is influenced by the seasonal deposition of a decimeters-thick translucent slab ice in late autumn/winter and its subsequent sublimation in spring. We mapped all gullies (n = 17.760) and measured their orientations. We also identified gullies with contemporary activity (n = 35) using multi-temporal HiRISE images for martian years (MY) 28 to 34. We observed two different kinds of activity: (1) dark flow-like features, and (2) movement of blocks. For both, sediment was transported from the source region (alcove and/or flanks of channels) down the gully. Using image data from HRSC, CTX, and HiRISE, we monitored the general defrosting of the study region. We also analyzed the maximum daytime surface temperatures of the complete study region based on TES data from MYs 24 to 26. To identify the origin and triggering mechanism of the observed activity, we used: (1) detailed topographic investigations (e.g., slope angles) of two extensively gullied slopes based on two HiRISE-DTMs, (2) identification of small scale displacements with Digital Image Correlation (DIC), and (3) orientation measurements of active gullies and comparison to non-active gullies. We found that for the active gullies studied, activity happens at the end of spring between L-S similar to 225 degrees and similar to 250 degrees. This is consistent with the timing of final stages of defrosting in the region. At this time, some surfaces are already defrosted while others still host the seasonal slab ice cover. For the surfaces with slab ice, dark defrosting spots (and flows, if the surface is inclined) are observed on dark dunes as well as on gully aprons and in gully channels. These spots form when, triggered by basal sublimation generated overpressure, sediment entrained in CO2-gas is transported through cracks within the ice and redeposited onto the frosted surface. We compared and linked both morphologic features (dark dune spots and dark flow-like features) and concluded that these features have comparable or even the same triggering mechanisms. Based on this extensive study, the most plausible mechanism for ongoing gully activity can be divided into two steps: 1) accumulation of material within gully channels via small dry flows on top of the slab ice (comparable to dark dune spots/flows), 2) when a critical mass is reached, the sediment flows down the still frosted gully on top of the sublimating ice or as a mixture of dry material and ice in a catastrophic flow. The triggering factor for the movement of blocks remains unclear, as their timing could not be constrained with the available data. We identified headwall erosion in one gully in the study region, whereas a discrete source could not be identified for the other sites, suggesting multiple failure mechanisms could be active in such gullies. Finally, through volume balance calculations we show that active gullies in Sisyphi Cavi could have been formed within decades to several tens of thousands of MY, but gully-morphology indicates a much-longer period for formation of the entire gully-landform.
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39.
  • Ramsdale, J. D., et al. (författare)
  • Grid-based mapping: A method for rapidly determining the spatial distributions of small features over very large areas
  • 2017
  • Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633. ; 140, s. 49-61
  • Tidskriftsartikel (refereegranskat)abstract
    • The increased volume, spatial resolution, and areal coverage of high-resolution images of Mars over the past 15 years have led to an increased quantity and variety of small-scale landform identifications. Though many such landforms are too small to represent individually on regional-scale maps, determining their presence or absence across large areas helps form the observational basis for developing hypotheses on the geological nature and environmental history of a study area. The combination of improved spatial resolution and near-continuous coverage significantly increases the time required to analyse the data. This becomes problematic when attempting regional or global-scale studies of metre and decametre-scale landforms. Here, we describe an approach for mapping small features (from decimetre to kilometre scale) across large areas, formulated for a project to study the northern plains of Mars, and provide context on how this method was developed and how it can be implemented. Rather than. "mapping" with points and polygons, grid-based mapping uses a "tick box" approach to efficiently record the locations of specific landforms (we use an example suite of glacial landforms; including viscous flow features, the latitude dependant mantle and polygonised ground). A grid of squares (e.g. 20 km by 20 km) is created over the mapping area. Then the basemap data are systematically examined, grid-square by grid-square at full resolution, in order to identify the landforms while recording the presence or absence of selected landforms in each grid-square to determine spatial distributions. The result is a series of grids recording the distribution of all the mapped landforms across the study area. In some ways, these are equivalent to raster images, as they show a continuous distribution-field of the various landforms across a defined (rectangular, in most cases) area. When overlain on context maps, these form a coarse, digital landform map. We find that grid-based mapping provides an efficient solution to the problems of mapping small landforms over large areas, by providing a consistent and standardised approach to spatial data collection. The simplicity of the grid-based mapping approach makes it extremely scalable and workable for group efforts, requiring minimal user experience and producing consistent and repeatable results. The discrete nature of the datasets, simplicity of approach, and divisibility of tasks, open up the possibility for citizen science in which crowdsourcing large grid based mapping areas could be applied.
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40.
  • Ramsdale, Jason D., et al. (författare)
  • Gridmapping the northern plains of Mars: Geomorphological, Radar and Water-Equivalent Hydrogen results from Arcadia Plantia.
  • 2019
  • Ingår i: Journal of Geophysical Research - Planets. - 2169-9100. ; 124:2, s. 504-27
  • Tidskriftsartikel (refereegranskat)abstract
    • A project of mapping ice‐related landforms was undertaken to understand the role of subsurface ice in the northern plains. This work is the first continuous regional mapping from CTX (ConTeXt Camera, 6 m/pixel; Malin et al., 2007) imagery in Arcadia Planitia along a strip 300 km across stretching from 30°N to 80°N centered on the 170°W line of longitude. The distribution and morphotypes of these landforms were used to understand the permafrost cryolithology. The mantled and textured signatures occur almost ubiquitously between 35°N and 78°N and have a positive spatial correlation with inferred ice stability based on thermal modeling, neutron spectroscopy, and radar data. The degradational features into the LDM (latitude‐dependent mantle) include pits, scallops, and 100‐m polygons and provide supporting evidence for subsurface ice and volatile loss between 35 and 70°N in Arcadia with the mantle between 70 and 78°N appearing much more intact. Pitted terrain appears to be much more pervasive in Arcadia than in Acidalia and Utopia suggesting that the Arcadia study area had more widespread near‐surface subsurface ice and thus was more susceptible to pitting or that the ice was less well buried by sediments. Correlations with ice stability models suggest that lack of pits north of 65–70°N could indicate a relatively young age (~1 Ma); however, this could also be explained through regional variations in degradation rates. The deposition of the LDM is consistent with an air fall hypothesis; however, there appears to be substantial evidence for fluvial processes in southern Arcadia with older, underlying processes being equally dominant with the LDM and degradation thereof in shaping the landscape.
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41.
  • Reiss, Dennis, et al. (författare)
  • MORPHOLOGIC AND MORPHOMETRIC COMPARISION OF GULLIES ON SVALBARD AND MARS.
  • 2009
  • Ingår i: 40th Lunar and Planetary Science Conference. ; :2362
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The morphology of gullies on Mars indi-cates that they were formed by the action of water. How-ever, it is not clear what the dominant gully forming process is. On Earth, gullies might have formed by the processes of overland flow or debris flows, or a combination of both. In this work we compare the morphologic and morphometric observations and measurements (slopes, depth-width ratios and sinuosities) of Martian gullies with terrestrial analogs from Svalbard, Norway, in order to constrain the formation process (fluvial and/or debris flow).
  •  
42.
  • Reiss, Dennis, et al. (författare)
  • Terrestrial gullies and debris-flow tracks on Svalbard as planetary analogs for Mars
  • 2011
  • Ingår i: The Geological Society of America, Special Paper. - : Geological Society of America. ; 483, s. 165-175
  • Tidskriftsartikel (refereegranskat)abstract
    • We compared the morphology of gully sedimentary fans on Svalbard as possible analogs to gullies on Mars in order to constrain whether fl uvial and/or debris-fl ow processes are predominantly responsible for the formation of Martian gullies. Our analysis is based on high-resolution imagery (High Resolution Stereo Camera [HRSC-AX], ~20 cm/pixel) acquired through a fl ight campaign in summer 2008 and ground truth during two expeditions in the summers of 2008 and 2009 in Svalbard, compared to highresolution satellite imagery (High Resolution Imaging Science Experiment [HiRISE], ~25 cm/pixel) from Mars. On Svalbard, fluvial and debris-fl ow processes are evident in the formation of gullies, but the morphological characteristics clearly show that the transport and sedimentation of eroded material are predominated by debris flows. Most investigated gullies on Mars lack clear evidence for debris-flow processes. The Martian gully fan morphology is more consistent with the deposition of small overlapping fans by multiple fluvial flow events. Clear evidence for debris flows on Mars was only found in one new location, in addition to a few previously published examples. The occurrence of debris-flow processes in the formation of Martian gullies seems to be rare and locally limited. If predominantly fl uvial processes caused the formation of gullies on Mars, then large amounts of water would have been required for their formation because of the relatively low sediment supply in stream and/or hyperconcentrated fl ows. Repeated seasonal or episodic snow deposition and melting during periods of higher obliquity in the recent past on Mars can best explain the formation of the gullies.
  •  
43.
  • Reiss, Dennis, et al. (författare)
  • TERRESTRIAL GULLIES ON SVALBARD AS PLANETARY ANALOGS FOR MARS
  • 2010
  • Ingår i: 41st Lunar and Planetary Science Conference. ; :2492
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Martian gullies resemble terrestrial gul-lies, which are formed by a combination of processes includ-ing mass wasting, overland flow and debris flows. The gullies on Mars show several morphologic features such as braided channels, multiple terraces, point bars and cutbanks, which indicate that fluvial processes were involved in their formation. However, it remains unclear whether fluvial processes or debris flows are dominating the formation of gullies on Mars. Debris flows are viscous slurry flows with water and fines as the interstitial fluid. The flowing mix-tures of fines, clastic debris and water has a relatively low water content (≤ 30 % water by weight). Stream flows and hyperconcentrated flows have a high water content and relatively low sediment supply (≥ 30 % water by weight). The morphologies of debris flows fans show typical fea-tures such as levées, lobes, snouts and debris plugs, which are not observed from purely fluvial processes. In this work we compare the morphology of terrestrial gully analogs from Svalbard with Martian gullies in order to constrain which formation process might be dominant on Mars, i.e. fluvial and/or debris flow processes.
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44.
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45.
  • Sturkell, Erik, 1962, et al. (författare)
  • Geologen - en filmhjälte
  • 2014
  • Ingår i: GeoArena.
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Hur vanligt är det med geologer på vita duken och hur blir han/hon framställd? Har geologen någon gång huvudrollen i en film? Är geologen hjälten eller skurken? Eller förekommer denne endast i biroller, där han eller hon kliver in på kontoret och säger “borra här” och sedan lämnar scenen? Alla dessa frågor som många av oss ställt men där inga enhetliga svar funnits - tills nu då vi har gjort en systematisk undersökning. Vi har därför försökt att hitta så många filmer med geologer som möjligt. Totalt har vi hittat 60 amerikanska och brittiska biofilmer hittills. I dessa filmer finns 94 geologer i rolluppsättningen och 32 av dessa geologer spelar en huvudroll (34 procent). Oftast har en film endast en geolog. Av de 60 filmerna har 19 stycken fler än en geolog och i åtta filmer finns det fler än två. Filmen “Dante’s Peak” har flest geologer med sju stycken. Kvinnliga geologer förekommer i elva filmer och de utgör 13 av totalt av 94 filmgeologer vilket motsvarar 14 procent. Filmgeologerna har olika karaktärer, de flesta är goda människor (86 procent); några räddar till och med världen. Endast några få geologer (2) av dessa är riktigt ondskefulla, Daniel Plainview från “There Will Be Blood” (2007), och Prof. Dent i Bondfilmen “Dr. No” (1962). Vår kultfilm är “Dante’s Peak” (1997), denna är utan tvekan den bästa geologfilmen genom tiderna. Slutsatsen är att geologen oftast är en trevlig person som jobbar i fält, har rutig skjorta och som gärna går ner och tar en (eller flera) öl.
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46.
  • Sturkell, Erik, 1962, et al. (författare)
  • Geologen – en filmstjärna!
  • 2013
  • Ingår i: Geologiskt Forum. - 1104-4721. ; 20:79, s. 16-21
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
  •  
47.
  • Sturkell, Erik, 1962, et al. (författare)
  • Rock stars: Geologists on the silver screen
  • 2015
  • Ingår i: Earth. The science behind the headlines. - 1943-345X. ; 60:6, s. 24-33
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • When geologists gather for a beer after work or around a campfire after a long day in the field, the conversation sometimes turns to how our profession is portrayed on film. Are geologists heroes or villains? Do they appear only in supporting roles — their parts limited to entering an office, uttering “Drill here,” and promptly leaving the scene — or are they main characters? Michael Easton of the Ontario Geological Survey and colleagues addressed some of these points in a 1990 article, “Hollywood’s Portrayal of Geologists: Earth Scientists on Celluloid,” in the pages of this magazine, then called Geotimes. The writers concluded that geologists are usually pictured as “good guys” — and they are most often guys — who work outdoors and love to seek out the local bar for a beer (or two). This stands in stark contrast to the customary film portrayals of physicists and chemists. In a 1988 study, “The Physicist as Mad Scientist,” science historian Spencer Weart, now retired from the American Institute of Physics, found that physicists and chemists are very often described as mad scientists striving for world domination or the total destruction of Earth. Even in cases where they were not portrayed as wholly evil, Weart found they were still often depicted as absent-minded or misunderstood geniuses. Much has changed in the last few decades, however, so we decided to reexamine the question of how geologists are portrayed on film, incorporating movies released since 1990.
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48.
  • Sundin, Maria, 1965, et al. (författare)
  • Mars - a target for teachers and science students
  • 2020
  • Ingår i: Contribution to IAU 367S, Education and Heritage in the Era of Big Data in Astronomy, 8-12 December 2020..
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • A case study is here presented of an interdisciplinary course about Mars for teachers and science students. We aim to share the experience of creating an interdisciplinary approach with lecturers spanning physics, geology, radiation physics and philosophy. Issues in ethics, morality, rights and obligations, conflict management and human psychology as well as rocket orbits, fuel economy, radiation hazards and knowledge of the solar system have proven to be a valued and successful initiative for the further training of teachers and science students. The focus of the course is on planning for a journey with humans to the planet Mars. This provides a great opportunity to package complex societal problems in a physics context. The course is offered with a special sustainability content mark. Mankind has always had a strong and dependent relationship with the physical landscape. The land has given us food and shelter but also imposed challenges and disasters. Understanding the physical environment has been crucial for our survival and development. The same will be equally, or more important for Mars where life conditions are much more extreme. We highlight similarities and differences in the geologic processes that have shaped Earth and Mars. What conditions do the future explorers on Mars have to manage? We then enter the modern era and explore the dynamic Martian landscape of today. Also, by learning to read the landscape we may find locations of shelter such as vast systems of lava tubes, or locations of essential resources such as preserved glacial ice etc. A journey to Mars will cause substantially higher personal irradiation than obtained on Earth. The radiation part of the course lectures starts with defining the different radiation types and the biological effects these different types of radiation will cause. Then, the difference between the irradiation on Earth to the elevated irradiation in space and on Mars is described. Thereafter, it is discussed if this elevated radiation burden can cause acute biological effects, e.g. fatigue, vomiting and death, and late biological effects as cancer induction. Last, possible radiation protection strategies are described and discussed. The philosophy of space exploration consists of philosophical approaches to ethics, presently applied to the topic of Mars exploration and colonization, with environmental ethics (anthropocentric vs ecocentric) and value theory at its core. Four main uses of philosophy are distinguished: ethics, aesthetics, cognition and existentialism. Research has shown that visual representation is an important part for students to be able to create a deeper understanding of concepts as well as context about the material that is taught. Interdisciplinary and complex societal problems have also been shown to be important in science teaching. One way for the teacher to develop his/her teaching is to take further education courses in universities whose focus is to seek and discuss the complex societal problems as well as its solutions from a physics and teacher perspective. Future research could be done on the impact of this course on the education in different levels.
  •  
49.
  • Sundin, Maria, 1965, et al. (författare)
  • Mars – a target for teachers and science students
  • 2021
  • Ingår i: Proceedings of the International Astronomical Union, Vol 15, Symposium 367S. - 1743-9213 .- 1743-9221.
  • Konferensbidrag (refereegranskat)abstract
    • An interdisciplinary course about Mars for teachers and science students is presented. The focus of the course is on planning for a journey with humans to the planet Mars. Issues in ethics, morality, rights and obligations, conflict management and human psychology as well as rocket orbits, fuel economy, radiation hazards and knowledge of the solar system are included. Examination of the teacher students include interpretation of the course material for future pedagogical usage.
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50.
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