| 1. |
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| 2. |
- Carlsson, Ella, et al.
(författare)
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FIELD STUDIES OF GULLIES AND PINGOS ON SVALBARD – A MARTIAN ANALOG.
- 2008
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Ingår i: European Planetary Science Congress, 21-26 September 2008. ; 3
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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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| 3. |
- Hauber, Ernst, et al.
(författare)
-
DEBRIS FLOW FANS AND PERMAFROST LANDFORMS ON SVALBARD (NORWAY): TERRESTRIAL ANALOGUES FOR MARTIAN MID-LATITUDE PERIGLACIAL LANDSCAPES.
- 2010
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Ingår i: 41st Lunar and Planetary Science Conference. ; :1922
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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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| 4. |
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| 5. |
- Hauber, Ernst, et al.
(författare)
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Landscape evolution in Martian mid-latitude regions: Insights from analogous periglacial landforms in Svalbard.
- 2011
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Ingår i: Geological Society, London, Special Publications. ; 356, s. 111-131
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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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| 6. |
- Hauber, Ernst, et al.
(författare)
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MORPHOMETRY OF ALLUVIAL FANS IN A POLAR DESERT (SVALBARD, NORWAY): IMPLICATIONS FOR INTERPRETING MARTIAN FANS.
- 2009
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Ingår i: 40th Lunar and Planetary Science Conference. ; :1648
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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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| 7. |
- Hauber, Ernst, et al.
(författare)
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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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| 8. |
- Hauber, Ernst, et al.
(författare)
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Svalbard (Norway) as a terrestrial analogue for Martian landforms: Results on
- 2009
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Ingår i: EPSC Abstracts. European Planetary Science Congress. ; 4, EPSC2009-772
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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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| 9. |
- Johnsson, Andreas, 1977, et al.
(författare)
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Evidence for very recent melt-water and debris flow activity in gullies in a young mid-latitude crater on Mars
- 2014
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Ingår i: Icarus. - : Elsevier BV. - 0019-1035 .- 1090-2643. ; 235, s. 37-54
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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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| 10. |
- Johnsson, Andreas, 1977, et al.
(författare)
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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
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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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| 11. |
- Johnsson, Andreas, 1977, et al.
(författare)
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LATITUDINAL SURVEY OF PERIGLACIAL LANDFORMS AND GULLIES IN EASTERN ARGYRE AND POLEWARDS ON MARS.
- 2009
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Ingår i: 40th Lunar and Planetary Science Conference. ; :2405
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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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| 12. |
- Johnsson, Andreas, 1977, et al.
(författare)
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Periglacial mass-wasting landforms on Mars suggestive of transient liquid water in the recent past: Insights from solifluction lobes on Svalbard
- 2012
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Ingår i: ICARUS. - 0019-1035. ; 218:1, s. 489-505
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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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| 13. |
- Johnsson, Andreas, 1977, et al.
(författare)
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POSSIBLE FREEZE AND THAW LANDFROMS ON HIGH-LATITUDE SLOPES ON MARS: INSIGHTS FROM TERRESTRIAL ANALOGS IN SPITSBERGEN, SVALBARD.
- 2011
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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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| 14. |
- Johnsson, Andreas, 1977, et al.
(författare)
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POSSIBLE FREEZE/THAW LANDFORMS ON MARTIAN SLOPES: USING SVALBARD ADVENT VALLEY AS AN ANALOGUE TO MARS.
- 2010
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Ingår i: Third European Conference on Permafrost. - 9788248100102 ; 2010, s. 58-58
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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.
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| 15. |
- Johnsson, Andreas, 1977, et al.
(författare)
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PRISTINE DEBRIS FLOWS IN A WELL-PRESERVED IMPACT CRATER IN THE AONIA REGION, MARS.
- 2010
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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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| 16. |
- Johnsson, Andreas, 1977, et al.
(författare)
-
Slow Periglacial Mass Wasting (Solifluction) on Mars
- 2018
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Ingår i: Dynamic Mars 1st Edition - Recent and Current Landscape Evolution of the Red Planet. - Cambridge, MA 02139, United States : Elsevier. - 9780128130193
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Bokkapitel (refereegranskat)
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| 17. |
- Johnsson, Andreas, 1977, et al.
(författare)
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Small scale polygonal patterns along the southern water ice margin on Mars.
- 2008
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Ingår i: Lunar and Planetary Science Conference 39. ; XXXIX:1753
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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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| 18. |
- Johnsson, Andreas, 1977, et al.
(författare)
-
Small scale polygonal patterns along the southern water ice margin on Mars.
- 2008
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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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| 19. |
- Johnsson, Andreas, 1977, et al.
(författare)
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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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| 20. |
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| 21. |
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| 22. |
- Reiss, Dennis, et al.
(författare)
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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).
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| 23. |
- Reiss, Dennis, et al.
(författare)
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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
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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.
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| 24. |
- Reiss, Dennis, et al.
(författare)
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TERRESTRIAL GULLIES ON SVALBARD AS PLANETARY ANALOGS FOR MARS
- 2010
-
Ingår i: 41st Lunar and Planetary Science Conference. ; :2492
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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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| 25. |
- Rothery, David, et al.
(författare)
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Mercury's surface and composition to be studied by BepiColombo
- 2010
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Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 58:1-2, s. 21-39
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Tidskriftsartikel (refereegranskat)abstract
- We describe the contributions that we expect the BepiColombo mission to make towards increased knowledge and understanding of Mercury's surface and composition. BepiColornbo will have a larger and more capable Suite of instruments relevant for determination of the topographic, physical, chemical and mineralogical properties of the surface than carried by NASA's MESSENGER mission. We anticipate that the insights gained into the planet's geological history and its current space weathering environment will enable us to understand the relationships between surface composition and the composition of different types of crust. This will enable estimation of the composition of the mantle from which the crust was derived, and lead to better constraints on models for Mercury's origin and the nature of the material from which it formed.
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