Augsburg, Germany
Augsburg, Germany

Time filter

Source Type

News Article | May 5, 2017
Site: phys.org

From early February to early April, the rover examined four sites near a linear dune for comparison with what it found in late 2015 and early 2016 during its investigation of crescent-shaped dunes. This two-phase campaign is the first close-up study of active dunes anywhere other than Earth. Among the questions this Martian dune campaign is addressing is how winds shape dunes that are relatively close together, on the same side of the same mountain, into different patterns. Others include whether Martian winds sort grains of sand in ways that affect the distribution of mineral compositions, which would have implications for studies of Martian sandstones. "At these linear dunes, the wind regime is more complicated than at the crescent dunes we studied earlier," said Mathieu Lapotre of Caltech, in Pasadena, California, who helped lead the Curiosity science team's planning for the dune campaign. "There seems to be more contribution from the wind coming down the slope of the mountain here compared with the crescent dunes farther north." The linear dunes lie uphill and about a mile (about 1.6 kilometers) south from the crescent dunes. Both study locations are part of a dark-sand swath called the Bagnold Dunes, which stretches several miles in length. This dune field lines the northwestern flank of Mount Sharp, the layered mountain that Curiosity is climbing. "There was another key difference between the first and second phases of our dune campaign, besides the shape of the dunes," Lapotre said. "We were at the crescent dunes during the low-wind season of the Martian year and at the linear dunes during the high-wind season. We got to see a lot more movement of grains and ripples at the linear dunes." To assess wind strength and direction, the rover team now uses change-detection pairs of images taken at different times to check for movement of sand grains. The wind-sensing capability of the Curiosity's Rover Environmental Monitoring Station (REMS) is no longer available, though that instrument still returns other Mars-weather data daily, such as temperatures, humidity and pressure. Two of the six wind sensors on the rover's mast were found to be inoperable upon landing on Mars in 2012. The remainder provided wind information throughout the rover's prime mission and first two-year extended mission. A sample of sand that Curiosity scooped up from a linear dune is in the sample-handling device at the end of the rover's arm. One portion has been analyzed in the Sample Analysis at Mars (SAM) instrument inside the rover. The science team plans to deliver additional sample portions to SAM and to the rover's Chemistry and Mineralogy (CheMin) instrument. One factor in choosing to drive farther uphill before finishing analysis of the scooped sand is the status of Curiosity's rock-sampling drill, which has not been used on a rock since a problem with the drill feed mechanism appeared five months ago. Engineers are assessing how the use of vibration to deliver samples may affect the drill feed mechanism, which is used to move the drill bit forward and backwards. In addition, high winds at the linear-dunes location were complicating the process of pouring sample material into the entry ports for the laboratory instruments. "A balky brake appears to be affecting drill feed mechanism performance," said Curiosity Deputy Project Manager Steven Lee, of NASA's Jet Propulsion Laboratory, Pasadena, California. "In some cases, vibration has been observed to change feed effectiveness, so we're proceeding cautiously until we better understand the behavior. In the meantime, the engineering team is developing several methods to improve feed reliability." Curiosity landed near Mount Sharp in August 2012. It reached the base of the mountain in 2014 after successfully finding evidence on the surrounding plains that ancient Martian lakes offered conditions that would have been favorable for microbes if Mars has ever hosted life. Rock layers forming the base of Mount Sharp accumulated as sediment within ancient lakes billions of years ago. On Mount Sharp, Curiosity is investigating how and when the ancient habitable conditions known from the mission's earlier findings evolved into drier conditions that were less favorable for life. More information: For more information about Curiosity, visit mars.jpl.nasa.gov/msl


News Article | December 13, 2016
Site: astrobiology.com

NASA's Curiosity rover is climbing a layered Martian mountain and finding evidence of how ancient lakes and wet underground environments changed, billions of years ago, creating more diverse chemical environments that affected their favorability for microbial life. Hematite, clay minerals and boron are among the ingredients found to be more abundant in layers farther uphill, compared with lower, older layers examined earlier in the mission. Scientists are discussing what these and other variations tell about conditions under which sediments were initially deposited, and about how groundwater moving later through the accumulated layers altered and transported ingredients. Effects of this groundwater movement are most evident in mineral veins. The veins formed where cracks in the layers were filled with chemicals that had been dissolved in groundwater. The water with its dissolved contents also interacted with the rock matrix surrounding the veins, altering the chemistry both in the rock and in the water. "There is so much variability in the composition at different elevations, we've hit a jackpot," said John Grotzinger, of Caltech in Pasadena, California. He and other members of Curiosity's science team presented an update about the mission Tuesday, Dec. 13, in San Francisco during the fall meeting of the American Geophysical Union. As the rover examines higher, younger layers, researchers are impressed by the complexity of the lake environments when clay-bearing sediments were being deposited, and also the complexity of the groundwater interactions after the sediments were buried. "A sedimentary basin such as this is a chemical reactor," Grotzinger said. "Elements get rearranged. New minerals form and old ones dissolve. Electrons get redistributed. On Earth, these reactions support life." Whether Martian life has ever existed is still unknown. No compelling evidence for it has been found. When Curiosity landed in Mars' Gale Crater in 2012, the mission's main goal was to determine whether the area ever offered an environment favorable for microbes. The crater's main appeal for scientists is geological layering exposed in the lower portion of its central mound, Mount Sharp. These exposures offer access to rocks that hold a record of environmental conditions from many stages of early Martian history, each layer younger than the one beneath it. The mission succeeded in its first year, finding that an ancient Martian lake environment had all the key chemical ingredients needed for life, plus chemical energy available for life. Now, the rover is climbing lower on Mount Sharp to investigate how ancient environmental conditions changed over time. "We are well into the layers that were the main reason Gale Crater was chosen as the landing site," said Curiosity Deputy Project Scientist Joy Crisp of NASA's Jet Propulsion Laboratory, in Pasadena, California. "We are now using a strategy of drilling samples at regular intervals as the rover climbs Mount Sharp. Earlier we chose drilling targets based on each site's special characteristics. Now that we're driving continuously through the thick basal layer of the mountain, a series of drill holes will build a complete picture." Four recent drilling sites, from "Oudam" this past June through "Sebina" in October, are each spaced about 80 feet (about 25 meters) apart in elevation. This uphill pattern allows the science team to sample progressively younger layers that reveal Mount Sharp's ancient environmental history. One clue to changing ancient conditions is the mineral hematite. It has replaced less-oxidized magnetite as the dominant iron oxide in rocks Curiosity has drilled recently, compared with the site where Curiosity first found lakebed sediments. "Both samples are mudstone deposited at the bottom of a lake, but the hematite may suggest warmer conditions, or more interaction between the atmosphere and the sediments," said Thomas Bristow of NASA Ames Research Center, Moffett Field, California. He helps operate the Chemistry and Mineralogy (CheMin) laboratory instrument inside the rover, which identifies minerals in collected samples. Chemical reactivity occurs on a gradient of chemical ingredients' strength at donating or receiving electrons. Transfer of electrons due to this gradient can provide energy for life. An increase in hematite relative to magnetite indicates an environmental change in the direction of tugging electrons more strongly, causing a greater degree of oxidation in iron. Another ingredient increasing in recent measurements by Curiosity is the element boron, which the rover's laser-shooting Chemistry and Camera (ChemCam) instrument has been detecting within mineral veins that are mainly calcium sulfate. "No prior mission has detected boron on Mars," said Patrick Gasda of the U.S. Department of Energy's Los Alamos National Laboratory, Los Alamos, New Mexico. "We're seeing a sharp increase in boron in vein targets inspected in the past several months." The instrument is quite sensitive; even at the increased level, boron makes up only about one-tenth of one percent of the rock composition. Boron is famously associated with arid sites where much water has evaporated away -- think of the borax that mule teams once hauled from Death Valley. However, environmental implications of the minor amount of boron found by Curiosity are less straightforward than for the increase in hematite. Scientists are considering at least two possibilities for the source of boron that groundwater left in the veins. Perhaps evaporation of a lake formed a boron-containing deposit in an overlying layer, not yet reached by Curiosity, then water later re-dissolved the boron and carried it down through a fracture network into older layers, where it accumulated along with fracture-filling vein minerals. Or perhaps changes in the chemistry of clay-bearing deposits, such as evidenced by the increased hematite, affected how groundwater picked up and dropped off boron within the local sediments. "Variations in these minerals and elements indicate a dynamic system," Grotzinger said. "They interact with groundwater as well as surface water. The water influences the chemistry of the clays, but the composition of the water also changes. We are seeing chemical complexity indicating a long, interactive history with the water. The more complicated the chemistry is, the better it is for habitability. The boron, hematite and clay minerals underline the mobility of elements and electrons, and that is good for life." Curiosity is part of NASA's ongoing Mars research and preparation for a human mission to Mars in the 2030s. Caltech manages JPL, and JPL manages the Curiosity mission for NASA's Science Mission Directorate in Washington.


News Article | December 13, 2016
Site: phys.org

Hematite, clay minerals and boron are among the ingredients found to be more abundant in layers farther uphill, compared with lower, older layers examined earlier in the mission. Scientists are discussing what these and other variations tell about conditions under which sediments were initially deposited, and about how groundwater moving later through the accumulated layers altered and transported ingredients. Effects of this groundwater movement are most evident in mineral veins. The veins formed where cracks in the layers were filled with chemicals that had been dissolved in groundwater. The water with its dissolved contents also interacted with the rock matrix surrounding the veins, altering the chemistry both in the rock and in the water. "There is so much variability in the composition at different elevations, we've hit a jackpot," said John Grotzinger, of Caltech in Pasadena, California. He and other members of Curiosity's science team presented an update about the mission Tuesday, Dec. 13, in San Francisco during the fall meeting of the American Geophysical Union. As the rover examines higher, younger layers, researchers are impressed by the complexity of the lake environments when clay-bearing sediments were being deposited, and also the complexity of the groundwater interactions after the sediments were buried. "A sedimentary basin such as this is a chemical reactor," Grotzinger said. "Elements get rearranged. New minerals form and old ones dissolve. Electrons get redistributed. On Earth, these reactions support life." Whether Martian life has ever existed is still unknown. No compelling evidence for it has been found. When Curiosity landed in Mars' Gale Crater in 2012, the mission's main goal was to determine whether the area ever offered an environment favorable for microbes. The crater's main appeal for scientists is geological layering exposed in the lower portion of its central mound, Mount Sharp. These exposures offer access to rocks that hold a record of environmental conditions from many stages of early Martian history, each layer younger than the one beneath it. The mission succeeded in its first year, finding that an ancient Martian lake environment had all the key chemical ingredients needed for life, plus chemical energy available for life. Now, the rover is climbing lower on Mount Sharp to investigate how ancient environmental conditions changed over time. "We are well into the layers that were the main reason Gale Crater was chosen as the landing site," said Curiosity Deputy Project Scientist Joy Crisp of NASA's Jet Propulsion Laboratory, in Pasadena, California. "We are now using a strategy of drilling samples at regular intervals as the rover climbs Mount Sharp. Earlier we chose drilling targets based on each site's special characteristics. Now that we're driving continuously through the thick basal layer of the mountain, a series of drill holes will build a complete picture." Four recent drilling sites, from "Oudam" this past June through "Sebina" in October, are each spaced about 80 feet (about 25 meters) apart in elevation. This uphill pattern allows the science team to sample progressively younger layers that reveal Mount Sharp's ancient environmental history. One clue to changing ancient conditions is the mineral hematite. It has replaced less-oxidized magnetite as the dominant iron oxide in rocks Curiosity has drilled recently, compared with the site where Curiosity first found lakebed sediments. "Both samples are mudstone deposited at the bottom of a lake, but the hematite may suggest warmer conditions, or more interaction between the atmosphere and the sediments," said Thomas Bristow of NASA Ames Research Center, Moffett Field, California. He helps operate the Chemistry and Mineralogy (CheMin) laboratory instrument inside the rover, which identifies minerals in collected samples. Chemical reactivity occurs on a gradient of chemical ingredients' strength at donating or receiving electrons. Transfer of electrons due to this gradient can provide energy for life. An increase in hematite relative to magnetite indicates an environmental change in the direction of tugging electrons more strongly, causing a greater degree of oxidation in iron. Another ingredient increasing in recent measurements by Curiosity is the element boron, which the rover's laser-shooting Chemistry and Camera (ChemCam) instrument has been detecting within mineral veins that are mainly calcium sulfate. "No prior mission has detected boron on Mars," said Patrick Gasda of the U.S. Department of Energy's Los Alamos National Laboratory, Los Alamos, New Mexico. "We're seeing a sharp increase in boron in vein targets inspected in the past several months." The instrument is quite sensitive; even at the increased level, boron makes up only about one-tenth of one percent of the rock composition. Boron is famously associated with arid sites where much water has evaporated away—think of the borax that mule teams once hauled from Death Valley. However, environmental implications of the minor amount of boron found by Curiosity are less straightforward than for the increase in hematite. Scientists are considering at least two possibilities for the source of boron that groundwater left in the veins. Perhaps evaporation of a lake formed a boron-containing deposit in an overlying layer, not yet reached by Curiosity, then water later re-dissolved the boron and carried it down through a fracture network into older layers, where it accumulated along with fracture-filling vein minerals. Or perhaps changes in the chemistry of clay-bearing deposits, such as evidenced by the increased hematite, affected how groundwater picked up and dropped off boron within the local sediments. "Variations in these minerals and elements indicate a dynamic system," Grotzinger said. "They interact with groundwater as well as surface water. The water influences the chemistry of the clays, but the composition of the water also changes. We are seeing chemical complexity indicating a long, interactive history with the water. The more complicated the chemistry is, the better it is for habitability. The boron, hematite and clay minerals underline the mobility of elements and electrons, and that is good for life."


Schmidl W.,CheMin GmbH | Herzog T.,CheMin GmbH | Magel G.,CheMin GmbH | Muller W.,CheMin GmbH | Spiegel W.,CheMin GmbH
VGB PowerTech | Year: 2011

Corrosion by chlorine at high temperatures and corrosion by salt melts sometimes cause severe risk and loss of operational availability in waste- and biomass-fired power plants [1]. This corrosion very often affects the superheater. Wear rates of up to 1 mm per 1000 hours can occur on unprotected carbon steel tubes, caused by a combination of locally occurring heat flux, flue gas composition and fouling. Due to high maintenance needs, several approaches to anti-corrosion coating have been developed. Nickel-based alloys such as alloy 625 are chosen to be applied as cladding or by thermal spraying. Operation periods have been considerably increased by these methods. But still there are some shortcomings in corrosion protection due to application and/or material. This article depicts some experiences with corrosion inhibiting applications, gathered by the authors during quality control on application or examination of damage. On the whole, the efficacy of both application forms, thermal spray and cladding, can be assumed. Especially local corrosion protection of discrete parts of a superheater can be a good alternative to complete white" or black" solutions.


Grahl S.,TU Dresden | Beckmann M.,TU Dresden | Magel G.,CheMin GmbH | Spiegel W.,CheMin GmbH
International Conference on Thermal Treatment Technologies and Hazardous Waste Combustors 2010 | Year: 2010

The combustion of biomass and heat-recoverable waste products often leads to corrosive deposits at the evaporator finned tube walls, which subsequently cause material damage, greater exhaust gas losses or unacceptably high material stress. For prevention the deposits are being cleaned regularly, largely mechanical, during the plant shutdowns. To reduce the maintenance and service efforts and thus increase the economic efficiency, plant shutdowns for cleaning and removal of corrosion damages should be minimized. Due to the obstruction of heat extraction caused by deposits as well as the large temperature gradient between the finned tube panel surface and the exhaust gas on one side and the appearance of a deposit material with corrosive, temperature-dependent properties on the other side, there exists a qualitative relationship between formation and structure of deposits and the heat flux hitting the evaporator wall. The latter can therefore be used to characterize deposits at finned tube walls of steam generators as well as to determine the point in time of cleaning and to assess the corrosion potential of the deposit. For this purpose a method was developed that can use the Fourier transform of the heat flux signal to determine the temperature-dependent material properties of the deposits. Currently, the change of heat flux density of a finned tube wall with deposits compared to the clean state is experimentally demonstrated and a further development takes place by means of signal processing to derive information about the deposit situation in practical application. The results are discussed in the following paper.


Heuss-Assbichler S.,Ludwig Maximilians University of Munich | Magel G.,CheMin GmbH | Fehr K.T.,Ludwig Maximilians University of Munich
Waste Management | Year: 2010

Long-term hydrogen generation was observed in a Bavarian mono-landfill for municipal solid waste incineration (MSWI) residues. Hydration reactions of non-noble metals, especially aluminum, predominantly produce hydrogen at alkaline reaction conditions. Microscopic investigations show that aluminum metal may occur in different forms: as larger single grains, as small particles embedded in a vitrified matrix or less frequently in blowholes together with metallic silica.Four types of corrosion texture were observed, indicating different reaction mechanisms: aluminum hydroxide rims caused by hydration reactions at alkaline reaction conditions (reaction type 1) and multiphase rims with ettringite and hydrocalumite due to the reaction of aluminum hydroxide with sulfate and chloride ions which are solved in the pore water (reaction type 2). Galvanic corrosion textures due to the electric potential difference between aluminum and embedded intermetallic Fe- or Cu-rich exsolution phases lead to two further corrosion textures: Strong hydration effects of aluminum except a border of aluminum remnant directly beside the Fe- or Cu-rich segregations were only observed in fresh samples (reaction type 3). The reaction type 4 shows a network of Al-hydroxide veins occurring along the embedded intermetallic Fe- or Cu-rich exsolution segregation pattern within the metallic aluminum grain. Metal particles enclosed in vitrified particles offers the potential for future corrosion processes.The occurrence of corrosion types 1, 2 and 3 in fresh bottom ashes indicates that these reaction mechanisms predominate during the first reaction period in the presence of chlorine in an alkaline solution. Corrosion type 4, however, was additionally observed in aged samples. Here aluminum acts as sacrificed anode implying electrochemical reaction due to electrolytic pore water. Chloride in the system keeps the reaction alive as Al-hydroxide is solved which normally builds a protection shield around the aluminum metal particles.Due to field observations and experimental results we have reasonable indications that after an initial strong formation of hydrogen the reaction time for hydrogen production in the landfill is lengthened for several decades by the presence of chloride in the alkaline pore water. © 2010 Elsevier Ltd.


News Article | December 21, 2015
Site: www.techtimes.com

NASA's Curiosity rover has detected a substantial amount of silica deposits in the Martian rock formations it had investigated in the past seven months. Scientists believe this discovery provides evidence that water activity could likely have existed on the Red Planet in the past. In a press conference held during the meeting of the American Geophysical Union (AGU) in San Francisco, researchers involved in the Mars mission reported that the rover found higher silica concentrations in some of the areas it had surveyed in the past few months than in any of the sites it had visited before. The team discovered that as much as nine-tenths of the rocks the rover had examined were composed of silica. Jens Frydenvang, a researcher from the Los Alamos National Laboratory and one of those analyzing the Curiosity's findings, said that while they are still trying to determine how the rocks were enriched with silica, many of their hypotheses point to the possibility that Mars experienced considerable water activity in the past. He explained that areas with high silica deposits on Earth typically make suitable environments for sustaining microbial life-forms. Frydenvang added that the discovery of silica in the Martian rocks has led the scientists to make a rare backtrack in their research in order to investigate the new findings further. Traces of silica were first spotted while the Curiosity rover was approaching the region called "Marias Pass". The area is known to have a lower geological unit that makes contact with an overlying one. Curiosity's laser-firing instrument known as ChemCam detected high amounts of silica in a number of targets the probe had passed on its way to the designated contact zone. The rover continued to detect silica readings during its succeeding missions, which the scientists combined with elemental composition data from Curiosity's Alpha Particle X-Ray Spectrometer (APXS) and mineral data from its Chemistry and Mineralogy (CheMin) instrument. "What we're seeing on Mount Sharp is dramatically different from what we saw in the first two years of the mission," Ashwin Vasavada, a researcher from NASA's Jet Propulsion Laboratory, said. "There's so much variability within relatively short distances." "The silica is one indicator of how the chemistry changed. It's such a multifaceted and curious discovery, we're going to take a while figuring it out." The researchers are following two primary hypotheses to figure out recent findings made on Mount Sharp, both of which have water playing a crucial role. One of the hypotheses involves having acidic water carry away other elements from the rocks and leaving only the silica deposits behind. The other hypothesis features neutral or alkaline water dissolving silica and depositing them on the rocks through the resulting solution. The latest findings made by the Curiosity have interesting threads associated with data collected by NASA's earlier Spirit rover in another part of Mars. The probe detected traces of sulfuric acidity in the region. "Buckskin" is one of the Martian rocks analyzed by the Curiosity rover that contained evidence of the rare mineral tridymite. On Earth, tridymite is formed when metamorphic or igneous rocks are exposed to high temperatures. The fine layers of sedimentary rocks the rover detected the mineral on, however, showed evidence that they may have been part of lakebed deposits. This proves that a magmatic evolution could likely have occurred on Mars.

Loading CheMin GmbH collaborators
Loading CheMin GmbH collaborators