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- Haberle, R. M., et al.
(författare)
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Preliminary interpretation of the REMS pressure data from the first 100 sols of the MSL mission
- 2014
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Ingår i: Journal of Geophysical Research - Planets. - : John Wiley & Sons. - 2169-9097 .- 2169-9100. ; 119:3, s. 440-453
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Tidskriftsartikel (refereegranskat)abstract
- We provide a preliminary interpretation of the Rover Environmental Monitoring Station (REMS) pressure data from the first 100 Martian solar days (sols) of the Mars Science Laboratory mission. The pressure sensor is performing well and has revealed the existence of phenomena undetected by previous missions that include possible gravity waves excited by evening downslope flows, relatively dust-free convective vortices analogous in structure to dust devils, and signatures indicative of the circulation induced by Gale Crater and its central mound. Other more familiar phenomena are also present including the thermal tides, generated by daily insolation variations, and the CO2 cycle, driven by the condensation and sublimation of CO2 in the polar regions. The amplitude of the thermal tides is several times larger than those seen by other landers primarily because Curiosity is located where eastward and westward tidal modes constructively interfere and also because the crater circulation amplifies the tides to some extent. During the first 100 sols tidal amplitudes generally decline, which we attribute to the waning influence of the Kelvin wave. Toward the end of the 100 sol period, tidal amplitudes abruptly increased in response to a nearby regional dust storm that did not expand to global scales. Tidal phases changed abruptly during the onset of this storm suggesting a change in the interaction between eastward and westward modes. When compared to Viking Lander 2 data, the REMS daily average pressures show no evidence yet for the 1-20 Pa increase expected from the possible loss of CO 2 from the south polar residual cap. Key Points REMS pressure sensor is operating nominally New phenomena have been discovered Familiar phenomena have been detected ©2014. American Geophysical Union. All Rights Reserved.
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- Haberle, R. M., et al.
(författare)
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Secular Climate Change on Mars : An Update Using MSL Pressure Data
- 2013
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Konferensbidrag (refereegranskat)abstract
- The South Polar Residual Cap (SPRC) on Mars is an icy reservoir of CO2. If all the CO2 trapped in the SPRC were released to the atmosphere the mean annual global surface pressure would rise by ~20 Pa. Repeated MOC and HiRISE imaging of scarp retreat rates within the SPRC have led to the suggestion that the SPRC is losing mass. Estimates for the loss rate vary between 0. 5 Pa per Mars Decade to 13 Pa per Mars Decade. Assuming 80% of this loss goes directly into the atmosphere, and that the loss is monotonic, the global annual mean surface pressure should have increased between ~1-20 Pa since the Viking mission (19 Mars years ago). Surface pressure measurements by the Phoenix Lander only 2 Mars years ago were found to be consistent with these loss rates. Here we compare surface pressure data from the MSL mission with that from Viking Lander 2 (VL-2) to determine if the trend continues. We use VL-2 because it is at the same elevation as MSL (-4500 m). However, based on the first 100 sols of data there does not appear to be a significant difference between the dynamically adjusted pressures of the two landers. This result implies one of several possibilities: (1) the cap is not losing mass and the difference between the Viking and Phoenix results is due to uncertainties in the measurements; (2) the cap has lost mass between the Viking and Phoenix missions but it has since gone back to the cap or into the regolith; or (3) that our analysis is flawed. The first possibility is real since post-mission analysis of the Phoenix sensor has shown that there is a 3 (±2) Pa offset in the data and there may also be uncertainties in the Viking data. The loss/gain scenario for the cap seems unlikely since scarps continue retreating, and regolith uptake implies something unique about the past several Mars years. That our analysis is flawed is certainly possible owing to the very different environments of the Viking and MSL landers. MSL is at the bottom of a deep crater in the southern tropics (~5°S), whereas VL-2 is at a high latitude (~48°N) in the northern plains. And in spite of the fact that the two landers are at nearly identical elevations, they are in very different thermal environments (e.g., MSL is warm when VL-2 is cold), which can have a significant affect on pressures. For these reasons, our confidence in the comparison will increase as more MSL data become available. We will report the results up through sol 360 at the meeting.
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- Harri, A.-M., et al.
(författare)
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Pressure observations by the Curiosity rover : Initial results
- 2014
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Ingår i: Journal of Geophysical Research - Planets. - : John Wiley & Sons. - 2169-9097 .- 2169-9100. ; 119:1, s. 82-92
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Tidskriftsartikel (refereegranskat)abstract
- REMS-P, the pressure measurement subsystem of the Mars Science Laboratory (MSL) Rover Environmental Measurement Station (REMS), is performing accurate observations of the Martian atmospheric surface pressure. It has demonstrated high data quality and good temporal coverage, carrying out the first in situ pressure observations in the Martian equatorial regions. We describe the REMS-P initial results by MSL mission sol 100 including the instrument performance and data quality and illustrate some initial interpretations of the observed features. The observations show both expected and new phenomena at various spatial and temporal scales, e.g., the gradually increasing pressure due to the advancing Martian season signals from the diurnal tides as well as various local atmospheric phenomena and thermal vortices. Among the unexpected new phenomena discovered in the pressure data are a small regular pressure drop at every sol and pressure oscillations occurring in the early evening. We look forward to continued high-quality observations by REMS-P, extending the data set to reveal characteristics of seasonal variations and improved insights into regional and local phenomena. Key Points The performance and data quality of the REMS / MSL pressure observations. MSL pressure observations exhibit local phenomena of the Gale crater area. Small pressure oscillations possibly linked to gravity waves. ©2013. American Geophysical Union. All Rights Reserved.
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- Conrad, P.G., et al.
(författare)
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Environmental Dynamics and the Habitability Potential at Gale Crater, Mars
- 2013
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Konferensbidrag (refereegranskat)abstract
- The assessment of environmental habitability potential involves measurement of the chemical and physical attributes of the system as well as their dynamic interplay. The environmental dynamics describe the availability of both energy sources and raw materials for meeting the requirements of organisms and for altering the environment. Energetic exchange can also determine the preservation potential for organic materials in the rock record. During its first year at Gale Crater, the Mars Science Laboratory payload has directly measured the chemistry and physical attributes, e.g., temperature, humidity, radiation, pressure, etc. of the martian atmosphere. Curiosity has also acquired chemical and mineralogical data, both from a wind drift deposit of fines and from two examples of a sedimentary rock formation in a region of Gale Crater called Yellowknife Bay, some 445 meters to the east of Bradbury Landing, where Curiosity initially touched down. These data enabled inferences to be made regarding depositional environment and past habitability potential at Gale Crater. The rock chemistry data reveal signs of aqueous interaction i.e., H2O, OH and H2 and sufficient elemental basis (C, H, O, S and possibly N) for plausible nutrient supply, should Mars have ever had autotrophic prokaryotes to exploit it, and a range of redox conditions tolerable to Earth microbes is indicated by the presence of clay minerals. Curiosity’s observations of the chemical, physical and geologic features of Yellowknife Bay point to a formerly habitable environment.
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| 8. |
- Harri, A.-M., et al.
(författare)
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Mars Science Laboratory relative humidity observations : Initial results
- 2014
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Ingår i: Journal of Geophysical Research - Planets. - 2169-9097 .- 2169-9100. ; 119:9, s. 2132-2147
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Tidskriftsartikel (refereegranskat)abstract
- The Mars Science Laboratory (MSL) made a successful landing at Gale crater early August 2012. MSL has an environmental instrument package called the Rover Environmental Monitoring Station (REMS) as a part of its scientific payload. REMS comprises instrumentation for the observation of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements. We concentrate on describing the REMS-H measurement performance and initial observations during the first 100 MSL sols as well as constraining the REMS-H results by comparing them with earlier observations and modeling results. The REMS-H device is based on polymeric capacitive humidity sensors developed by Vaisala Inc., and it makes use of transducer electronics section placed in the vicinity of the three humidity sensor heads. The humidity device is mounted on the REMS boom providing ventilation with the ambient atmosphere through a filter protecting the device from airborne dust. The final relative humidity results appear to be convincing and are aligned with earlier indirect observations of the total atmospheric precipitable water content. The water mixing ratio in the atmospheric surface layer appears to vary between 30 and 75 ppm. When assuming uniform mixing, the precipitable water content of the atmosphere is ranging from a few to six precipitable micrometers.
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- Renno, N.O., et al.
(författare)
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Ground-atmosphere interactions at Gale
- 2013
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Konferensbidrag (refereegranskat)abstract
- We analyze variations in environmental parameters and regolith properties along Curiosity’s track to determine the possible causes of an abrupt change in the thermal properties of the ground and the atmosphere observed around Sol 120, as the rover transitioned from an area of sandy soil (Rocknest) to an area of fractured bedrock terrain (Yellowknife). Curiosity is instrumented with the Rover Environmental Monitoring Station (REMS) and the Dynamic Albedo of Neutrons (DAN) sensors to measure the air temperature, the ground temperature, and the hydrogen content of the shallow subsurface along Curiosity’s track. Analysis of the REMS data is used to estimate the regolith’s heat budget. This analysis suggests that the abrupt decrease in the ground and atmosphere temperature and the difference between ground and air temperatures observed around Sol 120 is likely caused by an increase in the soil thermal inertia. The changes in thermal inertia have been known for some time so confirming this by the REMS package provides ground truthing. A new unexpected finding is that the regolith water content, as indicated by DAN’s detection of hydrogen content, is higher in the Yellowknife soil. Another interesting finding at this site are the holes and other signs of recent geological activity in the area of fractured terrain that may reflect large volumetric variations and facilitate gas exchange between the ground and atmosphere. Near-surface volumetric changes in soil and bedrock could reflect changes in the volume of subsurface H2O, or in the partitioning of H2O among its three phases. Volume increases could also result from salt crystal growth in rock pores and soil pores associated with the adsorption of water vapor. Crystallization in pores is a significant weathering process on Earth; it could well be active on Mars. Salts also inhibits the exchange of moisture between the ground and the atmosphere, and cements the soils of arid places such as in the McMurdo Dry Valleys in Antarctica. Indeed, salts might be responsible for the ubiquitous martian duricrust. More importantly, salt crusts have the potential to create pockets of wet regolith in the shallow martian subsurface that could be habitable. A better understanding of ground-atmosphere interactions has the potential to shed new light into aqueous processes in the shallow martian subsurface.
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- Agić, Heda, 1989-, et al.
(författare)
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Lateral growth of Late Pleistocene stromatolites from Walker Lake (Nevada) and proxy constraints on environmental change
- 2014
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Ingår i: 2014 GSA Annual Meeting in Vancouver. - : Geological Society of America. ; , s. 300-4-
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Konferensbidrag (refereegranskat)abstract
- Walker Lake, a terminal sodium bicarbonate lake in Western Nevada (Great Basin, USA) contains numerous carbonate structures, including stromatolites. The lake is a remnant of the larger Pleistocene Lake Lahontan system that has been isolated for the last ~12 ka. Stromatolites of unique macroscale morphology were collected at the ancient Lahontan shoreline during the 2014 International Geobiology Course.Initial observations of a stromatolite bed revealed a bowl-shaped carbonate framework composed of stacked, weakly laminated, vertical and horizontal petal-like structures with copious pore space. One laterally-oriented petal was taken off of the main structure and studied. Petrographical observations exhibit two types of alternating microfabrics and three transitions in microfabric. Both sparry crystal fans of calcite, and convex layers of fine micrite with occasional trapped crystals and fossils, were observed.Calibrated 14C ages (IntCal13) for the proximal and the distal end of the stromatolite are 35,540 YBP and 33,580 YBP, respectively. Clumped isotope (D47)-based estimates of temperature steadily increase throughout most of this interval, from the beginning of accretion, to the middle of the structure. By the distal end, values are at their peak, and at the tip temperatures decrease again. D47-temperatures correspond to microfabric, with textural changes associated with evidence for climatic fluctuations.We suggest the stromatolite formation may have been initiated during warmer intervals, induced by the chemical precipitation of calcite fans which served as a substrate for a biofilm growth. Microbial activity trapped the fine sediment and formed micrite. Colder conditions propagated fan precipitation. Microfabric alternation throughout the stromatolite records environmental change in the span of ca. 2000 years of Lake Lahontan history, likely in response to lake level fluctuations.
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| 11. |
- Gõmez-Elvira, Javier, et al.
(författare)
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Curiosity's rover environmental monitoring station : Overview of the first 100 sols
- 2014
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Ingår i: Journal of Geophysical Research - Planets. - 2169-9097 .- 2169-9100. ; 119:7, s. 1680-1688
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Tidskriftsartikel (refereegranskat)abstract
- In the first 100 Martian solar days (sols) of the Mars Science Laboratory mission, the Rover Environmental Monitoring Station (REMS) measured the seasonally evolving diurnal cycles of ultraviolet radiation, atmospheric pressure, air temperature, ground temperature, relative humidity, and wind within Gale Crater on Mars. As an introduction to several REMS-based articles in this issue, we provide an overview of the design and performance of the REMS sensors and discuss our approach to mitigating some of the difficulties we encountered following landing, including the loss of one of the two wind sensors. We discuss the REMS data set in the context of other Mars Science Laboratory instruments and observations and describe how an enhanced observing strategy greatly increased the amount of REMS data returned in the first 100 sols, providing complete coverage of the diurnal cycle every 4 to 6 sols. Finally, we provide a brief overview of key science results from the first 100 sols. We found Gale to be very dry, never reaching saturation relative humidities, subject to larger diurnal surface pressure variations than seen by any previous lander on Mars, air temperatures consistent with model predictions and abundant short timescale variability, and surface temperatures responsive to changes in surface properties and suggestive of subsurface layering. Key Points Introduction to the REMS results on MSL mission Overiview of the sensor information Overview of operational constraints
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