| 1. |
- Guzewich, Scott D., et al.
(författare)
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Mars Science Laboratory Observations of the 2018/Mars Year 34 Global Dust Storm
- 2019
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 46:1, s. 71-79
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Tidskriftsartikel (refereegranskat)abstract
- Mars Science Laboratory Curiosity rover observations of the 2018/Mars year 34 global/planet‐encircling dust storm represent the first in situ measurements of a global dust storm with dedicated meteorological sensors since the Viking Landers. The Mars Science Laboratory team planned and executed a science campaign lasting approximately 100 Martian sols to study the storm involving an enhanced cadence of environmental monitoring using the rover's meteorological sensors, cameras, and spectrometers. Mast Camera 880‐nm optical depth reached 8.5, and Rover Environmental Monitoring Station measurements indicated a 97% reduction in incident total ultraviolet solar radiation at the surface, 30K reduction in diurnal range of air temperature, and an increase in the semidiurnal pressure tide amplitude to 40 Pa. No active dust‐lifting sites were detected within Gale Crater, and global and local atmospheric dynamics were drastically altered during the storm. This work presents an overview of the mission's storm observations and initial results.
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| 2. |
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| 3. |
- 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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| 5. |
- Ming, D.W., et al.
(författare)
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Volatile and organic compositions of sedimentary rocks in Yellowknife Bay, Gale Crater, Mars
- 2014
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6169
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Tidskriftsartikel (refereegranskat)abstract
- H2O, CO2, SO2, O2, H2, H2S, HCl, chlorinated hydrocarbons, NO, and other trace gases were evolved during pyrolysis of two mudstone samples acquired by the Curiosity rover at Yellowknife Bay within Gale crater, Mars. H2O/OH-bearing phases included 2:1 phyllosilicate(s), bassanite, akaganeite, and amorphous materials. Thermal decomposition of carbonates and combustion of organic materials are candidate sources for the CO2. Concurrent evolution of O2 and chlorinated hydrocarbons suggests the presence of oxychlorine phase(s). Sulfides are likely sources for sulfur-bearing species. Higher abundances of chlorinated hydrocarbons in the mudstone compared with Rocknest windblown materials previously analyzed by Curiosity suggest that indigenous martian or meteoritic organic carbon sources may be preserved in the mudstone; however, the carbon source for the chlorinated hydrocarbons is not definitively of martian origin.
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| 6. |
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| 7. |
- 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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