The atmosphere of Mars

Mars, one of the most Earth-like of the planets, is today a cold, dry and barren world. However, there is good evidence that it may have been much warmer and wetter in the past and perhaps even supported life. The public interest aroused by these findings and by recent studies of 'SNC' meteorites, believed to have come from Mars, with their claims of the evidence of ancient Martian life, has focused attention on the ambitious programme of Mars Exploration currently being undertaken by NASA and ESA and has provided additional impetus. Improved measurements of the conditions on Mars' surface and in its atmosphere are central to both agencies' plans, and current atmospheric missions are reviewed in this paper together with possible future designs

Temperature, cloud structure, and dynamics of venus middle atmosphere by infrared remote sensing from pioneer orbiter.

Further results from the Venus orbiter radiometric temperature experiment (VORTEX) on the Pioneer orbiter are presented. These are used to characterize the three-dimensional temperature field, the cloud structure, and the dynamics of the 60-to 130-kilometer altitude region of the Venus atmosphere. One of the new discoveries is a "dipole" structure at high latitudes, with two hot spots rotating around the pole, surrounded by banks of cold cloud

Remote sounding of the Martian atmosphere in the context of the InterMarsNet mission: General circulation and meteorology

A concept has been developed for a remote sensing experiment to investigate the physics of the Martian atmosphere from a spin-stabilized orbiter, like that planned for the InterMarsNet mission. Using coincident infrared and microwave channels and limb-to-limb scanning, it can map the planet much more extensively than previously in temperature, atmospheric dust loading, and humidity. When combined with one or more surface stations measuring the same variables, the sounder experiment can contribute to major progress in understanding the general circulation and dust and water cycles of the atmosphere of Mars, and the characterization of medium-scale meteorological systems. Copyright © 1996 Elsevier Science Ltd

Test 601: John Deere 420/430 C

EXPLANATION OF TEST REPORT: John Deere 420/430 C TEST A: The manufacturer\u27s representative operates the tractor for a minimum of 12 hours using light to heavy drawbar loads in each gear. This serves as a period for limber up, general observation and adjustments. Adjustments that are permissible include valve tappet clearance, breaker ,point gap, spark plug gaps, clutch and others of a similar nature. No new parts or accessories can be installed without having mention made of it in the report. No data\u27 are recorded during this preliminary run except the time that the engine is operated. BELT HORSEPOWER TESTS TEST B: The throttle valve is hdd wide opened and the belt load on the dynamometer is adjusted so that the engine is at the rated speed recommended by the manufacturer. Carburetor, ignition timing and manifold adjustments are all set for maximum engine power. This test is designed to determine maximum belt horsepower of the tractor at ra.te.d speed and to measure fuel consumption at the maximum power on the belt. TEST C: For tractors with carburetors the best fuel economy does not always occur when the engine develops maximum power at rated speed. Test C is intended to allow the manufacturer\u27s representative to select a more economical fuel setting even though there is a slight loss of power. This more practical carburetor setting is used in all later tests except test F. The throttle valve is held wide open and load adjusted to give rated rpm. Tests Band C are the same for diesel tractors, which have an altogether different fuel system. TEST D: The throttle control lever is set so that the governor will maintain rated engine speed when rated load is applied. Rated load is 85% of 100% maximum, as obtained in test B, corrected to standard conditions. This rating is somewhat less than the maximum belt horsepower in order that the operator may have a certain amount of reserve. TEST E: Varying load serves to show the range of engine speeds when the engine is controlled by the governor during the following varied loads of 20 minutes each: rated load, no load, 1/2 rated load, maximum load at wide open throttle valve, 1/4 and 3/4 rated load. The average result of this test shows the average power and fuel consumption. Since the average tractor is subjected to varying loads, these data serve well in predicting fuel consumptionand efficiency of a tractor in general use. Torque, lb-ft at dynamometer, is obtained with wide open throttle and sufficient load is applied to give several readings. DRAWBAR HORSEPOWER TESTS In all drawbar tests the pull exerted by the tractor is transmitted by a hydraulic pressure cylinder to a recording instrument in the test car. All tests are made on the same dirt test course which is maintained by grading, sprinkling and rolling so that it remains very nearly the same throughout the season. The same tires, wheels and weights are used for all tests except J and K. TEST F: A drawbar test, the results of which are used to determine the rated drawbar horsepower in test H. The carburetor is set to develop maximum power as in test B. The rated gear recommended by manufacturer as plow gear is used in this test. The drawbar load is adjusted to give rated engine speed. TEST G: Maximum drawbar horsepower is determined in each gear when the carburetor is set for fuel economy as in test C. The throttle valve is held wide open and the load is applied so that the engine runs at rated engine speed. When operating in low gear it is not uncommon for the tractor to develop less drawbar horsepower than in rated gear because of excessive wheel slippage. When excessive wheel slippage occurs the load is reduced until slippage approaches 16%. When the load is reduced it is necessary to operate the tractor engine at part throttle and control engine speed by governor action. TEST H: Intended to test the ability of the tractor to run continuously for 10 hours at rated drawbar horsepower and to determine the fuel consumption during that time. Rated drawbar horsepower is 75% of 10°% maximum drawbar horsepower (Test F), corrected to standard conditions. When operating at rated load the throttle control lever is set to maintain rated engine speed. This rating is less than maximum drawbar horsepower in order that the operator may have a certain amount of reserve. TEST J: The tractor is operated in rated gear with all added weight removed. This test shows the effect of the removal of added weight on the performance of the tractor when compared with test G. Removal of wheel weights generally increases wheel slippage and decreases drawbar horsepower. TEST K: Similar to test J except that the smallest tires and lightest wheels offered by the manufacturer are used

Mars Climate Sounder: An investigation of thermal and water vapor structure, dust and condensate distributions in the atmosphere, and energy balance of the polar regions

Against a backdrop of intensive exploration of the Martian surface environment, intehded to lead to human exploration, some aspects of the modern climate and the meteorology of Mars remain relatively unexplored. In particular, there is a need for detailed measurements of the vertical profiles of atmospheric temperature, water vapor, dust, and condensates to understand the intricately related processes upon which the surface conditions, and those encountered during descent by landers, depend. The most important of these missing data are accurate and extensive temperature measurements with high vertical resolution. The Mars Climate Sounder experiment on the 2005 Mars Reconnaissance Orbiter, described here, is the latest attempt to characterize the Martian atmosphere with the sort of coverage and precision achieved by terrestrial weather satellites. If successful, it is expected to lead to corresponding improvements in our understanding of meteorological phenomena and to enable improved general circulation models of the Martian atmosphere for climate studies on a range of timescales. Copyright 2007 by the American Geophysical Union

Mars Climate Sounder limb profile retrieval of atmospheric temperature, pressure, and dust and water ice opacity

The Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter is the latest of a series of investigations devoted to improving the understanding of current Martian climate. MCS is a nine-channel passive midinfrared and far-infrared filter radiometer designed to measure thermal emission in limb and on-planet geometries from which vertical profiles of atmospheric temperature, water vapor, dust, and condensates can be retrieved. Here we describe the algorithm that is used to retrieve atmospheric profiles from MCS limb measurements for delivery to the Planetary Data System. The algorithm is based on a modified Chahine method and uses a fast radiative transfer scheme based on the Curtis-Godson approximation. It retrieves pressure and vertical profiles of atmospheric temperature, dust opacity, and water ice opacity. Water vapor retrievals involve a different approach and will be reported separately. Pressure can be retrieved to a precision of 1–2% and is used to establish the vertical coordinate. Temperature profiles are retrieved over a range from 5–10 to 80–90 km altitude with a typical altitude resolution of 4–6 km and a precision between 0.5 and 2 K over most of this altitude range. Dust and water ice opacity profiles also achieve vertical resolutions of about 5 km and typically have precisions of 10^(−4)–10^(−5) km^(−1) at 463 cm^(−1) and 843 cm^(−1), respectively. Examples of temperature profiles as well as dust and water ice opacity profiles from the first year of the MCS mission are presented, and atmospheric features observed during periods employing different MCS operational modes are described. An intercomparison with historical temperature measurements from the Mars Global Surveyor mission shows good agreement

Intense polar temperature inversion in the middle atmosphere on Mars

Current understanding of weather, climate and global atmospheric circulation on Mars is incomplete, in particular at altitudes above about 30 km. General circulation models for Mars are similar to those developed for weather and climate forecasting on Earth and require more martian observations to allow testing and model improvements. However, the available measurements of martian atmospheric temperatures, winds, water vapour and airborne dust are generally restricted to the region close to the surface and lack the vertical resolution and global coverage that is necessary to shed light on the dynamics of Mars' middle atmosphere at altitudes between 30 and 80 km. Here we report high-resolution observations from the Mars Climate Sounder instrument on the Mars Reconnaissance Orbiter. These observations show an intense warming of the middle atmosphere over the south polar region in winter that is at least 10–20 K warmer than predicted by current model simulations. To explain this finding, we suggest that the atmospheric downwelling circulation over the pole, which is part of the equator-to-pole Hadley circulation, may be as much as 50% more vigorous than expected, with consequences for the cycles of water, dust and CO2 that regulate the present-day climate on Mars

Investigations of the Mars upper atmosphere with ExoMars Trace Gas Orbiter

The Martian mesosphere and thermosphere, the region above about 60 km, is not the primary target of the ExoMars 2016 mission but its Trace Gas Orbiter (TGO) can explore it and address many interesting issues, either in-situ during the aerobraking period or remotely during the regular mission. In the aerobraking phase TGO peeks into thermospheric densities and temperatures, in a broad range of latitudes and during a long continuous period. TGO carries two instruments designed for the detection of trace species, NOMAD and ACS, which will use the solar occultation technique. Their regular sounding at the terminator up to very high altitudes in many different molecular bands will represent the first time that an extensive and precise dataset of densities and hopefully temperatures are obtained at those altitudes and local times on Mars. But there are additional capabilities in TGO for studying the upper atmosphere of Mars, and we review them briefly. Our simulations suggest that airglow emissions from the UV to the IR might be observed outside the terminator. If eventually confirmed from orbit, they would supply new information about atmospheric dynamics and variability. However, their optimal exploitation requires a special spacecraft pointing, currently not considered in the regular operations but feasible in our opinion. We discuss the synergy between the TGO instruments, specially the wide spectral range achieved by combining them. We also encourage coordinated operations with other Mars-observing missions capable of supplying simultaneous measurements of its upper atmosphere