TY - JOUR
AU - Strangeways, Ian
AB - Abstract Ian Strangeways looks at what we know about the weather on Mars – and how we might find out more With the first humans likely to set foot on Mars this century, it would be useful to understand the weather on the Red Planet. But better knowledge of the weather and climate of another planet would have wider significance, too, especially in the field of astrobiology. So far, the only meteorological measurements made on the surface of Mars have come from instruments on landers or rovers, with very restricted coverage over the surface of the planet and in time (see box “Meteorological measurements on Mars”). Something more is required: widespread, durable, stand-alone weather stations with long lifetimes. In this article I explore the problems inherent in operating weather stations on Mars, which sensors are best suited to the environment, how they should be exposed, and what new research and development is required so we can explore martian weather and climate more deeply. Apart from precipitation, which of course is absent on Mars, the variables to be measured are the same as those on Earth, namely: air temperature a metre or so above the surface, relative humidity, wind speed and direction, solar radiation, albedo and barometric pressure (Strangeways 2003). The main adverse characteristics that affect weather stations on Mars are: the very low atmospheric pressure, around 6 hPa (6 mbar), compared with Earth's 1000 hPa; temperature extremes from 20°C at the equator to −150°C at the poles; and fine dust blown in the wind. Martian weather stations are not going to get regular service visits, so the chosen sensors and systems must work unattended for long periods. Overview: Meteorological measurements on Mars There have been 58 missions to Mars, from October 1960 onwards; 27 were successful. The successful missions were a mix of fly-by, orbiters, landers and rovers. This year, NASA's Perseverance rover has landed successfully, and the United Arab Emirates orbiter Hope and the Chinese Space Agency's Tianwen-1 spacecraft have entered orbit. Meteorological measurements on Mars have been made on the Viking, Mars Pathfinder, Phoenix, Mars Science Laboratory (Curiosity rover) and InSight missions. They are all very similar in principle, using thermocouples or thermo-capacitors for air temperature and hot-film wind sensors. Pressure sensors are based on flexing diaphragms, although more recently miniature sensors developed for radiosondes on Earth have been used. Humidity is also now measured by miniature sensors of the type developed for radiosondes. All of the meteorological instruments on Mars so far have been additions to a lander or a rover, generally in the form of a small cluster of sensors on a boom, for example the REMS on the Mars Science Laboratory Mission. A good review of all of the missions is provided by Martínez et al. (2017). mission . landed . type . instruments . Viking 1, 2 20 Jul 1976 3 Sep 1976 lander Viking Meteorological Instrument System (VMIS) atmospheric pressure (variable reluctance transducer operating over 0–18 hPa) atmospheric temperature (chromel–constantan thermocouple) wind speed and direction (two hot-film anemometers exposed at right angles to give direction) Mars Pathfinder 4 Jul 1997 lander Atmosphere Structure Instrument/Meteorology package (ASI/MET) Similar sensors to VMIS: atmospheric pressure atmospheric temperature 0.25 m, 0.5 m and 1 m above lander deck wind speed 1 m above lander deck wind direction (three windsocks 1.1 m above lander deck) Mars Exploration Rovers Spirit and Opportunity 4 Jan 2004 25 Jan 2004 rovers No weather station, but miniature thermal emission spectrometer ground temperature atmospheric temperature at 1 m, and at heights from 30–2000 m Phoenix 25 May 2008 lander Meteorological Station (MET) Similar sensors to VMIS (Taylor et al. 2008): ground temperature air temperature sensors at three heights up to 2 m above the surface, barometric pressure wind speed and direction (“telltale” recorded with Surface Stereo Imager) humidity Curiosity 6 Aug 2012 rover Rover Environmental Monitoring Station (REMS) (Gómez-Elvira et al. 2012, 2014 and mars.nasa.gov/msl/spacecraft/instruments/rems) ground temperature atmospheric temperature atmospheric pressure wind speed and direction humidity InSight 26 Nov 2018 lander Temperature and Winds for InSight (TWINS), based on REMS with enhanced dynamic range and resolution: wind speed and direction atmospheric temperature provides continuous wind and air temperature measurements mission . landed . type . instruments . Viking 1, 2 20 Jul 1976 3 Sep 1976 lander Viking Meteorological Instrument System (VMIS) atmospheric pressure (variable reluctance transducer operating over 0–18 hPa) atmospheric temperature (chromel–constantan thermocouple) wind speed and direction (two hot-film anemometers exposed at right angles to give direction) Mars Pathfinder 4 Jul 1997 lander Atmosphere Structure Instrument/Meteorology package (ASI/MET) Similar sensors to VMIS: atmospheric pressure atmospheric temperature 0.25 m, 0.5 m and 1 m above lander deck wind speed 1 m above lander deck wind direction (three windsocks 1.1 m above lander deck) Mars Exploration Rovers Spirit and Opportunity 4 Jan 2004 25 Jan 2004 rovers No weather station, but miniature thermal emission spectrometer ground temperature atmospheric temperature at 1 m, and at heights from 30–2000 m Phoenix 25 May 2008 lander Meteorological Station (MET) Similar sensors to VMIS (Taylor et al. 2008): ground temperature air temperature sensors at three heights up to 2 m above the surface, barometric pressure wind speed and direction (“telltale” recorded with Surface Stereo Imager) humidity Curiosity 6 Aug 2012 rover Rover Environmental Monitoring Station (REMS) (Gómez-Elvira et al. 2012, 2014 and mars.nasa.gov/msl/spacecraft/instruments/rems) ground temperature atmospheric temperature atmospheric pressure wind speed and direction humidity InSight 26 Nov 2018 lander Temperature and Winds for InSight (TWINS), based on REMS with enhanced dynamic range and resolution: wind speed and direction atmospheric temperature provides continuous wind and air temperature measurements Open in new tab mission . landed . type . instruments . Viking 1, 2 20 Jul 1976 3 Sep 1976 lander Viking Meteorological Instrument System (VMIS) atmospheric pressure (variable reluctance transducer operating over 0–18 hPa) atmospheric temperature (chromel–constantan thermocouple) wind speed and direction (two hot-film anemometers exposed at right angles to give direction) Mars Pathfinder 4 Jul 1997 lander Atmosphere Structure Instrument/Meteorology package (ASI/MET) Similar sensors to VMIS: atmospheric pressure atmospheric temperature 0.25 m, 0.5 m and 1 m above lander deck wind speed 1 m above lander deck wind direction (three windsocks 1.1 m above lander deck) Mars Exploration Rovers Spirit and Opportunity 4 Jan 2004 25 Jan 2004 rovers No weather station, but miniature thermal emission spectrometer ground temperature atmospheric temperature at 1 m, and at heights from 30–2000 m Phoenix 25 May 2008 lander Meteorological Station (MET) Similar sensors to VMIS (Taylor et al. 2008): ground temperature air temperature sensors at three heights up to 2 m above the surface, barometric pressure wind speed and direction (“telltale” recorded with Surface Stereo Imager) humidity Curiosity 6 Aug 2012 rover Rover Environmental Monitoring Station (REMS) (Gómez-Elvira et al. 2012, 2014 and mars.nasa.gov/msl/spacecraft/instruments/rems) ground temperature atmospheric temperature atmospheric pressure wind speed and direction humidity InSight 26 Nov 2018 lander Temperature and Winds for InSight (TWINS), based on REMS with enhanced dynamic range and resolution: wind speed and direction atmospheric temperature provides continuous wind and air temperature measurements mission . landed . type . instruments . Viking 1, 2 20 Jul 1976 3 Sep 1976 lander Viking Meteorological Instrument System (VMIS) atmospheric pressure (variable reluctance transducer operating over 0–18 hPa) atmospheric temperature (chromel–constantan thermocouple) wind speed and direction (two hot-film anemometers exposed at right angles to give direction) Mars Pathfinder 4 Jul 1997 lander Atmosphere Structure Instrument/Meteorology package (ASI/MET) Similar sensors to VMIS: atmospheric pressure atmospheric temperature 0.25 m, 0.5 m and 1 m above lander deck wind speed 1 m above lander deck wind direction (three windsocks 1.1 m above lander deck) Mars Exploration Rovers Spirit and Opportunity 4 Jan 2004 25 Jan 2004 rovers No weather station, but miniature thermal emission spectrometer ground temperature atmospheric temperature at 1 m, and at heights from 30–2000 m Phoenix 25 May 2008 lander Meteorological Station (MET) Similar sensors to VMIS (Taylor et al. 2008): ground temperature air temperature sensors at three heights up to 2 m above the surface, barometric pressure wind speed and direction (“telltale” recorded with Surface Stereo Imager) humidity Curiosity 6 Aug 2012 rover Rover Environmental Monitoring Station (REMS) (Gómez-Elvira et al. 2012, 2014 and mars.nasa.gov/msl/spacecraft/instruments/rems) ground temperature atmospheric temperature atmospheric pressure wind speed and direction humidity InSight 26 Nov 2018 lander Temperature and Winds for InSight (TWINS), based on REMS with enhanced dynamic range and resolution: wind speed and direction atmospheric temperature provides continuous wind and air temperature measurements Open in new tab Fewer problems On the positive side, there are far fewer problems in operating a weather station on Mars compared to Earth: there are none of the many difficulties associated with liquid water, water vapour and ice, nor are there damaging strong winds. And it is in the operational sense that many benefits ensue: no cities encroaching on the sites of stations to produce urban heat islands; no changes to the sites from tree growth and other vegetation; and, for the moment, no-one to build round them. The landscape around the sites will stay unchanged virtually indefinitely. Furthermore, while on Earth we have two extremely different environments – land and sea – on Mars there is but the one, making the same measurements possible globally. And the land environment on Mars is not affected by different conditions caused by the variable availability of water and the great variety of vegetation found on Earth. Finally, martian weather stations can expect no human vandalism, instrument invasion by insects nor damage by animals. Indeed, Mars is a near-perfect place on which to operate a weather station. And because of the planet's fairly unchanging aspect and relatively homogeneous land types, a global average temperature would be easy to calculate using just a few stations, perhaps as few as 10. We could soon be following contemporary climate change on Mars. But if we are to think about how we might design weather stations for Mars, understanding how automatic weather stations are operated on Earth is a good place to start. One of the world's first automatic weather stations (AWSs) came out of work at the Institute of Hydrology, now the UK Centre for Ecology and Hydrology, in the late 1960s (Strangeways 1972, 1976, 1985). All modern AWSs measure combinations of atmospheric temperature and humidity, wind speed and direction, solar radiation, atmospheric pressure and precipitation. Some will also include net radiation, ground temperatures at different depths and more specialized variables such as UV radiation. They record their measurements on data loggers and many also telemeter their measurements by telephone, radio or satellite – as those on Mars would need to do. Challenges But you cannot simply send a terrestrial AWS to Mars: it wouldn't work. For one thing, they are too big and too heavy, but there are more subtle factors, which we explore here. For thermometers, it is vital to get the exposure correct, otherwise large errors can occur. If a thermometer of any type, be it a mercury-in-glass thermometer or the most common type today, a platinum resistance thermometer (PRT), is placed in a liquid such as water, the exchange of heat between the two takes place by conduction, convection (usually stirring) and, to a much lesser, even negligible, extent, by radiation. In a gas such as air, which has a much lower density than water, conduction plays only a very small part: it is radiation that brings the thermometer into equilibrium. Unlike liquids, air is very transparent to infrared radiation so that the radiative exchange is between the thermometer and any bodies that are in visual range of the thermometer, however far away, including the sky and the ground. In the case of Mars landers, the structure of the lander itself – which might also warm the atmosphere around it – also contributes. To this long-wave radiation must be added short-wave radiation directly from the Sun, reflected sunlight and diffuse scattered radiation from the sky. If the heat exchange were by radiation alone, the thermometer would read a mean of the temperature of every object in sight around it, not that of the surrounding atmosphere. This is particularly the case in thin air such as in Earth's stratosphere and the atmosphere at the martian surface. Radiation screens There are two ways that a terrestrial thermometer can be made to read just the temperature of the air around it. The first is to ensure that every object in view of it is at air temperature, usually achieved by enclosing the thermometer in a screen that keeps out all external radiation, but which itself attains a temperature as close as possible to that of the air – although screens often fail to achieve this goal in high-radiation conditions and low wind. A familiar example is the white-louvered Stevenson screen; most professional AWSs now use much smaller thermometer screens for both temperature and humidity sensors (figure 2). The second, much less common, technique increases the exchange of heat by convection to the extent that radiation becomes negligible. This is achieved by placing the thermometer in a tube, with a fan drawing air through the tube over the thermometer. These aspirated screens require electrical power to drive the fan. 1 Open in new tabDownload slide A conventional automatic weather station, this one in the Sahara Desert in Libya. Stations on Earth do not suffer from any serious dust problems. The logger is buried in the sand to protect it from the heat. (I Strangeways) 1 Open in new tabDownload slide A conventional automatic weather station, this one in the Sahara Desert in Libya. Stations on Earth do not suffer from any serious dust problems. The logger is buried in the sand to protect it from the heat. (I Strangeways) 2 Open in new tabDownload slide Typical screens used on Earth. (a) This Stevenson thermometer screen includes three mercury-in-glass thermometers measuring air temperature, wet bulb temperature and the maximum air temperature. The minimum temperature is measured with a spirit-in-glass thermometer. Also included are mechanical recorders measuring air temperature (bi-metallic thermograph) and humidity (hair hygrometer) recording on paper charts. (b) This type of compact screen is used on most automatic weather stations and typically contains a platinum resistance thermometer and a humidity sensor. (I Strangeways) 2 Open in new tabDownload slide Typical screens used on Earth. (a) This Stevenson thermometer screen includes three mercury-in-glass thermometers measuring air temperature, wet bulb temperature and the maximum air temperature. The minimum temperature is measured with a spirit-in-glass thermometer. Also included are mechanical recorders measuring air temperature (bi-metallic thermograph) and humidity (hair hygrometer) recording on paper charts. (b) This type of compact screen is used on most automatic weather stations and typically contains a platinum resistance thermometer and a humidity sensor. (I Strangeways) Radiation screens perform adequately, but not perfectly, at the high atmospheric pressures at Earth's surface, where the air is dense. Any form of screen presents problems as the pressure falls: their surfaces become much warmer or cooler than the atmosphere around them, driven by the terrestrial and solar radiation they are exposed to; none would be suitable for use on Mars. At high altitudes on Earth, screens made of two concentric polished aluminium cylinders with a spacing of 1 or 2 cm can be acceptable, but measurements are more accurate when using very small sensors, exposed without any protection (figure 3). In these sensors, extremely small PRTs made of very fine wire, thermocouples, or miniature thermo-capacitors, radiative heating will be negligible; the latter are used in modern radiosondes. To minimize the radiation errors that result from having no screen, even these very small sensors must have a surface that absorbs as little solar and infrared radiation as possible and this is achieved by coating them in a very thin metallic film. 3 Open in new tabDownload slide (a) This radiosonde thermometer consists of two fine platinum wires separated by a glass-ceramic dielectric, the capacitance of which changes with temperature. It is coated in glass and covered in an aluminium film to reflect radiation. A needle is included for scale. (b) Two radiosonde humidity sensors. These are alternately heated, during a sonde's ascent, to prevent calibration drift in cloud. This would not be necessary on Mars, but two sensors would provide useful cross-checking and would guard against the failure of one of them. (I Strangeways) 3 Open in new tabDownload slide (a) This radiosonde thermometer consists of two fine platinum wires separated by a glass-ceramic dielectric, the capacitance of which changes with temperature. It is coated in glass and covered in an aluminium film to reflect radiation. A needle is included for scale. (b) Two radiosonde humidity sensors. These are alternately heated, during a sonde's ascent, to prevent calibration drift in cloud. This would not be necessary on Mars, but two sensors would provide useful cross-checking and would guard against the failure of one of them. (I Strangeways) Radiosondes are expendable: they work for only a few hours and are rarely recovered. If such sensors were to be used on Mars, they would have to work for much longer. They would, slowly but inevitably, become coated with a thin film of martian dust, increasing their absorption of radiation and thereby heating the sensor above the atmospheric temperature by day and cooling it more at night. Humidity has traditionally been measured on Earth by the “wet and dry bulb” method, using two identical thermometers, one with a moist cloth sleeve covering its bulb. Evaporation from the sleeve cools the thermometer, the cooling giving a measure of the relativity humidity (RH) of the air. This would not work in the arid atmosphere of Mars. Human hair has been used to measure RH in very simple mechanical instruments in which the change in length of a hair with humidity is converted into the movement of a pointer on a scale or chart. It is conceivable that such a principle might be developed for Mars, given a suitable material and research. In the 1970s, electrical RH sensors began to be developed, such as the PCRC-11, based on a conductive ion-exchange surface of styrene copolymer, in which water-vapour molecules are adsorbed onto the surface causing a change in resistance as the RH changes. Now RH is widely measured by capacitive thin-film sensors (figure 3b), developed initially for use on radiosondes. In this type of sensor, a thin layer of amorphous organic polymer acts as the dielectric of a capacitor; the capacitance changes with the RH (Strangeways 2003). This type of sensor is now widely used on AWSs at ground level as well as in radiosondes. It would be suitable for use on Mars, but with certain reservations: it can suffer from contamination, calibration-drift and aging; its response time at the lower martian temperatures would be quite slow; and if dust was to collect on the sensor, this would affect its calibration. An alternative could be optical methods of sensing humidity, in which the absorption of radiation in the infrared and ultraviolet spectrums by water vapour in the atmosphere gives a direct measure of the water content. Miniature instruments, using a tunable diode laser and diode detector would be practicable for Mars, but would need development. Blowing in the wind Rotating cup anemometers and wind vanes are still widely used with AWSs on Earth to measure wind speed and direction (figure 4). This type of sensor has proved to be extremely reliable and can operate for decades; they have a beautiful, rugged simplicity to them. Closely related to vanes and cups are the Telltale sensor on the Phoenix lander (Gunnlaugsson et al. 2008) and the wind socks on the Mars Pathfinder (mars.nasa.gov/MPF/science/windsocks.html) (figures 4b, 4c). These are simple lightweight tubes that swing in the wind, their movement being recorded optically. If the martian wind has sufficient force to move such structures, it would be worth investigating whether cups and vanes would also operate in the thin martian air. If they do, they would be an excellent, simple choice, worth investigation in a low-pressure wind tunnel. Sonic wind sensors are also available and worthy of consideration for Mars. They are becoming more widely used on Earth, in place of the cups and vanes. Hot-film anemometers have been used on previous Mars missions (figure 5) and remain a feasible choice. 4 Open in new tabDownload slide (a) Cup anemometers and wind vanes are still widely used on AWSs, but can be made smaller, which could suit a Mars station very well. (b) Phoenix's Telltale mechanical wind sensor in situ on Mars. (c) The windsocks on Mars Pathfinder. (I Strangeways) (Phoenix Mission Team, NASA, JPL-Caltech, U. Arizona) (NASA/JPL) 4 Open in new tabDownload slide (a) Cup anemometers and wind vanes are still widely used on AWSs, but can be made smaller, which could suit a Mars station very well. (b) Phoenix's Telltale mechanical wind sensor in situ on Mars. (c) The windsocks on Mars Pathfinder. (I Strangeways) (Phoenix Mission Team, NASA, JPL-Caltech, U. Arizona) (NASA/JPL) 5 Open in new tabDownload slide The two weather-instrument booms on the Rover Environmental Monitoring Station (REMS) on the Mars Science Laboratory Mission, during setup. (NASA/JPL) 5 Open in new tabDownload slide The two weather-instrument booms on the Rover Environmental Monitoring Station (REMS) on the Mars Science Laboratory Mission, during setup. (NASA/JPL) To measure both the incoming solar radiation (and outgoing reflected solar radiation – the albedo) many AWSs on Earth use silicon photodiodes in place of the bulkier, more expensive, but spectrally superior thermal pyranometers. The same diodes would be adequate for use on Mars and have the advantage of being mechanically robust, small, cheap and lightweight. But they would need to be kept dust-free, otherwise their readings would gradually reduce. On Mars, the atmospheric pressure is low and changes little. The small thin-film pressure sensors developed for use on radiosondes on Earth are now accurate and reliable, and have been used on previous Mars missions. Variable-reluctance (magnetic) sensors have also been used. However, a more robust sensor, and one that is likely to have good long-term stability, would be the vibrating cylinder, which can measure to 0.1 hPa with a long-term drift of 0.05 hPa. Pressure sensors do not have to be exposed directly to the environment and so do not present problems with dust build-up, being housed within the body of the AWS. The exposure problem Martian dust is a serious problem for meteorologists. Conventional AWSs have proved to be quite resilient in deserts, although sand-blasting of glass and of anodized aluminium can be a problem (figure 1). Desert environments on Earth would seem to present similar dust problems to those on Mars, but there is an important difference. The dust on Mars is much finer, particles having an average size of only around 3 µm (not much larger than cigarette smoke), while a sand grain can be from 1.0 to 0.1 mm across. Martian dust coats solar panels on landers and rovers and would be expected to do the same for AWSs. The major question is how to expose the sensors. All require protection from the dust if they are to operate reliably in the long term. In looking for solutions to the exposure problem, it helps to look at work done on Earth to operate AWSs under difficult environmental conditions. On Earth, blowing snow is more of a problem than dust, and many solutions rely on human actions – impracticable at martian sites. Although dust will act in a totally different way to ice, and over a longer timescale, the solutions to both problems can be similar. Two designs for AWSs in cold regions and mountains have potential for use on Mars. One (figure 6) involves sensors under a cover that flexes pneumatically to break off ice cover (Strangeways 1986, 2014), the other (figure 7) is an AWS with a cover that opens and closes periodically (Curran et al. 1977). The general concept of the latter is a cylinder that opens every hour for one minute, during which time readings are taken once a second, giving one-minute averages. This would suit Mars well, because it would protect, comprehensively, against dust. 6 Open in new tabDownload slide (a) In this AWS, developed for cold regions (here on test on the summit of Cairn Gorm), a plate holds cavities containing the sensors. On the underside are the temperature, humidity and albedo sensors. On top is the drag-force wind sensor and the solar sensor cavity. The cavities are covered in different materials, to suit the variable concerned, the whole structure being housed within a cover that is flexed pneumatically to remove ice and snow. (b) A design, possibly suitable for Mars, based on the Cairn Gorm developments (Strangeways 2014). A: Cavity containing three PRT sensors. B: Cavity containing three humidity sensors. C: Cup anemometer. D: Three capacitive temperature sensors. E: Cavity containing photodiode measuring albedo. F: Cavity containing photodiode measuring solar radiation. G: Pressure sensor. H: Drag-force wind sensor. (I Strangeways) 6 Open in new tabDownload slide (a) In this AWS, developed for cold regions (here on test on the summit of Cairn Gorm), a plate holds cavities containing the sensors. On the underside are the temperature, humidity and albedo sensors. On top is the drag-force wind sensor and the solar sensor cavity. The cavities are covered in different materials, to suit the variable concerned, the whole structure being housed within a cover that is flexed pneumatically to remove ice and snow. (b) A design, possibly suitable for Mars, based on the Cairn Gorm developments (Strangeways 2014). A: Cavity containing three PRT sensors. B: Cavity containing three humidity sensors. C: Cup anemometer. D: Three capacitive temperature sensors. E: Cavity containing photodiode measuring albedo. F: Cavity containing photodiode measuring solar radiation. G: Pressure sensor. H: Drag-force wind sensor. (I Strangeways) 7 Open in new tabDownload slide The Heriot-Watt University opening-and-closing AWS, operating on the summit of Cairn Gorm. (a) In the closed position. (b) Close-up in its open state, showing the sensors. (c) A possible design for Mars, based on the Heriot-Watt station. Any of the sensors discussed here would suit this design. It would protect the sensors from dust, almost completely. It would also reduce power consumption by the sensors, by limiting operation to the time it was open (one minute per hour). (I Strangeways) 7 Open in new tabDownload slide The Heriot-Watt University opening-and-closing AWS, operating on the summit of Cairn Gorm. (a) In the closed position. (b) Close-up in its open state, showing the sensors. (c) A possible design for Mars, based on the Heriot-Watt station. Any of the sensors discussed here would suit this design. It would protect the sensors from dust, almost completely. It would also reduce power consumption by the sensors, by limiting operation to the time it was open (one minute per hour). (I Strangeways) Any of the sensors discussed above could be used with such an opening-and-closing construction; the principle has great versatility and much to recommend it, including limiting the power needed. Those sensors that require power need only be active when the station is open, that is for a total of 24 minutes a day. Most importantly, the dust problem is greatly reduced or eliminated completely, because the sensors are under cover most of the time and the station could remain closed during dust storms. To reduce the problem of dust further, the power supply would, ideally, be provided by a small radioisotope thermoelectric generator (RTG; 1–20 W), as used on spacecraft. This would overcome the problem of dust collecting on solar panels. It would also allow operation in Mars's polar regions. As well as running the sensors, the power supply also has to support data collection and transmission. As with Earth-based AWSs, sensor measurements would be processed and recorded on a data logger and telemetered to a suitable satellite. If located correctly, an RTG should not warm the sensors, but apart from the air temperature sensor, this may not be a problem, and could be an advantage. Should a radioisotope power supply be impractical, solar power would have to be used. An important characteristic of AWS designs for Mars is redundancy, provided by the duplication or triplication of some sensors. This not only protects against sensor failure over a long lifetime, but also allows the cross-checking of readings. This could be achieved by measuring a variable with two or three different types of sensor. Concluding remarks All meteorological instrumentation on Mars has, so far, been included as part of a lander or rover, which has limited what can be achieved and the accuracy of the measurements – not to mention the limited sample sites and durations across the whole planet. Research is needed in both instrument design and development to make reliable, long-lived sensors suitable for the martian environment. But because of the fairly homogeneous nature of the surface of Mars, compared to that of Earth, a network of five to ten stations would be sufficient to give a good indication of the weather and, eventually, of the climate of Mars. This is an important next step in understanding and exploring the planet: it is just as important as looking for traces of life. AUTHOR Open in new tabDownload slide Open in new tabDownload slide Dr Ian Strangeways is an environmental instrumentation consultant, director of TerraData and former head of applied physics at the Institute of Hydrology REFERENCES Curran J C et al. 1977 Weather 32 ( 2 ) 61 Crossref Search ADS Gómez-Elvira J et al. 2012 Space Sci. Rev. 170 ( 1–4 ) 583 Gómez-Elvira J et al. 2014 J. Geophys. Res. Planets 119 ( 7 ) 1680 Crossref Search ADS Gunnlaugsson H P et al. 2008 J. Geophys. Res. Planets 113 E00A04 Crossref Search ADS Martínez G M et al. 2017 Space Sci Rev. 212 295 Crossref Search ADS Strangeways I C 1972 Weather 27 ( 10 ) 403 Crossref Search ADS Strangeways I C 1976 Proc. COST Tech. Conf . Reading University 24 Strangeways I C 1985 Weather 40 ( 9 ) 277 Crossref Search ADS Strangeways I C 1986 PhD thesis, University of Reading Strangeways I C 2003 Measuring the Natural Environment ( Cambridge University Press ) Google Scholar Crossref Search ADS Google Preview WorldCat COPAC Strangeways I C 2014 Weather 69 8 Crossref Search ADS Taylor P A et al. 2008 Geophys. Res. 113 E00A10 Crossref Search ADS © 2021 Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
TI - Weather stations for Mars
JF - Astronomy & Geophysics
DO - 10.1093/astrogeo/atab066
DA - 2021-06-01
UR - https://www.deepdyve.com/lp/oxford-university-press/weather-stations-for-mars-jWCGjqlG4S
SP - 3.20
EP - 3.23
VL - 62
IS - 3
DP - DeepDyve
ER -