Water vapor adsorption on Mars

Near-surface air moisture observations from Phoenix and Curiosity display diurnal adsorption, which appears insensitive to mineralogy of regolith. To study this, adsorptive column model simulations are made for midsummer at Phoenix, validated against recalibrated TECP water vapor pressures p. Two standard-form (= obeying the van't Hoff equilibrium law) adsorption isotherms with quite different specific surface areas A s do produce nearly identical and good matches with the observed p, whereas a widely used non-standard isotherm fails. When made standard, it also produces good results. Adsorbed amounts differ in the three good simulations but their surface fluxes and surface vapor concentrations are nevertheless nearly identical. Properties of regolith except enthalpy are shown to disappear in the model's adsorption term, explaining insensitivity to A(s). The van't Hoff plot of observed In p vs. model's 1/T-g during adsorption and desorption suggests enthalpy of about 22 kJ/mol. Enthalpies of the three standard-form isotherms are close to this, explaining their excellent match with each other and with observations. Hence the low-pressure water vapor adsorption to martian regolith appears essentially nonspecific and is associated with low enthalpy, as is typical for physisorption in general.Peer reviewe

In situ observations of the atmospheres of terrestrial planetary bodies

Direct observations of planetary atmospheres are scarce and significantly more data are needed for the understanding of their behavior. The principal theme of this dissertation is the exploration of planetary atmospheres by means of in situ observations, focusing on investigations performed by payloads operating on the planetary surface. The contextual frame includes the whole palette of planetary exploration including definition of scientific objectives, observational strategies, scientific payload and data analysis, as well as development of technological solutions and simulation models for planetary missions. This approach also led to the initiation of the planetary missions MetNet and NetLander to Mars. This work contributes to both in situ atmospheric observations and atmospheric modeling, which are strongly intertwined. Modeling efforts require observations to give solid background and foundation for the simulations, and on the other hand, definition of observational strategies and instrumentation gets guidance from modeling efforts to optimize the use of mission resources, as is successfully demonstrated in this dissertation. The dissertation consists of Summary and nine original scientific publications. Publications 1 to 7 and Summary address the development of new atmospheric science payloads for exploration missions to Mars and Titan, a Saturnian moon. Actual and planned missions included are the Mars-96 Program and its Small Surface Stations and Penetrators during the years 1988-1996, PPI/HASI onboard the Cassini/Huygens spacecraft to Saturn and its moon Titan in 1989-2005, the MET-P payload onboard the Mars Polar Lander in 1997-1999, the BAROBIT instrument for the Beagle 2 lander in 2001-2003, the NetLander Mars Mission in 1997-2001 and the ongoing Mars MetNet Mission, started in 2000. Specifically, Publication 4 reviews the sensor qualification process that facilitated the use of new type of atmospheric sensors at Mars, while Publications 2 and 7, as well as Summary, address the highly successful determination of the Titan atmospheric pressure profile. Publication 8 combines in situ observations and simulations by analyzing Mars Pathfinder measurements with the help of a Martian mesoscale atmospheric model. Finally, in Publication 9 the effect of airborne dust and CO2 on the radiative transfer in the Martian atmosphere is assessed and a new radiative transfer paramerization scheme for the mesoscale model is introduced.reviewe

Annual and diurnal water vapor cycles at Curiosity from observations and column modeling

Local column precipitable water contents (PWC) for more than a martian year from 113 Curiosity ChemCam passive-mode sky scans were used to force a column model with subsurface adsorption. ChemCam volume mixing ratios (vmr) and T, RH and vmr from REMS-H were compared with model results. The REMS-H observations point to decrease of vmr (i.e. depletion of near-surface water vapor) during every evening and night throughout the year. The model's pre-dawn results are quite similar to the REMS-H observations, if adsorption is allowed. The indicated porosity is about 30% and the night depletion ratio about 0.25. If adsorption is not allowed, RH and vmr become excessive during every night at all seasons, leading to ground frost between Ls 82 degrees-146 degrees; frost has not been observed. As brine formation is unlikely along the Curiosity track, adsorption thus appears to be the depleting process. During daytime the ChemCam vmr is in general close to surface values from the Mars Climate Database (MCD) vmr profiles for the Curiosity site when those profiles are scaled to match the ChemCam PWC. Our simulated daytime surface-vmr is in turn close to the ChemCam vmr when moisture is assumed well-mixed to high altitudes, whereas a low moist layer (15 km) leads to overestimates, which are worse during the warm season. Increased TES-like regional PWC also leads to large overestimates of daytime surface-vmr. Hence the crater appears to be drier than the region surrounding Gale and the results support a seasonally varying vertical distribution of moisture with a dry lower atmosphere (by Hadley circulation), as suggested by MCD and other GCM experiments.Peer reviewe

A user-orientated column modelling framework for efficient analyses of the Martian atmosphere

As spacecraft missions return ever more data from Mars, additional tools will be required to explore and analyse these datasets efficiently. To streamline research into the atmosphere of Mars, a user-orientated modelling capability is developed that enables automatic initialisation and running of a column model. As a demonstration we utilise the modelling framework to provide additional verification for the University of Helsinki and Finnish Meteorological Institute Mars column model temperature profiles above the height of typical lander meteorological measurements, i.e. above 2 m. We utilise the framework at landing site locations that are well characterised to understand the model's applicability and to identify future opportunities for modifications to the framework. We do this by using the framework to compare the column model to temperature soundings made by the Mars Reconnaissance Orbiter. We find that the column model, without any modification, is able to reproduce the observed lapse rates and average temperatures closely in most cases except for a 20-60 K increase over the northern hemisphere mid-winter. We can reproduce this discrepancy by incorporating an adiabatic heating term into the column model. Fitting of the modified column model to the observations results in estimated maximum downward vertical wind velocities of similar to 10 cm s(-1) at altitudes of 15-20 km over the winter solstice at the VL-1 and VL-2 sites. The approach developed here may possibly provide a way to independently estimate or observe the vertical motion in the Martian atmosphere. However, even though the magnitude of the vertical wind speed appears reasonable, it is not clear at this point how much the atmospheric heating is due to other mechanisms such as advection. We have introduced new application software that can quickly find and display the requested data and can be immediately analysed using the included tools. We have demonstrated the potential of this type of software application with a glimpse into the upper atmosphere of Mars.Peer reviewe

Humidity observations and column simulations for a warm period at the Mars Phoenix lander site : Constraining the adsorptive properties of regolith

Two recalibrated sets of Phoenix (PHX) near-surface TECP air humidity measurements were compared with results from adsorptive single column model simulations during a warm clear-sky polar midsummer period, PHX sols 50-60. The model's 2 m temperatures were close to the observed values. Relative humidity (RH) is very low during the day but at night RH at 2 m reaches nearly 100% by the Zent et al. (2016) recalibration (Z), and 60-70% by the Fischer et al. (2019) recalibration (F). Model values of RH2m are close to Z and F at night and to F during the day. All three imply low water vapor pressures near the surface at night, 0.03-0.05 Pa, with a rapid increase each morning to 0.3-1 Pa and a decrease in the evening by both F and the model simulation. The model's daily adsorbed and desorbed water is in balance for regolith porosity of 16% (instead of 35% for lower latitudes). The depleted layer of nighttime air moisture extends to only about 200 m above the surface; hence the model's precipitable water content stays around the observed similar to 30 mu m throughout the sol. The model's moisture cycle is not sensitive to tortuosity of the regolith but the in-pore molecular diffusivity should be at least 5 cm(2)/s for fair agreement with the observations. In the adsorption experiments there is no fog and just a hint of ground frost, as observed during this period. Strong night frosts appear if adsorption is made weak or absent in the model.Peer reviewe

AVAUS : Avaruuden uuden toimintaympäristön turvallisuusulottuvuudet ja liiketoiminta

Avaruustoiminnalla on jo kauan ollut suuri strateginen merkitys yhteiskunnan toimivuudelle, kansalliselle turvallisuudelle ja eri hallinnonalojen päätöksenteolle. Yhteiskunnan toiminnot hyödyntävät satelliittien tuottamaa ja välittämää dataa, jonka määrä ja maantieteellinen kattavuus ovat laajentuneet radikaalisti viime vuosina. Aiemmin laajamittainen avaruustoiminta oli mahdollista vain suurilla taloudellisilla panostuksilla ja sitä harjoittivat vain muutamat maailman suurvallat. Nyt teknologinen kehitys ja avaruusteknologian halventuminen on mahdollistanut myös pienimuotoisemman avaruustoiminnan, jolla voidaan vastata tehokkaasti yhteiskunnan ja elinkeinoelämän tarpeisiin ja toiveisiin. Tämä mahdollistaa täysin uusia sovelluksia ja palveluita, jotka perustuvat avaruudesta ja Maan pinnalta tehtyjen havaintojen tehokkaaseen yhdistämiseen. Tämä on New Space -ilmiö, johon liittyvää liiketoimintaa kutsutaan nimellä New Space Economy – uusi avaruusliiketoiminta. Uuden avaruusteknologian ja sen tuomien sovellusmahdollisuuksien esiinmarssi ei ole korvaamassa perinteisellä avaruusteknologialla toteutettuja järjestelmiä. Tämä on oleellista. Uudet teknologiat sekä tuovat mukanaan uusia avaruuden hyödyntämismahdollisuuksia että täydentävät perinteisiä avaruusjärjestelmiä. Tämä tutkimus tarkastelee uutta avaruustoimintaympäristöä kansallisen hyödyntämisen kannalta: miten sen tarjoama yhteiskunnan turvallisuuteen vaikuttava teknologia sekä liiketoimintapotentiaali voitaisiin valjastaa parhaiten palvelemaan suomalaista yhteiskuntaa. Jos saamme luotua uutta teknistieteellistä kyvykkyyttä kansallisella perusrahoituksella, sillä on tärkeä vipuvaikutus sekä liiketoimintaan että suomalaisten turvallisuuteen. Osaaminen ja innovaatiot houkuttelevat kasvurahoitusta, mikä mahdollistaa liiketoiminnan nopean kasvun. Avaruuden turvallisuuskäyttö edellyttää korkealaatuista osaamista ja hyötyy menestyvästä liiketoiminnasta. Aktiivisilla toimilla Suomi pystyy hyödyntämään avaruusteknisen murroksen tarjoamat laajat liiketoiminnalliset mahdollisuudet sekä toisaalta varautumaan turvallisuuteen liittyviin uusiin haasteisiin. Toimenpidesuosituksemme ovat tämän mukaisia.Tämä julkaisu on toteutettu osana valtioneuvoston selvitys- ja tutkimussuunnitelman toimeenpanoa. (tietokayttoon.fi) Julkaisun sisällöstä vastaavat tiedon tuottajat, eikä tekstisisältö välttämättä edusta valtioneuvoston näkemystä

Soil disturbance by cut-to-length machinery on midgrained soils

Article id 10134201

Phobos eclipse detection on Mars : theory and practice

We present a general approach to study solar eclipses by Phobos on Mars: its parameterization and prediction.The validation of the model and the involved parameters is made with the already observed eclipses by previous Mars missions. Eclipse prediction is applied for the past Mars lander missions: Viking, Pathfinder and Phoenix, as well as for the future Mars MetNet Precursor Mission. A successful detection of eclipses could be used for the localization of landers and to study atmospheric properties. We also consider the data analysis, with special emphasis in the tomographic method to identify events which are very localized in space and time. Large computation requirements are needed for the implemented methods. To this propose an efficient Cloud Computing Network Infrastructure has been used.Esittelemme yleisen lähestymistavan Phoboksen auringonpimennysten tutkimiseen, parametrisointiin ja ennustamiseen. Mallin ja sen parametrien validointi tehdään menneiden ja nykyisten Mars-missioiden havaitsemien pimennysten avulla. Pimennysten ennustamista käytetään menneisiin Viking-, Pathfinder- ja Phoenix-laskeutujiin, samoin kuin tulevaan Mars MetNet Precursor missioon. Pimennysten onnistuneita havaintoja voitaisiin käyttää laskeutujien paikantamiseen ja kaasukehän ominaisuuksien tutkimiseen. Käsittelemme myös data-analyysiä, painottaen erityisesti tomografiamenetelmää, havaitaksemme tapahtumia jotka ovat paikallisia ajan ja sijainnin suhteen. Menetelmien toteuttamiseen vaaditaan suuri laskentakapasiteetti. Tämän toteuttamiseen on käytetty pilvilaskentaa

Auroral imaging with combined Suomi 100 nanosatellite and ground-based observations: A case study

Auroras can be regarded as the most fascinating manifestation of space weather and they are continuously observed by ground-based and, nowadays more and more, also by space-based measurements. Investigations of auroras and geospace comprise the main research goals of the Suomi 100 nanosatellite, the first Finnish space research satellite, which has been measuring the Earth's ionosphere since its launch on Dec. 3, 2018. In this work, we present a case study where the satellite's camera observations of an aurora over Northern Europe are combined with ground-based observations of the same event. The analyzed image is, to the authors' best knowledge, the first auroral image ever taken by a cubesat. Our data analysis shows that a satellite vantage point provides complementary, novel information of such phenomena. The 3D auroral location reconstruction of the analyzed auroral event demonstrates how information from a 2D image can be used to provide location information of auroras under study. The location modelling also suggests that the Earth's limb direction, which was the case in the analyzed image, is an ideal direction to observe faint auroras. Although imaging on a small satellite has some large disadvantages compared with ground-based imaging (the camera cannot be repaired, a fast moving spinning satellite), the data analysis and modelling demonstrate how even a small 1-Unit (size: 10 cm x 10 cm x 10 cm) CubeSat and its camera, build using cheap commercial off-the-shelf components, can open new possibilities for auroral research, especially, when its measurements are combined with ground-based observations.Comment: Accepted manuscript 34 pages, 17 figure

Microphysical Properties of Snow and Their Link to Z(e)-S Relations during BAECC 2014

This study uses snow events from the Biogenic Aerosols-Effects on Clouds and Climate (BAECC) 2014 campaign to investigate the connection between properties of snow and radar observations. The general hydrodynamic theory is applied to video-disdrometer measurements to retrieve masses of falling ice particles. Errors associated with the observation geometry and the measured particle size distribution (PSD) are addressed by devising a simple correction procedure. The value of the correction factor is determined by comparison of the retrieved precipitation accumulation with weighing-gauge measurements. Derived mass-dimensional relations are represented in the power-law form m = a(m)D(m)(b). It is shown that the retrieved prefactor a(m) and exponent b(m) react to changes in prevailing microphysical processes. From the derived microphysical properties, event-specific relations between the equivalent reflectivity factor Z(e) and snowfall precipitation rate S (Z(e) = a(zs)S(zs)(b)) are determined. For the studied events, the prefactor of the Z(e)-S relation varied between 53 and 782 and the exponent was in the range of 1.19-1.61. The dependence of the factors a(zs) and b(zs) on the m(D) relation and PSD are investigated. The exponent of the Z(e)-S relation mainly depends on the exponent of the m(D) relation, whereas the prefactor a(zs) depends on both the intercept parameter N-0 of the PSD and the prefactors of the m(D) and nu(D) relations. Changes in a(zs) for a given N-0 are shown to be linked to changes in liquid water path, which can be considered to be a proxy for degree of riming.Peer reviewe