The optical constants of gypsum particles as analog of Martian sulfates

Various indications seem to suggest that in the past the Martian climate allowed the presence of liquid water on the surface of the planet. It is therefore reasonable to think that bodies of standing water were once present in basins such as craters or depressions and that evaporite deposits of sulfates could have formed in these basins. The identification of such deposits, which might have survived in some regions of the planet, could confirm the present hypothesis about the ancient climate on Mars. Recent analyses of Mars spectra, obtained by ground-based observations, show bands consistent with sulfate features. If such data have to be interpreted with the aid of synthetic spectra, the knowledge of the complex refractive index of some sulfate is necessary. In this work we present the optical constants of submicron particles of gypsum (a typical hydrate–sulfate very common on Earth), derived by means of the dispersion theory from transmission spectra. We have performed the calculation of the optical constants in the wavelength range 2–70 μm, also in view of the wide spectral range covered by the Planetary Fourier Spectrometer (PFS) on board of the ESA space mission Mars Express. The data have been compared with optical constants obtained by other authors from reflectance measurements of particulate samples.     

Characteristics of solar particle events at Mars relative to Earth

While not specifically designed to detect solar energetic particle radiation, the Electron Reflectometer onboard Mars Global Surveyor (MGS/ER) collected such data from January 1999 through October 2006. Energetic protons (?25 MeV) and other ions penetrated the MGS/ER shielding and registered counts within the instrument’s electronics. During solar particle events (SPE’s), prolonged enhancements in the particle background were observed at Mars with time intensity profiles similar to Earth based SPE observations. Throughout the lifespan of MGS/ER, 85 distinct SPE’s were observed. Basic characteristics of Mars based SPE observations and the frequency of SPE occurrences at Mars are compared to corresponding Earth based observations. Approximately 22% of SPE’s that occurred during MGS/ER operation were observed at Earth but not Mars. Similarly, 19% of SPE’s were observed at Mars but not Earth. Time intensity profiles at Earth and Mars match predictions provided in the literature, based on the physical location of the detector with respect to the motion of the interplanetary shock wave. Note: The work described herein was largely conducted as part of a doctoral dissertation produced by the author.     

Longitudinal distribution of thermospheric densities and ionization rates in the upper atmosphere of Mars at mid-latitude using MGS ACC data

The Accelerometer Experiment (ACC) onboard Mars Global Surveyor (MGS) measured 1600 density profiles in the upper atmosphere of Mars during aerobraking. These measurements reveal large-scale and small-scale structure in the thermosphere of Mars. Here, the measurements of mass density for 115 orbits (#P0670–P0789) from November 1 to 30, 1998, under spring equinox and medium solar activity conditions (average F_10.7 ∼ 137) during phase 2 of the aerobraking in the thermosphere of Mars at different altitudes and longitudes are presented for northern mid-latitude (17–42°N) in the dayside atmosphere using ACC onboard MGS. From these mass densities, the neutral densities of different gases are derived from their mixing ratios. Using these neutral densities, the longitudinal distribution of photoionization rates and photoelectron impact ionization rates are calculated at wavelength range 1–102.57 nm due to EUV and soft X-ray radiation under photochemical controlled region using Analytical Yield Spectrum approach (AYS). These conditions are appropriate for MGS Phase 2 aerobraking period from which the accelerometer data is used. Under the photochemical equilibrium condition, the electron density near the peak varies as the square root of the total peak ionization rate. Using this fact, an attempt is being made to estimate the mean primary and secondary peak electron density by averaging the longitudinal variations of total peak ionization rates in the northern mid-latitude (17–42°N) ionosphere of Mars, as there is no radio science measurement at this latitude region by MGS.     

An overview of radar soundings of the martian ionosphere from the Mars Express spacecraft

The Mars Express spacecraft carries a low-frequency radar called MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) that is designed to study the subsurface and ionosphere of Mars. In this paper, we give an overview of the ionospheric sounding results after approximately one year of operation in orbit around Mars. Several types of ionospheric echoes are commonly observed. These include vertical echoes caused by specular reflection from the horizontally stratified ionosphere; echoes from a second layer in the topside ionosphere, possibly associated with O⁺ ions; oblique echoes from upward bulges in the ionosphere; and a variety of other echoes that are poorly understood. The vertical echoes provide electron density profiles that are in reasonable agreement with the Chapman photo-equilibrium model of planetary ionospheres. On the dayside of Mars the maximum electron density is approximately 2 × 10⁵ cm⁻³. On the nightside the echoes are often very diffuse and highly irregular, with maximum electron densities less than 10⁴ cm⁻³. Surface reflections are sometimes observed in the same frequency range as the diffuse echoes, suggesting that small isolated holes exist in the nightside ionosphere, possibly similar to those that occur on the nightside of Venus. The oblique echoes arise from upward bulges in the ionosphere in regions where the crustal magnetic field of Mars is strong and nearly vertical. The bulges tend to be elongated in the horizontal direction and located in regions between oppositely directed arch-like structures in the crustal magnetic field. The nearly vertical magnetic field lines in the region between the arches are thought to connect into the solar wind, thereby allowing solar wind electrons to heat the lower levels of the ionosphere, with an attendant increase in the scale height and electron density.     

Autonomous navigation of Mars probe using X-ray pulsars: Modeling and results

Autonomous navigation of Mars probe is a main challenge due to the lack of dense ground tracking network measurements. In this paper, autonomous navigation of the Mars probe Orbits is investigated using the X-ray pulsars. A group of X-ray pulsars with high ranging accuracy are selected based on their properties and an adaptive extended Kalman filter is developed to incorporate the Mars probe dynamics and pulsar-based ranging measurements. Results of numerical experiment show that the three-dimensional positioning accuracy can achieve 750m in X-axis, 220m in Y-axis and 230m in Z-axis, which is much better than the positioning results by current Very Long Baseline Interferometry (VLBI) or Doppler observations with the accuracy of 150 km or several kilometers, respectively.     

火星多光谱相机的地面几何标定研究

随着航空航天技术的飞速发展,作为地球近邻的火星成为当今国际空间大国的主要研究目标。为完成火星巡视区形貌和地质探测任务,可直接使用多光谱相机获取的高分辨率真彩色图像作为观测手段。为寻找着陆点,火星多光谱相机应具备精确定位的测绘功能,因此需进行几何标定估计其内方位元素。通过张正友标定算法提供初值,然后以改进的Heikkil?算法完成几何标定,经过分析标定结果的不确定度,探究实验误差来源,提出改进方法,最终获得满足要求的标定参数,为实现图像融合、三维重建等计算机视觉领域奠定坚实的基础。     

South polar permanent CO2 ice cap presentation in the Global Mars Multiscale Model

The atmospheric influence caused by the Martian permanent south CO₂ ice cap is examined to improve the Global Mars Multiscale Model (GM3) to see if it can significantly improve the representation of south polar meteorology. However, the seasonal carbon dioxide ice in the polar regions is presented in the surface ice simulation by the Global Mars Multiscale Model but the model does not produce a permanent south CO₂ ice cap, and the physics code must modify to capture the realistic physical such as ice process detail; probably makes a bias in terms of total CO₂ ice and meteorological processes in the model aside from ice formation. The permanent south CO₂ ice cap in the model can significantly improve the representation of south polar meteorology for example in predicted surface temperatures, surface pressures, horizontal and zonal winds over the south cap and possible initiation of dust storms at south polar region during the southern summer period.     

Survival and death of the haloarchaeon Natronorubrum strain HG-1 in a simulated martian environment

Halophilic archaea are of interest to astrobiology due to their survival capabilities in desiccated and high salt environments. The detection of remnants of salty pools on Mars stimulated investigations into the response of haloarchaea to martian conditions. Natronorubrum sp. strain HG-1 is an extremely halophilic archaeon with unusual metabolic pathways, growing on acetate and stimulated by tetrathionate. We exposed Natronorubrum strain HG-1 to ultraviolet (UV) radiation, similar to levels currently prevalent on Mars. In addition, the effects of low temperature (4, −20, and −80 °C), desiccation, and exposure to a Mars soil analogue from the Atacama desert on the viability of Natronorubrum strain HG-1 cultures were investigated. The results show that Natronorubrum strain HG-1 cannot survive for more than several hours when exposed to UV radiation equivalent to that at the martian equator. Even when protected from UV radiation, viability is impaired by a combination of desiccation and low temperature. Desiccating Natronorubrum strain HG-1 cells when mixed with a Mars soil analogue impaired growth of the culture to below the detection limit. Overall, we conclude that Natronorubrum strain HG-1 cannot survive the environment currently present on Mars. Since other halophilic microorganisms were reported to survive simulated martian conditions, our results imply that survival capabilities are not necessarily shared between phylogenetically related species.     

Report of the COSPAR mars special regions colloquium

In this paper we present the findings of a COSPAR Mars Special Regions Colloquium held in Rome in 2007. We review and discuss the definition of Mars Special Regions, the physical parameters used to define Mars Special Regions, and physical features on Mars that can be interpreted as Mars Special Regions. We conclude that any region experiencing temperatures > −25 °C for a few hours a year and a water activity > 0.5 can potentially allow the replication of terrestrial microorganisms. Physical features on Mars that can be interpreted as meeting these conditions constitute a Mars Special Region. Based on current knowledge of the martian environment and the conservative nature of planetary protection, the following features constitute Mars Special regions: Gullies and bright streaks associated with them, pasted-on terrain, deep subsurface, dark streaks only on a case-by-case basis, others to be determined. The parameter definition and the associated list of physical features should be re-evaluated on a regular basis.     

Distribution and variability of accelerated electrons at Mars

We investigate accelerated electrons observed by Mars Global Surveyor (MGS), using data from the Electron Reflectometer (ER) instrument. We find three different types of accelerated electron events. Current sheet events occur over regions with weak or no crustal fields, have the highest electron energy fluxes, and are likely located on draped magnetotail fields. Extended events occur over regions with moderate crustal magnetic fields, and are most often observed on closed magnetic field lines. Localized events have the lowest energy fluxes, occur in strong magnetic cusp regions, and are the most likely kind of event to be found on open magnetic field lines. Some localized events have clear signatures of field-aligned currents; these events have much higher electron fluxes, and are preferentially observed on radially oriented open magnetic field lines. Electron acceleration events, especially localized events, are similar in many ways to events observed in the terrestrial auroral zone. However, physical processes related to those found in the terrestrial cusp and/or plasmasheet could also be responsible for accelerating electrons at Mars.     

Bacterial survival in response to desiccation and high humidity at above zero and subzero temperatures

Earthly microorganisms might have contaminated Mars for millions of years by intellectual activities or natural transfer. Knowledge on the preservation of microorganisms may help our searching for life on outer planets, particularly Mars-contaminated earthly microorganisms at ancient time. Extreme dryness is one of the current Mars characteristics. However, a humid or watery Mars at earlier time was suggested by evidence accumulated in recent decades. It raises the question that whether water helps preservation of the microorganisms or not, particularly those with high possibility of interplanetary transfer like spores and Deinococci. In this study, we examined the effects of desiccation and high humidity on survival and DNA double strand breaks (DSB) of Escherichia coli, Deinococcus radiodurans and spores of Bacillus pumilus at 25, 4 and −70 °C. They exhibited different survival rates and DSB patterns under desiccation and high humidity. Higher survival and less DSB occurred at lower temperature. We suggest that some Mars-contaminated bacteria might have been viably preserved on cold Mars regions for long periods, regardless of water availability. It is more likely to find ancient spores than ancient Deinococci on Mars. In our search for preserved extraterrestrial life, priority should be given to the Mars Polar Regions.     

Spectroscopic evaluation of polyurea crosslinked aerogels,as a substitute for RTV-based chromatic calibration targets for spacecraft

Room temperature vulcanizing (RTV)-based components have been used on Mars Pathfinder, the Mars rovers, Spirit and Opportunity, as well as the Phoenix Lander as a support matrix for pigmented panoramic camera calibration targets. RTV 655 has demonstrated superiority to other polymers due to its unique range of material properties namely mechanical stability between −115 and 204 °C and UV radiation tolerance. As a result, it has been the number one choice for many space-related missions. However, due to the high mass density and the natural tendency for electrostatic charging RTV materials have caused complications by attracting and retaining dust particles (Sabri et al., 2008). In the current project we have investigated the relevant properties of polymer-reinforced (crosslinked) silica aerogels with the objective of substituting RTV-based calibration targets with an aerogel based design. The lightweight, mechanical strength, ability to accept color pigments, and extremely low dust capture makes polyurea crosslinked aerogels a strong candidate as a chromatic standard for extraterrestrial missions. For this purpose, the reflection spectra, gravimetric analysis, and low temperature response of metal oxide pigmented, polyurea crosslinked silica aerogels have been investigated and reported here.     

Mars Phobos and Deimos Survey (M-PADS) – A martian Moons orbiter and Phobos lander

We describe a Mars ‘Micro Mission’ for detailed study of the martian satellites Phobos and Deimos. The mission involves two ∼330 kg spacecraft equipped with solar electric propulsion to reach Mars orbit. The two spacecraft are stacked for launch: an orbiter for remote investigation of the moons and in situ studies of their environment in Mars orbit, and another carrying a lander for in situ measurements on the surface of Phobos (or alternatively Deimos). Phobos and Deimos remain only partially studied, and Deimos less well than Phobos. Mars has almost always been the primary mission objective, while the more dedicated Phobos project (1988–89) failed to realise its full potential. Many questions remain concerning the moons’ origins, evolution, physical nature and composition. Current missions, such as Mars Express, are extending our knowledge of Phobos in some areas but largely neglect Deimos. The objectives of M-PADS focus on: origins and evolution, interactions with Mars, volatiles and interiors, surface features, and differences. The consequent measurement requirements imply both landed and remote sensing payloads. M-PADS is expected to accommodate a 60 kg orbital payload and a 16 kg lander payload. M-PADS resulted from a BNSC-funded study carried out in 2003 to define candidate Mars Micro Mission concepts for ESA’s Aurora programme.     

Electric discharge in the Martian atmosphere,Paschen curves and implications for future missions

Electric discharge between two electrically charged surfaces occurs at a well-defined, gas-dependent combination of atmospheric pressure and the distance between those two surfaces, as described by Paschen’s law. The understanding of when the discharge will occur in the conditions present on Mars is essential for designing space-flight hardware that will operate on the Martian surface as well as understanding electrical discharge processes occurring in the Martian atmosphere. Here, we present experimentally measured Paschen curves for a gas mixture representative of the Martian atmosphere and compare our results to breakdown voltages of carbon dioxide, nitrogen, and helium as measured with our system and from the literature. We will discuss possible implications for instrument development as well as implications for processes in the Martian atmosphere. The DC voltage at which electric discharge occurred between two stainless steel spheres was measured at pressures from 10⁻² to 100 torr in all gases. We measured a minimum voltage for discharge in the Mars ambient atmosphere of 410 ± 10 V at 0.3 torr cm. As an application, the breakdown properties of space-qualified, electrical wires to be used in the Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) were studied.     

Atmospheric photochemistry above possible martian hot spots

Considering the possibility of outgassing from some localized sources on Mars, we have developed a one-dimensional photochemical model that includes methane (CH₄), sulfur dioxide (SO₂) and hydrogen sulfide (H₂S). Halogens were considered but were found to have no significant impact on the martian atmospheric chemistry. We find that the introduction of methane into the martian atmosphere results in the formation of mainly formaldehyde (CH₂O), methyl alcohol (CH₃OH) and ethane (C₂H₆), whereas the introduction of the sulfur species produces mainly sulfur monoxide (SO) and sulfuric acid (H₂SO₄). Depending upon the flux of the outgassed molecules from possible hot spots, some of these species and the resulting new molecules may be detectable locally, either by remote sensing (e.g., with the Planetary Fourier Spectrometer on Mars Express) or in situ measurements.     

Four-month Moon and Mars crew water utilization study conducted at the Flashline Mars Arctic Research Station,Devon Island,Nunavut

A categorized water usage study was undertaken at the Flashline Mars Arctic Research Station on Devon Island, Nunavut in the High Canadian Arctic. This study was conducted as part of a long duration four-month Mars mission simulation during the summer of 2007. The study determined that the crew of seven averaged 82.07 L/day over the expedition (standard deviation 22.58 L/day). The study also incorporated a Mars Time Study phase which determined that an average of 12.12 L/sol of water was required for each crewmember. Drinking, food preparation, hand/face, oral, dish wash, clothes wash, shower, shaving, cleaning, engineering, science, plant growth and medical water were each individually monitored throughout the detailed study phases. It was determined that implementing the monitoring program itself resulted in an approximate water savings of 1.5 L/day per crewmember. The seven person crew averaged 202 distinct water draws a day (standard deviation 34) with high water use periods focusing around meal times. No statistically significant correlation was established between total water use and EVA or exercise duration. Study results suggest that current crew water utilization estimates for long duration planetary surface stays are more than two times greater than that required.     

Radio beacons/IMU integrated navigation for Mars entry

High precision entry navigation capability is essential for future Mars pinpoint landing missions, together with the entry guidance and aerodynamic lift control. This paper addresses the issue of Mars entry navigation using inertial measurement unit (IMU) and orbiting or surface radiometric beacons. The range and Doppler information sensed from orbiting or surface radio beacons and the entry vehicle state information derived from IMU are integrated in Unscented Kalman filter to correct the inertial constant bias and suppress the navigation measurement noise. Computer simulations show that the integrated navigation algorithm proposed in this paper can achieve 50 m position error and 2 m/s velocity error, which satisfies the need of future pinpoint Mars landing missions.     

火星着陆探测任务关键环节技术途径分析

火星进入、下降与着陆技术(entry,descent and landing,EDL)是火星着陆探测最为关键的环节。火星与地球再入返回过程相比,由于火星大气成分、物理性质与地球大气存在较大差别,且具有较大不确定性,使火星EDL过程历经时间短、状态变化快,对减速性能要求高,时序紧张。从工程实现角度分阶段开展了任务分析,识别了火星EDL环节面临的问题和挑战,提出了关键环节技术途径选择。     

Ground-based millimeter-wave observations of water vapor emission (183 GHz) at Atacama,Chile

We report the first results of ground-based millimeter-wave measurements of 183 GHz atmospheric water vapor spectra from Atacama highland (4800 m alt.), Chile. The measurements were carried out in December 2005 by using a spectroscopic radiometer equipped with a superconductive heterodyne receiver. A conspicuous H₂O spectrum at 183 GHz was detected with an integration time of only 1.5 min, and this is the first high frequency-resolution H₂O spectrum at 183 GHz obtained in the southern subtropical region. The vertical profile of H₂O volume mixing ratio between 40 and 64 km were retrieved from the spectrum by using the modified optimal estimation method.     

γ-ray spectroscopy in Mars orbit during solar proton events

Understanding the evolution of Mars requires determining the composition of the surface and atmosphere of the planet. The European Space Agency’s ExoMars rover mission, which is expected to launch in 2016, is part of the Aurora programme. The instruments on the rover will search for evidence of life on Mars and will map a sub-section of the Martian surface, extracting compositional information. Currently our understanding of the bulk composition (and mineralogy) of Mars relies on orbital data from instruments on-board satellites such as 2001 Mars Odyssey, Mars Reconnaissance Orbiter and Mars Express, in addition to in-situ instrumentation on rovers such as Spirit and Opportunity. γ-ray spectroscopy can be used to determine the composition of Mars, but it has yet to be successfully carried out in-situ on Mars. This study describes some of the results obtained from the γ-ray spectrometer on 2001 Mars Odyssey during solar proton events and discusses whether the increased emissions are useful in γ-ray spectroscopy. The study shows that although increased γ-ray emissions were expected from the Martian surface during a solar proton event, they were not detected from orbit probably due to insufficient signal-to-background. However, this does not preclude the possibility of measuring changes in γ-ray flux corresponding to changes in solar activity on the surface of the planet.