Mars Express Mission Research Articles

The Atmosphere of Mars as Constrained by Remote Sensing

In addition to the Viking in-situ mass spectrometry measurements, our knowledge of the Martian atmosphere comes from remote sensing spectroscopy from the ground and from space. In particular, infrared measurements from the Mariner 9, Viking, Phobos and MGS orbiters have provided information upon the thermal profile, the chemical composition, the stratospheric winds, some isotopic ratios, and the properties of suspended dust. However, further remote sensing monitoring is still needed for a better understanding of the water cycle, a more accurate knowledge of the minor species and the aerosol composition, an improved measurement of the hydrogen and oxygen isotopic ratios, and for a full mapping of the middle altitude winds. Some of these information will be provided with the Mars Express mission.

Development of the “planetary underground tool” subsurface soil sampler for the Mars express “Beagle 2” lander

On the “Beagle 2” Mars lander for ESA's mission Mars Express, a self-penetrating mechanical Mole for sampling of subsarface soil from a maximum depth of 1…1.5 m will be utilized to supply samples to a Gas Analysis Experiment which are thought to have been protected from oxidizing conditions at the immediate surface and thus may have preserved organic matter from meteorite influx and possibly from earlier microbial life on the planet. The design, operations scheme and technical heritage of the Mole sampling system are described.

PFS on Mars Express: preparing the analysis of infrared spectra to be measured by the Planetary Fourier Spectrometer

A radiative transfer simulation and retrieval technique (RRT) is described that will be applied to derive atmospheric and surface properties of Mars from measured infrared signatures recorded by the Planetary Fourier Spectrometer (PFS) onboard the Mars Express mission in 2003. The RRT considers absorption, emission and multiple scattering of thermal and solar radiation by molecular (CO 2, H 2O, CO) and particulate (palagonite, montmorillonite) species. Precalculated sets of absorption cross-sections which are based on quasi-monochromatic line-by-line calculations are used to predict molecular transmission functions at 2.0 cm −1 spectral resolution in a layered atmosphere. Synthetic infrared spectra have been calculated in the 200– 8000 cm −1 wavenumber range (1.25– 50 μm ) for a variety of atmospheric models and surface conditions. The influence of multiple aerosol scattering on the spectra is investigated on the basis of a successive approximation technique. Numerical results are compared with the spherical harmonics discrete ordinate method. Different retrieval procedures and results of a simultaneous retrieval of vertical temperature profiles and aerosol optical depths as well as surface temperature, pressure and reflectance are discussed. Real measurements performed by the IRIS instrument onboard Mariner 9 are also examined.

The exobiology exploration of Mars: a survey of the European approaches

The similarities between the early histories of Mars and Earth raise the concomitant basic question: does our knowledge of primitive terrestrial life and of the early history of Mars allow us to expect life to have developed on Mars? The paper by McKay et al. (1996. Science 273, 924–930.) reported possible relic biogenic activity in a Martian meteorite. Although this discovery is certain to be controversial, it gave a new impetus to the search for fossil life on Mars. American, European and Japanese space agencies have planned a very intensive exploration of Mars with a great emphasis on exobiology. Here are summarized the European approaches including the European Space Agency (ESA) Exobiology Multi-user Facility and the Beagle 2 exobiology lander of the ESA Mars Express mission.

Sensitivity of temperature retrieval in the Martian atmosphere to transmittance simulation accuracy and instrumental noise

The Mars-Express mission in 2003 will carry the Planetary Fourier Spectrometer (PFS) for measurement of infrared radiation emitted by the atmosphere and surface. The retrieval of vertical temperature profiles is based on an iterative comparison of measured and simulated spectra in the 15 μm CO 2 band. A sensitivity study is performed to define the required accuracy of line-by-line CO 2 transmittance simulations to obtain reliable temperature results. The influence of instrumental noise on the temperature retrieval is also discussed. Synthetic measurements as well as selected spectra from the Mariner 9-IRIS data were used in the study.

Mars 96 landers planetary protection implementation and planetary protection specifications for the upcoming ESA planetary missions

Abstract According to the article IX of the OUTER SPACE TREATY (London / Washington January 27., 1967), extraterrestrial missions should be conducted in a manner that protects the planets and the Earth from contamination. Consequently, COSPAR (Committee of Space Research) has established Planetary Protection recommendations 1 which are taken into account by all project teams involved in solar system exploration missions. The Mars 96 mission was launched in November 1996. Unfortunately, the mission failed a few hours after launch. Nevertheless, all tasks concerning Planetary Protection were accomplished before the launch of the spacecraft. Taking into account this experience, similar specifications have been developed by CNES for the Mars Express mission in which the anticipated involvement of CNES is the construction of small landers named Netlanders. Exobiological experiments are not foreseen at this time. It must be added that NASA and CNES are presently studying a common Mars sample return mission for 2005. In addition to the sample return module, CNES may also provide Netlanders with exobiological experiments. A final decision about this cooperation will be reached early in 1999. A brief status of Rosetta mission will also be included. For this mission, the DLR (Deutsches Gesellschaft fur Luft und Raumfahrt) provides a cometary lander including experiments and lander subsystems provided by CNES.

A new method of remote sounding of the Martian aerosols by means of spectroscopy in the 2.7 μm CO 2 band

We present a new method of sounding of aerosols in the atmosphere of Mars. It is based on the remote spectroscopic measurements of the solar radiation reflected by the planet in the region of the 2.7 μm absorption band of atmospheric CO 2. The band is so strong that the radiance in its center is equal to 0 for the dust-free Martian atmosphere. The presence of suspended dust results in that some fraction of solar photons is scattered back to space without reaching the surface. Thus the intensity measured in the bottom of the band differs from 0 and can be used to determine the aerosol optical depth and to estimate its vertical distribution. We formulate general requirements for the spectroscopic observations that can provide optimal sounding of the atmospheric dust on Mars. The aerosol sounding capabilities of the Planetary Fourier Spectrometer experiment for the Mars Express mission are discussed in more detail. The equations for the radiation reflected by the non-homogeneous atmosphere derived in this work in a single scattering approximation can find applications beyond the scope of the paper.

The radiometric performances of the Planetary Fourier Spectrometer for Mars exploration

The Planetary Fourier Spectrometer (PFS) is a Fourier transform interferometer, operating in the range 1.2–45 μm. The instrument, previously included in the payload of the failed mission Mars ′96, is proposed for the future space mission Mars Express, under study by ESA. The present paper is aimed at presenting the radiometric performances of PFS. The two channels (LW and SW) forming PFS were analysed and characterised in terms of sensitivity and noise equivalent brightness. To cover the wide spectral range of PFS, different blackbodies were used for calibration. The built-in blackbodies, needed for the in-flight calibrations, were also characterised. The results show that the LW channel is comparable with IRIS Mariner 9 in terms of noise equivalent brightness. The SW channel performances, while satisfactorily, could be improved by lowering the sensor operative temperature. A simple model of the Mars radiance is used in order to calculate the signal-to-noise ratio on the spectra in typical observation conditions. The computed signal-to-noise ratio for the LW channel varies between 430 and 40, while for the SW channel it ranges from 150 to 30. The radiometric analyses confirm that PFS performances are compliant with the design requirements of the instrument. PFS is fully validated for future remote exploration of the atmosphere and the surface of Mars.

Simulation of the Martian spectral radiance in the presence of atmospheric dust

The interest towards Mars is nowadays renewed as various satellites, already launched or foreseen for the future, will visit this planet, providing a new wealth of data. In particular, infrared spectroscopic observations need a parallel modelling effort for a proper interpretation of observations. The goal of our modelling is to evaluate the influence of a non negligible fraction of dust particles on intensity and profile of atmospheric Martian spectra. The joint effects of the atmosphere and the surface materials have been also accounted for. For the modelling, a version of the MODTRAN code, expressly modified for application to the Mars environment, has been used. As an example of the materials forming dust dispersed in the atmosphere and on the surface, we have considered andesite. Indices of refraction (n and k) of this material have been derived from laboratory measurements. The obtained results can have an important impact on the interpretation of infrared spectra that instruments such as TES (Thermal Emission Spectrometer), on board the Mars Global Surveyor, and PFS, in the Mars Express mission, will provide.

Beagle 2: A proposed exobiology lander for ESA's 2003 Mars Express mission

The aim of the proposed Beagle 2 small lander for ESA's 2003 Mars Express mission is to search for organic material on and below the surface of Mars and to study the inorganic chemistry and mineralogy of the landing site. The lander will have a total mass of 60kg including entry, descent, and landing system. Experiments will be deployed on the surface using a robotic arm. It will use a mechanical mole and grinder to obtain samples from below the surface, under rocks, and inside rocks. Sample analysis by a mass spectrometer will include isotopic analysis. An optical microscope, an X- ray spectrometer and a Mossbauer spectrometer will conduct in-situ rock studies.

Retrieval of atmospheric and surface parameters of Mars based on synthetic spectra (1.25 – 50 μm)

The retrieval of atmospheric thermal structure and composition as well as surface properties from measured spectra recorded by a spaceborne instrument is based on an iterative comparison with synthetic spectra of planetary radiation. Synthetic infrared spectra of Mars have been calculated for a variety of atmospheric models and surface conditions. The radiative transfer simulation method uses prestored sets of temperature and pressure dependent absorption cross-sections of CO 2, H 2O and CO obtained from quasi-monochromatic line-by-line calculations. Aerosol absorption and scattering efficiencies are determined from laboratory data on refractive indices applying Mie theory. Multiple aerosol scattering is considered by a successive order technique. The 15 and 2 μm CO 2 bands are used to retrieve temperature profiles and surface pressure simultaneously, while the 2.0 and 2.7 μm bands allow to separate radiance contributions from atmospheric dust extinction and surface reflectance. Aerosol optical depths are primarily determined in the 8–13 μm window region. The modelling results will serve as the base for interpreting the spectroscopic measurements of the Planetary Fourier Spectrometer PFS onboard the European Mars-Express mission in 2003.

⃛ while UK scientists seek private backing

munich British space scientists are making an urgent appeal to private funders to support a small equipment package to land on the surface of the planet Mars as part of the Mars Express mission.

Scientific applications of robotic systems on planetary missions

This paper focusses on Mars landing missions. It gives a brief survey of past international missions and outlines the objectives of the European science community concerning Mars surface exploration. It reviews the studies performed by the ESA science programme in the past (Marsnet, InterMarsnet), culminating in the current efforts to prepare the Mars Express mission for launch in 2003. From the scientific objectives, the functional and performance requirements of robotic systems are derived which are perceived as essential for unmanned Mars surface exploration. The very severe constraints on robot systems from the launch, cruise, and Mars surface environment are described as well as the need for extremely lightweight and low-power solutions with very high science support efficiency. Five typical classes of A&R systems for Mars exploration are specifically identified: simple masts or booms, automation systems for drilling and sample handling, micro rovers for instrument deployment, mini rovers for long range exploration, and “mole” type penetrators. Of these, the drilling/sample handling devices and the micro rovers are covered in more detail, with references to papers describing their developments.