I. Weber

Mineralogy and Petrology of Comet 81P/Wild 2 Nucleus Samples

The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.

Aggregate dust particles at comet 67P/Churyumov–Gerasimenko

Comets are thought to preserve almost pristine dust particles, thus providing a unique sample of the properties of the early solar nebula. The microscopic properties of this dust played a key part in particle aggregation during the formation of the Solar System. Cometary dust was previously considered to comprise irregular, fluffy agglomerates on the basis of interpretations of remote observations in the visible and infrared and the study of chondritic porous interplanetary dust particles that were thought, but not proved, to originate in comets. Although the dust returned by an earlier mission has provided detailed mineralogy of particles from comet 81P/Wild, the fine-grained aggregate component was strongly modified during collection. Here we report in situ measurements of dust particles at comet 67P/Churyumov–Gerasimenko. The particles are aggregates of smaller, elongated grains, with structures at distinct sizes indicating hierarchical aggregation. Topographic images of selected dust particles with sizes of one micrometre to a few tens of micrometres show a variety of morphologies, including compact single grains and large porous aggregate particles, similar to chondritic porous interplanetary dust particles. The measured grain elongations are similar to the value inferred for interstellar dust and support the idea that such grains could represent a fraction of the building blocks of comets. In the subsequent growth phase, hierarchical agglomeration could be a dominant process and would produce aggregates that stick more easily at higher masses and velocities than homogeneous dust particles. The presence of hierarchical dust aggregates in the near-surface of the nucleus of comet 67P also provides a mechanism for lowering the tensile strength of the dust layer and aiding dust release.

Developing of MERTIS as an advanced process from the study up to the flight model

ESA’s mission BepiColombo will be launched in 2016. MERTIS (Mercury Radiometer and Thermal imaging Spectrometer) is one of the key instruments. MERTIS is an imaging infrared spectrometer and radiometer using an uncooled detector technology with very small resources in terms of mass and power. The incentive of the MERTIS development is scientific requirements to study the surface composition and temperatures of Mercury under the extreme environmental condition at Mercury. Therefore, the state-of-the-art optical performance of MERTIS is unique. Components based on innovative technologies have been developed and qualified to realize the project. This approach required an advanced model philosophy and development process from the study up to the flight model completed in 2013. This paper describes the development process as well as challenges from the management and system engineering point of view up to a lessons learnt that lead to important conclusions.

Application of Raman Spectroscopy as in situ Technology for the search for life

In preparation to future space missions it is necessary to study the circumstances when faced with performing Raman measurements in a non-Earth like environment. The differences and difficulties compared to the established measurement approaches on Earth need to be recognized and solutions must be found. As an example for extraterrestrial application Raman spectroscopy with the same specifications as those onboard the future ExoMars mission are conducted to test their potential of identifying biological material on martian analogue samples. Appropriate measurement parameters for the detection of biological material as well as for the determination of the mineral composition are derived.

MERTIS: the thermal infrared imaging spectrometer onboard of the Mercury Planetary Orbiter

The MERTIS instrument is a thermal infrared imaging spectrometer onboard of ESA’s cornerstone mission BepiColombo to Mercury. MERTIS has four goals: the study of Mercury’s surface composition, identification of rock-forming minerals, mapping of the surface mineralogy, and the study of the surface temperature variations and thermal inertia. MERTIS will provide detailed information about the mineralogical composition of Mercury’s surface layer by measuring the spectral emittance in the spectral range from 7-14 μm at high spatial and spectral resolution. Furthermore MERTIS will obtain radiometric measurements in the spectral range from 7-40 μm to study the thermo-physical properties of the surface material. The MERTIS detector is based on an uncooled micro-bolometer array providing spectral separation and spatial resolution according to its 2-dimensional shape. The operation principle is characterized by intermediate scanning of the planet surface and three different calibration targets – free space view and two on-board black body sources. In the current project phase, the MERTIS Qualification Model (QM) is under a rigorous testing program. Besides a general overview of the instrument principles, the papers addresses major aspects of the instrument design, manufacturing and verification.