Tardigrades as a potential model organism in space research

Exposure of living organisms to open space requires a high level of tolerance to desiccation, cold, and radiation. Among animals, only anhydrobiotic species can fulfill these requirements. The invertebrate phylum Tardigrada includes many anhydrobiotic species, which are adapted to survive in very dry or cold environmental conditions. As a likely by-product of the adaptations for desiccation and freezing, tardigrades also show a very high tolerance to a number of other, unnatural conditions, including exposure to ionizing radiation. This makes tardigrades an interesting candidate for experimental exposure to open space. This paper reviews the tolerances that make tardigrades suitable for astrobiological studies and the reported radiation tolerance in other anhydrobiotic animals. Several studies have shown that tardigrades can survive gamma-irradiation well above 1 kilogray, and desiccated and hydrated (active) tardigrades respond similarly to irradiation. Thus, tolerance is not restricted to the dry anhydrobiotic state, and I discuss the possible involvement of an efficient, but yet undocumented, mechanism for DNA repair. Other anhydrobiotic animals (Artemia, Polypedium), when dessicated, show a higher tolerance to gamma-irradiation than hydrated animals, possibly due to the presence of high levels of the protective disaccharide trehalose in the dry state. Tardigrades and other anhydrobiotic animals provide a unique opportunity to study the effects of space exposure on metabolically inactive but vital metazoans.     

Application of numerical Fourier transformation on measurements made on board rotating spacecrafts

Signals obtained on board rocket payloads or satellites are often “spin modulated”. The relevant information is then found within the envelope and the phase of the signal. The most efficient method of extracting this information is the numerical Fourier analysis.     

Thermal model and thermo-mechanical stresses in cometary nuclei

Spherically symmetric radial temperature profiles of cometary nuclei have been determined numerically (and for simplified models analytically) in dependence on the orbital position of the periodic comet Halley. These temperature fields in the nucleus are connected with thermal stress fields which have been calculated with the assumption of elastic properties of cometary matter. The remarkable result is the possible existence of stresses, strong enough to cause internal cracking of the nucleus and break-ups of the cometary surface. This may be essential understanding normal cometary activity as well as outbursts and splits.     

Stratigraphy and Isotope Ages of Lunar Geologic Units: Chronological Standard for the Inner Solar System

The absolute ages of cratered surfaces in the inner solar system, including Mars, are derived by extrapolation from the impact flux curve for the Moon which has been calibrated on the basis of absolute ages of lunar samples. We reevaluate the lunar flux curve using isotope ages of lunar samples and the latest views on the lunar stratigraphy and the principles of relative and absolute age dating of geologic surface units of the Moon. The geological setting of the Apollo and Luna landing areas are described as far as they are relevant for this reevaluation. We derive the following best estimates for the ages of the multi-ring basins and their related ejecta blankets and present alternative ages for the basin events (in parentheses): 3.92 ± 0.03 Gyr (or 3.85 ± 0.05 Gyr) for Nectaris, 3.89 ± 0.02 Gyr (or 3.84 ± 0.04 Gyr) for Crisium, 3.89 ± 0.01 Gyr (or 3.87 ± 0.03 Gyr) for Serenitatis, and 3.85 ± 0.02 Gyr (or 3.77 ± 0.02 Gyr) for Imbrium. Our best estimates for the ages of the mare landing areas are: 3.80 ± 0.02 Gyr for Apollo 11 (old surface), 3.75 ± 0.01 Gyr for Apollo 17, 3.58 ± 0.01 Gyr for Apollo 11 (young surface), 3.41 ± 0.04 Gyr for Luna 16, 3.30 ± 0.02 Gyr for Apollo 15, 3.22 ± 0.02 Gyr for Luna 24, and 3.15 ± 0.04 Gyr for Apollo 12. The ages of Eratosthenian and Copernican craters remain: ～ 2.1 (?) Gyr (Autolycus), 800 ± 15 Myr (Copernicus), 109 ± 4 Myr (Tycho), 50.3 ± 0.8 (North Ray crater, Apollo 16), and 25.1 ± 1.2 (Cone crater, Apollo 14). When plotted against the crater densities of the relevant lunar surface units, these data result in a revised lunar impact flux curve which differs from the previously used flux curve in the following respects: (1) The ages of the stratigraphically most critical impact basins are notably younger, (2) the uncertainty of the calibration curve is decreased, especially in the age range from about 4.0 to 3.0 Gyr, (3) any curve for ages older than 3.95 Gyr (upper age limit of the Nectaris ejecta blanket) is abandoned because crater frequencies measured on such surface formations cannot be correlated with absolute ages obtained on lunar samples. Therefore, the impact flux curve for this pre-Nectarian time remains unknown. The new calibration curve for lunar crater retention ages less than about 3.9 Gyr provides an updated standard reference for the inner solar system bodies including Mars.     

Concepts for the curation,primary examination,and allocation of comet nucleus samples by a comet sample receiving laboratory

The Comet Nucleus Sample Return Mission ROSETTA, a cornerstone mission of ESA jointly planned with NASA, requires the implementation of a highly sophisticated curatorial facility for the returned samples. A concept for the instrumentation and the mode of operation of a Comet Sample Receiving Laboratory (CSRL) is proposed. The main elements of the facility are: (1) cryogenic evacuated cabinets with robotic manipulators, (2) devices for sample dissection, aliquotisation, phase separation, and thin section preparation, and (3) instrumentation for non-destructive chemical and physical analyses and facilities for destructive mineralogical, textural, and (micro)chemical analyses. It is recommended that a very detailed Primary Sample Examination and Analysis be performed on a small representative fraction of the samples at the P-T-conditions of the parent comet nucleus before sample aliquots are released to Principal Investigators. The CSRL should be staffed with top rank personnel and supervised by an international peer review panel which may also be responsible for the selection of investigators and the allocation of samples.