Long-term Exploration Missions Research Articles

Unraveling astrocyte behavior in the space brain: Radiation response of primary astrocytes.

Exposure to space conditions during crewed long-term exploration missions can cause several health risks for astronauts. Space radiation, isolation and microgravity are major limiting factors. The role of astrocytes in cognitive disturbances by space radiation is unknown. Astrocytes' response toward low linear energy transfer (LET) X-rays and high-LET carbon (12C) and iron (56Fe) ions was compared to reveal possible effects of space-relevant high-LET radiation. Since astronauts are exposed to ionizing radiation and microgravity during space missions, the effect of simulated microgravity on DNA damage induction and repair was investigated. Primary murine cortical astrocytes were irradiated with different doses of X-rays, 12C and 56Fe ions at the heavy ion accelerator GSI. DNA damage and repair (γH2AX, 53BP1), cell proliferation (Ki-67), astrocytes' reactivity (GFAP) and NF-κB pathway activation (p65) were analyzed by immunofluorescence microscopy. Cell cycle progression was investigated by flow cytometry of DNA content. Gene expression changes after exposure to X- rays were investigated by mRNA-sequencing. RT-qPCR for several genes of interest was performed with RNA from X-rays- and heavy-ion-irradiated astrocytes: Cdkn1a, Cdkn2a, Gfap, Tnf, Il1β, Il6, and Tgfβ1. Levels of the pro inflammatory cytokine IL-6 were determined using ELISA. DNA damage response was investigated after exposure to X-rays followed by incubation on a 2D clinostat to simulate the conditions of microgravity. Astrocytes showed distinct responses toward the three different radiation qualities. Induction of radiation-induced DNA double strand breaks (DSBs) and the respective repair was dose-, LET- and time-dependent. Simulated microgravity had no significant influence on DNA DSB repair. Proliferation and cell cycle progression was not affected by radiation qualities examined in this study. Astrocytes expressed IL-6 and GFAP with constitutive NF-κB activity independent of radiation exposure. mRNA sequencing of X-irradiated astrocytes revealed downregulation of 66 genes involved in DNA damage response and repair, mitosis, proliferation and cell cycle regulation. In conclusion, primary murine astrocytes are DNA repair proficient irrespective of radiation quality. Only minor gene expression changes were observed after X-ray exposure and reactivity was not induced. Co-culture of astrocytes with microglial cells, brain organoids or organotypic brain slice culture experiments might reveal whether astrocytes show a more pronounced radiation response in more complex network architectures in the presence of other neuronal cell types.

Quantitative Inversion of Lunar Surface Chemistry Based on Hyperspectral Feature Bands and Extremely Randomized Trees Algorithm

In situ resource utilization (ISRU) is required for the operation of both medium and long-term exploration missions to provide metallic materials for the construction of lunar base infrastructure and H2O and O2 for life support. The study of the distribution of the lunar surface elements (Fe, Ti, Al, and Si) is the basis for the in situ utilization of mineral resources. With the arrival of the era of big data, the application of big data concepts and technical methods to lunar surface chemistry inversion has become an inevitable trend. This paper is guided by big data theory, and the Apollo 17 region and the area near the Copernicus crater are selected for analysis. The dimensionality of the first-order differential spectral features of lunar soil samples is reduced based on Pearson correlation analysis and the successive projections algorithm (SPA), and the extremely randomized trees (Extra-Trees) algorithm is applied to Chang’E-1 Interference Imaging Spectrometer (IIM) data to establish a prediction model for the lunar surface chemistry and generate FeO, TiO2, Al2O3, and SiO2 distribution maps. The results show that the optimum number of variables for FeO, TiO2, Al2O3, and SiO2 is 17, 5, 8, and 30, respectively. The accuracy of the Extra-Trees model using the best variables was improved over that of the original band model, with determination coefficients (R2) of 0.962, 0.944, 0.964, and 0.860 for FeO, TiO2, Al2O3, and SiO2, and root mean square errors (RMSEs) of 1.028, 0.672, 0.942, and 0.897, respectively. The modeling feature variables and model preference methods in this study can improve the inversion accuracy of chemical abundance to some extent, demonstrating the potential of IIM data in predicting chemical abundance and providing a good data basis for lunar geological evolution studies and ISRU.

Response of Arabidopsis thaliana and Mizuna Mustard Seeds to Simulated Space Radiation Exposures.

One of the major concerns for long-term exploration missions beyond the Earth’s magnetosphere is consequences from exposures to solar particle event (SPE) protons and galactic cosmic rays (GCR). For long-term crewed Lunar and Mars explorations, the production of fresh food in space will provide both nutritional supplements and psychological benefits to the astronauts. However, the effects of space radiation on plants and plant propagules have not been sufficiently investigated and characterized. In this study, we evaluated the effect of two different compositions of charged particles-simulated GCR, and simulated SPE protons on dry and hydrated seeds of the model plant Arabidopsis thaliana and the crop plant Mizuna mustard [Brassica rapa var. japonica]. Exposures to charged particles, simulated GCRs (up to 80 cGy) or SPEs (up to 200 cGy), were performed either acutely or at a low dose rate using the NASA Space Radiation Laboratory (NSRL) facility at Brookhaven National Lab (BNL). Control and irradiated seeds were planted in a solid phytogel and grown in a controlled environment. Five to seven days after planting, morphological parameters were measured to evaluate radiation-induced damage in the seedlings. After exposure to single types of charged particles, as well as to simulated GCR, the hydrated Arabidopsis seeds showed dose- and quality-dependent responses, with heavier ions causing more severe defects. Seeds exposed to simulated GCR (dry seeds) and SPE (hydrated seeds) had significant, although much less damage than seeds exposed to heavier and higher linear energy transfer (LET) particles. In general, the extent of damage depends on the seed type.

ВЛИЯНИЕ ДЛИТЕЛЬНОГО ФРАКЦИОНИРОВАННОГО γ-ОБЛУЧЕНИЯ НА ПРОДОЛЖИТЕЛЬНОСТЬ ЖИЗНИ МЫШЕЙ

The bio-effect of long-term fractionated γ-irradiation with a low total dose was assessed by the criteria of lifespan and death rate in certain life periods. The experiment was made with 40 female ICR (CD-1) mice. Fractionated irradiation of the animals with γ-quants 60Co (50 mGy×33 wks) brought about reduction of the mice mean life by more than 150 days. The total dose of 1.65 Gy is approximate to the admissible career dose limit for cosmonauts. Untimely deaths, in comparison with the control mice, were observed both in the early and terminal periods. Also, body mass of the irradiated animals was increased throughout the follow-up time. The data can be used for evaluation of the risks of tumor and cardiovascular diseases from chronic irradiation of crews during long-term exploration missions.

Modeling curiosity in a mobile robot for long-term autonomous exploration and monitoring

This paper presents a novel approach to modeling curiosity in a mobile robot, which is useful for monitoring and adaptive data collection tasks, especially in the context of long term autonomous missions where pre-programmed missions are likely to have limited utility. We use a realtime topic modeling technique to build a semantic perception model of the environment, using which, we plan a path through the locations in the world with high semantic information content. The life-long learning behavior of the proposed perception model makes it suitable for long-term exploration missions. We validate the approach using simulated exploration experiments using aerial and underwater data, and demonstrate an implementation on the Aqua underwater robot in a variety of scenarios. We find that the proposed exploration paths that are biased towards locations with high topic perplexity, produce better terrain models with high discriminative power. Moreover, we show that the proposed algorithm implemented on Aqua robot is able to do tasks such as coral reef inspection, diver following, and sea floor exploration, without any prior training or preparation.

Radiation protective agents in the radiation safety system for long-term exploration missions

Radiation environment in long-term exploration missions is scrutinized in the context of the risks of deterministic and stochastic effects of radiation. The probability of severe radiation damage as a result of solar flares is very low; nevertheless, interplanetary crews must be provided with the appropriate protective agents, including pharmacological ones. The current nomenclature of radioprotectors comprises short-term agents against acute radiation damage. Among them, B-190 preparation has been distinguished by particularly high effectiveness, large window of radioprotection, and good tolerance even during the exposure to extreme factors of space flight. The therapeutic regimens for B-190, separately and in combination with radioprotectors from aminothiol family, have been developed for the treatment duing multiple solar events. The efficiency of radioprotectors can be substantially enhanced by the local shielding of abdomen and pelvis. The most promising nonspecific stimulators of total resistance of the body are riboxin (inosine) and the combined preparation aminotetravit, as well as the tocopherol and retinol (vitamins E and A). The possibility of B-190 combination therapy with riboxin and aminotetravit has been considered. The cytokine neupogen (G-CSF) is also considered as a candidate agent for early therapy of acute radiation syndrome. Attention has been paid to the possible development of chronic oxidative stress in long-term exploration missions. The significance of adequate nutrition supplemented with fresh vegetables as a source of the most valuable bioflavonoids has been highlighted. The antioxidants L-selenomethionine and melatonin proved to be efficient against heavy nuclei of galactic radiation. The possible scenarios of implementation of the effects of natural antioxidants under oxidative stress low-rate-dose galactic radiation have been considered.

Ultralight deployable booms for solar sails and other large gossamer structures in space

Future solar sail spacecraft which do not need any rocket motors and propellants are a promising option for long-term exploration missions in the solar system. However, they will require ultralight reflective foils and deployable booms which will allow for the unfolding of huge sails. The achievement of an acceptable ratio of reflective sail area and structural mass, which results in a still small, but significant acceleration under the photon pressure of sunlight, is extremely challenging. The same challenging deployment technique is required for the unfolding of large reflector membranes or antennas (gossamer structures). The key elements are the booms which must be stowable in a very small envelope before they reach their destination in space. Such booms were developed by DLR and have been successfully tested under zero-g-conditions during a parabolic flight campaign in February 2009. It could be convincingly demonstrated that the unfolding process is both controllable and reproducible. The booms consisted of two co-bonded omega-shaped carbonfiber half shells with 0.1mm wall thickness each and had a weight of only 62g per meter. Two different deployment technologies were tested, one based upon an inflatable 12μm thick polymer hose inside the boom, the other one using an electromechanical uncoiling device at the tip of each boom. In the latter case, the uncoiling devices will radially fly away from the spacecraft, such that they become “expendable deployment mechanisms” and their mass does not count any more for the spacecraft mass that needs to be accelerated or actively controlled.

Packaging Technology for High Temperature Capacitive Pressure Sensors

High temperature pressure sensors are critical sensing elements for the next generation of intelligent aerospace engine technology, as well as long-term exploration missions to Venus, where the surface temperature is 485°C. Various high temperature pressure sensors based on different sensing mechanisms are under development at the NASA Glenn Research Center. In order to test long-term performance and reliability of these sensors in a high temperature environment, and eventually commercialize these sensors, high temperature durable and long-term reliable packaging is essential. A prototype packaging technology for micro-sensors designated for applications in high temperature and high differential pressure environments has been developed and reported previously. Packaged high temperature silicon carbide pressure sensors have been successfully tested between room temperature and 500°C. This paper reports an improved version of this packaging technology and testing results of a packaged commercial Si capacitive pressure sensor at elevated temperatures. The parasitic parameters of the packaging are electrically characterized from room temperature to 500°C at 120Hz, 1kHz, 10kHz, and 100kHz. This packaging is primarily designed for high temperature capacitive pressure sensors, but it also applies to other high temperature sensors, especially those for high differential pressure environments.