Simulated Martian Conditions Research Articles

Effects of Long-Term Simulated Martian Conditions on a Freeze-Dried and Homogenized Bacterial Permafrost Community

Indigenous bacteria and biomolecules (DNA and proteins) in a freeze-dried and homogenized Arctic permafrost were exposed to simulated martian conditions that correspond to about 80 days on the surface of Mars with respect to the accumulated UV dose. The simulation conditions included UV radiation, freeze-thaw cycles, the atmospheric gas composition, and pressure. The homogenized permafrost cores were subjected to repeated cycles of UV radiation for 3 h followed by 27 h without irradiation. The effects of the simulation conditions on the concentrations of biomolecules; numbers of viable, dead, and cultured bacteria; as well as the community structure were determined. Simulated martian conditions resulted in a significant reduction of the concentrations of DNA and amino acids in the uppermost 1.5 mm of the soil core. The total number of bacterial cells was reduced in the upper 9 mm of the soil core, while the number of viable cells was reduced in the upper 15 mm. The number of cultured aerobic bacteria was reduced in the upper 6 mm of the soil core, whereas the community structure of cultured anaerobic bacteria was relatively unaffected by the exposure conditions. As explanations for the observed changes, we propose three causes that might have been working on the biological material either individually or synergistically: (i) UV radiation, (ii) UV-generated reactive oxygen species, and (iii) freeze-thaw cycles. Currently, the production and action of reactive gases is only hypothetical and will be a central subject in future investigations. Overall, we conclude that in a stable environment (no wind-/pressure-induced mixing) biological material is efficiently shielded by a 2 cm thick layer of dust, while it is relatively rapidly destroyed in the surface layer, and that biomolecules like proteins and polynucleotides are more resistant to destruction than living biota.

Survivability of Psychrobacter cryohalolentis K5 Under Simulated Martian Surface Conditions

Spacecraft launched to Mars can retain viable terrestrial microorganisms on board that may survive the interplanetary transit. Such biota might compromise the search for life beyond Earth if capable of propagating on Mars. The current study explored the survivability of Psychrobacter cryohalolentis K5, a psychrotolerant microorganism obtained from a Siberian permafrost cryopeg, under simulated martian surface conditions of high ultraviolet irradiation, high desiccation, low temperature, and low atmospheric pressure. First, a desiccation experiment compared the survival of P. cryohalolentis cells embedded, or not embedded, within a medium/salt matrix (MSM) maintained at 25 degrees C for 24 h within a laminar flow hood. Results indicate that the presence of the MSM enhanced survival of the bacterial cells by 1 to 3 orders of magnitude. Second, tests were conducted in a Mars Simulation Chamber to determine the UV tolerance of the microorganism. No viable vegetative cells of P. cryohalolentis were detected after 8 h of exposure to Mars-normal conditions of 4.55 W/m(2) UVC irradiation (200-280 nm), -12.5 degrees C, 7.1 mbar, and a Mars gas mix composed of CO(2) (95.3%), N(2) (2.7%), Ar (1.6%), O(2) (0.2%), and H(2)O (0.03%). Third, an experiment was conducted within the Mars chamber in which total atmospheric opacities were simulated at tau = 0.1 (dust-free CO(2) atmosphere at 7.1 mbar), 0.5 (normal clear sky with 0.4 = dust opacity and 0.1 = CO(2)-only opacity), and 3.5 (global dust storm) to determine the survivability of P. cryohalolentis to partially shielded UVC radiation. The survivability of the bacterium increased with the level of UVC attenuation, though population levels still declined several orders of magnitude compared to UVC-absent controls over an 8 h exposure period.

Do fungi survive under actual space conditions? Searching for evidence in favour of lithopanspermia

Cryptoendolithic communities and black meristematic fungi from the Antarctic desert have been shown to survive under simulated space and Martian conditions in ground‐based Experiment Verification Tests. An experiment was set to test their resistance under actual space and simulated Martian conditions on the International Space Station in the framework of the EXPOSE‐EuTEF Consortium, LIFE‐ESA project.

The H 2O and CO 2 adsorption properties of phyllosilicate-poor palagonitic dust and smectites under martian environmental conditions

The recent detection of up to ∼10 wt% water-equivalent H heterogeneously distributed in the upper meter of the equatorial regions of the martian surface and the presence of the 3-μm hydrations feature across the entire planet raises the question whether martian surficial dust can account for this water-equivalent H. We have investigated the H 2O and CO 2 adsorption properties of palagonitic dust (<5 μm size fraction of phyllosilicate-poor palagonitic tephra HWMK919) as a martian dust analog and two smectites under simulated martian equatorial surface conditions. Our results show that the palagonitic dust, which contains hydrated and hydroxylated volcanic glass of basaltic composition, accommodates significantly more H 2O under comparable humidity and temperature conditions than do the smectites nontronite and montmorillonite.

Controlled particle removal from surfaces by electrodynamic methods for terrestrial, lunar, and Martian environmental conditions

An Electrodynamic Dust Shield to remove already deposited micron-size particles from surfaces and to prevent the accumulation of such particles on surfaces has been developed. In addition to terrestrial application, our NASA laboratory is adapting this technology for the dusty and harsh environments of the Moon and Mars. The Apollo missions to the moon showed that lunar dust can hamper astronaut surface activities due to its ability to cling to most surfaces. NASA's Mars exploration landers and rovers have also shown that the problem is equally hard if not harder on Mars. In this paper, we show that an appropriate design can prevent the electrostatic breakdown at the low Martian atmospheric pressures. We are also able to show that uncharged dust can be lifted and removed from surfaces under simulated Martian environmental conditions. This technology has many potential benefits for removing dust from visors, viewports and many other surfaces as well as from solar arrays. We have also been able to develop a version of the electrodynamic dust shield working under hard vacuum conditions. This version should work well on the moon. We present data on the design and optimization of both types of dust shields as well substantial data on the clearing factors for transparent dust shields designed to protect solar panels for Martian exploration.

Effects of atmospheric pressure on the survival of photosynthetic microorganisms during simulations of ecopoesis

AbstractThree cyanobacteria (Anabaenasp.,Plectonema boryanumandChroococcidiopsisCCMEE171) and an alga (Chlorella ellipsoidea) were grown under simulated martian ecopoesis conditions. A xenon arc lamp with a solar filter provided simulated martian sunlight, and temperature cycled diurnally from −80°C to 26°C. A Mars-like atmosphere of 100% CO2was provided at 50, 100, 300, 500 and 1000 mbar. The cyanobacteria and alga were inoculated into JSC Mars-1 soil simulant and exposed to each atmospheric pressure for five weeks. Survival and growth were determined via extractable chlorophyllaand total esterase (fluorescein diacetate hydrolysis) activity. Maximum survival occurred at 100 and 300 mbar. At 50, 500 and 1000 mbar, esterase activity was near zero, and extractable chlorophyllawas less than 10% of control samples. Overall, the cyanobacteria survived better than the alga. Low survival at 50 mbar was probably due to desiccation. Low survival at 500 and 1000 mbar may have been due to CO2toxicity.

Persistence of Biomarker ATP and ATP-Generating Capability in Bacterial Cells and Spores Contaminating Spacecraft Materials under Earth Conditions and in a Simulated Martian Environment

Most planetary protection research has concentrated on characterizing viable bioloads on spacecraft surfaces, developing techniques for bioload reduction prior to launch, and studying the effects of simulated martian environments on microbial survival. Little research has examined the persistence of biogenic signature molecules on spacecraft materials under simulated martian surface conditions. This study examined how endogenous adenosine-5'-triphosphate (ATP) would persist on aluminum coupons under simulated martian conditions of 7.1 mbar, full-spectrum simulated martian radiation calibrated to 4 W m(-2) of UV-C (200 to 280 nm), -10 degrees C, and a Mars gas mix of CO(2) (95.54%), N(2) (2.7%), Ar (1.6%), O(2) (0.13%), and H(2)O (0.03%). Cell or spore viabilities of Acinetobacter radioresistens, Bacillus pumilus, and B. subtilis were measured in minutes to hours, while high levels of endogenous ATP were recovered after exposures of up to 21 days. The dominant factor responsible for temporal reductions in viability and loss of ATP was the simulated Mars surface radiation; low pressure, low temperature, and the Mars gas composition exhibited only slight effects. The normal burst of endogenous ATP detected during spore germination in B. pumilus and B. subtilis was reduced by 1 or 2 orders of magnitude following, respectively, 8- or 30-min exposures to simulated martian conditions. The results support the conclusion that endogenous ATP will persist for time periods that are likely to extend beyond the nominal lengths of most surface missions on Mars, and planetary protection protocols prior to launch may require additional rigor to further reduce the presence and abundance of biosignature molecules on spacecraft surfaces.

Stability of ice on Mars and the water vapor diurnal cycle: Experimental study of the sublimation of ice through a fine-grained basaltic regolith

In order to advance our understanding of the long-term stability of subsurface ice, the diurnal martian water cycle, and implications for liquid water, we determined diffusion coefficients and adsorption kinetics for the water vapor produced by the sublimation of ice buried beneath various layers of fine-grained (<63, 63–125, and 125–250 μm) basaltic powder under simulated martian conditions. Sublimation rates at shallower depths, <10 mm, were determined to be affected by mass transfer through the atmosphere in addition to the basalt layer. For greater depths, the measured diffusion coefficients for water vapor moving through basalt grains were 1.56 ± 0.53 × 10 −4 , 2.05 ± 0.82 × 10 −4 , and 3.42 ± 1.36 × 10 −4 m 2 s −1 for the <63, 63–125, and 125–250 μm basaltic layers, respectively. Through the Brunauer, Emmett and Teller (BET) isotherm, which assumes multiple molecular layers of adsorbed water, we determined the adsorption constants of 52.6 ± 8.3 at 270 K for <63 μm, 39.0 ± 6.4 at 267 K for 63–125 μm, and 54.3 ± 9.3 at 266 K for 125–250 μm, resulting in surface areas of 2.6 ± 0.1 × 10 4 , 1.7 ± 0.3 × 10 4 , 1.5 ± 0.3 × 10 4 m 2 kg −1 , respectively. These results suggest that while diffusion is too rapid to explain the purported diurnal cycle in water content of the atmosphere, adsorption is efficient and rapid, and does provide an effective mechanism to explain such a cycle. The present diffusion data suggest that very thin, <50 pr μm, shallow, 10 mm, ice deposits would last for >10 h at ∼224 K, just above the freezing point of saturated CaCl 2. Temperatures can remain above ∼224 K over most of the planet, which means that water, even as saturated brine, will sublimate before the freezing point is reached and liquid could be formed. On the other hand, 1 m ice layers below 1 m of fine-grained basaltic regolith at 235 K and 10 Pa of atmospheric water could last 600 to 1300 years. At deeper depths and lower temperatures, ice could last since the last major obliquity change 400,000 years ago.

Effect of shadowing on survival of bacteria under conditions simulating the Martian atmosphere and UV radiation.

Spacecraft-associated spores and four non-spore-forming bacterial isolates were prepared in Atacama Desert soil suspensions and tested both in solution and in a desiccated state to elucidate the shadowing effect of soil particulates on bacterial survival under simulated Martian atmospheric and UV irradiation conditions. All non-spore-forming cells that were prepared in nutrient-depleted, 0.2-microm-filtered desert soil (DSE) microcosms and desiccated for 75 days on aluminum died, whereas cells prepared similarly in 60-microm-filtered desert soil (DS) microcosms survived such conditions. Among the bacterial cells tested, Microbacterium schleiferi and Arthrobacter sp. exhibited elevated resistance to 254-nm UV irradiation (low-pressure Hg lamp), and their survival indices were comparable to those of DS- and DSE-associated Bacillus pumilus spores. Desiccated DSE-associated spores survived exposure to full Martian UV irradiation (200 to 400 nm) for 5 min and were only slightly affected by Martian atmospheric conditions in the absence of UV irradiation. Although prolonged UV irradiation (5 min to 12 h) killed substantial portions of the spores in DSE microcosms (approximately 5- to 6-log reduction with Martian UV irradiation), dramatic survival of spores was apparent in DS-spore microcosms. The survival of soil-associated wild-type spores under Martian conditions could have repercussions for forward contamination of extraterrestrial environments, especially Mars.

RASP-based sample acquisition of analogue Martian permafrost samples: Implications for NASA's Phoenix scout mission

Sample acquisition studies of ice–dirt mixtures under simulated Martian conditions approximating the 2007/8 Phoenix Scout mission are reported. The experiments were performed using a prototype rapid acquisition sampling package (RASP) that is similar to the one mounted on the 2007/8 Phoenix scout robotic arm. This mission will acquire a sample from permafrost-like regolith that is estimated at strengths near 45 MPa to measure the volatile composition including H 2O. Sublimation loss during sample acquisition and transfer will have a significant effect on the determination of water content, a major Phoenix mission goal. Laboratory sample acquisition was performed under Martian ambient pressures (5 Torr) in which water is unstable and ice quickly sublimates. Basalt samples consisting of various size, and shapes subjected to various temperature ranges were used as the aggregate material of the water saturated permafrost analogues expected to be found at the Phoenix landing site. In our laboratory experiments roughly 5–6% of the initial water–ice was sublimed due to energy imparted by the tool to the sample during sample acquisition. This loss is in addition to any others from passive sublimation as the samples are transferred to the instruments for analysis. We determined that the energy necessary to excavate the permafrost samples with the RASP to be on the order of 0.05 W h/cm 3. Finally, we discuss the potential to use a RASP on future in situ Martian missions.

Laser induced breakdown spectroscopy of soils, rocks and ice at subzero temperatures in simulated martian conditions

We applied Laser Induced Breakdown Spectroscopy (LIBS) on moist soil/rock samples in simulated Martian conditions. The signal behavior as a function of the surface temperature in the range from + 25 °C to − 60 °C was studied at pressure of 7 mbar. We observed the strong signal oscillations below 0 °C with different negative peaks, whose position, width and magnitude depend on the surface roughness. In some cases, the signal was reduced for one order of magnitude with consequences for the LIBS analytical capability. We attribute such a signal behavior to the presence of supercooled water inside the surface pores, which freezing point depends on the pore size. On a same rock samples with different grades of the surface polishing, the signal has different temperature dependence. Its decrease was always registered close to 0 °C, corresponding to the freezing/melting of normal disordered ice, which can be present inside larger pores and scratching. An amount of the signal reduction at the phase transition temperatures does not seem to change with the laser energy density in the examined range. Comparative measurements were performed on a frozen water solution. A large depression, for two orders of magnitude, of the LIBS intensity was observed close to − 50 °C. The same negative peak, but with a smaller magnitude, was also registered on some rock/soil samples. Ablation rates and plasma parameters as a function of the sample temperature are also discussed, and their consequences for in-situ analyses.

Stability of hydrated minerals on Mars

The validity of recent identification of various hydrated minerals (kieserite, gypsum, hexahydrite, nontronite, chamosite, and montmorillonite) on Mars was assessed by exposing these minerals to simulated Martian surface conditions of atmospheric composition and pressure, temperature, and ultraviolet light irradiation. When exposed to such conditions the hydrated minerals exhibit in general, greater losses of interlayer H2O than structural OH. Minerals such as gypsum that contain structural H2O are more resistant to H2O loss than phyllosilicates. The partial loss of OH in some of the phyllosilicates is not accompanied by a measurable and systematic change in the wavelength position or intensity of metal‐OH absorption bands. The characteristic absorption features that allow for identification of these minerals on Mars may be reduced in intensity, but are nevertheless largely preserved.

Survival of Methanogenic Archaea from Siberian Permafrost under Simulated Martian Thermal Conditions

Methanogenic archaea from Siberian permafrost complementary to the already well-studied methanogens from non-permafrost habitats were exposed to simulated Martian conditions. After 22 days of exposure to thermo-physical conditions at Martian low- and mid-latitudes up to 90% of methanogenic archaea from Siberian permafrost survived in pure cultures as well as in environmental samples. In contrast, only 0.3%-5.8% of reference organisms from non-permafrost habitats survived at these conditions. This suggests that methanogens from terrestrial permafrost seem to be remarkably resistant to Martian conditions. Our data also suggest that in scenario of subsurface lithoautotrophic life on Mars, methanogenic archaea from Siberian permafrost could be used as appropriate candidates for the microbial life on Mars.

Interactive effects of hypobaria, low temperature, and CO 2 atmospheres inhibit the growth of mesophilic Bacillus spp. under simulated martian conditions

Robotic spacecraft are launched with finite levels of terrestrial microorganisms that are similar to the microbial communities within facilities in which spacecraft are assembled. In particular, spores of mesophilic aerobic Bacillus species are common spacecraft contaminants considered most likely to survive interplanetary transfer to Mars. During the cruise phase to Mars, and then again during surface operations, microbial bioloads are exposed to a diversity of biocidal factors that are likely to render the microbial species either dead or significantly inhibited from active metabolic activity and replication. We report here, for the first time, that interactive effects of low pressure, low temperature, and high CO 2 atmospheres approaching conditions likely to be encountered on the martian surface strongly inhibit the growth and replication of seven common Bacillus spp. isolated from spacecraft. Tests were conducted within a small glass bell-jar system maintained in a low-temperature microbial incubator. Atmospheric pressures were controlled at 1013 (Earth-normal), 100, 50, 35, 25, or 15 mb, and temperatures were maintained at 30, 20, 15, 10, or 5 °C. Experiments were carried out for 48 h or 7 days under either Earth-normal O 2/N 2 or pure CO 2 atmospheres. Results indicated that low pressure, low temperature, and high CO 2 atmospheres, applied separately or in combination, were capable of inhibiting the growth and replication of B. pumilus SAFR-032, B. pumilus FO-36B, B. subtilis HA-101, B. subtilis 42HS-1, B. megaterium KL-197, B. licheniformis KL-196, and B. nealsonii FO-092 under simulated martian conditions. Endospores of all seven Bacillus spp. strains failed to germinate and grow at 25 mb at 30 °C. Although, vegetative cells of these strains exhibited a slightly greater ability to replicate at lower pressures than did endospores, vegetative cells of these species failed to grow at pressures below 25 mb. Interactive effects of these environmental parameters acted to generally increase the inhibitory nature of the low-pressure conditions on growth and replication of the seven Bacillus spp. tested.

Characterization of Substituted Polyphosphazene Membranes − Pure and Mixed Gas Results

Here, we report the transport properties of substituted polyphosphazenes membranes for separation and purification of CO2 for in-situ resource utilization (ISRU) processes. This paper includes pure and mixed gas permeation data of gases for the methoxy ethoxy ethanol (MEE)-substituted polyphosphazenes. Significant differences in transport properties of gases have been observed for the cross-linked and un-cross-linked polymer membranes. The CO2/N2 ideal separation factors for the un-cross-linked and cross-linked membrane for 74% MEE polyphosphazene were 16 and 43 at 22 °C, respectively. An effort has been made to relate these differences to polymer structure through apparent energy of activation calculations and observed glass transition temperatures. The CO2 permeability for the cross-linked 74% MEE polyphosphazene membrane decreased from 71 to 20 barrrers with an increase in the CO2/N2 ideal separation factor from 43 to 110 as the membrane temperature is reduced from 22 to −20 °C. Also, experiments were performed under simulated Martian atmospheric conditions for the 48% MEE polyphosphazene at 80 and 800 mbar feed pressure. The permeability of all gases is independent of the feed pressure in the range 1500−3000 mbar for the 74% MEE polyphosphazene and at low pressures (80−800 mbar) for 48% MEE polyphosphazene. The variations in permeability of gases with temperature for both the 74% and the 48% MEE polyphosphazenes are also reported in this article.

An integrated laser anemometer and dust accumulator for studying wind-induced dust transport on Mars

Windborne dust is one of the most important and dynamic factors affecting the Martian surface and its atmosphere, yet there lacks a detailed physical understanding how it is transported. We present a miniature laser-based optoelectronic instrument for use on a Mars lander. It integrates sensors capable of quantifying important parameters needed for the understanding and modeling of dust transport on Mars, these include wind speed, wind direction, suspended dust concentration, dust deposition and removal rates as well as the electrification of the Martian dust. Dust electrification has been seen from experimental simulations to be of considerable importance to the processes of adhesion and cohesion, specifically prompting the formation of low mass density dust aggregates. Testing of this prototype instrument has been performed under simulated Martian conditions in a wind tunnel facility. The results and analysis of its functionality will be presented.

Survival and Germinability ofBacillus subtilisSpores Exposed to Simulated Mars Solar Radiation: Implications for Life Detection and Planetary Protection

Bacterial spores have been considered as microbial life that could survive interplanetary transport by natural impact processes or human spaceflight activity. Deposition of terrestrial microbes or their biosignature molecules onto the surface of Mars could negatively impact life detection experiments and planetary protection measures. Simulated Mars solar radiation, particularly the ultraviolet component, has been shown to reduce spore viability, but its effect on spore germination and resulting production of biosignature molecules has not been explored. We examined the survival and germinability of Bacillus subtilis spores exposed to simulated martian conditions that include solar radiation. Spores of B. subtilis that contain luciferase resulting from expression of an sspB-luxAB gene fusion were deposited on aluminum coupons to simulate deposition on spacecraft surfaces and exposed to simulated Mars atmosphere and solar radiation. The equivalent of 42 min of simulated Mars solar radiation exposure reduced spore viability by nearly 3 logs, while germination-induced bioluminescence, a measure of germination metabolism, was reduced by less than 1 log. The data indicate that spores can retain the potential to initiate germination-associated metabolic processes and produce biological signature molecules after being rendered nonviable by exposure to Mars solar radiation.

On laboratory simulation and the temperature dependence of the evaporation rate of brine on Mars

We have determined the evaporation rate of brine under simulated martian conditions at temperatures from 0°C to −26.0°C as part of our efforts to better understand the stability of water on Mars. Correcting for the effect of water build‐up in the atmosphere and the lower gravity on Mars relative to Earth we observed a factor of almost 30 decrease in evaporation, from 0.88 mm/h at ∼0°C to 0.04 mm/h at −25.0°C. The results are in excellent agreement with the predictions of Ingersoll's (1970) theoretical treatment, lending support to the theory and our procedures. Thus brine formation will increase the stability of water on Mars not only by extending the liquid temperature range, but also by considerably decreasing the evaporation rate.

Activity and stability of a complex bacterial soil community under simulated Martian conditions

A simulation experiment with a complex bacterial soil community in a Mars simulation chamber was performed to determine the effect of Martian conditions on community activity, stability and survival. At three different depths in the soil core short-term effects of Martian conditions with and without ultraviolet (UV) exposure corresponding to 8 Martian Sol were compared. Community metabolic activities and functional diversity, measured as glucose respiration and versatility in substrate utilization, respectively, decreased after UV exposure, whereas they remained unaffected by Martian conditions without UV exposure. In contrast, the numbers of culturable bacteria and the genetic diversity were unaffected by the simulated Martian conditions both with and without UV exposure. The genetic diversity of the soil community and of the colonies grown on agar plates were evaluated by denaturant gradient gel electrophoresis (DGGE) on DNA extracts. Desiccation of the soil prior to experimentation affected the functional diversity by decreasing the versatility in substrate utilization. The natural dominance of endospores and Gram-positive bacteria in the investigated Mars-analogue soil may explain the limited effect of the Mars incubations on the survival and community structure. Our results suggest that UV radiation and desiccation are major selecting factors on bacterial functional diversity in terrestrial bacterial communities incubated under simulated Martian conditions. Furthermore, these results suggest that forward contamination of Mars is a matter of great concern in future space missions.

Bacillus subtilisSpore Survival and Expression of Germination-Induced Bioluminescence After Prolonged Incubation Under Simulated Mars Atmospheric Pressure and Composition: Implications for Planetary Protection and Lithopanspermia

Bacterial endospores in the genus Bacillus are considered good models for studying interplanetary transfer of microbes by natural or human processes. Although spore survival during transfer itself has been the subject of considerable study, the fate of spores in extraterrestrial environments has received less attention. In this report we subjected spores of a strain of Bacillus subtilis, containing luciferase resulting from expression of an sspB-luxAB gene fusion, to simulated martian atmospheric pressure (7-18 mbar) and composition (100% CO(2)) for up to 19 days in a Mars simulation chamber. We report here that survival was similar between spores exposed to Earth conditions and spores exposed up to 19 days to simulated martian conditions. However, germination-induced bioluminescence was lower in spores exposed to simulated martian atmosphere, which suggests sublethal impairment of some endogenous spore germination processes.