Soil carbon distribution and site characteristics in hyper-arid soils of the Atacama Desert: A site with Mars-like soils

The soil carbon content and its relation to site characteristics are important in evaluating current local, regional, and global soil C storage and projecting future variations in response to climate change. In this study we analyzed the concentration of organic and inorganic carbon and their relationship with in situ climatic and geological characteristics in 485 samples of surface soil and 17 pits from the hyper-arid area and 51 samples with 2 pits from the arid–semiarid region from the Atacama Desert located in Peru and Chile. The soil organic carbon (SOC) in hyperarid soils ranged from 1.8 to 50.9 μg C per g of soil for the 0–0.1 m profile and from 1.8 to 125.2 μg C per g of soil for the 0–1 m profile. The analysis of climatic (temperature and precipitation), elevation, and some geologic characteristics (landforms) associated with hyper-arid soils explained partially the SOC variability. On the other hand, soil inorganic carbon (SIC) contents, in the form of carbonates, ranged from 200 to 1500 μg C per g of soil for the 0–0.1 m profile and from 200 to 3000 μg C per g of soil for the 0–1.0 m profile in the driest area. The largest accumulations of organic and inorganic carbon were found near to arid–semiarid areas. In addition, the elemental carbon concentrations show that the presence of other forms of inorganic carbon (e.g. graphite, etc.) was negligible in these hyperarid soils. Overall, the top 1 m soil layer of hyperarid lands contains ∼11.6 Tg of organic carbon and 344.6 Tg of carbonate carbon. The total stored carbon was 30.8-fold the organic carbon alone. To our knowledge, this is the first study evaluating the total budget carbon on the surface and shallow subsurface on ∼160,000 km² of hyperarid soils.     

Seasonal patterns of condensation and sublimation cycles in the cryptic and non-cryptic regions of the South Pole

The South Pole of Mars is characterized by an asymmetric residual ice cap composed of water ice and CO₂ ice. On the opposite side of the residual cap, there exists an area called cryptic region which is relatively free of ice during summer time. Many fan-shaped km-scale structures apparently caused by a wind-blown system of dust-laden gas jets occurred dozens degrees of Ls before the complete sublimation of the CO₂ frost layer. We have examined the seasonal cycles of condensation and sublimation in the cryptic and non-cryptic regions by using the topographic data from the MOLA/MGS measurements. Using the MOLA topography data collected over one Martian year (1999–2001), we have studied the temporal elevation change and the seasonal cycle of the carbon dioxide frost on the southern polar caps. We have produced mapping of the seasonal CO₂ frost thickness variation for seven Ls (30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270° and 330°). It is found that the time variations of the CO₂ frost thickness in these two regions are quite similar. The greatest thickness of the CO₂ frost layer is about 0.76–0.78 m in both places occurs at Ls = 150°.     

Cowpeas and pinto beans: Performance and yields of candidate space crops in the laboratory biosphere closed ecological system

An experiment utilizing cowpeas (Vigna unguiculata L.), pinto beans (Phaseolus vulgaris L.) and Apogee ultra-dwarf wheat (Triticum sativa L.) was conducted in the soil-based closed ecological facility, Laboratory Biosphere, from February to May 2005. The lighting regime was 13 h light/11 h dark at a light intensity of 960 μmol m⁻² s⁻¹, 45 mol m⁻² day⁻¹ supplied by high-pressure sodium lamps. The pinto beans and cowpeas were grown at two different planting densities. Pinto bean production was 341.5 g dry seed m⁻² (5.42 g m⁻² day⁻¹) and 579.5 dry seed m⁻² (9.20 g m⁻² day⁻¹) at planted densities of 32.5 plants m⁻² and 37.5 plants m⁻², respectively. Cowpea yielded 187.9 g dry seed m⁻² (2.21 g m⁻² day⁻¹) and 348.8 dry seed m⁻² (4.10 g m⁻² day⁻¹) at planted densities of 20.8 plants m⁻² and 27.7 plants m⁻², respectively. The crop was grown at elevated atmospheric carbon dioxide levels, with levels ranging from 300–3000 ppm daily during the majority of the crop cycle. During early stages (first 10 days) of the crop, CO₂ was allowed to rise to 7860 ppm while soil respiration dominated, and then was brought down by plant photosynthesis. CO₂ was injected 27 times during days 29–71 to replenish CO₂ used by the crop during photosynthesis. Temperature regime was 24–28 °C day/deg 20–24 °C night. Pinto bean matured and was harvested 20 days earlier than is typical for this variety, while the cowpea, which had trouble establishing, took 25 days more for harvest than typical for this variety. Productivity and atmospheric dynamic results of these studies contribute toward the design of an envisioned ground-based test bed prototype Mars base.     

Probing the method of correcting Faraday rotation in vector magnetograms

By analyzing the vector magnetograms of Huairou Solar Observing Station (HSOS) taken at the line center (0.0 Å) and the line wing (−0.12 Å) of FeI λ5324.19 Å, we make an estimate of the measured errors in transversal azimuths (δ?) caused by Faraday rotation. Since many factors, such as the magnetic saturation and scattered light, can affect the measurement accuracy of the longitudinal magnetic field in the umbrae of sunspots, we limit our study in the region ∣B_z∣ < 800 G. The main mean azimuth rotations are about 4°, 6°, 7° and 9°, while ∣B_z∣ are in the ranges of 400–500 G, 500–600 G, 600–700 G and 700–800 G, respectively. Moreover, we find there is also an azimuth rotation of about 8° at the wavelength offset −0.12 Å of the line compared against a previous numerical simulation.     

Carbon dioxide dynamics of combined crops of wheat,cowpea, pinto beans in the Laboratory Biosphere closed ecological system

A mixed crop consisting of cowpeas, pinto beans and Apogee ultra-dwarf wheat was grown in the Laboratory Biosphere, a 40 m³ closed life system equipped with 12,000 W of high pressure sodium lamps over planting beds with 5.37 m² of soil. Similar to earlier reported experiments, the concentration of carbon dioxide initially increased to 7860 ppm at 10 days after planting due to soil respiration plus CO₂ contributed from researchers breathing while in the chamber for brief periods before plant growth became substantial. Carbon dioxide concentrations then fell rapidly as plant growth increased up to 29 days after planting and subsequently was maintained mostly in the range of about 200–3000 ppm (with a few excursions) by CO₂ injections to feed plant growth. Numerous analyses of rate of change of CO₂ concentration at many different concentrations and at many different days after planting reveal a strong dependence of fixation rates on CO₂ concentration. In the middle period of growth (days 31–61), fixation rates doubled for CO₂ at 450 ppm compared to 270 ppm, doubled again at 1000 ppm and increased a further 50% at 2000 ppm. High productivity from these crops and the increase of fixation rates with elevated CO₂ concentration supports the concept that enhanced CO₂ can be a useful strategy for remote life support systems. The data suggests avenues of investigation to understand the response of plant communities to increasing CO₂ concentrations in the Earth’s atmosphere. Carbon balance accounting and evapotranspiration rates are included.     

Predicting the effects of gas diffusivity on photosynthesis and transpiration of plants grown under hypobaria

As part of a Bio-regenerative Life Support System (BLSS) for long-term space missions, plants will likely be grown at reduced pressure. This low pressure will minimize structural requirements for growth chambers on missions to the Moon or Mars. However, at reduced pressures the diffusivity of gases increases. This will affect the rates at which CO₂ is assimilated and water is transpired through stomata. To understand quantitatively the possible effects of reduced pressure on plant growth, CO₂ and H₂O transport were calculated for atmospheres of various total pressures (101, 66, 33, 22, 11 kPa) and CO₂ concentrations (0.04, 0.1 and 0.18 kPa). The diffusivity of a gas is inversely proportional to total pressure and shows dramatic increases at pressures below 33 kPa (1/3 atm). A mathematical relationship based on the principle of thermodynamics was applied to low pressure conditions and can be used for calculating the transpiration and photosynthesis of plants grown in hypobaria. At 33 kPa total pressure, the stomatal conductance increases by a factor of three with the boundary layer conductance increasing by a factor of ∼1.7, since the leaf conductance is a function of both stomatal and the boundary layer conductance, the overall conductance will increase resulting in significantly higher levels of transpiration as the pressure drops. The conductance of gases is also regulated by stomatal aperture in an inverse relationship. The higher CO₂ concentration inside the leaf air space during low pressure treatments may result in higher CO₂ assimilation and partial stomata closure, resulting in a decrease in transpiration rate. The results of this analysis offer guidelines for experiments in pressure and high CO₂ environments to establish ideal conditions for minimizing transpiration and maximizing the plant biomass yield in BLSS.     

Study of complex dielectric properties of lunar simulants and comparison with Apollo samples at microwave frequencies

Laboratory characterization of dielectric properties of terrestrial analogues of lunar soil (JSC-1A) and comparison with lunar samples returned from various Apollo missions is made at different as well as normalized bulk density. Here measurements of dielectric constants and losses were made at four microwave frequencies such as 1.7 GHz, 2.5 GHz, 6.6 GHz and 31.6 GHz. Complex permittivity of lunar simulant was measured at temperature ranging from −190 °C to + 200 °C using Wave-Guide cell method. Comparison of permittivity of JSC-1A with Apollo sample also has been done at similar microwave frequencies. The investigations reveal that dielectric constant and loss factor of terrestrial analogues of lunar soil are temperature dependent. As temperature is gradually increased both these parameter (storage factor and loss factor) also gradually increases. These temperatures were chosen because the Moon undergoes at that extremes level of temperature. It is scorching heat at 110 °C during the day and freezing cold at −180 °C during night. The measured value of ε can be useful for designing passive as well as active sensors.     

Status of the GAMMA-400 project

The preliminary design of the new space gamma-ray telescope GAMMA-400 for the energy range 100 MeV–3 TeV is presented. The angular resolution of the instrument, 1–2° at E_γ ∼ 100 MeV and ∼0.01° at E_γ > 100 GeV, its energy resolution ∼1% at E_γ > 100 GeV, and the proton rejection factor ∼10⁶ are optimized to address a broad range of science topics, such as search for signatures of dark matter, studies of Galactic and extragalactic gamma-ray sources, Galactic and extragalactic diffuse emission, gamma-ray bursts, as well as high-precision measurements of spectra of cosmic-ray electrons, positrons, and nuclei.     

An evaluation of the IRI-2007 storm time model at low latitude stations

This paper discusses the ability of the International Reference Ionosphere IRI-2007 storm time model to predict foF2 ionospheric parameter during geomagnetic storm periods. Experimental data (based on availability) from two low latitude stations: Vanimo (geographic coordinates, 2.7 °S, 141.3 °E, magnetic coordinates, 12.3 °S, 212.50 °E) and Darwin (geographic coordinates, 12.45 °S, 130.95 °E, magnetic coordinates, 22.9 °S, 202.7 °E) during nine storms that occurred in 2000 (Rz₁₂ = 119), 2001(Rz₁₂ = 111) and 2003 (Rz₁₂ = 64) are compared with those obtained by the IRI-2007 storm model. The results obtained show that the percentage deviation between the experimental and IRI predicted foF2 values during these storm periods is as high as 100% during the main and recovery phases. Based on the values of “relative deviation module mean” (RDMM) obtained (i.e. between 0.08 and 0.60), it is observed that there is a reasonable to poor agreement between measured foF2 values and the IRI-storm model prediction values during main and recovery phases of the storms under investigation. As a result, in addition to other studies that have been carried out from different sectors, more studies are required to be carried out. This will enable IRI community to improve on the present performance of the model. In general the IRI-storm model predictions follow normal trend of the foF2 measured values but does not reproduce well the measured values.     

Solar cycle and latitude dependence of high-beta suprathermal plasma conditions in interplanetary space between 1.3 and 5.4 AU

The analysis of energetic particles and magnetic field measurements from the Ulysses spacecraft has shown that in a series of events, the energy density contained in the suprathermal tail particle distribution is comparable to or larger than that of the magnetic field, creating conditions of high-beta plasma. In this work we analyze periods of high-beta suprathermal plasma occurrences (β_ep > 1) in interplanetary space, using the ratio (β_ep) of the energetic particle (20 keV to ∼5 MeV) and magnetic field energy densities from measurements covering the entire Ulysses mission lifetime (1990–2009) in order to reveal new or to reconfirm some recently defined interesting characteristics. The main key-results of the work are summarized as follows: (i) we verify that high-beta events are detected within well identified regions corresponding mainly to the vicinity of shock surfaces and magnetic structures, and associated with energetic particle intensity enhancements due to (a) reacceleration at shock-fronts and (b) unusually large magnetic field depressions. (ii) We define three considerable features for the high-beta events, concentrated on the next points: (a) there is an appreciable solar-activity influence on the high-beta events, during the maximum and middle solar-cycle phase, (b) the annual peak magnitude and the number of occurrences of high events are well correlated with the sunspot number, (c) the high-beta suprathermal plasma events present a spatial distribution in heliographic latitudes (HL) up to ∼±80°, and a specific important concentration on the low (−25° ? HL < −6°, 6° < HL ? 25°) and median (−45° ? HL < −25°, 25° < HL ? 45°) latitudes. We also reconfirm by a statistical analysis the results of Marhavilas and Sarris (2011), that the high-beta suprathermal plasma (β_ep > 1) events are characterized by a very large parameter β_ep (up to 1732.5), a great total duration (406 days) and a large percentage of the Ulysses-mission lifetime (which is equal to 6.34% of the total duration with usable measurements, and 11.3% of the duration in presence of suprathermal particles events).     

Comparing IRI and a regional model with ionosonde measurements in Pakistan

We have used the technique of expansion in Empirical Orthogonal Functions (EOFs) to develop regional models of the critical frequencies of E and F₂ layers (f_oE, f_oF₂), peak height (h_mF₂), and semi-thickness of F₂ layer (Y_mF₂) over Pakistan. In the present study levels of solar activity specified by Smoothed Sunspot Number (R) from 10 to 200 are taken into account. The magnetic dip angle for the model ranges from 30° to 60°. We have compared the regional model and the International Reference Ionosphere (IRI) with measurements of three ionosondes in Pakistan. The model parameters f_oE and f_oF₂ are found overall comparable to the observed hourly median values during daytime at Karachi (geographic latitude = 24.95°N, longitude = 67.13°E, magnetic inclination = 37°), Multan (30.18°N, 71.48°E, 45°) and Islamabad (33.75°N, 73.13°E, 51.5°) during the years 1988, 1996 and 2000. For h_mF₂ the computed values by regional and IRI model for the year 1995 are found close to each other. However, for Y_mF₂the results are better during daytime as compared to nighttime.     

Quantifying the relationship between the measurement precision and specifications of a UV/visible sensor on a geostationary satellite

To investigate the feasibility of new satellite observations, including air quality (AQ) observations from geostationary (GEO) orbit, it is essential to link the measurement precision (ε) with sensor specifications in advance. The present study attempts to formulate the linkage between ε and specifications of a UV/visible sensor (signal-to-noise ratio (SNR), full width at half maximum (FWHM) of the slit function, and sampling ratio (SR)) on a GEO satellite. A sophisticated radiative transfer model (JACOSPAR) is used to calculate synthetic radiance spectra that would be measured by a UV/visible sensor observing the atmosphere over Tokyo (35.7°N, 139.7°E) from GEO orbit at 120°E longitude. The spectra, modified according to given sensor specifications, are analyzed by the differential optical absorption spectroscopy technique to estimate the ε for slant column densities of O₃ and NO₂. We find clear relationships: for example, the ε of the O₃ slant column density (molecules cm⁻²) and SNR at 330 nm are linked by the equation log(ε) = −1.06 · log(SNR) + 20.71 in the UV region, and the ε of the NO₂ slant column density and SNR at 450 nm are linked by log(ε) = −0.98 · log(SNR) + 18.00, at a FWHM = 0.6 nm (for the Gaussian slit function) and SR = 4. The relationships are mostly independent of other specifications (e.g., horizontal and temporal resolutions), as they affect ε primarily through SNR, providing constraints in determining the optimal SNR (and alternatively FWHM and SR) for similar UV/visible sensors dedicated for AQ studies.     

Efficacy of oxygen-supplying capacity of Azolla in a controlled life support system

Azolla shows high growth and propagation rates, strong photosynthetic O₂-releasing ability and high nutritional value. It is suitable as a salad vegetable and can be cultured on a multi-layered wet bed. Hence, it possesses potential as a fresh vegetable, and to release O₂ and absorb CO₂ in a Controlled Ecological Life Support System in space. In this study, we investigated the O₂-providing characteristics of Azolla in a closed chamber under manned, controlled conditions to lay a foundation for use of Azolla as a biological component in ground simulation experiments for space applications. A closed test chamber, representing a Controlled Ecological Life Support System including an Azolla wet-culture device, was built to measure the changes in atmospheric O₂ and CO₂ concentrations inside the chamber in the presence of coexisting Azolla, fish and men. The amount of O₂ consumed by fish was 0.0805–0.0831 L kg⁻¹ h⁻¹ and the level of CO₂ emission was 0.0705–0.0736 L kg⁻¹ h⁻¹; O₂ consumption by the two trial volunteers was 19.71 L h⁻¹ and the volume of respiration-released CO₂ was 18.90 L h⁻¹. Under 7000–8000 Lx artificial light and Azolla wet-culture conditions, human and fish respiration and Azolla photosynthesis were complementary, thus the atmospheric O₂ and CO₂ concentrations inside chamber were maintained in equilibrium. The increase in atmospheric CO₂ concentration in the closed chamber enhanced the net photosynthesis efficiency of the Azolla colony. This study showed that Azolla has strong photosynthetic O₂-releasing ability, which equilibrates the O₂ and CO₂ concentrations inside the chamber in favor of human survival and verifies the potential of Azolla for space applications.     

Effects of different carbon dioxide and LED lighting levels on the anti-oxidative capabilities of Gynura bicolor DC

Gynura bicolor DC is not only an edible plant but also a kind of traditional Chinese herbal medicine. G. bicolor DC grown in controlled environmental chambers under 3 CO₂ concentrations [450 (ambient), 1500 (elevated), 8000 (super-elevated) μmol mol⁻¹] and 3 LED lighting conditions [white (WL), 85% red + 15% blue (RB15), 70% red + 30% blue (RB30) ] were investigated to reveal plausible antioxidant anabolic responses to CO₂ enrichment and LED light quality. Under ambient and elevated CO₂ levels, blue light increasing from 15% to 30% was conducive to the accumulation of anthocyanins and total flavonoids, and the antioxidant activity of extract was also increased, but plant biomass was decreased. These results demonstrated that the reinforcement of blue light could induce more antioxidant of secondary metabolites, but depress the effective growth of G. bicolor DC under ambient and elevated CO₂ levels. In addition, compared with the ambient and elevated CO₂ levels, the increased anthocyanins, total flavonoids contents and antioxidant enzyme activities of G. bicolor DC under super-elevated CO₂ level could serve as important components of antioxidative defense mechanism against CO₂ stress. Hence, G. bicolor DC might have higher tolerance to CO₂ stress.     

Quantifying the role of solar radiative forcing over the 20th century

The 20th century temperature anomaly record is reproduced using an energy balance model, with a diffusive deep ocean. The model takes into account all the standard radiative forcings, and in addition the possibility of a non-thermal solar component. The model is parameterized and then optimized to produce the most likely values for the climate parameters and radiative forcings which reproduce the 20th century global warming. We find that the best fit is obtained with a negligible net feedback. We also show that a non-thermal solar component is necessarily present, indicating that the total solar contribution to the 20th century global warming, of ΔT_solar = 0.27 ± 0.07 °C, is much larger than can be expected from variation in the total solar irradiance alone. However, we also find that the largest contribution to the 20th century warming comes from anthropogenic sources, with ΔT_man = 0.42 ± 0.11 °C.     

Physiologic and metabolic responses of wheat seedlings to elevated and super-elevated carbon dioxide

The metabolic consequence of suboptimal (400 μmol mol⁻¹ or ppm), near-optimal (1500 ppm) and supra-optimal (10,000 ppm) atmospheric carbon dioxide concentrations [CO₂] was investigated in an attempt to reveal plausible underlying mechanisms for the differential physiological and developmental responses to increasing [CO₂]. Both non-targeted and targeted metabolite profiling by GC–MS and LC–MS were employed to examine primary and secondary metabolites in wheat (Triticum aestivum, cv Yocoro rojo) continuously exposed to these [CO₂] levels for 14, 21 and 28 days. Metabolite profile was altered by both [CO₂] and physiological age. In general, plants grown under high [CO₂] exhibited a metabolite profile characteristic of older plants under ambient CO₂. Elevated [CO₂] resulted in higher levels of phosphorylated sugar intermediates, though no clear trend in the content of reducing sugars was observed. Transient starch content was enhanced by increasing [CO₂] to a much greater extent at 10,000 ppm CO₂ than at 1500 ppm CO₂. The percentage increase of starch content resulting from CO₂ enrichment declined as plants develope. In contrast, elevated [CO₂] promoted the accumulation of secondary metabolites (flavonoids) progressively to a greater extent as plants became mature. Elevated [CO₂] to 1500 ppm induced a higher initial growth rate, while super-elevated [CO₂] appeared to negate such initial growth promotion. However, after 4 weeks, there was no difference in vegetative growth between 1500 and 10,000 ppm CO₂-grown plants, both elevated CO₂ levels resulted in an overall 25% increase in biomass over the control plants. More interestingly, elevated atmospheric [CO₂] reduced evapotranspiration rate (ET), but further increase to the supra-optimal level resulted in increased ET (a reversed trend), i.e. ET at 1500 ppm < ET at 10,000 ppm < ET at 400 ppm. The differential effect of elevated and super-elevated CO₂ on plants was further reflected in the nitrogen dynamics. These results provide the potential metabolic basis for the differential productivity and stomatal function of plants grown under elevated and super-elevated CO₂ levels.     

Variability of the ionosphere over Irkutsk at low solar activity

Statistical and spectral analyses are performed to investigate variations of two ionosphere F2 layer key parameters, the critical frequency (foF2) and the peak height (hmF2), that were measured over Irkutsk (52.5°N, 104.0°E) from December 2006 to January 2008 under solar minimum. The analyses showed that both parameters contain quasi-harmonic oscillations with periods of T_n = 24/n hours (n = 1–7), among which the diurnal (n = 1) and semidiurnal (n = 2) ones are the strongest. Seasonal variations are explored of mean and median values, spectrum, amplitude, and phase of the diurnal and semidiurnal components of foF2 and hmF2.     

Studies of electron and ion temperatures at 500 km altitude during sunrise using Indian SROSS C2 satellite

Solar dependence of electron and ion temperatures (T_e and T_i) in the ionosphere is studied using RPA data onboard SROSS C2 at an altitude of ∼500 km and 77°E longitude during early morning hours (04:00–07:00 LT) for three solar activities: solar minimum, moderate and maximum during winter, summer and equinox months in 10°S–20°N geomagnetic latitude. In winter the morning overshoot phenomenon is observed around 06:00 LT (T_e enhances to ∼4000 K) during low-solar activity and to T_e ∼ 3800 K, during higher solar activity. In summer, it is observed around 05:30 LT, but the rate of T_e enhancement is higher during moderate solar activity (∼2700 K/hr) than the low-solar activity (∼1700 K/hr). During equinox, this phenomenon is delayed and is observed around 06:00 LT (∼4200 K) during all three activities.     

Plants survive rapid decompression: Implications for bioregenerative life support

Radish (Raphanus sativus), lettuce (Latuca sativa), and wheat (Triticum aestivum) plants were grown at either 98 kPa (ambient) or 33 kPa atmospheric pressure with constant 21 kPa oxygen and 0.12 kPa carbon dioxide in atmospherically closed pressure chambers. All plants were grown rockwool using recirculating hydroponics with a complete nutrient solution. At 20 days after planting, chamber pressures were pumped down as rapidly as possible, reaching 5 kPa after about 5 min and ∼1.5 kPa after about 10 min. The plants were held at 1.5 kPa for 30 min and then pressures were restored to their original settings. Temperature (22 °C) and humidity (65% RH) controls were engaged throughout the depressurization, although temperatures dropped to near 16 °C for a brief period. CO₂ and O₂ were not detectable at the low pressure, suggesting that most of the 1.5 kPa atmosphere consisted of water vapor. Following re-pressurization, plants were grown for another 7 days at the original pressures and then harvested. The lettuce, radish, and wheat plants showed no visible effects from the rapid decompression, and there were no differences in fresh or dry mass when compared to control plants maintained continuously at 33 or 98 kPa. But radish storage root fresh mass and lettuce head fresh and dry masses were less at 33 kPa compared to 98 kPa for both the controls and decompression treatment. The results suggest that plants are extremely resilient to rapid decompression, provided they do not freeze (from evaporative cooling) or desiccate. The water of the hydroponic system was below the boiling pressure during these tests and this may have protected the plants by preventing pressures from dropping below 1.5 kPa and maintaining humidity near 1.5 kPa. Further testing is needed to determine how long plants can withstand such low pressure, but the results suggest there are at least 30 min to respond to catastrophic pressure losses in a plant production chamber that might be used for life support in space.