Volume 10 (2022): Issue 1 (January 2022)

A study of like-charged, bimodal colloidal suspensions was conducted in microgravity aboard the International Space Station as part of NASA's Advanced Colloids Experiments-Heated-2 (ACE-H-2) experiments. Samples comprised of silsesquioxane microparticles (600 nm) and zirconia nanoparticles (5–15 nm) in 1.5 pH nitric acid were mixed and allowed to agglomerate over time while being imaged with NASA's Light Microscopy Module (LMM). The samples contained 1% of microparticles with varying concentrations of nanoparticles in 0.1%, 0.055%, and 0.01% by volume. Digital images were captured periodically by the LMM over 12 days. Image analysis, including cluster size and distribution, was performed in Python using the “Colloidspy” package. The study found that cluster size had increased over time in at least seven of nine samples, but two samples exhibited nonlinear growth rates, while others showed very slow growth with cluster sizes two orders of magnitude greater than the free microparticles. We hypothesize that all samples experienced nonlinear growth, but early transient effects after mixing were missed due to timing limitations in image acquisition. Transport limitations of clusters in these systems may have dominated agglomeration behavior in microgravity, despite the samples being thermodynamically unstable, but more study is required.

The reduction in growth and development of plants constantly exposed to different ranges of hypergravity (acceleration more than 1 g) is adequately documented. However, earlier studies did not reveal the threshold hypergravity value at which these effects were seen. The understanding of the threshold g-value is an important consideration while we plan hypergravity experiments as different plants can perceive and respond differently at the same g-value. The aim of the present work is to study the effect on growth and photosynthetic parameters as well as to assess the threshold values in wheat seedlings grown from hypergravity-exposed seeds. Healthy wheat seeds were immersed in distilled water for 24 hours and exposed to hypergravity values ranging from 200 g to 1,000 g for a short duration of 10 minutes and sown on 0.8% agar gel. All the measurements were done on the fifth day after sowing. Results obtained showed significant reduction in growth and photosynthetic parameters in seedlings raised from hypergravity-treated wheat seeds. Interestingly, the reduction was started at 400 g and was found to reach a maximum at 1,000 g. Probably this would be the first study reporting the threshold of high g forces for growth and photosynthetic parameters when seeds were exposed to hypergravity.

It is often a challenge to arouse much interest, motivation, and engagement in physical science courses among non-STEM majors. We attempt to address this difficulty and at the same time strive to achieve high levels of student learning by choosing a novel as the main text of the course. We created a context-rich course on astrobiology—the science of life in the universe—that uses Carl Sagan's Contact as the main text. We were able to teach the entire subject matter of a conventional course without omitting any topic. A typical class session included discussion of the science content of one chapter of Contact after students are assigned to read it and answer questions before the lecture. We assessed our approach with pretests and posttests that measure students’ knowledge of the key content areas, as well as students’ perceptions. We then calculate the students’ normalized gains, the effect size, and perform hypothesis testing. Our results show that this approach can result in substantial learning gains for students and at the same time improve students’ self-assessment and perceptions of science while not compromising the absolute learning gains.

Plant biology experiments in microgravity face many challenges, among which are the constraints of the growth platforms available on the International Space Station (ISS). Protocols for preservation and sample return to Earth often limit efficient dissection of seedlings for downstream tissue-specific analysis. The Advanced Plant Experiment (APEx)-07 spaceflight experiment required a large quantity of dissectible, well-preserved seedlings suitable for omics analysis. During preflight tests, protocols were developed for using an agar-polyethersulfone (PES) membrane platform for seedling growth that allowed for seedling germination and growth aboard the ISS and rapid freezing to provide intact seedlings for dissection and extraction of high-quality DNA, RNA, and protein. Each component of the growth setup was carefully examined: membrane color, hydration and growth substrate, capacity for delayed germination, growth duration, harvest approach, and preservation pipelines were all individually optimized. Sterilized Arabidopsis seeds were adhered to PES membrane with guar gum. Membranes were laid onto 0.8% agar containing 0.5x Murashige and Skoog (MS) in 10 cm square Petri dishes and held at 4 °C until the experiment was actuated by placing the Petri dishes at room temperature. Seedlings were grown vertically for 12 days. PES membranes were removed from the agar, placed in the Petri dish lid, wrapped in foil, and frozen at −80 °C. Seedlings were dissected into roots and shoots and provided high-quality DNA, RNA, and protein. The system is simple, potentially adaptable for seedlings of multiple species, scalable and cost effective, and offers added versatility to existing ISS plant growth capabilities.

Plant growth experiments on near-term lunar landers need to be relatively small, lightweight, and self-contained. Here, we report on the design of a ~1 liter volume (1U Cubesat size) hermetically sealed habitat suitable for plant growth experiments during the first 10 days of seedling development of Arabidopsis thaliana and Brassica nigra. Images from a single interior camera show germination and provide quantitative data on seedling height, leaf area, and circumnutations. After 10 days with illumination from LEDs, the photosynthetic area of Arabidopsis cotyledons per seedling reached 300 mm². Seedling height, inferred from the overhead camera using reference markers, reached was 15 ± 5 mm. Robust circumnutation in seedlings was observed. CO₂ increased as expected due to respiration in the seeds during germination reaching levels of 5000 ppm after 3 days before declining to 3000 ppm on day 10 due to photosynthetic uptake. No CO₂ was added to the sealed chamber during the experiments. These results show that fundamental studies of germination and initial growth can be conducted in a small volume (1 L) hermetically sealed unit with only an overhead camera and CO₂ sensor. Hardware based on this approach would be suitable for lunar experiments on robotic landers.