Assessing The Susceptibility Of Microalgae To Space Conditions Using Stratospheric Balloons

[Scientific Reports via Xmol] Biological exposure experiments under near-space conditions remain limited by the high cost and low accessibility of spaceflight platforms, motivating low-cost analog approaches for initial screening.

Stratospheric balloon flights offer a practical route to near-space exposure experiments relevant to space biology and astrobiology. Here we report an exploratory assessment of four green microalgae (Chlamydomonas reinhardtii, Chlorella vulgaris, Scenedesmus obliquus, and Parachlorella kessleri) flown in a custom-built ~ 2 kg payload equipped with heating, LED illumination, UV sensing, and GPS.

Thirty-six microalgal samples (4 mL each) were flown during a ~ 2.5 h stratospheric mission, including ~ 30–60 min at 25–35 km altitude, within a total mission cost of < $4000. In total, 54 microalgal cuvettes were flown in two stratospheric missions to evaluate post-flight integrity, and recovered samples were recultivated under standardized conditions and analyzed two weeks post-flight for pigment composition and antioxidant-related parameters.

After flight, 29/54 samples (53.7%) were classified as visually undamaged after landing, while damage was associated with freezing (13/54; 24.1%), thermal damage (13/54; 24.1%, partly overlapping), loss due to containment failure (5/54; 9.3%), or non-recoverable material (3/54; 5.6%).

In recultivated biomass, Near-space-exposed cultures showed significant shifts in pigment profiles (reduced chlorophyll a and/or b in multiple species) and increased total antioxidant capacity, indicating persistent physiological differences following the mission workflow.

These results provide quantitative benchmarks for microalgal near-space exposure using a low-cost balloon platform and motivate follow-up studies with higher replication and direct functional stress readouts.

General Condition of Chlamydomonas reinhardtii Samples After Landing. This supplement presents visual documentation of each Chlamydomonas reinhardtii sample following landing. The images capture the overall condition, including pigmentation, density, and potential signs of stress, providing a comparative overview of sample responses after exposure and transport. – -Scientific Reports