Abstract

The Earth possesses many environmental extremes that mimic conditions on extraterrestrial worlds. Earth’s stratospheric conditions at 30–40 km altitude are very similar to the surface of Mars: with same pressure, average temperature, and even same levels of solar UV and proton radiation, and Galactic cosmic rays. Microbial (bacteria and fungi) habitation in troposphere is known and well documented, however, very little is known about the true upper limit, or extent, of the Earth’s biosphere. Stratosphere provides a good opportunity to study the existence, or the survival, of life in these conditions. Despite the importance of this topic to astrobiology, stratospheric microbial diversity/survival remains largely unexplored, probably due to significant difficulties in the access and in ensuring the absence of contamination. To conduct a detailed study into this, we have designed the balloon-borne payload system SAMPLE (Stratospheric Altitude Microbiology Probe for Life Existence) to collect dust samples from stratosphere and bring them in to a suitable environment, where further study will be conducted in establishing the possibility of microbial life in the upper atmosphere. The entire design was created in-house and is entirely novel, with modifications made to the materials chosen for weight reduction and stress reduction of all kinds. The main payload consists of three pre-sterilized sampling trays, and a controller which will determine the altitude of the payload system to actively monitor the opening and closing of the collection trays. For additional contamination control, one of sampling trays will fly but not open, and one will remain closed on the ground in the cleanroom. Other on-board devices include environmental sensors, GPS tracking devices, cameras, and an FTU (Flight Termination Unit) to terminate the flight after the payload has reached the desired altitude and on completion of the sample collection. A parachute attached to the payload ensures safe descent of the payload on its way back to the surface. On retrieving the payload, the sampling trays (including controls) will be sent to a suitable laboratory where the samples will be examined for the nature of collected material.

Keywords

high-altitude balloons, stratosphere, astrobiology, biota