Searching for Life in the Skies: Our Preliminary Findings from the BEXUS 30 Stardust Mission
The beautiful coastal city of Biarritz, France, with its endless ocean views, felt like the edge of one world while we were there to discuss another—the stratosphere. It was at the 25th ESA Symposium in May 2022 that our team had the privilege to present the preliminary findings from our Stardust experiment, which flew on the BEXUS 30 balloon.
Our primary goal with the Stardust project was to investigate the stratospheric microbiome. We wanted to move beyond just detecting microbial DNA and attempt to capture and cultivate living organisms from this extreme environment. To do this, we combined classical microbiology with modern techniques, hoping to better understand how life can survive the low temperatures, low pressure, and intense radiation found miles above our heads.
The launch from the Esrange Space Center in Sweden on September 30th, 2021, was the culmination of years of work. Our payload, the “flightbox,” contained a sophisticated sampling system with six filters—three for sampling and three for control, to ensure our results weren’t due to contamination from the ground. At an altitude of 15 km, our valves opened, and for 244 minutes, pumps drew stratospheric air through our filters, capturing any microorganisms present.
One of our biggest challenges was preventing contamination. We followed strict sterilization procedures for every component, from the silicone tubes to the valves, using autoclaves and filtered isopropanol. We even ran an identical “groundbox” experiment at the launch pad to compare the stratospheric biome to the one in the lower troposphere.
The results were fascinating. As expected, the stratosphere is sparse in microorganisms compared to the air we breathe. From the stratospheric samples, we managed to cultivate eight colonies—seven bacterial strains and one mold. A key finding was that all the bacteria we found were Gram-positive. Their thick cell walls likely provide the necessary protection against the harsh stratospheric conditions. This contrasts with the mix of Gram-positive and Gram-negative bacteria we found in our ground samples.
The microorganisms from the stratosphere also took much longer to grow in the lab, suggesting they are well-adapted to their extreme home and need time to readjust to more benign conditions. Using MALDI-TOF mass spectrometry, we were able to identify some of the species, such as Microbacterium oleivorans and Bacillus licheniformis, but others remained unspecified, hinting that we may have found new strains or even species.
Sharing these preliminary results in Biarritz was an incredible experience. The discussions with experts and peers were invaluable and reinforced that despite the challenges, we are on the right track. Our work shows that it is possible to conduct clean microbiological research in the stratosphere and that this environment holds a diverse and resilient population of microorganisms waiting to be discovered.