MARSBOX: FUNGAL SPORES SURVIVE MARS-LIKE CONDITIONS ABOARDSTRATOSPHERIC BALLOON FLIGHT
2021
The ability of terrestrial life to survive in the Martian environment is of particular interest
for both planetary protection measures and for future colonization endeavors. Many studies
have examined bacterial spore survival and decontamination, however, little is known about
fungal spore resistance properties. To understand the survival potential of fungal spores to
Mars conditions, Aspergillus niger spores were sent on a 6.5-hour balloon flight to Earth’s
stratosphere ( 38 km), where UV radiation and temperature conditions were similar to levels
typical for equatorial Mars. Spores were carried inside the TREX unit – a sealed aluminum
container filled with a Mars gas mixture – and flown aboard the MARSBOx balloon payload.
Two different spore concentrations were tested on the TREX, exposed as dried samples in small
quartz discs (20 µL). Discs were set in two different layers: a top layer exposed to direct UV
radiation [M(+)UV, in a total dose of 1500 J/m²], and a bottom layer that was shielded from
radiation [M(-)UV]. After the flight, fungal spore survival was determined by plating on agar
and determining colony forming units (CFU/ml). A germination rate was calculated based
on light microscopy analysis and revival metabolism assay was completed with resazurin dye.
Results show that A. niger spores can survive Mars-like conditions [M(+)UV] for the 6.5 htime period tested in the middle stratosphere with only a 2-log reduction and slight delays in
germination and revival metabolism compared to unflown lab controls. When shielded from
UV, but exposed to Mars
gas, pressure and temperature [M(-)UV] spore survival and germination were not affected.
This study provides valuable insights on whether fungal spores could survive on Mars, and
underscores the need for longer-duration exposure studies in Earth’s stratosphere to better
characterize microbial
resistance to space-related conditions.
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