Ultraviolet light measurements (280–400 nm) acquired from stratospheric balloon flight to assess influence on bioaerosols

Abstract

Viable microorganisms collected from the Earth's upper atmosphere are mysterious considering the intensely biocidal ultraviolet (UV) light conditions dominating rarefied air. Historically, most investigations examining the relationship between bioaerosols and UV conditions in the upper atmosphere have relied upon model-generated data. To address the shortage of in situ UV measurements in the upper troposphere and lower/middle stratosphere, we flew a meteorological balloon equipped with a UV radiometer and other core environmental sensors. The balloon payload launched from Illinois, USA, on 6 October 2018 and acquired UVA (315-400 nm) +UVB (280-315 nm) measurements for ~2 hours up to 30.9 km. Above the atmospheric boundary layer, UVA+UVB values registered around 6 mW•cm -2 , results that were largely consistent with Tropospheric Ultraviolet-Visible (TUV) model predictions. Performed in a lowcost, reusable manner with commercially available instruments, we show that reliable UV flux data can be acquired with meteorological balloon payload systems. This short communication provides relevant UVA+UVB results for aerobiology and astrobiology studies evaluating the survivability of microorganisms in the upper atmosphere.

MARSBOx: Fungal and Bacterial Endurance From a Balloon-Flown Analog Mission in the Stratosphere

“…Above the concentration of atmospheric ozone, where large scientific balloon missions float, UV radiation levels nearly match those expected on the surface of equatorial Mars. For instance, Caro et al (2019) recently measured an average instantaneous UVA-UVB flux of ∼6 mW cm −2 on a meteorological balloon mission flown to the middle stratosphere; the total combined dose measured was 1.9 kJ. In comparison, ∼5 mW cm –2 was the reported value to be expected at the surface of Mars for UVA-UVB according to calculations from Schuerger et al (2003) .…”

“…where UV fluence [mW cm –2 ] values for UVA-UVB (280–400 nm) in the middle stratosphere were taken from a previous flight = 6 mW cm –2 ( Caro et al, 2019 ), and sample exposure time [in seconds] = 19140 s. Samples were exposed to an estimated total of 1148 kJ m –2 of UVA-UVB radiation. Previously modeled UVC (206–280 nm) values by Caro et al (2019) ranged from about 0.1–1 μW cm −2 for the altitude flown during the MARSBOx mission (∼38 km).…”

“…However, high above Earth’s surface in the stratosphere (∼15–50 km), another Mars analog environment exists, presenting a unique combination of environmental insults that more closely resemble conditions on the Red Planet. In the middle stratosphere during daytime hours, the following Mars-like factors are simultaneously present: intense, full spectrum ultraviolet (UV) radiation, high energy ionizing radiation (including secondary scattering), desiccation, hypoxia, and ultralow temperatures and pressures ( Clark and McCoy, 1965 ; Potemra and Zmuda, 1970 ; Vampola and Gorney, 1983 ; Keating et al, 1987 ; Clancy and Muhleman, 1993 ; Von Engeln et al, 1998 ; Seele and Hartogh, 1999 ; Shepherd, 2000 ; Lambert et al, 2007 ; Mertens et al, 2016 ; Caro et al, 2019 ). Taken together, these combined conditions cannot be found naturally anywhere on the surface of the Earth and would be challenging to easily reproduce in laboratory-based experiments.…”

“…Reaching the middle stratosphere is relatively achievable compared to suborbital and orbital spaceflight investigations. High-altitude scientific balloons have been used for more than eight decades to study the atmosphere and atmospheric phenomena ( Winckler et al, 1959 ; Winckler, 1960 ; Murcray et al, 1969 ; Mertens et al, 2016 ; Caro et al, 2019 ) and more recently for conducting biological exposure experiments ( Stevens, 1936 ; Simons, 1954 ; Sullivan and Smith, 1960 ; Rainwater and Smith, 2004 ; Beck-Winchatz and Bramble, 2014 ; Coleman and Mitchell, 2014 ; Smith et al, 2014 ; Khodadad et al, 2017 ; Smith and Sowa, 2017 ; Pulschen et al, 2018 ). In this study, we take advantage of a large scientific balloon mission to the middle stratosphere (∼38 km altitude) for exposing microorganisms and measuring their survival and metabolic responses while monitoring ionizing radiation levels and other pertinent environmental conditions.…”

The Cytoprotective Role of Antioxidants in Mammalian Cells Under Rapidly Varying UV Conditions During Stratospheric Balloon Campaign

“…Dynamic development of this technique enabled the advanced research in atmospheric science, aerobiology, and meteorology (Jones, 2014) to flourish, remaining a promising tool in astrobiology and space biology. Stratospheric balloon flights allow to mimic Mars-like conditions, which is why they have been used to analyse the effect of the exposure of the polyextremophilic species to the harsh environment of upper atmosphere (Smith, 2013; Smith et al, 2014; Caro et al, 2019). In the stratosphere, the temperature reaches −40°C, atmospheric pressure is at 1 kPa, which is roughly equivalent to the surface pressure on Mars (0.5–1 kPa), the relative humidity of air is lower than 1%, solar UV irradiance is ∼100 W/m 2 , and cosmic radiation is at the level of 0.1 mGy/day (Murgatroyd, 1970; Reitz, 1993; Smith and Sowa, 2017).…”