TABLE 3.

Environmental conditions aboard balloon flight compared to martian conditions.

Parameters	Balloon Flight + Trex-Box (7–38 km alt.)	Mars (at equator)
UV fluence (280 – 400 nm)	∼6 mW cm–2a	∼5 mW/cm–2b
Temperature (min.)	–51°C	–73°C
Temperature (max.)	+21°C	+20°C
Sample exposure duration	5 h 19 min	–
Atmosphere composition	95% CO2	96% CO2
	1.9% Ar	1.9% Ar
	2.6% N2	1.9% N2
	0.17% O2	0.14% O2
	0.07% COc	0.07% COd
Atmospheric pressure	5–10 mbar	5–10 mbare
Total UV dose (est.)	∼1148 kJ m–2f	-

^aFluence rates for stratospheric UVA-UVB were measured in a previous balloon flight (Caro et al., 2019).

^bSchuerger et al., 2003.

^cMars gas in Trex-Box was ordered from Boggs Gases, Inc. (Titusville, FL, United States) as a commercial mixture of the top five gasses in the martian atmosphere (Schuerger et al., 2008).

^dMahaffy et al., 2013.

^eBarlow, 2008.^fTotal estimated UV dose that samples were exposed to during the balloon flight (see section “Estimated UV radiation dose”).