Protective Effects of Halite to Vacuum and Vacuum-Ultraviolet Radiation: A Potential Scenario During a Young Sun Superflare

ABREVAYA, XIMENA C.; GALANTE, DOUGLAS; TRIBELLI, PAULA M.; OPPEZZO, OSCAR J.; NÓBREGA, FELIPE; ARAUJO, GABRIEL G.; RODRIGUES, FABIO; ODERT, PETRA; LEITZINGER, MARTIN; RICARDI, MARTINIANO M.; VARELA, MARIA EUGENIA; GALLO, TAMIRES; SANZ-FORCADA, JORGE; RIBAS, IGNASI; PORTO DE MELLO, GUSTAVO F.; RODLER, FLORIAN; CERINI, MARIA FERNANDA; HANSLMEIER, ARNOLD; HORVATH, JORGE E.

ASTROBIOLOGY

MARY ANN LIEBERT INC

Lugar: New York; Año: 2022

1531-1074

Halite (NaCl mineral) has exhibited the potential to preserve microorganisms for millions of years on Earth.This mineral was also identified on Mars and in meteorites. In this study, we investigated the potential of halitecrystals to protect microbial life-forms on the surface of an airless body (e.g., meteorite), for instance, during alithopanspermia process (interplanetary travel step) in the early Solar System. To investigate the effect of theradiation of the young Sun on microorganisms, we performed extensive simulation experiments by employing asynchrotron facility. We focused on two exposure conditions: vacuum (low Earth orbit, 10-4 Pa) and vacuum-ultraviolet (VUV) radiation (range 57.6–124 nm, flux 7.14 W/m2), with the latter representing an extremescenario with high VUV fluxes comparable to the amount of radiation of a stellar superflare from the youngSun. The stellar VUV parameters were estimated by using the very well-studied solar analog of the young Sun,k1 Cet. To evaluate the protective effects of halite, we entrapped a halophilic archaeon (Haloferax volcanii) anda non-halophilic bacterium (Deinococcus radiodurans) in laboratory-grown halite. Control groups were cells entrapped in salt crystals (mixtures of different salts and NaCl) and non-trapped (naked) cells, respectively. Allgroups were exposed either to vacuum alone or to vacuum plus VUV. Our results demonstrate that halite canserve as protection against vacuum and VUV radiation, regardless of the type of microorganism. In addition, wefound that the protection is higher than provided by crystals obtained from mixtures of salts. This extends theprotective effects of halite documented in previous studies and reinforces the possibility to consider the crystalsof this mineral as potential preservation structures in airless bodies or as vehicles for the interplanetary transferof microorganisms.