Extended survival of several organisms and amino acids under simulated martian surface conditions

Abstract

1Recent orbital and landed missions have provided substantial evidence for 2 ancient liquid water on the Martian surface as well as evidence of more recent 3 sedimentary deposits formed by water and/or ice. These observations raise 4 serious questions regarding an independent origin and evolution of life on Mars. 5Future missions seek to identify signs of extinct Martian biota in the form of 6 biomarkers or morphological characteristics, but the inherent danger of space 7 craft-borne terrestrial life makes the possibility of forward contamination a 8 serious threat not only to the life detection experiments, but also to any extant 9Martian ecosystem. A variety of cold and desiccation-tolerant organisms were 10 exposed to 40 days of simulated Martian surface conditions while embedded 11 within several centimeters of regolith simulant in order to ascertain the 12 plausibility of such organisms' survival as a function of environmental parameters 13 and burial depth. Relevant amino acid biomarkers associated with terrestrial life 14 were also analyzed in order to understand the feasibility of detecting biomarker 15 evidence for previous biological activity. Results indicate that stresses due to 16 desiccation, oxidation, and UV-associated damage were the primary deterrent to 17 organism survival, and that the effect of diurnal temperature variations and 18 reactive atmospheric species were minimal. Organisms with resistance to 19 desiccation and radiation environments showed increased levels of survival after 20the experiment compared to organisms characterized as psychrotolerant. Amino 21 2 acid biomarker analyses indicated the presence of an oxidation mechanism that 22 migrated downward through the samples during the course of the experiment and 23 likely represents the formation of various oxidizing species at mineral surfaces as 24 water vapor diffused through the regolith. Current sterilization protocols may 25 specifically select for organisms best adapted to survival at the Martian surface, 26 namely species that show tolerance to radical-induced oxidative damage and low 27 water activity environments. Additionally, any hypothetical Martian ecosystems 28 may have evolved similar physiological traits that allow sporadic metabolism 29 during periods of increased water activity. 30

Life at the Wedge: the Activity and Diversity of Arctic Ice Wedge Microbial Communities

“…are known to be hardy, cosmopolitan organisms capable of surviving long periods of high stress such as starvation, exposure to radiation, and temperature shifts, and are well adapted for living in the extreme conditions of ice wedges and other cryoenvironments (Nelson and Parkinson, 1978;Mongodin et al, 2006). Arthrobacter psychrolactophilus, a psychrotolerant organism, demonstrated an impressive hardiness when exposed to Mars-like conditions; from a starting population of 10 9 cells$g -1 , a population of 10 5 cells$g -1 survived 30 days of fluctuating diurnal temperature ( -40°C to 24°C), low pressure (13.3 mbar), and high background UV radiation ( Johnson et al, 2011). Bacterial diversity estimates based on 16S rRNA gene libraries placed the Axel Heiberg ice wedge community (H': 4.10) at a similar level of diversity as Axel Heiberg permafrost (H': 4.00) (Wilhelm et al, 2011) and an Arctic ice shelf microbial mat (H': 4.41) (Bottos et al, 2008).…”

Applicability of cryoconite consortia of microorganisms and glacier-dwelling animals in astrobiological studies

“…Takeuchi et al 2001;Vonnahme et al 2015;Gokul et al 2016). So far, astrobiological studies have been conducted on a single strains of prokaryotes or microinvertebrates (e.g., Johnson et al 2011) but never on a consortium of microorganisms like cryoconite granules. Only ca.…”

The persistence of a chlorophyll spectral biosignature from Martian evaporite and spring analogues under Mars-like conditions

“…It is unlikely that there is near-surface extant life presently on Mars due to high levels of ultraviolet (UV) irradiation, low temperatures and pressures, as well as oxidative and desiccating conditions (Kminek & Bada 2006;Dartnell et al 2007;Johnson et al 2011;Gómez et al 2012), however, in its history it may have possessed more habitable conditions (Farmer & Des Marais 1999;Cockell et al 2000;Summons et al 2011). The Noachian era of Mars' history was warmer and wetter than present day, as evidenced by accumulations of phyllosilicates, carbonates and sulphates (Squyres et al 2004(Squyres et al , 2012Gendrin et al 2005;Mustard et al 2008;Murchie et al 2009;Rice et al 2010;Elhmann & Mustard 2012), implying the past presence of water, which is essential to carbon-based life as it is currently understood.…”

“…While in its past, Mars is believed to have had warm and wet surface conditions, at least intermittently, with the potential to harbour life (Mustard et al 2008;Squyres et al 2012), the present surface is hostile to life as we know it Johnson et al 2011). The search for evidence of past life on Mars requires the identification of regions of past habitable conditions as well as biomarkers that can withstand the harsh present Martian surface conditions (Summons et al 2011).…”