Table 4.

The Known Limits of Life on Earth

Factor	Extremophile	Earth environments	Limit	References
High temperature	Thermophile or hyperthermophile	Submarine hydrothermal vents, terrestrial hot springs, deep subterranean environments	121–122°C	1–3
Low temperature	Psychrophile	Ice, permafrost, Antarctic dry valleys	−20°C	4–5
High pressure	Barophile or piezophile	Subseafloor, deep subterranean environments such as the Mariana Trench	>1300 atm	6–8
High pH	Alkaliphile	Soda lakes	11.3–11.4	9–11
Low pH	Acidophile	Acid mine drainage, hot springs	−0.06	12–14
High salinity	Halophile	Brines, evaporite deposits	NaCl ∼5 M	15–17
Desiccation	Xerophile	Antarctic dry valleys, deserts	<10% relative humidity	18–20
Ionizing radiation	Radioresistant	High-radiation environments (from radioactive waste, nuclear reactors, cosmic rays, gamma rays, X-rays)	>6000 Gy	21–23
UV radiation	Radioresistant	High deserts, upper atmosphere	5000 J/m2	21, 24
Toxic element concentrations	—	Acid mine drainage, hot springs	Depends on element	25–26

¹Blochl et al., 1997; ²Bryer et al., 2000; ³Takai et al., 2008; ⁴Carpenter et al., 2000; ⁵Joyce et al., 2004; ⁶Horikoshi, 1998; ⁷Sharma et al., 2002; ⁸Margosch et al., 2006; ⁹Sturr et al., 1994; ¹⁰Jones et al., 1998; ¹¹Sorokin et al., 2001; ¹²Schleper et al., 1995; ¹³Johnson, 1998; ¹⁴Edwards et al., 2000; ¹⁵Antón et al., 2008; ¹⁶Oren, 2010; ¹⁷Bowers and Wiegel, 2011; ¹⁸Potts, 1994; ¹⁹Alpert, 2005; ²⁰García, 2011; ²¹Battista, 1997; ²²Ferreira et al., 1999; ²³DeVeaux et al., 2007; ²⁴Altiero et al., 2011; ²⁵Nies, 2000; ²⁶Robbins et al., 2000.