Science Direct via PubMed Archives

The lifespan of the biosphere is necessarily constrained between the onset of Earth’s habitability (the “habitability window,” constrained between ~4.5 and ~3.9 Ga) (147) and its end (the extinction of all life, constrained to ~1.0 ± 0.5 Gyr into the future) (40–42).

Atmospheres, Climate, Weather, Habitable Zones, Intelligence & Language, Origin & Evolution of Life, SETI & Technosignatures, Status Report

A Reassessment Of The “hard-steps” Model For The Evolution Of Intelligent Life

by Keith CowingOctober 29, 2025

According to the “hard-steps” model, the origin of humanity required “successful passage through a number of intermediate steps” (so-called “hard steps”) that were intrinsically improbable in the time available for […]

SEM image of M. barkeri cluster collected from a MAC unit following a 14-day incubation at 7–12 mbar. -- Science Direct via PubMed

Biosignatures & Paleobiology, Extremeophiles and Extreme Environments, Habitable Zones, Mars, Microbiology & Virology, Status Report

Hydrogenotrophic methanogenesis at 7–12 mbar by Methanosarcina barkeri Under Simulated Martian Atmospheric Conditions

by Keith CowingJanuary 27, 2025January 27, 2025

Mars, with its ancient history of long-lived habitable environments, continues to captivate researchers exploring the potential for extant life. This study investigates the biosignature potential of Martian methane by assessing […]