Soru

The following passage is adapted from an essay on the history of astrobiology and subsurface ecology:

For decades, biology textbooks defined the biosphere as a thin, sunlit envelope clinging to Earth's surface, where photosynthesis fueled virtually all ecological chains. This surface-centric view began to fracture in the late twentieth century with the discovery of microbes living miles beneath the seafloor and deep within continental basalt. These subsurface organisms, collectively termed the 'deep biosphere,' operate in complete darkness under crushing pressures, drawing energy not from sunlight but from chemolithoautotrophy—the chemical weathering of rocks and radioactive decay. While initial discoveries were dismissed as surface contamination, subsequent sterile drilling initiatives confirmed that these deep-dwelling prokaryotes constitute a massive fraction of Earth's total biomass. However, the significance of the deep biosphere extends beyond mere numbers or exotic metabolic pathways. It challenges our understanding of the conditions necessary for life, suggesting that planetary habitability is not solely determined by stellar proximity or surface water. Instead, the interior of a planet, long considered inert, may serve as a primary incubator of life, rendering geothermal activity far more critical than solar radiation in astrobiological models. Consequently, the search for extraterrestrial life has shifted from a preoccupation with surface liquid water to the investigation of sub-surface heat and chemistry.

Which statement best summarizes the author's primary argument in the passage as a whole?