By Andrew Grant
Deadly invisible jets of high-energy radiation may short-circuit life throughout the universe. A study reported in the Dec. 5 Physical Review Letters concludes that these gamma-ray bursts occur frequently enough in about 90 percent of galaxies to sterilize planets, including Earthlike worlds that would otherwise be ideal for life. Earth itself has been zapped, the study suggests, perhaps contributing to one or more of the planet’s mass extinctions.
Some scientists say the study doesn’t properly account for the resilience of life, particularly if that life is protected by an ocean or an ice shell. Nonetheless, the paper’s sobering conclusions may temper recent optimism about the prospects for extraterrestrial life, particularly regarding the discovery of Earth-sized planets orbiting other stars.