Astronomers explained the impossibility of life on desert planets

Planets with minimal surface water are practically unable to support life, scientists at the University of Washington have concluded. This was reported on April 15 on the news portal Phys.org .

"We were interested in arid planets with very limited reserves of surface water — significantly less than one terrestrial ocean. Many of them are located in the habitable zone of their star, but we weren't sure if they could really be habitable," explained the study's lead author, Haskel White-Janella, a doctoral student at the University of Washington.

According to the publication, an Earth—sized planet needs at least 20-50% of the water in the Earth's oceans to maintain the geological carbon cycle, a key natural mechanism for regulating surface temperature. It is this process, driven by water, that ensures the exchange of carbon between the atmosphere and the bowels of the planet for millions of years.

The mechanism works as follows: carbon dioxide coming from volcanoes accumulates in the atmosphere, then dissolves in rainwater and is washed out of rocks. Rivers transport carbon to the ocean, from where it sinks to the seabed and goes into the mantle in subduction zones. After millions of years, carbon returns to the surface during mountain formation.

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If there is not enough water for precipitation, this cycle is disrupted: volcanic carbon dioxide stops being absorbed and accumulates in the atmosphere. The greenhouse effect evaporates the remaining water, triggering uncontrolled warming, and the planet becomes uninhabitable.

Such a scenario, according to the researchers, could be realized on Venus. The planet is comparable to Earth in size and age, but today its surface is heated to several hundred degrees, and atmospheric pressure is 90 times higher than Earth's. The authors suggest that Venus could have originally formed with slightly less water than Earth, which destabilized the carbon cycle and eventually destroyed any possible life.

To search for extraterrestrial life, scientists tend to focus on planets in the so—called habitable zone, a range of orbits at which liquid water can exist on the surface. More than 6,000 exoplanets have been confirmed, but only a fraction of them are considered candidates for life. A new study suggests an additional selection criterion — the availability of sufficient water reserves to maintain the carbon cycle.

On March 30, an international group of astronomers using the James Webb Space Telescope (JWST) recorded a unique energy burst of GRB 250702B, the duration of which was hundreds of times longer than the known explosions.

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