Venus could have started its life as a lush and water rich paradise but we would never be able to tell today.
Thick carbon dioxide atmospheres are often seen as proof that a planet was born hot and dry. New atmospheric modeling shows that three completely different histories can lead to the exact same environment seen on Venus. A planet could have been a habitable world that suffered a climate collapse, or it could have simply leaked gas from its volcanoes for eons. This means an exoplanet that looks like a dead rock today might have once harbored life, but all the evidence was erased by atmospheric recycling. Finding a Venus twin around another star tells us nothing about its past habitability without much deeper geological data.
Equifinality of Venus-like CO$_2$ Atmospheres
arXiv · 2604.25810
While Earth locks much of its carbon in its crust as carbonates, Venus retains a comparable carbon inventory almost entirely in its atmosphere as CO$_2$. On Earth, the geological carbon cycle that has produced this vast crustal carbonate inventory is regulated by biology, liquid water, and plate tectonics, which together have stabilised climate over geological timescales. Venus presently lacks all these processes. We test whether Venus's massive CO$_2$ atmosphere is diagnostic of a specific evol