Venus: Evolution Through Time – Editorial

Why are the terrestrial planets so different from each other?Venus, our nearest neighbor, should be the most Earth-like of all our planetary siblings.Its size and presumed bulk composition are very similar to those of the Earth.Like Earth, the primordial atmosphere would have been H-dominated from the nebula.Then a secondary atmosphere would have outgassed, with expected large atmospheric abundances of carbon dioxide and water.The current state of Venus is the result of the cumulative effects of many processes from the planet's formation, and its magma ocean phase up to present-day.Venus's interior thermal evolution, volcanic, tectonic and outgassing history, as well as interaction with the atmosphere have left clues to piece back together what made Earth and Venus evolve differently.Therefore, due to its position at the inner edge of the Solar System habitable zone (HZ), Venus evolution through time provides insights on surface habitability of rocky exoplanets.How and why did things go differently for Venus?What lessons can we learn about the history of life and habitability on Earth-sized planets and terrestrial planets in general, whether in our solar system or elsewhere?Such questions are examples of the major gaps in our understanding of how and when Venus's evolutionary path diverged from Earth's.Now is a pivotal time in Venus exploration.A new fleet of Venus missions is being developed including the radar-equipped orbiters (ESA's EnVision and NASA's VERITAS missions) and an entry probe (NASA's DAVINCI).These missions will not only answer key questions about present day Venus, but also about Venus's long-term evolution and comparative planetary science.Their current definition phase is an ideal time to collate knowledge of Venus long-term evolution scenarios and the observations needed to discriminate between them.Future missions will greatly advance our knowledge of Venus.A broad range of research approaches including Earth-based observations, laboratory and modeling studies are needed to prepare to interpret future data.