Was Venus the first habitable world of our solar system?. Issue 16 (29th August 2016) - Way, M. J.
Abstract: Present‐day Venus is an inhospitable place with surface temperatures approaching 750 K and an atmosphere 90 times as thick as Earth's. Billions of years ago the picture may have been very different. We have created a suite of 3‐D climate simulations using topographic data from the Magellan mission, solar spectral irradiance estimates for 2.9 and 0.715 Gya, present‐day Venus orbital parameters, an ocean volume consistent with current theory, and an atmospheric composition estimated for early Venus. Using these parameters we find that such a world could have had moderate temperatures if Venus had a prograde rotation period slower than ~16 Earth days, despite an incident solar flux 46–70% higher than Earth receives. At its current rotation period, Venus's climate could have remained habitable until at least 0.715 Gya. These results demonstrate the role rotation and topography play in understanding the climatic history of Venus‐like exoplanets discovered in the present epoch. Key Points: Venus may have had a climate with liquid water on its surface for approximately two billion years The rotation rate and topography of Venus play crucial roles in its surface temperature and moisture Young Venus‐like exoplanets may be considered candidates for the search for life beyond Earth