We can learn a lot about climate change in Venus, our sister planet. Currently, the surface temperature of Venus is 450℃, and carbon dioxide (96%) with a density 90 times higher than Earth prevails in the atmosphere.
Venus is a very strange place, completely uninhabited, with the exception of perhaps clouds at an altitude of about 60 kilometers, where the recent discovery of phosphine may suggest floating microbial life.
However, Venus once had an earthly climate. According to recent climate modelling, for most of its history, Venus had a surface temperature similar to modern Earth. Probably there were also oceans, rains, possibly snow, possibly continents and plate tectonics, and even possibly surface life.
Less than a billion years ago, the climate changed dramatically due to the uncontrolled greenhouse effect. It can be assumed that an intense period of volcanism pumped the atmosphere with a huge amount of carbon dioxide, which caused climate change, which evaporated the oceans and ended the water cycle.
Since the early 1990s, a research team from Carleton University, and more recently a Siberian team from Tomsk State University, has been mapping and interpreting the geological and tectonic history of the wonderful planet Venus.
The Soviet missions on planet and Vega of the 1970s and 1980s landed on Venus, managed to photograph and evaluate the composition of rocks before the equipment failed due to high temperature and pressure on the surface of the planet. However, the most complete view of the surface of planet was provided by the NASA Magellan spacecraft in the early 1990s, which used radar to view through a dense layer of clouds and to obtain detailed images of the surface of Venus. Magellan examined more than 98 percent of the surface of Venus.
Our search for geological evidence of great climate change has led us to focus on the oldest type of rock on Venus, called tesserae, which have a complex appearance that suggests a long, complex geological history. We believed that these oldest rocks had the greatest chance of preserving evidence of water erosion, which is such an important process on Earth and which should have been on Venus before climate change.
Given the poor resolution of altitude data, we used an indirect method to try to recognize ancient river valleys. We showed that younger lava flows from the surrounding volcanic plains filled the valleys on the outskirts of the tessera.
