How long will the Venusian atmosphere remain hostile?

"One orbiter would not be enough"

Do your simulations show what transformed Venus from a planet with a mild climate to a greenhouse without water?

Well, there has been some speculation among scientists that Venus had temperate conditions in its early history and that the increase in radiant power from our Sun brought it to the infernal state it is in today. These speculations are based on what we know about the earth. There is the paradox of the weak young sun: If you take today's earth's atmosphere and transfer it to the earth as it existed four billion years ago, then you get an earth that is an ice world, because the radiation power of the sun was back then by 20 to 25 percent less than today. The sun has gradually increased in brightness over the years, and the reason the earth was not in a frozen state all the time could be related to the atmospheric change over that period. So there were these early ideas that moderate conditions must have prevailed on Venus, since the radiation output of our sun was not always at today's level.

But according to your simulations, that's not the case?

No, our simulations show that this is definitely not the case. If there were moderate conditions on the young Venus, these would have remained despite the increase in solar radiation. However, we note that the surface of Venus is quite young. In the past 750 million years, around 80 percent of the planet's surface has formed anew. And as a result of this phenomenon, the planet's climate has probably also changed. There have been similar events in the history of the earth, such as the formation of the Siberian trap or the Deccan trap due to volcanic activity. Of course, there are also large impactors such as the Chicxulub impactor and the like. But in a certain way we were fortunate that several of these magmatic large provinces, which are basically volcanic activity on an enormous scale, did not form at the same time. But there is no reason why that couldn't happen.

So if several igneous large provinces had formed at the same time at a certain point in the history of the earth, would the earth look like Venus today?

Well, such an event, releasing huge amounts of carbon dioxide into the atmosphere, would cause a climate catastrophe. The planet would enter an uncontrollable greenhouse state that would result in water loss. And as the water is lost, the subducting plate tectonics, which keep the carbon and nitrogen cycles on earth and keep the atmosphere in balance, weaken. The result would be a stagnant state in which there are no more cycles of volatile substances. In such a case, a one-sided process arises in which there is only outgassing. Due to the lack of subduction, there is no longer any possibility of absorbing gases from the atmosphere, as is happening on earth today. And that's why Venus got into the state it is in today.

They talk about climate change and the role of carbon dioxide in creating an uncontrollable greenhouse state. Is it therefore possible that what we observe on Venus also allows us a glimpse into the future of the earth?

I believe that it is very difficult to compare these two planets in this sense, because the state in which Venus is today was formed over millions of years. On Earth we have very serious short term problems to deal with, but something much more catastrophic would have to happen to create a condition comparable to Venus. Our planet is in a very delicate state of equilibrium and we are doing some very terrible things, but to get into the state of Venus it takes a very great geological process. So it is not directly comparable. There are, however, some lessons for us about how the climate will evolve when large amounts of carbon dioxide are released, but we are talking about magnitudes well in excess of the amounts of carbon dioxide currently being released into the atmosphere. So it's a difficult comparison. I know that this comparison is made because it seems obvious at first glance. But what happened on Venus cannot be compared to what is currently happening on Earth.