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The next Venus missions will tell us about worlds that live in other places

As our exoplanet continues to accumulate discoveries (and we’ve seen it More than 11,000 exoplanets so far) we need to know if an Earth-sized planet looks like Earth or looks like Venus. “We don’t know which of these results is expected or likely,” says Paul Byrne, a planetary scientist at North Carolina State University. And to know that we need to understand Venus much better.

Most scientists would agree that all living exoplanets would need water.

With surface temperatures of 471 ° C and 89 times worse than Earth’s, it seems impossible for water to be on Venus. But Venus and Earth are the same size, the same age, and we think it is best that they are made of comparable materials and were born with very similar initial conditions. Venus is 30% closer to the sun than the Earth, which is very noticeable, but not absolute. And yet, after 4.5 billion years, these two planets have become very different.

In fact, there is growing evidence that Venus may have been home to water for a long time. The Venus Pioneer missions, launched in 1978, made fascinating measurements of the atmospheric deuterium-hydrogen ratio, suggesting that Venus had lost tons of water over time. But we have never had a proper role in studying the history of Venus water, in searching for or understanding the characteristics of ancient surface water flow, and whether geological and climatological conditions are essential for water and living conditions. .

“Maybe there could be two stimulating worlds next to each other in our solar system at an unknown time,” says Giada Arney, senior researcher at DAVINCI +. Although Venus may not be able to live today, being able to live in a moment means that it was not always possible to have such a hellish fate if the situation was broken a little better.

And that’s good news for evaluating distant exoplanets. “Looking beyond the solar system, this may suggest that habitable planets are more common than we previously thought,” says Arney.

There are two main theories about what happened to Venus, and both have implications for what we might expect in other exoplanets. The first is consistent with the notes we still have today that Venus began as a hot mess from the beginning and never left. See, the more a planet orbits its host star, the more likely it is to rotate slowly (or even more neatly locked to one side facing the final star, just as the moon is around the Earth).

Slow rotations like Venus generally make it harder to maintain a global climate that keeps the atmosphere cool and comfortable, and it was thought for a while that this was probably what drove Venus to be hot and unbearable. The sun’s rays bombarded the hot planet and the steam-rich atmosphere never condensed on the ground in liquid water. Meanwhile, carbon dioxide, water, and sulfur dioxide in the air functioned as greenhouse gases that served to capture all of this heat. And so it has been for 4 billion years, give or take.

Then there’s a new theory that Michael Way and others have recently developed in NASA’s Goddard Space Studies. This pattern shows that if you make some small adjustments to the climates of these planets, they can develop long hemisphere cloud shapes that are constantly facing the host star. reflecting a lot of stellar heat. As a result, a planet like Venus stays warm and atmospheric vapor condenses into liquid oceans on the surface. Way’s work shows that when this point is reached, the planet can self-regulate its temperature, as long as other Earth-like processes, such as plate tectonics (which help remove carbon dioxide from the atmosphere), can alleviate the accumulation of greenhouse gases.

It’s a complicated hypothesis, full of warnings. And while Venus proves that slow rotators can develop more stimulating conditions, it also proves that these conditions can be brittle and transient. People who buy the Way model believe that what happened on Venus is probably a huge number volcanic activity it flooded the planet with carbon and converted 96% carbon dioxide into the atmosphere, dominating what tectonics of relief plates could provide.

However, it is a hypothesis worth testing with DAVINCI + and VERITAS, as Arney points out that many of the stimulant exoplanets we have found are slow rotations that orbit low-mass stars. Because these stars are more fuzzy, planets usually have to orbit around them to receive enough heat to form liquid water. Forming long hemisphere clouds will enable them to take care of favorable climates. The only way to examine whether this hypothesis makes sense today is to first see if it happened on Venus.

But before we apply the Way model to other exoplanets, we need to determine whether Venus explains it. DAVINCI + will descend to Venus and study the chemistry and composition of the atmosphere directly, as well as imagine the surface going down. Venus should be able to collect the kind of data that tells us whether it was wet earlier in its life, and it could further elaborate on the history of the climate and create a long hemisphere cloud.

The VERITAS orbiter will interrogate the geology of the planet by taking high-resolution images through radar observations capable of detecting evidence of land or landforms created by water flows or past tectonics. The most exciting target may be the tesserae: highly deformed high mountain regions believed to be the oldest geological features on the planet. If VERITAS detects evidence from ancient oceans — or at least about the type of geological activity that could have kept the planet warm for a long time — it will accept the idea that another rotating exoplanet could achieve the same conditions.

“Thinking about going together is really a complementary mega mission,” says Lauren Jozwia, a planetary scientist in the Johns Hopkins Laboratory of Applied Physics working on the VERITAS mission. “This idea that you would like to do geological mapping and atmospheric sounding has been at the core of what you wanted to study on Venus,” says Jozwia.

In the end, if Venus was always inanimate, then the reason has to do with its proximity to the sun. So an exoplanet of similar size that is proportionally close to its star will be like Venus. And we better focus more research on exoplanets farther from their stars.

On the other hand, if Venus was fresh before it became a permanent furnace, it means that we should take the “Venus zone” exoplanets seriously because they can still be stimulating. It suggests that factors such as plate tectonics and volcanism play a critical role in the mediation of living conditions, and we need to find ways to investigate these things even in distant worlds.

The more we think about what DAVINCI + and VERITAS can achieve, the more we seem to be underestimating how excited we should be. Jozwiak says these next missions will “completely change the way we think about Venus and the formation of planets in general.” “It’s an exciting time to find out if Venus is’ the Earth of the future.”


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