Often times a piece of research comes along that isn’t really about a discovery, but rather about a mistake we didn’t know we were making. This is one of those, and it happens to orbit one of our closest neighboring planets.
Venus takes 243 Earth days to rotate once on its axis, one of the slowest rotations of anything in the solar system. But if you only watched his draw, you would conclude something completely different. Venus’ upper atmosphere orbits the planet in about four flat days, a phenomenon astronomers call superrotation, which makes the entire planet appear to be rotating nearly sixty times faster than it actually is. Look at the wrong layer, measure the wrong thing, and you’ll get an answer about two orders of magnitude wrong.
Image source NASA/JPL-Caltech Image source NASA/JPL-Caltech Image source NASA/JPL-Caltech Image source NASA/JPL-Caltech Image source NASA/JPL-Caltech
That’s the warning at the heart of new research by Stephen Kane at the University of California, Riverside, and it’s important for a reason beyond curiosity about our closest neighbors. Rotation is not a footnote in planetary science, it is fundamental. The speed of the world’s rotation controls how the heat emanating from its star is redistributed, how weather systems form, and how oceans and atmospheres communicate with each other. If we get the rotation rate wrong, every climate model built on it inherits that error.
The problem is that for planets orbiting other stars, we can’t watch a solid surface orbiting in the same way we can with Mars. Most exoplanets can only be seen through their atmospheres, which means astronomers often measure winds, not rotation, and confuse one with the other. Ken’s research doesn’t just diagnose the problem, it offers a solution. By observing the same planet across multiple wavelengths, including infrared, it allows you to delve deeper into the atmosphere where wind speeds decrease, on Venus at least, the closer you get to the surface. Combine measurements at different depths and you can start to reconstruct what the actual planet is doing underneath, rather than just what the weather is doing.
The reason this is relegated now rather than remaining on a neat artistic footnote comes down to timing. ESA’s PLATO mission will launch in March 2027, and in an accompanying paper, Kane and his colleagues, including PhD student Emma Miles, predict it will reveal several hundred Venus-like worlds. This is not a small number in this field, but rather an unexpected gain. For the first time, scientists will have a decent number of exoplanets to compare to the real thing, rather than one crazy data point.
An artist’s image of the European Space Agency’s PLATO spacecraft, equipped with 26 ultra-sensitive cameras designed to detect tiny dimmings of starlight as planets pass in front of their host stars. The mission is expected to reveal several hundred Venus-like worlds after its launch in 2027.
This comparison could finally begin to answer a question that has been troubling planetary scientists for decades: Why did Venus, a world built roughly the same size as Earth, end up a crushing hellscape and melting lead, while Earth retained its balmy oceans and skies? If most of those exoplanets turn out to be slow rotators like Venus itself, that’s a strong hint that slow rotation is a real ingredient in the runaway greenhouse recipe. If their turnover rates turn out to be ubiquitous, the research moves elsewhere.
The Earth’s 24-hour rotation quietly performs a huge amount of climate work, transporting solar energy around and driving the circulation of the atmosphere and oceans that keeps things livable. As we begin to look for potentially habitable worlds elsewhere, this paper is a reminder to check that the number we call a “day” on some distant planet is actually a day, and not just the planet’s weather about which it has a very quick opinion.
source : Slow rotation could explain why planets become hellish
