Venus has an “electric wind” powerful enough to remove all the water from its atmosphere, something which may have led a significant role in stripping the planet of its oceans.
It’s so strong that it took astronomers by surprise.
“It’s amazing and shocking,” said Glyn Collinson, previously at UCL Mullard Space Science Laboratory and now a scientist at NASA’s Goddard Space Flight Center. “We never dreamt an electric wind could be so powerful that it can suck oxygen right out of an atmosphere into space. This is something that definitely has to be on the checklist when we go looking for habitable planets around other stars.”
The Venusian electric field is so strong that it accelerates the heavy electrically charged component of water – oxygen – to speeds fast enough to escape the planet’s gravity. So any water in the atmosphere, and even on the planet, gets broken into hydrogen and oxygen. The oxygen then gets blown away by the electric field. This could explain how Venus (and other bodies like it) have become so barren in terms of water.
Venus is the planet most like Earth in terms of its size and gravity, and there is reason to believe that it once had oceans full of water. But Venus is also very different from the Earth: it’s the hottest planet in the solar system, and it’s pretty much a hellish environment.
If Venus did have water, then most or all of it likely boiled away at temperatures of around 860 degrees Fahrenheit (460 Celsius). But if all the water boiled, then where’s all the steam? There is no evidence of what must have been a huge quantity of water, and now scientists believe this “electric wind” is to blame. Previously, solar wind was the main culprit.
The same thing may be happening on other bodies as well. Co-author, Professor Andrew Coates of the UCL MSSL, who leads the electron spectrometer team, said:
“We’ve been studying the electrons flowing away from Titan and Mars as well as from Venus, and the ions they drag away to space to be lost forever. We found that over 100 metric tons per year escapes from Venus by this mechanism – significant over billions of years. The new result here is that the electric field powering this escape is surprisingly strong at Venus compared to the other objects. This will help us understand how this universal process works.”
But this discovery poses just as many questions as it answers. How exactly did this electric field become so strong on Venus?
Just like any planet has its own gravitational field, it is believed that every planet with an atmosphere is also surrounded by a weak electric field. The two fields are trapped in a tug of war, with the electric field trying to rip the atmosphere’s top layers and gravity trying to keep them down; on Earth, gravity won, but on Venus, this wasn’t the case – but we don’t really know why.
“We don’t really know why it is so much stronger at Venus than Earth,” said Collinson, “but, we think it might have something to do with Venus being closer to the sun, and the ultraviolet sunlight being twice as bright. It’s a really challenging thing to measure and to date all we have are upper limits on how strong it might be here.”
This could also have significant implications for Mars. The Red Planet may have undergone a similar process. NASA’s current MAVEN mission is orbiting Mars to see what caused it to lose all the water. Titan is also a place of interest, as it’s in a mid-water-losing process.
“With ESA’s Mars Express, we have already caught this process in action at Mars, and MAVEN can now determine its relative importance. With NASA’s Cassini spacecraft we found that Titan loses 7 metric tonnes per day this way.”
