Venus is losing water faster than previously thought – here's what that might mean for the early planet's habitability

Today the atmosphere of our neighboring planet Venus is as hot as a… Pizza oven and drier than that driest desert on earth – but that wasn’t all the time the case.

Billions of years ago, Venus had as much water as Earth has today. If this water was ever liquid, Venus may once have been habitable.

Over time, this water has been almost completely lost. It helps to learn how, when and why Venus lost its water Planetary scientists like me Understand what makes a planet habitable – or what could cause a habitable planet to show into an uninhabitable world.

Scientists have theories that designate why many of the water has disappeared, but more water has disappeared than they predicted.

In a May 2024 studymy colleagues and I actually have revealed a brand new water removal process that went unnoticed for a long time but may explain this water loss mystery.

Energy balance and early water loss

The solar system has one habitable zone – a narrow ring across the sun wherein planets can have liquid water on their surface. Earth is in the center, Mars is out on the too cold side, and Venus is out on the too hot side. Where a planet sits on this habitability spectrum will depend on how much energy the planet receives from the Sun and the way much energy the planet radiates.

The theory as to how most of Venus's water loss occurred is said to this energy balance. On early Venus, sunlight split the water in its atmosphere into hydrogen and oxygen. Atmospheric hydrogen heats up a planet – like having too many blankets in your bed in summer.

When the planet gets too hot, it throws off the quilt: the hydrogen escapes into space in a stream, a so-called process hydrodynamic escape. Through this process, Venus was deprived of one among the foremost components of water. It is unknown Exactly When This process occurred, but probably inside the first billion years or so.

After many of the hydrogen was removed, hydrodynamic escape stopped, but some hydrogen remained. It's like pouring out a water bottle – there’ll all the time be a number of drops left at the underside. These leftover drops cannot escape in the identical way. There should be one other process occurring on Venus that continues to remove hydrogen.

Small reactions could make a giant difference

Our New study shows that an ignored chemical response in Venus' atmosphere may produce enough escaping hydrogen to shut the gap between expected and observed water loss.

This is how it really works. In the atmosphere, gaseous HCO⁺ molecules, which consist of 1 atom each of hydrogen, carbon and oxygen and are positively charged, mix with negatively charged electrons because opposites attract.

But when the HCO⁺ and electrons react, the HCO⁺ breaks down right into a neutral carbon monoxide molecule, CO, and a hydrogen atom, H. This process prompts the hydrogen atom, which might then exceed the planet's escape velocity and escape into space. The entire response is known as HCO⁺ dissociative recombination, but we prefer to call it DR for brief.

Water is the unique source of hydrogen on Venus, so DR effectively dries out the planet. DR has likely existed throughout Venus' history, and our work shows that it likely continues into the current. This doubles the quantity of hydrogen escaping previously calculated by planetary scientists who’re turning our understanding of today's hydrogen leaks on Venus the other way up.

Understanding Venus with data, models and Mars

To study DR on Venus, we used each computer modeling and data evaluation.

The modeling actually began as a Mars project. My Ph.D. The research involved studying the conditions that make planets habitable for all times. There was once water on Mars tooalthough lower than Venus, and likewise lost most of it to space.

To understand hydrogen escape on Mars, I developed one Computational model of the Martian atmosphere that simulates the atmospheric chemistry of Mars. Although Mars and Venus are very different planets, they really have similar upper atmospheres, so my colleagues and I were in a position to extend the model to Venus.

We found that dissociative recombination of HCO⁺ within the atmospheres of each planets produces a whole lot of escaping hydrogen, consistent with the planet's measurements Mars Atmosphere and Volatile EvolutioN or MAVEN missiona satellite orbiting Mars.

It can be invaluable to gather data in Venus' atmosphere to support the model, but previous missions to Venus didn’t measure HCO⁺ – not since it wasn't there, but because they weren't designed to detect it. However, they measured the reactants that produce HCO⁺ in Venus' atmosphere.

By analyzing measurements prepared by Pioneer Venusa combined orbiter and probe mission that studied Venus from 1978 to 1992, and using our knowledge of chemistry, we’ve got shown that HCO⁺ must be present within the atmosphere in quantities much like those in our model.

Follow the water

Our work has solved a part of the mystery of how water is lost from planets, which affects how habitable a planet is for all times. We learned that water loss doesn't just occur , but over time through a mix of methods.

Today's faster lack of hydrogen from DR implies that overall it’s going to take less time to remove the remaining water from Venus. This implies that if oceans were ever present on early Venus, they could have been present longer than scientists thought before water loss through hydrodynamic escape and the DR began. This would give more time for possible life to emerge. However, our results don’t mean that there have been definitely oceans or life – answering this query would require far more science for a few years to return.

There can also be a necessity for brand new Venus missions and observations. Future Venus Missions will provide some atmospheric measurements, but they may not give attention to the upper atmosphere, where most HCO⁺ dissociative recombination occurs. A future Venus upper atmosphere mission, much like the MAVEN mission on Mars, could significantly expand everyone's knowledge of how the atmospheres of terrestrial planets form and evolve over time.

With technological advances in recent a long time and a growing latest interest in Venus, now is a wonderful time to show our attention to Earth's sister planet.