Today, the atmosphere of our neighbor planet Venus is as hot as a pizza oven and drier than the driest desert on Earth – but it wasn’t always that way.

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

Over time, that water has nearly all been lost. Figuring out how, when and why Venus lost its water helps planetary scientists like me understand what makes a planet habitable — or what can make a habitable planet transform into an uninhabitable world.

Scientists have theories explaining why most of that water disappeared, but more water has disappeared than they predicted.

In a May 2024 study, my colleagues and I revealed a new water removal process that has gone unnoticed for decades, but could explain this water loss mystery.

Energy balance and early loss of water

The solar system has a habitable zone – a narrow ring around the Sun in which planets can have liquid water on their surface. Earth is in the middle, Mars is outside on the too-cold side, and Venus is outside on the too-hot side. Where a planet sits on this habitability spectrum depends on how much energy the planet gets from the Sun, as well as how much energy the planet radiates away.

The theory of how most of Venus’ water loss occurred is tied to this energy balance. On early Venus, sunlight broke up water in its atmosphere into hydrogen and oxygen. Atmospheric hydrogen heats up a planet — like having too many blankets on the bed in summer.

When the planet gets too hot, it throws off the blanket: the hydrogen escapes in a flow out to space, a process called hydrodynamic escape. This process removed one of the key ingredients for water from Venus. It’s not known exactly when this process occurred, but it was likely within the first billion years or so.

Hydrodynamic escape stopped after most hydrogen was removed, but a little bit of hydrogen was left behind. It’s like dumping out a water bottle – there will still be a few drops left at the bottom. These leftover drops can’t escape in the same way. There must be some other process still at work on Venus that continues to remove hydrogen.

Little reactions can make a big difference

Our new study reveals that an overlooked chemical reaction in Venus’ atmosphere can produce enough escaping hydrogen to close the gap between the expected and observed water loss.

Here’s how it works. In the atmosphere, gaseous HCO⁺ molecules, which are made up of one atom each of hydrogen, carbon and oxygen and have a positive charge, combine with negatively charged electrons, since opposites attract.

But when the HCO⁺ and the electrons react, the HCO⁺ breaks up into a neutral carbon monoxide molecule, CO, and a hydrogen atom, H. This process energizes the hydrogen atom, which can then exceed the planet’s escape velocity and escape to space. The whole reaction is called HCO⁺ dissociative recombination, but we like to call it DR for short.

Water is the original source of hydrogen on Venus, so DR effectively dries out the planet. DR has likely happened throughout the history of Venus, and our work shows it probably still continues into the present day. It doubles the amount of hydrogen escape previously calculated by planetary scientists, upending our understanding of present-day hydrogen escape on Venus.

Understanding Venus with data, models and Mars

To study DR on Venus we used both computer modeling and data analysis.

The modeling actually began as a Mars project. My Ph.D. research involved exploring what sort of conditions made planets habitable for life. Mars also used to have water, though less than Venus, and also lost most of it to space.

To understand martian hydrogen escape, I developed a computational model of the Mars atmosphere that simulates Mars’ atmospheric chemistry. Despite being very different planets, Mars and Venus actually have similar upper atmospheres, so my colleagues and I were able to extend the model to Venus.

We found that HCO⁺ dissociative recombination produces lots of escaping hydrogen in both planets’ atmospheres, which agreed with measurements taken by the Mars Atmosphere and Volatile EvolutioN, or MAVEN, mission, a satellite orbiting Mars.

Having data collected in Venus’ atmosphere to back up the model would be valuable, but previous missions to Venus haven’t measured HCO⁺ – not because it’s not there, but because they weren’t designed to detect it. They did, however, measure the reactants that produce HCO⁺ in Venus’ atmosphere.

By analyzing measurements made by Pioneer Venus, a combination orbiter and probe mission that studied Venus from 1978-1992, and using our knowledge of chemistry, we demonstrated that HCO⁺ should be present in the atmosphere in similar amounts to our model.

Follow the water

Our work has filled in a piece of the puzzle of how water is lost from planets, which affects how habitable a planet is for life. We’ve learned that water loss happens not just in one fell swoop, but over time through a combination of methods.

Faster hydrogen loss today via DR means that less time is required overall to remove the remaining water from Venus. This means that if oceans were ever present on early Venus, they could have been present for longer than scientists thought before water loss through hydrodynamic escape and DR started. This would provide more time for possible life to arise. Our results don’t mean oceans or life were definitely present, though – answering that question will require lots more science over many years.

There is also a need for new Venus missions and observations. Future Venus missions will provide some atmospheric measurements, but they won’t focus on the upper atmosphere where most HCO⁺ dissociative recombination takes place. A future Venus upper atmosphere mission, similar to the MAVEN mission at Mars, could vastly expand everyone’s knowledge of how terrestrial planets’ atmospheres form and evolve over time.

With the technological advancements of recent decades and a flourishing new interest in Venus, now is an excellent time to turn our eyes toward Earth’s sister planet.

Eryn Cangi, Research Scientist in Astrophysical & Planetary Sciences, University of Colorado Boulder

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Across much of the United States, spring is in full force. With warmer weather, people are taking their furry family members out on longer walks and spending more time outside. Alongside blooming flowers and trees, your pet might run into a small, unassuming grass seed pod known as a foxtail. Despite the cute name, foxtails can pose a major threat to your pet’s health.

I am a veterinarian in California’s Central Valley, and foxtails are a daily issue where I work, especially during the spring and summer months.

What exactly are foxtails?

A foxtail isn’t a specific plant. It is a type of grass seed pod that resembles a fox’s tail. Multiple species of grass can create this type of seed pod, and foxtails are found across much of the United States. Regions of the western U.S., especially California, have the most foxtails.

The outside of the foxtail is covered in small sticky hairs designed to stick to things. You can feel them yourself if you pull a foxtail off a plant. Rub your fingers against the seed one way, and then the other, and you’ll feel that one direction is smooth and the other direction is sticky.

Foxtails aren’t a big deal for people, as we don’t have a lot of hair and tend to remove things that are itchy or painful, but it’s a different story for pets.

A segment of the foxtail pod sticks to an animal’s fur, where it’s carried around until it eventually drops off and grows into grass. This sticky feature is great for the grass, as it helps spread the seeds around, but it also results in foxtail segments getting stuck to pets.

Once on the cat or dog, a segment of a foxtail can burrow into the skin, get stuck in the eyes, creep into ears, be inhaled into the nose, or even make its way into the lungs.

The health dangers of foxtails

The most common place where foxtails will burrow into a pet is the skin, especially in between dogs’ toes. A foxtail embedded into the skin can cause irritation, redness, pain and infection. As the foxtail gets deeper into the skin, it brings harmful bacteria with it and creates a path of infection known as a draining tract.

If a foxtail makes it into a dog’s or a cat’s ear, the pet will likely start shaking its head back and forth – it might look like it has an ear infection. The embedded foxtail can cause discomfort and sometimes infection.

A foxtail can stick to a pet’s eye tissues, especially in cats, and migrate around the outer portions of the eye or behind the third eyelid, which is the protective tissue near the inner corner of their eye. This will cause discharge from the eye and discomfort and may scratch the eye’s surface.

One of the most serious locations for a foxtail is in the lungs. Dogs may inhale foxtails while running through fields and breathing hard. The foxtail can sometimes get stuck in the nose, which will cause the pet to sneeze and look uncomfortable. Occasionally, a piece of a foxtail makes its way into the lungs, which can result in severe infection, trauma and even death. Surgery and hospitalization are almost always required in these cases.

Foxtail symptoms

Pet owners can learn what symptoms to look out for in order to make sure their pet gets prompt care if they end up with a foxtail embedded somewhere.

If you see your dog or cat chewing on their paws, this might indicate that a foxtail has ended up in between the toes. Their paws may swell or grow red. If you see even a small pimplelike swelling in between your pet’s toes, they may have a foxtail stuck in their paw.

If your pet is frequently shaking its head, this can indicate that a foxtail made its way into the ear canal. Drainage or discharge from the eye can indicate that foxtail may have made its way around the eye. Sneezing or pawing at the nose can mean the foxtail may have made its way into the nose. Foxtails in the ear canal, eyes or nose will need to be removed by a veterinarian.

Coughing or hacking might mean a foxtail has made it to the tissues around the throat or the tonsils, or even deeper into the lungs. Each one of these symptoms requires care from a veterinarian, as they can grow serious if left untreated.

Preventing foxtail risks

Foxtails are everywhere in the environment, but there are some preventive steps pet owners can take to minimize the risks to their pets.

If you have foxtails in your yard, you can remove them. Sometimes you can get rid of foxtails permanently, but this isn’t always easy, as grasses are particularly good at reproducing and growing quickly.

Some locations have very few foxtails, while others have lots. Bring your pet to areas with fewer foxtails, if possible.

Some companies make mesh nets that can cover a dog’s head to prevent exposure to the ears, nose, eyes and mouth. Pet boots can prevent foxtails from getting stuck in their paws.

Grooming your pet regularly may help catch foxtails before they burrow into the skin. Removing mats and unkempt fur can also help reduce the risk. If you get your pet examined at the vet at least once a year, the veterinarian may be able to find foxtails during these checkups before they escalate into a larger problem.

Foxtails are part of living in the United States. But a few simple steps can help keep pets safe while they enjoy the outdoors.

Erik Olstad, Health Sciences Assistant Professor of Clinical Veterinary Medicine, University of California, Davis

This article is republished from The Conversation under a Creative Commons license. Read the original article.