Science

Venus was potentially habitable until a mysterious event happened


Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Research suggests Venus may have had water oceans billions of years ago. A land-ocean pattern was used in a climate model to show how storm clouds could have shielded ancient Venus from strong sunlight and made the planet habitable.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Jupiter's moon Europa, which has a subsurface ocean beneath an icy crust, has also been found to contain table salt. Tara Regio is the yellowish area to left of center where researchers identified an abundance of sodium chloride.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Europa has also been found to have plumes that eject water vapor and icy material.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

An artistic impression of the Mars Express spacecraft probing the southern hemisphere of Mars. Radar detected a lake of liquid water beneath the surface.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Two meteorites, called Monahans and Zag, are the first discovered to contain the ingredients for life: liquid water, amino acids, hydrocarbons and other organic matter. The organic matter was found in purple and blue salt and potassium crystals that were part of the meteorites.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

NASA's Cassini mission has evidence of an ocean inside Saturn's largest moon, Titan, which might be as salty as the Earth's Dead Sea.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

NASA is exploring the ocean worlds in our solar system as part of the search for life outside of Earth.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Life as we know it is carbon-based and requires liquid water. About 70% of the Earth's surface is covered with water, making life possible.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

The Eagle lunar module of Apollo 11 ascends from the surface of Earth's moon in 1969. The presence of water on the moon has been confirmed by scientists.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Mercury is the closest planet to the sun and very hot, but its polar regions may have water ice and other frozen volatile materials, according to NASA studies.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Water still flows across the surface of Mars from time to time, NASA scientists said in 2015. In the photo above, dark, narrow streaks called recurring slope lineae are seen flowing downhill on Mars. Scientists have inferred that they were formed by contemporary flowing water.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Dwarf planet Ceres, composed of rock and ice, is the largest object in the asteroid belt.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

In this artist's concept, the moon Ganymede, right, orbits the giant planet Jupiter. NASA's Hubble Space Telescope observed auroras on the moon generated by Ganymede's magnetic fields. A saline ocean under the moon's icy crust best explains shifting in the auroral belts measured by Hubble.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

The trailing hemisphere (the side that faces away from its direction of motion) of Jupiter's moon Europa was captured by the Galileo spacecraft. The left image shows Europa in approximately true color and the right image shows Europa in enhanced color to bring out details. NASA data suggest that Europa has a subsurface ocean.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Voyager 1 captured this image of Jupiter's moon Callisto. Scientists have detected ice and carbon dioxide on its surface.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Gravity measurements by NASA's Cassini spacecraft and Deep Space Network indicate that Saturn's moon Enceladus, which has jets of water vapor and ice gushing from its south pole, also harbors a large interior ocean beneath an ice shell, as this illustration depicts.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Mimas, the smallest and closest of Saturn's eight main moons, is heavily cratered and has a low density that suggests it is mostly composed of water ice. The moon's main 88-mile-long crater makes it resemble "Death Star" from "Star Wars Episode IV."

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

Neptune's largest moon, Triton, is so cold that its surface is composed mainly of nitrogen ice.

 

Venus was potentially habitable until a mysterious event happened

Photos: Water in the solar system

An artist's concept shows Pluto and its moons. Pluto's moon Charon has cracks that suggest it once had underground water.

 

Venus likely maintained stable temperatures and hosted liquid water for billions of years before an event triggered drastic changes in the planet, according to a new study.

Now, Venus is a mostly dead planet with a toxic atmosphere 90 times thicker than ours and surface temperatures that reach 864 degrees, hot enough to melt lead. It's often called Earth's twin because the planets are similar in size. But the modern comparisons stop there.

However, a recent study compared five climate simulations of Venus' past and every scenario suggested that the planet could support liquid water and a temperate climate on its surface for at least three billion years. Like the other planets in our solar system, Venus formed 4.5 billion years ago.

Those temperatures could have included a maximum of 122 degrees Fahrenheit and a minimum of 68 degrees Fahrenheit.

But between 700 and 750 million years ago, something triggered the release of carbon dioxide from rocks on the planet, transforming its climate.

"Our hypothesis is that Venus may have had a stable climate for billions of years. It is possible that the near-global resurfacing event is responsible for its transformation from an Earth-like climate to the hellish hothouse we see today," said Michael Way, study author at The Goddard Institute of Space Science. Way presented his study this week at the European Planetary Science Congress - Division for Planetary Sciences Joint Meeting 2019 in Geneva.

Previously, Way authored a 2016 study about climate and oceans on Venus in its past.

The ocean was first suggested by NASA's Pioneer mission in the 1980s. But given its placement as the second planet from the sun, Venus wasn't considered conducive to sustaining an ocean.

Venus receives more sunlight than Earth, which would evaporate liquid water, sending hydrogen into space and trapping a buildup of carbon dioxide. That would lead to a nonstop greenhouse effect that would create its current toxic atmosphere. Venus' topography was completely altered by volcanic eruptions that most likely filled in lowland regions and potential ocean basins over the past billion years.

Out of the five simulations, three of them included Venus' current topography and added a deep 1,017-foot ocean, a shallow 32-foot ocean and trace amounts of water in the soil. Researchers compared this to two other simulations, one using Earth's topography with a deep ocean and an ocean world.

To recreate likely conditions on Venus that happened 4.2 billion years ago and changed over time, they gradually increased solar radiation to reflect the sun as it warmed. This also shifted atmospheric conditions over time.

Previously, researchers believed that Venus is too close to the sun to sustain liquid water on its surface, beyond the inner limit of the sun's habitable zone. The new simulations shift that belief for Way and his colleagues.

"Venus currently has almost twice the solar radiation that we have at Earth. However, in all the scenarios we have modeled, we have found that Venus could still support surface temperatures amenable for liquid water," Way said.

The simulations suggest that Venus went through a rapid cooling phase a few billion years after it formed. Then, the atmosphere would have been full of carbon dioxide. If Venus evolved similarly to Earth, that carbon dioxide would have come down from the atmosphere, drawn by silicates, and become trapped in the surface. This would allow the atmosphere to be full of nitrogen with tiny amounts of carbon dioxide and methane, providing stability.

But something happened around 700 million years ago that remains a mystery, although the researchers think its connected to volcanic activity. Magma would have released carbon dioxide into the atmosphere, and as the magma cooled, the gas couldn't be reabsorbed in the surface.

Whatever happened, so much carbon dioxide in the atmosphere caused a runaway greenhouse effect, evidenced in the scorching hot temperatures on the planet now.

"Something happened on Venus where a huge amount of gas was released into the atmosphere and couldn't be re-absorbed by the rocks. On Earth we have some examples of large-scale outgassing, for instance the creation of the Siberian Traps 500 million years ago which is linked to a mass extinction, but nothing on this scale. It completely transformed Venus," Way said.

Besides the mystery of the event's cause, the researchers need to know how quickly Venus cooled after its formation and if water could have existed on the surface, as well as if the outgassing event only happened once or was merely one in a series of events.

"We need more missions to study Venus and get a more detailed understanding of its history and evolution," Way said. "However, our models show that there is a real possibility that Venus could have been habitable and radically different from the Venus we see today. This opens up all kinds of implications for exoplanets found in what is called the 'Venus Zone', which may in fact host liquid water and temperate climates."


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