Earth's evil twin: What stripped Venus of water, and now oxygen, carbon

According to a study published in Nature Astronomy journal, the Mercury-bound BepiColombo spacecraft performed its second fly-by of Venus on August 10, 2021. The fleeting visit of the ESA/JAXA mission "provided a short-lived observation of its induced magnetosphere".

ALSO READ: Why future missions to Venus will not be as easy as they look

What is induced magnetosphere: Unlike Earth, Venus does not generate an magnetic field in its core. The planet is rather surrounded by "a weak, comet-shaped induced magnetosphere", Phys.org explained in a report. 

This magnetosphere is created around the planet "by the interaction of charged particles emitted by sun (the solar wind) with electrically charged particles in Venus's upper atmosphere. "Draped around the magnetosphere is a region called the 'magnetosheath' where the solar wind is slowed and heated," it explained further.

Early in its history, interactions with the solar wind had stripped away the water on Venus, leaving an atmosphere composed mainly of carbon dioxide and smaller amounts of nitrogen and other trace species, the report added.

What new study revealed?

As per a report in Phys.org, the "detections in a previously unexplored region of Venus's magnetic environment" show that carbon and oxygen are travelling at such accelerated speeds that "they can escape the planet's gravitational pull".

The research noted that most of the heavy ions in Venus's ionosphere are cold and slow moving. "This is the first time that positively charged carbon ions have been observed escaping from Venus's atmosphere," said Lina Hadid, CNRS researcher at the Plasma Physics Laboratory (LPP) and lead author of the study.

How is it possible?: "These are heavy ions that are usually slow moving, so we are still trying to understand the mechanisms that are at play. It may be that an electrostatic 'wind' is lifting them away from the planet, or they could be accelerated through centrifugal processes," Hadid was quoted as saying.

Earlier, scientists at Nasa and University College London (UCL) discovered that Venus' electric field is so strong that it can accelerate the heavy electrically charged component of water — oxygen — to speeds fast enough to escape the planet's gravity.

Why is this new study important?

The researchers said in their study that these results have important implications regarding the evolution of Venus's atmosphere and, in particular, the evolution of water on the surface of the planet.

Dominique Delcourt, researcher at LPP and the Principal Investigator of the MSA instrument, was quoted by Phys.org as saying, "Characterising the loss of heavy ions and understanding the escape mechanisms at Venus is crucial to understand how the planet's atmosphere has evolved and how it has lost all its water."

Besides, the European Space Agency (ESA) says, "There is no human activity on Venus, but studying its atmosphere provides a natural laboratory to better understand a runaway greenhouse effect."

Venus once had 'oceans like Earth'

The European Space Agency and the National Aeronautics and Space Administration have time and again explained how the Venus lost all of its water on the surface. According to the space agencies, Venus, at some point in its history, began trapping too much heat. 

Venus has a dense atmosphere and it is hotter than planet Mercury, which orbits closer to the Sun. This is because of its thick atmosphere that traps heat in a runaway greenhouse effect. This makes it the hottest planet in our solar system, with surface temperatures hot enough to melt lead.

"It was once thought to host oceans like Earth, but the added heat turned water into steam, and in turn, additional water vapour in the atmosphere trapped more and more heat until entire oceans completely evaporated. Water vapour is still escaping from Venus' atmosphere and into space today," the ESA said.

Meanwhile, NASA explained that a "runaway greenhouse effect" turned all surface water into vapor, which then leaked slowly into space. 

In a dramatic twist, study co-author, Moa Persson of the Swedish Institute of Space Physics said, "Recent results suggest that the atmospheric escape from Venus cannot fully explain the loss of its historical water content…".

Is life possible on Venus?

"The present-day surface of volcanic rock is blasted by high temperatures and pressures. Asked if the surface of Venus is likely to be life-bearing today, we can give a quick answer: a hard 'no'," the NASA explained.

Then why researchers and astronomers are interested in Venus? The NASA says that although Venus is not currently habitable, the planet lies within the Sun's "Goldilocks zone," and may have been habitable before Earth.

Impact in Earth?

"Earth's nearness to Venus is a matter of perspective," the NASA says.

Meanwhile, the ESA explains that in the very long term - billions of years into the future - a 'greenhouse Earth' is an inevitable outcome at the hands of the aging Sun.

"Our once life-giving star will eventually swell and brighten, injecting enough heat into Earth's delicate system that it will eventually become Venus' true twin," the ESA says.

Venus — Earth's evil twin

Venus is known as Earth's "evil twin" as the two planets are similar in many way, but also opposite in some aspects. The NASA says that in some ways, Venus is more an opposite of Earth than a twin.

Venus is the second planet from the Sun, and the sixth largest planet. It's the hottest planet in our solar system. It is similar in structure and size to Earth. However, the planet spins backward, has a day longer than its year, and lacks any semblance of seasons. 

Venus might once have been a habitable ocean world, like Earth, but that was at least a billion years ago. "The atmosphere [of Venus] is so thick that, from the surface, the Sun is just a smear of light," the NASA says.

"Scientists think that Venus once looked a lot like Earth, but underwent an irreversible climate change that is often used as an extreme example of what happens in a runaway greenhouse effect," the ESA said.

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Published: 13 Apr 2024, 03:02 PM IST