Volcanoes may have turned Venus into blistering hell: ScienceAlert

Is there anything good about volcanoes? They can be violent, dangerous and unpredictable. For modern humans, volcanoes are mostly an inconvenience, sometimes an intriguing visual spectacle, and occasionally deadly.

But when there are enough of them, and when they are powerful and sustained, they can kill their host planet.

Modern Venus is a hot hell. The temperature exceeds 464°C (850°F, 737°K), which is, as readers of Universe Today know, hot enough to melt lead (and spacecraft).

That’s why, of all the missions Russia has sent to the planet’s surface, only four have managed to transmit images before quickly succumbing to the extreme conditions on Venus.

But modern Venus may be radically different from ancient Venus. Some research shows that ancient Venus had an atmosphere similar to that of ancient Earth.

The planet may also have had significant amounts of water on its surface. It’s possible that simple life once existed on Venus, but there’s still not enough evidence to prove or disprove it.

A new study shows that massive volcanic eruptions over a long period of time may be responsible for changing the planet into what it is today. If there was simple life on ancient Venus, volcanism was its destiny.

The study also shows how powerful volcanic activity played a role in shaping Earth’s habitability and how Earth only narrowly avoided the same fate as Venus.

The study is titled “Large-scale Volcanism and the Heat Death of Terrestrial Worlds”, and is published on The Planetary Journal. Dr. Michael J. Way of NASA’s Goddard Institute is the lead author. Way has been researching Venus for years and has authored and co-authored several articles on the planet, especially its former habitability.

“By understanding the record of large igneous provinces on Earth and Venus, we can determine whether these events may have caused Venus’ current condition,” Way said in a press release announcing the study.

The Earth has experienced prolonged periods of sustained volcanic eruptions in its history. Large igneous provinces (LIPs) are evidence of periods, which can last hundreds of thousands of years, perhaps even millions of years.

LIPs can deposit more than 100,000 cubic miles of rock on the surface. That’s enough to bury Texas half a mile deep. We know many LIPs on Earth and we know that in the last 500 million years they coincide with periods of climate change and mass extinctions.

The study suggests that Venus experienced massive volcanic explosions that created the modern-day atmosphere of Venus, with its extreme temperatures and pressures. More specifically, he claims that intense explosions over a period of just a million years created a runaway greenhouse effect.

The runaway greenhouse effect occurs when an atmosphere blocks a planet’s heat from radiating out into space. Without the possibility of cooling down, the temperature rises to extreme levels, like a greenhouse with all the vents closed.

Venus’ greenhouse effect is exacerbated by its apparent lack of plate tectonics. The Earth’s plate tectonics allows heat from the planet’s interior to reach the surface by periodically opening the mantle blanket.

It also carries carbon dioxide out of the atmosphere and into rock through erosion and subduction.

Our planet has experienced five mass extinctions, and all are associated with increased volcanic activity, according to this work. (Some researchers point to a sixth mass extinction that has just begun, as human activity causes greater species loss.)

The Chicxulub impact event was the main driver of the Permian-Triassic extinction event that wiped out the dinosaurs, but volcanic activity also played a role. While the Chicxulub dinosaur extinction is well known and dramatically popularized, volcanic activity has been the main driver of the extinctions on Earth.

Life on Earth has suffered greatly from powerful and sustained volcanic activity. But it always recovered, and volcanoes never caused a runaway greenhouse effect, while Venus still suffers today. What is the difference?

The scale of the eruptions had something to do with it. The surface of Venus is 80% covered by solidified volcanic rock. Sulfur in the atmosphere is also evidence of pronounced volcanic activity. And Venus’ surface has fewer craters than expected, indicating abundant volcanic activity over the last few hundred million years.

But the study should make anyone uncomfortable. Although the Earth avoided the runaway greenhouse effect, it may have only narrowly avoided it.

Untangling the history of volcanism, impacts and extinctions in Earth’s history is a challenge because craters are obliterated. There are scientific efforts to understand the conditions in the Earth’s mantle that lead to LIPs, but that too is a difficult task.

The magmatic events that create LIPs are typically short-lived on geological timescales, less than 5 million years in duration. They can also be a series of pulses over a few tens of millions of years. Although they push a lot of rock to the surface, the chemicals they emit into the atmosphere are what drive the extinctions.

Large amounts of CO2 dramatically warmed Earth’s atmosphere and sulfur dioxide (SO2) aggravated the warming. Toxic compounds such as hydrogen sulfide (H2S) and carbon monoxide (CO) also come from eruptions, but only in small quantities.

Earth’s volcanic activity is similar to that of Venus because the planets are “sister planets”. They are very close in size and are both rocky planets in the inner Solar System.

But the key thing they share when it comes to volcanism is their mass composition. Since they formed in the same region of the Solar System, they have very similar compositions.

In their study, the authors recreated Earth’s volcanic history in random simulations based on what is known about Earth’s volcanic activity and LIPs. ‘In one approach, we make a conservative estimate of the rate at which sets of nearly simultaneous LIPs (pairs, triplets and quartets) occur in a random history statistically equal to that of the Earth,’ the authors write.

“We find that LIPs closer in time than 0.1-1 million years are likely; significantly, this is less than the time environmental effects of terrestrial LIP are known to persist.”

This means that the LIP events overlap and before the planet can remove the CO2 released into its atmosphere by one event, another is busy releasing more. String enough of those together and you get the runaway greenhouse effect. Separate LIPs over different parts of the globe, even under the oceans, exacerbate the effect.

A key part of their study concerns variability. Are LIPs causally related to each other? This is important because if the LIP rate fluctuates, this increases the likelihood of overlapping or simultaneous events, which would contribute to a runaway greenhouse effect.

“How would LIP rate variability over time affect the chances of concurrent events?” write the authors.

“During periods of rising rates, the probability of simultaneous events is increased relative to that of the average rate. On the other hand, during periods of decreasing rates, this probability is decreased relative to the mean. It is not obvious which of these effects predominates.”

An interesting point in all of this concerns the longest-lasting LIPs on Earth. The longer it lasts, the more likely it is to overlap another.

“[W]We found that the probability that the largest LIP recorded in Earth’s history would overlap with an event of similar size (in area) is about 30 percent. Multiple simultaneous LIPs may be important drivers of the transition from a serene habitable surface to a greenhouse state for terrestrial worlds, assuming they have Earth-like geochemistry and mantle convection dynamics,” says the paper.

There is a point where all of this diverges. While we have fairly complete and reliable data on Earth’s LIPs, we have nowhere near any for Venus. But research shows that, even with our lack of detailed data, Venus is likely to have suffered from overlapping LIPs that led to her fate.

Fortunately, upcoming missions to Venus will open this investigation with better data.

The Venus VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) mission is an orbiter developed by NASA. Its launch date has not yet been scheduled, but it will be a three-year mission to image the surface of Venus in high resolution using radar and near-infrared spectroscopy.

It will provide detailed information on the planet’s impact history, volcanism, geochemistry and more.

The DAVINCI (Deep Atmosphere Venus Investigation of Noble gas, Chemistry, and Imaging) mission is also a NASA mission, but will have an atmospheric probe along with an orbiter. Once scientists have more detailed information about Venus’ atmosphere and its surface, they can begin untangling the planet’s past.

“A primary goal of DAVINCI is to narrow down the history of water on Venus and when it might have disappeared by providing more insight into how Venus’ climate changed over time,” Way said.

Both DAVINCI and VERITAS will launch in the late 2020s, with DAVINCI launching first.

ESA is also planning an orbiter mission to Venus. It’s called EnVision and is expected to be launched in the early 1930s. EnVision will also study Venus’ atmosphere, but will dig deeper, using its suite of tools to investigate the planet’s internal structure.

These findings will also play a role in understanding exoplanets. Exoplanets are a burgeoning area of ​​research, and the James Webb Space Telescope is starting to provide better data on exoplanet atmospheres.

But it will be difficult for scientists to interpret the JWST findings without better overall models, and a more detailed understanding of our sister planet’s history will surely refine our models for planetary atmospheres.

For some reason, Earth has remained habitable for billions of years, and Venus is much worse off. If Venus ever harbored ancient and simple life, it’s long gone now.

(Apologies to people who think life could live on in the clouds of Venus.)

While we may never have a complete understanding of all the factors that made Earth and Venus so different from one another, volcanic activity clearly played a part. Once VERITAS, DAVINCI, and EnVision do their thing, we should understand Venus’ divergent path in more detail.

This article was originally published by Universe Today. Read the original article.

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