Is there anything good in volcanoes? They can be violent, dangerous and unpredictable. For modern humans, volcanoes are mostly an inconvenience, sometimes an intriguing and sometimes deadly visual display.
But when there are enough of them, and when they are powerful and prolonged, they can kill the planet that hosts them.
Modern-day Venus is a breathtaking hellish landscape. The temperature exceeds 464°C (850°F, 737°K), which is, as Universe Today readers 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 managed to transmit images before quickly succumbing to the extreme conditions of Venus.
But the modern Venus could be radically different from the 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 isn’t enough evidence yet to prove or disprove this.
Massive volcanic eruptions over a long period of time may be responsible for transforming the planet into what it is today, a new study shows. If there was simple life on ancient Venus, volcanism was its downfall.
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 Heat Death of Terrestrial Worlds”, and it is published in 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 papers on the planet, particularly on its ancient habitability.
“By understanding the record of large igneous provinces on Earth and Venus, we can determine whether these events may have caused the current state of Venus,” Way said in a press release announcing the study.
Earth has experienced long periods of sustained volcanic eruptions in its history. Large igneous provinces (LIPs) are evidence of these periods, which can last for hundreds of thousands of years, or even millions of years.
LIPs can deposit over 100,000 cubic miles of rock to the surface. That’s enough to bury Texas half a mile deep. On Earth, we know of many LIPs, and we know that over the past 500 million years they coincide with periods of climate change and mass extinctions.
The study suggests that Venus suffered its own massive volcanic explosions that created Venus’ modern atmosphere, with its extreme temperatures and pressures. Specifically, it indicates that intense explosions over a period as short as 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 a means of cooling, the temperature reaches extreme levels, like a greenhouse with all its vents closed.
Venus’ greenhouse effect is exacerbated by its apparent lack of plate tectonics. Earth’s plate tectonics allow heat from the planet’s interior to reach the surface by periodically opening up the mantle cover.
It also takes carbon dioxide from the atmosphere and into rock through weathering and subduction.
According to this work, our planet has experienced five mass extinctions, and all of them are associated with increased volcanic activity. (Some researchers point to a sixth mass extinction just beginning, as human activity leads to increased species loss.)
The Chicxulub impact event was the main driver of the Permian-Triassic extinction 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 primary driver of extinctions on Earth.
Life on Earth has suffered greatly from powerful and sustained volcanic activity. But it always recovered, and the volcanoes never caused an uncontrollable greenhouse effect, while Venus still suffers from it today. What is the difference?
The magnitude of the eruptions had something to do with it. The surface of Venus is covered with 80% of 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 past hundreds of millions of years.
But the study should make everyone uncomfortable. Although the Earth avoided the runaway greenhouse effect, it may have only narrowly avoided it.
Unraveling the history of volcanism, impacts and extinctions in Earth’s history is a challenge as craters fade away. There are scientific efforts to understand the conditions in the Earth’s mantle that lead to LIPs, but this is also a difficult task.
Magmatic events that create LIPs are generally short-lived on geologic timescales, less than 5 million years. It 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 causing the extinctions.
Massive amounts of CO2 heated the Earth’s atmosphere dramatically and sulfur dioxide (SO2) exacerbated the warming. Toxic compounds like hydrogen sulfide (H2S) and carbon monoxide (CO) also come from eruptions, but only in trace amounts.
Earth’s volcanic activity is similar to that of Venus because the planets are “sister planets”. They are very close in size and both are rocky planets in the inner solar system.
But the essential thing they share when it comes to volcanism is their bulk 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 near-simultaneous LIPs (pairs, triplets, and quartets) occur in a random history statistically identical to that of Earth,” the authors write.
“We find that LIPs closer in time than 0.1 to 1 million years are likely; significantly, this is less than the time the environmental effects of terrestrial LIPs are known to persist.”
This means that the LIP events overlap, and before the planet can remove CO2 released into its atmosphere from an event, another is busy releasing more. Chain enough of them together and you get the runaway greenhouse effect. Separate LIPs on different parts of the globe, even under the oceans, exacerbate the effect.
A key element of their study concerns variability. Are LIPs causally related to each other? This is important because if the LIP rate is variable, it increases the likelihood of overlapping or simultaneous events, which would contribute to a runaway greenhouse effect.
“How would variability in LIP rate over time affect the odds of concurrent events?” write the authors.
“During periods of rising rates, the probability of simultaneous events is higher than that of the average rate. On the other hand, during periods of reduced rates, this probability is decreased compared to the average. It is not not clear which of these effects predominates.”
An interesting point in all of this concerns the longest-lasting LIPs on Earth. The longer one lasts, the more likely it is to overlap with another.
“[W]We find that the probability of the largest LIP recorded in Earth’s history overlapping an event of similar size (in area) is about 30%. Multiple simultaneous LIPs may be important drivers of the transition from a serene habitable surface to a hothouse state for terrestrial worlds, assuming they have Earth-like geochemistries and mantle convection dynamics.” , indicates the document.
There is a point where it all diverges. Although we have fairly comprehensive and reliable data on Earth’s LIPs, we don’t have any for Venus at all. But research shows that, even with our lack of detailed data, it’s likely that Venus suffered LIP overlaps that led to its loss.
Fortunately, future missions to Venus will open this investigation with better data.
The Venus VERITAS mission (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) is an orbiter developed by NASA. Its launch date is not yet 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 it will have an atmospheric probe with an orbiter. Once scientists have more detailed information about Venus’ atmosphere and its surface, they can begin to unravel the planet’s past.
“One of DAVINCI’s main goals is to reduce the history of water on Venus and when it may have disappeared, providing better insight into how Venus’s climate has changed over time.” , said Way.
DAVINCI and VERITAS will launch in the late 2020s, with DAVINCI launching first.
ESA is also planning an orbital mission to Venus. It’s called EnVision and is slated for launch in the early 2030s. EnVision will also study Venus’ atmosphere, but it will dig deeper, using its suite of instruments to study the planet’s internal structure.
These results will also play a role in understanding exoplanets. Exoplanets are a growing area of research, and the James Webb Space Telescope is beginning to provide better data on exoplanet atmospheres.
But it will be difficult for scientists to interpret the JWST findings without better global models, and a more detailed understanding of our sister planet’s history will certainly refine our models for planetary atmospheres.
For some reason, Earth has remained habitable for billions of years, and Venus is far worse. If Venus ever hosted an ancient and simple life, it is long gone.
(My apologies to people who think life might still live on in the clouds of Venus.)
Although we may never have a full understanding of all the factors that made Earth and Venus so different from each other, volcanic activity clearly played a role. Once VERITAS, DAVINCI and EnVision have done their job, we should understand Venus’ diverging trajectory in more detail.
This article was originally published by Universe Today. Read the original article.