Massive global volcanism, which covered 80% of Venus’s surface in lava, may have been the deciding factor in turning Venus from a wet, bland world into the suffocating, sulphurous, hellish planet it is today.
The surface temperature of Venus is 867 degrees Fahrenheit (464 degrees Celsius), hot enough to melt lead, and there is a crushing pressure of 90 atmospheres under dense clouds of carbon dioxide soaked in corrosive sulfuric acid. Venus, often referred to as Earth’s “evil twin”, is the victim of a runaway greenhouse effect, which is no doubt exacerbated by the fact that Venus is about 25 million miles (40 million kilometers) closer to the Sun than Earth, and therefore receives more heat. .
However, there is growing evidence that Venus has not always been like this and could once have been a temperate world, something similar to Earth – perhaps, geologically speaking, more recently than expected.
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Michael Way of NASA’s Goddard Space Flight Center in Maryland led much of the research to develop this new vision of Venus. In his latest paper, he and his team argue that Venus’ volcanism may have ultimately been what pushed the planet to the brink, sending massive amounts of carbon dioxide – a potent greenhouse gas, as we know it – into Venus’s atmosphere.
In the 1990s, NASA’s Magellan spacecraft made a radar map of the surface of Venus, hidden by the planet’s thick atmosphere, and found that much of the surface was covered in volcanic basalt rocks. Such “large igneous provinces” are the result of massive volcanism lasting tens of thousands, if not millions of thousands of years, that occurred at some point in the last billion years.
In particular, some of these events, which took place perhaps over a million years and each covered millions of thousands of square miles or kilometers of lava, could fill the atmosphere of Venus with so much carbon dioxide that the climate would not be able to do it. deal. Any oceans would boil away, adding moisture to the atmosphere, and since water vapor is also a greenhouse gas, accelerating the runaway greenhouse effect. Over time, the water would have gone into space, but carbon dioxide and an inhospitable world remained.
“While we are not yet sure how often the events that created these fields occurred, we should be able to narrow it down by studying the Earth’s own history,” Way said in a statement.
The frequency with which massive volcanic events have occurred on Earth, forming large igneous provinces, suggests that it is likely that several such events could have occurred on Venus over a million years. These incidents could scar Venus forever.
The Earth itself had some close challenges. So-called “supervolcanoes” have been linked to numerous mass extinction events on Earth over the past half a billion years. For example, the Late Devonian mass extinction 370 million years ago is attributed by some to supervolcanism in what is now Russia and Siberia, as well as a separate supervolcanic eruption in Australia. The Triassic-Jurassic mass extinction is widely blamed for the formation of Earth’s largest igneous province, the Central Atlantic Igneous Province, 200 million years ago. Even the death of the dinosaurs 65 million years ago could have been caused by a double asteroid impact and supervolcanism in the Deccan Traps, a large igneous province in India.
For unknown reasons, similar volcanic events on Venus were much more common and provoked a runaway greenhouse effect that changed the planet. Meanwhile on Earth, the carbon-silicate cycle, which acts as the planet’s natural thermostat, exchanging carbon dioxide and other greenhouse gases between the mantle and atmosphere over millions of years, may have prevented Earth from going down the same path as Venus.
(Image credit: ESA/AOES)
Two future NASA missions will attempt to answer some of these questions. DAVINCI, the Venusian Noble Gas, Chemistry and Imaging Mission in the Deep Atmosphere of Venus, will launch later this decade and will be followed by VERITAS, the Venusian Emissivity, Radioscience, InSAR, Topography and Spectroscopy mission in the early 2030s. The European Space Agency’s EnVision mission is also aiming for a launch sometime in the 2030s, while China has proposed a possible mission called VOICE, the Venus Volcano Imaging and Climate Explorer, which if launched will reach Venus in 2027 to study the atmosphere and geology of the planet.
“DAVINCI’s main goal is to narrow down the history of water on Venus and learn when it may have disappeared to better understand how Venus’s climate has changed over time,” Way said.
The results were published in the Planetary Science Journal earlier this year.
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