Venus the Temperate, Earth’s "Twisted Sister"
A new study gives insight into Venus' climatic history.
It can be hard to imagine — given the hellish conditions on Venus’ surface today, but for 2 to 3 billion years the planet may have made a decent home. A new study indicates that our sister planet may have contained water and possibly even the building-blocks to support life.
"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 hot-house we see today."
Dr. Michael Way (NASA)
In 1978, NASA's Pioneer Venus spacecraft discovered evidence that Earth’s "twisted sister" may have once had shallow oceans on its surface. Since then, numerous missions have surveyed the planet's surface and atmosphere. Recent findings have revealed that approximately 750 million years ago, a massive resurfacing event may have triggered a runaway greenhouse effect, causing the planet’s atmosphere to become incredibly dense and hot, and rendering it inhabitable.
- Venus is second from the sun and the second brightest natural object in our night sky.
- Venus boasts the densest atmosphere of the four terrestrial planets in the solar system — consisting of more than 96% carbon dioxide.
- Venus’ atmospheric pressure is 92 times that of Earth.
- Venus boasts the hottest surface temperature -- 735 K (462 °C; 863 °F) -- of any planet in the solar system, despite Mercury being closer in proximity to the Sun.
To see if Venus might ever have had a stable climate capable of supporting liquid water – an essential ingredient to supporting life as we know it – Dr. Way and his colleague, Anthony Del Genio, created a series of five simulations utilizing a 3D general-circulation model that accounted for atmospheric conditions as they were 4.2 billion years ago, 715 million years ago, and conditions as they are today. This model also accounted for the steady increase in solar radiation, as the sun increases in temperature over the course of its lifetime.
"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."
Dr. Michael Way (NASA)
Three of the five models assumed a similar topography to today’s Venus, an ocean depth averaging 1017 feet, a shallow layer of water averaging 10 meters, and a small amount of water locked into the soil. For comparison, one scenario applied Earth's topography and an ocean depth of 1017 feet. A final scenario exhibited a world completely covered by an ocean — averaging 1700 feet in depth. In all five scenarios, Venus was able to maintain stable temperatures between 122 °F and 68 °F for around three billion years.
Venus may still have had a temperate climate today, had there not been a series of catastrophic climate events that caused a discharge, or 'outgassing', of carbon dioxide stored in the rocks. While the cause for the planet’s outgassing is relatively unknown, researchers have speculated that it is most likely linked to the planet’s volcanic activity. Similar events have occurred in Earth’s history.
While additional studies on Venus are necessary to understand the planet’s history and evolution; models have shown that there is a real possibility that Venus could have been habitable and drastically dissimilar to the planet of today.
Two major unknowns still remain. Foremost, how rapidly Venus cooled initially and whether it was able to condense liquid water on its surface, to begin with. Secondly, was this global resurfacing event an anomaly or was this calamitous occurrence – the latest in a series of catastrophes dating back billions of years?
A study presented at the EPSC-DPS Joint Meeting 2019 by Michael Way of The Goddard Institute for Space Science gives a new insight into Venus's climatic history.