New Study Reveals Evidence That Venus Was Once Habitable

Artist's Representation of Habitable Venus

Venus may have been a temperate planet hosting liquid water for 2-3 billion years, until a dramatic transformation starting over 700 million years ago resurfaced around 80% of the planet. A study presented today at the EPSC-DPS Joint Meeting 2019 by Michael Way of The Goddard Institute for Space Science gives a new view of Venus’s climatic history and may have implications for the habitability of exoplanets in similar orbits.

Forty years ago, NASA’s Pioneer Venus mission found tantalizing hints that Earth’s ‘twisted sister’ planet may once have had a shallow ocean’s worth of water. To see if Venus might ever have had a stable climate capable of supporting liquid water, Dr Way and his colleague, Anthony Del Genio, have created a series of five simulations assuming different levels of water coverage.

In all five scenarios, they found that Venus was able to maintain stable temperatures between a maximum of about 50 degrees Celsius and a minimum of about 20 degrees Celsius for around three billion years. A temperate climate might even have been maintained on Venus today had there not been a series of events that caused a release, or ‘outgassing,’ of carbon dioxide stored in the rocks of the planet approximately 700-750 million years ago.

“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,” said Way.

Three of the five scenarios studied by Way and Del Genio assumed the topography of Venus as we see it today and considered a deep ocean averaging 310 meters, a shallow layer of water averaging 10 meters and a small amount of water locked in the soil. For comparison, they also included a scenario with Earth’s topography and a 310-meter ocean and, finally, a world completely covered by an ocean of 158 meters depth.

To simulate the environmental conditions at 4.2 billion years ago, 715 million years ago and today, the researchers adapted a 3D general circulation model to account for the increase in solar radiation as our Sun has warmed up over its lifetime, as well as for changing atmospheric compositions.

Although many researchers believe that Venus is beyond the inner boundary of our Solar System’s habitable zone and is too close to the Sun to support liquid water, the new study suggests that this might not be the case.

“Venus currently has almost twice the solar radiation that we have at Earth. However, in all the scenarios we have modeled, we have found that Venus could still support surface temperatures amenable for liquid water,” said Way.

At 4.2 billion years ago, soon after its formation, Venus would have completed a period of rapid cooling and its atmosphere would have been dominated by carbon-dioxide. If the planet evolved in an Earth-like way over the next 3 billion years, the carbon dioxide would have been drawn down by silicate rocks and locked into the surface. By the second epoch modeled at 715 million years ago, the atmosphere would likely have been dominated by nitrogen with trace amounts of carbon dioxide and methane – similar to the Earth’s today – and these conditions could have remained stable up until present times.

The cause of the outgassing that led to the dramatic transformation of Venus is a mystery, although probably linked to the planet’s volcanic activity. One possibility is that large amounts of magma bubbled up, releasing carbon dioxide from molten rocks into the atmosphere. The magma solidified before reaching the surface and this created a barrier that meant that the gas could not be reabsorbed. The presence of large amounts of carbon dioxide triggered a runaway greenhouse effect, which has resulted in the scorching 462-degree average temperatures found on Venus today.

“Something happened on Venus where a huge amount of gas was released into the atmosphere and couldn’t be re-absorbed by the rocks. 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,” said Way.

There are still two major unknowns that need to be addressed before the question of whether Venus might have been habitable can be fully answered. The first relates to how quickly Venus cooled initially and whether it was able to condense liquid water on its surface in the first place. The second unknown is whether the global resurfacing event was a single event or simply the latest in a series of events going back billions of years in Venus’s history.

“We need more missions to study Venus and get a more detailed understanding of its history and evolution,” said Way. “However, our models show that there is a real possibility that Venus could have been habitable and radically different from the Venus we see today. This opens up all kinds of implications for exoplanets found in what is called the ‘Venus Zone,’ which may in fact host liquid water and temperate climates.”

8 Comments on "New Study Reveals Evidence That Venus Was Once Habitable"

  1. Venusian Cataclysm:

    An alternative cause of the global resurfacing event was a former moon in a decaying retrograde orbit that spiraled in to merge with Venus at 541 Ma, causing its present retrograde rotation. The moony merger contaminated the inner solar system with Venusian fauna, causing the Cambrian Explosion on Earth, and fogged the inner solar system, causing the Baykonurian glaciation on Earth.

    An alternative planet formation ideology suggests that our 3 sets of twin-binary planets (Jupiter-Saturn, Uranus-Neptune, and Venus-Earth) formed by ‘trifurcation’ of a former brown dwarf (protostar) which was spun up to the point of trifurcation fragmentation by way of bar-mode instability during orbital interplay with a much-more massive twin-binary pair of disk instability objects that became our former binary-Sun. Trifurcation occurred in 4 generations, forming twin-binary pairs like Russian nesting dolls, namely; 1st gen. binary-Companion, 2nd gen. Jupiter-Saturn, 3rd gen. Uranus-Neptune, and 4th gen. Venus-Earth, with residual core Mercury(?).

    Binary-Sun spiraled in to merge at 4,567 Ma in a luminous red nova whose resulting solar-merger debris disk condensed the asteroids and chondrites. Binary-Companion components spiraled in for the almost 4 billion years, causing the Sun-Companion tidal inflection point to spiral out through the Kuiper belt, causing the late heavy bombardment. Binary-Companion ultimately merged ~ 650 Ma in an asymmetrical merger explosion that gave the newly-merged Companion escape velocity from the Sun, and the high-angular-momentum Companion-merger debris disk condensed the young cold-classical KBOs. Additionally, the Companion-merger explosion fogged the inner solar system, causing the Marinoan glaciation of Snowball Earth, with the earlier Sturtian glaciation caused by multiple mergers of the super-Jupiter-mass binary components with their former moons during spiral in.

    Trifurcation fragmentation spin up occurred by way of bar-mode instability, whose trailing pin-wheel tails gravitationally pinched off to form oversized ‘Titan’ moons, half in prograde orbits and half in retrograde orbits, with prograde Moon at Earth, former retrograde moon at Venus (541 Ma merger), prograde Titan at Saturn, former retrograde moon at Jupiter (4,562.5 Ma merger, forming enstatite chondrites and the Galilean moons), lost prograde moon at Uranus, and retrograde Triton at Neptune.

  2. Your ideas don’t seem very well thought through.

  3. A lot of noise many people reading your comment may not understand. Good way to throw complete bs out into the aether.

  4. Unlikely venus would have had a chance. A large moon like earth’s would have helped. It’s what helps earth. Creates tides, slightly, however continiously helping regulate temperatures in some regions. Contributes to keeping our core molten, in turn maintaining our magnetic field, to keep our atmosphere.

  5. Torbjörn Larsson | September 23, 2019 at 3:43 am | Reply

    This is interesting, if it can be tested. It would mean that the shielding from a magnetic field means very little for a habitable atmosphere on Earth (or Venus) analogs.

    @Mat: Well, we may agree to disagree then, especially on the magnetic field, see above. But as for the Moon, it is an open question if it has had any effect on life (apart from easing nocturnal traits) and in the classical models it does not affect Earth core (but for a recent alternative, see here: https://www.sciencedaily.com/releases/2016/04/160401075118.htm ).

    @David Carlsom: Velikovsky-like pseudoscience conspiracy theory lives on, I see. If you had bothered to study science, which is not ‘ideology’, you would have liked to test your ideas.
    But they fail before being publishable. For instance, “Venusian fauna” has not “contaminated” us, since the observation of a universal common ancestor for all Earth life is the most likely observation in all of science: it is more likely than your notion of multiple ancestry with a factor 10^2000+ [!; https://www.nature.com/articles/nature09014 ].

  6. BUT….we just don’t know! All theories should be welcome as they will all have a bit of truth.
    Perhaps when we finally, or another country that gets tired of waiting, launches a new telescope, we’ll have some more facts that don’t fit the current theory.
    I suspect Milton-DeGrazie theory is closest to the truth, our inner rocky planets being formed between Jupiter and Sol.

  7. Maybe it had a technological civilization and they did what we are doing to their atmosphere.

  8. Venus has about 100 times as much air as Earth. There isn’t anywhere near enough organic material to burn to reach that amount or enough oxidizing agents either. Man-made emissions are irrelevant to such catastrophic change. And the suggestion in the article is that Venus COULD have been habitable before. It doesn’t mean that it ever was.

Leave a comment

Email address is optional. If provided, your email will not be published or shared.