Venus might not be such a tantalizing target for alien hunters after all.
In recent years, the researchers increasingly come to regard Venus, second rock from the sun, as a potential place for life. For illustration, model studies suggested that the ancient Venus had big oceans, and a clement climate that might have persisted for many billion years.
Venus is well known hellish today, of course; its surface is bone dry & hot enough to melt lead. But several scientists argued that Venus life, if it ever existed, could persist there still, floating in the clouds around 30 miles (50 kilometers) up, where temperatures & pressures are similar to what we enjoy at sea-level here on Earth.
A new study throws little amount of cold water onto such hopes, however.
Dueling models of ancient Venus
Just like all new-born planets, young Venus was very hot, far-too-toasty for liquid-water oceans. Its available water was enough much all vaporized, developing sauna conditions on a planetary scale.
The previous, life-friendly modeling work determined that planet cooled-down pretty much to host liquid surface water because in large part to clouds, which bounced much of solar radiation back into space. The “faint young sun“ was a contributing factor also; in early days of the solar system, our star was only 70 percent as luminous as it’s now.
In new study, which was published online on Thursday (Oct. 13) in the journal Nature, scientists led by Martin Turbet, a post-doctoral researcher at Geneva Astronomical Observatory in Switzerland, simulated the climate of ancient Venus through a new model. And they came-up with variety of results.
Turbet & his team have found that the conditions on young Venus likely limited clouds to planet’s nightside, where they were worse than useless as-far-as the establishment of life is concerned. (Venus is not tidally locked to the sun, so it does not have a permanent nightside; the term here refers to whatever hemisphere happens to be facing-away from the sun at the time.)
Not just did these clouds bounce no sunlight away, they really warmed Venus by a greenhouse effect, trapping much of heat. So, Venus never cooled-down pretty much for rain to fall and for gutters, lakes & oceans to form.
“If authors are correct, Venus was always a hell-hole,” astronomers James Kasting & Chester Harman, of the Penn State University and the NASA’s Ames Research Center, respectively, wrote in an accompanying “News & Views” piece in the same issue of Nature. (Kasting & Harman aren’t members of the study team.)
Further in-depth study of Venusian surface could give some clarity on the planet’s ancient climate. For example, Kasting & Harman point to “highly deformed regions” of the planet, known as tesserae, which are believe to be similar in composition to continental rocks on Earth.
“On our planet, such rocks form-by metamorphic processes (in which minerals change form without melting) that occur in the presence of liquid-water,” Kasting & Harman wrote. “If tesserae turn-out rather to be basaltic, like normal sea-floor on Earth, liquid water wouldn’t have been needed to generate them, further supporting Turbet & colleagues’ hypothesis.”
NASA’s newly-named VERITAS ( short for “Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy”) mission, which is scheduled to launch in 2028, will study tesserae from orbit, if all goes consistent with plan. But it might take a Venus lander to get a firm understanding of these interguing-features, Kasting & Harman wrote.
Implications for Earth & beyond
The new study even found that Earth would probably have taken Venusian route if sun had been a little brighter long ago: A young sun with 92 percent of current brightness instead of 70 percent would probably have consigned our planet to hothouse status, consistent with the model developed by Turbet & his team.
The results even have implications for worlds that orbit other suns and for researchers who aim to understand them, as Kasting & Harman pointed-out.
“Exoplanets that orbit near inner edge of conventional inhabitable zone where liquid water can exist on a planet’s surface, may not actually be habitable,” duo wrote.
The article originally published on Space.
