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posted by martyb on Sunday May 26 2019, @03:07PM   Printer-friendly
from the 'habitable-zone'-is-more-of-a...guideline dept.

Venus is believed to have once been a much more hospitable place with a cooler atmosphere and liquid oceans. However tidal braking in a large ocean could have slowed Venus to its current rate of rotation (243 Earth Days to complete a Venusian day) within 10-50 million years taking it away from being habitable in a short time frame.

[The relatively habitable climate on Venus] changed billions of years ago as Venus experienced a runaway greenhouse effect, changing the landscape into the hellish world we know today. According to a NASA-supported study by an international team of scientists, it may have actually been the presence of this ocean that caused Venus to experience this transition in the first place.

On Earth, tidal torque changes the length of our day by around 20 seconds every million years.

The team simulated what Venus would be like with oceans of varying depth and a rotational period ranging from 243 to 64 sidereal Earth days. They then calculated the tidal dissipation rates and associated tidal torque that would result from each. What they found was that ocean tides would have been enough to slow it down by up to 72 Earth [days] every million years, depending on its initial rate of rotation.

This suggests that the tidal brake could have slowed down Venus to its current rotation in just 10 to 50 million years. Since it was this reduced rotation rate that caused Venus' oceans to evaporate on its Sun-facing side, leading to the runaway greenhouse effect, this tidal disruption effectively robbed Venus of its habitability in what was (from a geological standport) a pretty short time frame.

The study provide an alternative explanation of why Venus rotates the way it does which previously was assumed to be due to a massive impact slowing its rotation, additionally

These findings could also have implications for the study of extrasolar planets, where many "Venus-like" worlds have already been found.

Journal Reference : Consequences of Tidal Dissipation in a Putative Venusian Ocean (pdf)


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  • (Score: 1) by RandomFactor on Sunday May 26 2019, @08:14PM

    by RandomFactor (3682) Subscriber Badge on Sunday May 26 2019, @08:14PM (#847972) Journal

    Flash will save us.

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