Tag Archives: oceans

The Lost Oceans of Venus

“Is it deranged to build a good part of a career studying something that may or may not have been?” asks David Grinspoon at the beginning of the chapter 2 of “Alien Seas”, the one about the oceans of Venus.

Grinspoon is the author of “Venus revealed”, a book about the scientific exploration of Venus, and “Lonely Planets”, about the possibility of alien life.

His chapter in Alien Seas explains the two main pieces of evidence of oceans on Venus in the past, namely

– the excess of deuterium in the present atmosphere, that implies that a lot of water, at least in vapour form, was present  in the early atmosphere of Venus (now bone-dry)

– the more circumstantial evidence from our improved understanding of how planets form. We expect the surface early Venus to have been water-rich, like Earth, given how violent and random is the formation of small rocky planets.

Neither argument is entirely fool-proof.  We are like detectives who arrive at the crime scene years after the events, and have no direct clue to work with, only a senile eyewitness with severe memory lapses and the charred remains of a burned note left by the victim.

David Grinspoon makes three points: the first is that Earth-style life could have developed in Venus’s atmosphere, because conditions were very similar to early Earth, with water oceans, volcanoes to provide the carbon and lightnings to provide the energy. The second is that Earth’s version of life could even be Venusian, or the other way around, because exchange of flying rocks was frequent between the planets in the turbulent early days of the Solar System (rocks from Mars still regularly reach Earth today). The third is that Venusian life could have migrated in the cloudtop when the atmosphere got caught in runaway greenhouse and evolved into the present hellish conditions.

You can see a webcast of the talk of David Grinspoon on the topic at Exoclimes 2010 here.

A possible timeline for Venus according to D. Grinspoon, with a long-lasting ocean (blue). [Figure 8.7 of Alien Skies]
A possible timeline for Venus according to D. Grinspoon, with a long-lasting ocean (blue). [Figure 8.7 of Alien Skies]

Earth’s atmosphere and oceans in motion

Two mesmerizing visualizations of dynamics on planet Earth with scientific data have recently been made public. The first shows ocean currents measured over a two-year interval, and the second traces atmospheric winds in real time.

Together they illustrate the main features of dynamics on a rotating planets, the Coriolis effect.

NASA Ocean currents
Still from the movie of ocean currents over the 2005-2007 period. Notice how the gap betwen Africa and Madagascar, combined with the Coriolis effect, generates a train of vortices drifting past the Cape of Good Hope.

The movie of ocean currents, produced by NASA, is available on this site or or as a youtube movie .

The real time flow of winds can be accessed here.

Screen shot 2014-05-11 at 11.07.56
Still from the movie of wind motions.

 

Note in the first image how the ocean currents share a similar “typical radius”, defining the size of the vortices, and the length of the loops in the snaky flow. Wind system also have a characteristic size in the second image, which is much larger.

The size of the loops and swirls is defined by the Coriolis effect, that makes currents on a rotating sphere veer aside.  The faster the rotation, the smaller the swirls. And the heavier and slower the fluid, the smaller the swirl, hence the difference between ocean currents and atmospheric winds.

Some planetary atmosphere behave more like Earth’s ocean than its air. For instance, long-lasting vortices form in Jupiter’s atmosphere, analogous to loops in ocean currents.