The Death of Venus

2015-07-08

O Venus, beauty of the skies,
To whom a thousand temples rise,
Gaily false in gentle smiles,
Full of love-perplexing wiles;
O goddess, from my heart remove
The wasting cares and pains of love.

Sappho

Those of you who enjoy a look at the sky of an evening may have seen the Venus/Jupiter conjunction recently. I would have loved to have seen it, if it weren’t for an inconvenient cloud. I am sure many of us have admired the shining beauty of our ‘Evening Star’, as have artists and poets throughout history. Named for the Roman goddess of love and beauty, it is the brightest natural object in the sky after the Moon, bright enough to cast shadows. Venus has long been considered to be Earth’s twin as they are so similar in size.

A few Venus facts

Venus is a terrestrial rocky planet like Earth, Mars and Mercury and has a surface temperature of 462C (864F), making it the hottest planet in the Solar system. Its day lasts 243 of our days and is longer than its year of 225 Earth days. It has retrograde rotation (it spins counter-clockwise), likely due to an impact in its early history, and has virtually no axial tilt, thus no seasons.

It has no natural satellites, although it may have had one once but got hit again causing any moon to spiral back into the planet and also cause its retrograde spin. Venus’ atmospheric pressure is 92 times greater than Earth’s, much like the pressure we would experience in a deep sea environment. Venus has a very thick and until modern times, impenetrable atmosphere, leading many to speculate that it could perhaps have a tropical climate. Sadly, when radio mapping was developed in the 1960s, its extreme nature was discovered: a surface hot enough to melt lead, an atmosphere consisting of 96.5 carbon dioxide, considerable volcanism and highly reflective clouds of sulphuric acid which means it is also dark and dim on the surface. Plus, all of those volcanoes.

So, far from being the embodiment of love and beauty, it is inhospitable to say the least! Venus doubtlessly started its life in the same way Earth did, it is after all on the inner edge of our Solar system’s habitable zone and yet does a pretty good impression of the fiery pits of hell. You have to wonder what the heck went wrong?

Venus, like Earth and Mars, probably looked much the same a few billion years ago. It may even have had oceans or even life on the surface at one point, although we cannot be absolutely sure of this. As we know today, the planet suffered from a myriad of interlinked calamities that have made it the hot, arid hellhole it is today. With no water, there is nothing fluid to drive plate tectonics which recycles the surface and dissipate heat from the mantle, without this, the planet cannot draw down carbon dioxide from the atmosphere. Volcanic outgassing just adds to the problem by belching out yet more chemicals! This of course means a runaway greenhouse effect had to have occurred.

On Earth, we stay more or less in equilibrium temperature wise and have maintained it for a considerably long time. What is clear though is that the catastrophic positive feedback mechanism on Venus effectively shut the planet down so it cannot get rid of heat fast enough or generate a strong enough magnetic field to protect it from cosmic radiation. What magnetosphere it has is generated between the Solar wind and its ionosphere, not from its core, so it has no internal dynamo and little protection from solar radiation stripping away light elements like hydrogen and photodissociation eroding its water. Its interior heat just bakes the crust, this heat is trapped under its thick atmosphere and has nowhere to go. It is interesting to speculate how it may have been if chance had not set off the unfortunate chain of events that rendered the place uninhabitable. It has been suggested that life could exist high up in the atmosphere however.

There have been assorted missions to Venus, notably NASA’s Messenger and ESA’s Venus Express. there are fly-bys planned as well as well as a Venus landing mission proposed by NASA under the New Horizons program. Naturally making a lander sturdy enough to handle the conditions is, I am sure, a challenge to give even the geniuses at JPL a headache! It is a fascinating place however forbidding it seems. I feel that for myself, I just cannot help but wonder what could have been.

This article originally appeared on TheMittani.com, written by Feiryred.

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