Does Venus need a Moon?

Tom Kalbfus · 2016-03-05 13:30:11

See this picture? Imagine it was a scene from the surface of a future Venus that was terraformed? Would it be worth doing? The Moon in the scene is actually Mercury. I don't know whether we'd bother to make dinosaurs, but compared to putting Mercury in orbit around Venus, and terraforming Venus, creating a dinosaur should be easy. But back to the basic question, would we want to move Mercury and place in in orbit around Venus as its Moon? My guess is the surface of Mercury would not be unaltered by the process of moving it. If we placed it at a similar distance as the Earth's moon is from Earth, then Mercury would appear 150% the size of our Moon in our own sky.

RobertDyck · 2016-03-05 14:09:10

Tom Kalbfus · 2016-03-05 15:09:48

Are you a fan of Robert Heinlein? Funny those old books, they always like to give alien creatures too many eyes, arms and legs. In reality, you don't often see creatures with more than two eyes., multi-limbed animals are more common, but 2 eyes seem sufficient to determine distance, three eyes are redundant. that picture, I admit, I altered it a bit, it wasn't originally Mercury in that sky. Dinosaurs seem associated with the Pulp version of Venus, so it seemed appropriate.

Last edited by Tom Kalbfus (2016-03-05 15:12:08)

RobertDyck · 2016-03-05 15:40:05

I grew up with Robert A. Heinlein books. Great stories. Cover art didn't always match the story, but in this case it's supposed to be a Venusian physicist who could speak English with the aid of a portable device. The author tried to think of something alien, and was part of his "juvenile" series of books, targeted at tween and teenage readers. Read those books in grades 5-9, so I guess it worked. My mother wanted me to practice reading.

You wanted dinosaurs on Venus. Sounds like this book.

To answer your question: no. I don't think Venus needs a moon. Our moon causes tides, not only in the ocean but the crust itself. Rise/fall of the crust is slow so the bulge is slightly ahead of rotation. That bulge is pulled by the Moon's gravity, which slows the Earth's rotation. Our length of day is still increasing, though very slowly. This slows rotation of the crust, but not the inner core. A book called "Rare Earth" proposed that this effect causes Earth's dynamo that creates a strong magnetic field. That magnetic field creates the magnetosphere, which protects our planet from solar wind. That prevents solar wind from breaking water in the upper atmosphere into hydrogen and hydroxyl, and accelerating the hydrogen to escape velocity. So it keeps our water.

Venus has a molten core. In fact belief is that the crust of Venus is far thinner than Earth's. That's due to high surface temperature, causing slower planetary cooling. The thick atmosphere and complete cloud cover trap heat in. The issue is how to organize the molten core to form a dynamo. Convection of heat from Earth's core is believed to power the dynamo. The book "Rare Earth" speculates that Earth's inner core spins faster than the rest of the planet, the liquid outer core forms a liquid bearing. Convection currents in the liquid iron outer core do not counter-rotate because of the bearing effect. The inner core spins faster than the mantle, so that causes convection currents to rotate in the same direction, like ball bearings. There's also friction. All this creates electric currents in the liquid outer core, which forms the dynamo. That creates the magnetic field.

Venus would provably have a solid inner core and liquid outer core like Earth. It's practically Earth's twin: 90% surface gravity, and 90% surface area. However, convection currents in the outer core probably counter-rotate. That means any magnetic effects of one cell cancels the next. Venus does have tides from the Sun, causing it's length of day to lengthen as well. It already has a ridiculously long day, but it's getting longer. So this should cause some dynamo in the outer core. Venus does have a magnetic field, but it's ridiculously weak. Could we do something to organize convection cells in the out core of the planet? Something to cause a strong dynamo? That would form a strong planetary magnetic field, which would form a strong magnetosphere, which would hold onto what water Venus has left. It may even trap hydrogen from solar wind, which could burn with free oxygen on Venus atmosphere (it does have a tiny bit). That would increase water over time, instead of eroding it away.

I had suggested strong magnets round the equator. With fields strong enough to penetrate to the outer core. Cause the magnetic fields to move around the planet. Not by moving anything physical, but creating a dynamic circuit in electromagnets so the artificial magnetic field "stirs" the liquid outer core consistently in one direction. Leverage your efforts by organizing currents in the core, then power the planetary magnetic field primarily from the core. That does mean big magnets. It would be a big construction job. And with Venus current surface conditions, difficult to build. But still easier than moving Mercury.

Tom Kalbfus · 2016-03-07 12:10:33

Yes the Venusians had to be alien, and of course he needed a whole cluster of eyes on eyestalks and at least six limbs to make them look alien. I think on the whole, a humanoid looking Venusian would be more likely, since it would likely be us terraforming the planet and making it Earthlike.

Last edited by Tom Kalbfus (2016-03-07 12:11:12)

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#1 2016-03-05 13:30:11

Does Venus need a Moon?

#2 2016-03-05 14:09:10

Re: Does Venus need a Moon?

#3 2016-03-05 15:09:48

Re: Does Venus need a Moon?

#4 2016-03-05 15:40:05

Re: Does Venus need a Moon?

#5 2016-03-07 12:10:33

Re: Does Venus need a Moon?

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