[Space] Terraformed Venus as a setting

[Johnny1A.2]

Originally Posted by Vaevictis Asmadi

To give Venus a magnetosphere, you need to get the core dynamo working. The core may still be molten, but it needs convection, right? How big a moon would Venus need to provide big enough tides? Wouldn't Mars be enough?

What crash are you referring to?

Luke's proposal to coalesce Venus and Mars into a single body.

Originally Posted by lwcamp

Kill two birds with one stone. Move Venus out to Mars's orbit (it will not threaten Earth there), and move the now superfluous Mars into orbit around Venus as a big impressive red moon.

(Personally, I always thought the best way to teraform Mars was to crash Venus into it.)
Luke

[lwcamp]

Originally Posted by Nereidalbel

Venus lacks a magnetic field, just like Mars. Without it, solar radiation and cosmic rays are fairly good at sterilizing the surface. Gonna need some way to kick-start that dynamo and get a field going! Granted, just speeding up the rotation from painfully slow to somewhat decent may help with that.

And yeah, no magnetic field = first solar flare aimed at the planet killing everything on the day side of the planet.

Here's a link to a study on the effect of a lack of a magnetic field on the surface radiation dose

http://phys.org/news/2013-11-cosmic-...t-chances.html

and an excerpt

"Unexpectedly, 'we found the thickness of a planet's atmosphere is a much more important factor in determining a planet's radiation dose,' Atri told Astrobiology Magazine. 'If you took the Earth and you completely removed the magnetic field, the radiation dose rate will increase by two, which is a big increase, but it would still have very small effects, and would not have any effects on us. However, if you keep the magnetic field and decreased the atmosphere so it is a tenth as thick, the radiation dose will increase by more than two orders of magnitude.'"

Luke

[Anthony]

Originally Posted by lwcamp

"Unexpectedly, 'we found the thickness of a planet's atmosphere is a much more important factor in determining a planet's radiation dose,' Atri told Astrobiology Magazine.

Not sure why it's unexpected that ~1,000 g/cm^2 of shielding strongly influences surface dose, it's something like 10-20 times the mean penetration of cosmic rays in atmosphere and cosmic rays being higher at high altitudes is well known.

[Vaevictis Asmadi]

Originally Posted by Johnny1A.2

Luke's proposal to coalesce Venus and Mars into a single body.

No, he proposed using Mars as Venus' moon. Not crashing them.

[Johnny1A.2]

Originally Posted by Vaevictis Asmadi

No, he proposed using Mars as Venus' moon. Not crashing them.

He proposed both, albeit in passing, I embolded the part I was talking about above.

[malloyd]

Originally Posted by Anthony

Not sure why it's unexpected that ~1,000 g/cm^2 of shielding strongly influences surface dose, it's something like 10-20 times the mean penetration of cosmic rays in atmosphere and cosmic rays being higher at high altitudes is well known.

Despite the fact that radiation levels underneath auroras are not deadly even though they are where the magnetic field is *concentrating* the charged particle radiation, lots of people somehow believe that magnetic fields are important radiation shields for the Earth. Presumably because they actually are fairly important for determining the radiation dose experienced by low orbiting spacecraft.

[Nereidalbel]

Originally Posted by malloyd

Despite the fact that radiation levels underneath auroras are not deadly even though they are where the magnetic field is *concentrating* the charged particle radiation, lots of people somehow believe that magnetic fields are important radiation shields for the Earth. Presumably because they actually are fairly important for determining the radiation dose experienced by low orbiting spacecraft.

More that they help keep your upper atmosphere (including ozone layers and such) from being blown away by the solar wind. The spiral of Venusian atmosphere being blown off is measurable all the way out to the orbit of the Earth.

[Vaevictis Asmadi]

Originally Posted by Nereidalbel

More that they help keep your upper atmosphere (including ozone layers and such) from being blown away by the solar wind. The spiral of Venusian atmosphere being blown off is measurable all the way out to the orbit of the Earth.

Yup. There is a current scientific theory that Mars lost its atmosphere and liquid water after the core cooled and shut off its magnetosphere. I read a paper showing that remnants of that magnetosphere exist today in the southern hemisphere, driven by patches of magnetized crust, and that the air columns can be much taller there. The authors of that paper found evidence that suggested a huge impact may have messed up the remnant magnetosphere in the northern hemisphere, and smaller impacts may have broken up the southern cover.

I don't know if anyone has reliably calculated how long a terraformed Mars (or Venus) would be able to keep a breathable atmosphere without magnetospheric cover. If it's longer than the main-sequence lifespan of Sol, it probably wouldn't matter.

[Mailanka]

Slightly to the side of the main thrust of this topic:

Listening to people discuss solar shades for Venus instantly brought to mind the image of a "black sun", an eclipsed sun with its ring of fire staring balefully down at the alien landscape of this terraformed world.

So let's say you left most of Venus alone, merely placed a solar shade, cleaned up the atmosphere to make it breathable, added a bunch of water, but left rotation and orbit and everything else the same. You wouldn't get the "We didn't know it wasn't Earth!" that the OP wanted, but I don't mind. I like it being alien and strange.

What would you get? Is it workable? How stable is it? Could it be shirtsleeves weather?

[Nereidalbel]

Originally Posted by Mailanka

Slightly to the side of the main thrust of this topic:

Listening to people discuss solar shades for Venus instantly brought to mind the image of a "black sun", an eclipsed sun with its ring of fire staring balefully down at the alien landscape of this terraformed world.

So let's say you left most of Venus alone, merely placed a solar shade, cleaned up the atmosphere to make it breathable, added a bunch of water, but left rotation and orbit and everything else the same. You wouldn't get the "We didn't know it wasn't Earth!" that the OP wanted, but I don't mind. I like it being alien and strange.

What would you get? Is it workable? How stable is it? Could it be shirtsleeves weather?

If you could fix the serious greenhouse problem Venus has, it would probably feel like some of the hotter periods of Earth's past. The only problems would be terrible conditions for farming, and the lack of a magnetic field being bad for forming an ozone layer. If you could artificially generate one to keep the upper atmosphere stable, it would just be a hot Earth. No volcanos, though. Venus' period of hyper volcanism went on a lot longer than any volcanic period Earth has experienced.