How long after a global nuclear disaster would the world become habitable by humans again?

So at some point in the future, humans have small colonies on the Moon, on Mars and many space stations in orbit of all the planets in the solar system. Everything is going great until one day something happens on Earth that sparks a global nuclear war.

The USA, Russia, China, India, Pakistan, UK, France, Israel and North Korea shoot off all their missiles and nuke the world. Most of humanity on Earth is wiped out and the entire surface is irradiated.

So how long until the humans who live off-world could return to earth and safely (without the need for rad suits or other preventative measures) begin farming again?

Parameters for the question:

• Assume 2016 level nuclear weapon capability when the war happens.
• No large scale terraforming capability.
• Don't worry about the space colonies' survivability without the earth.
• Don't worry about what started the war.
• Don't worry about any survivors on surface of the earth.
• All defences against the warheads making groundfall are ineffective. All nukes hit their targets, every continent is targeted with basically 100% coverage.
• Not looking for a super exact answer, just a general best case/worst scenario...is it like 5 years, 10 years, 1000 years, 10000 years?

NOTE: People seems to stuck on the fact that this nuclear event isn't possible. My question doesn't care about that, in my scenario just assume this happens, that there are enough missiles with 2016 tech to devastate the entire habitable surface of the earth. How long before the Earth is safe and radiation free so that humans can live there again?

posted about 8 years ago

fiend‭

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