Alternative colonisation targets - Venus and Titan

The conventional wisdom is that Mars it the best candidate for a human colony. Some others would argue getting something going on the Moon would be a more achievable target. They would be right, of course, but both Moon and Mars come with two major drawbacks. The biggest challenge is the lack of any meaningful atmosphere and magnetosphere to shield humans from radiation and solar flares. The second would be the relatively low gravities. Of course, we could adapt to the lower gravity, and either go underground or build large scale shields against radiation (though realistically the first colonies would be well underground). But could there be a better alternative?

Titan

Titan is not going to solve the gravity problem. Indeed, it is slightly less than that of the moon at 0.13g. Our bodies can adapt and evolve to this, over time, though some medium term concerns will remain - such as childbirth and general strength.

What Titan does offer is an incredibly thick atmosphere and a surface bathed in the richest trove of organic compounds seen in the Solar System. Speculated to be hundreds of times more than all natural gas and oil on Earth! There are quite literally lakes of hydrocarbons, and the Titan does have a hydrocarbon cycle quite like our Earth's water cycle, including it's own clouds and rain.

With such an abundance of raw material, it would be quite easy to create all necessary ingredients for life. At temperatures approaching -200 °C, Titan's incredibly cold. But hey, you've got an endless amount of fuel to burn, and the greenhouse effect generated would be beneficial on Titan. It's also much further away than Venus, Moon or Mars.

Most importantly, you can live on the surface of Titan - just a resilient glass dome would be more than enough protection.

Billions of years from now, when the Sun starts its journey to becoming a Red Giant, Earth will be toast. But Titan could become hot enough to sustain liquid water!

But today, you could fly on Titan with wings attached. Who wouldn't want that?!

Venus

Venus is pretty much Earth gone totally wrong. The surface of Venus is a hellish inferno - a true warning as to what runaway greenhouse effect does to an Earth-like planet. But up in the clouds of Venus is a pretty familiar place. 50 km - 60 km above Venus' surface, we have Earth-like temperature, atmospheric pressure and of course gravity! Indeed, it's the only place in the Solar System that gets closest to the Earth's conditions.

Flying cities may seem like a fantasy, but given Venus' dense Carbon dioxide dominant atmosphere, it's achievable according to NASA's HAVOC project. The risk of leaks would be greatly minimised as well. The greatest challenge for living up in the skies would be extracting raw materials. And preventing corrosion from the Sulphuric acid clouds, of course!

Mars and the Moon are much more achievable objectives, but it's hard to argue against Venus or Titan for being more familiar in many ways.

_{Further reading -
http://www.penguinrandomhouse.com/books/239536/beyond-earth-by-charles-wohlforth-and-amanda-r-hendrix-phd/9780804197977/
http://ia600609.us.archive.org/26/items/JulianNott2/JulianNott2.pdf
http://www.esa.int/esaSC/SEMCSUUHJCF_index_0.html
http://www.science20.com/robert_inventor/will_we_build_colonies_that_float_over_venus_like_buckminster_fullers_cloud_nine-127573
https://arstechnica.com/science/2017/05/forget-mars-lets-go-colonize-titan/
http://sacd.larc.nasa.gov/branches/space-mission-analysis-branch-smab/smab-projects/havoc/
All images from Wikimedia.}