Once again, I've been thinking while off medication. Earth seems to have acquired a rather unique terraformed signature that's very much unlike all the other planets. Correct me if I'm wrong but, are there other planets with this much of any magnetic shield?
For our size, Earth seems to have a relatively large degree of magnetic flux that's not actually needed for much of anything except as for primitive and/or migration navigation and otherwise as for creating and sustaining those Van Allen belts. Most forms of life, if not all recorded forms, seem physiologically to survive without any magnetic field. Obviously without those Van Allen belts, life as we know it may not ever have gotten past go, let alone matured into the sorts of life we see today, as for having good atmosphere or not, if you're radiated, you're most certainly dead.
Is it possible that Earth was terraformed?
Just as if some day in the future mankind were to have it's pick of viable planets to terraform (hopefully a whole lot better off than anything Mars) and, obviously of having the necessary space travel and science/physics technology at hand (wisdom certainly should be in there somewhere), there are but a few options for sustaining life as we know it.
It does life little good as to having a reasonable degree of O2 (say 10+% or whatever is proportional to the available atmospheric pressure, such as 0.1% for Venus might suffice) if that doesn't already incorporate a sufficient degree of atmospheric density that's rather necessary as to blocking the solar flare radiation and, not to be forgetting about all fending off all that other nasty cosmic radiation. Earth's magnetic shields does most of the work as for keeping us alive, Mars has almost nothing magnetic nor atmospheric, where at least Venus offers considerably greater atmospheric density that should be capable of doing the job, at least as for sufficiently evolved sorts and especially if they can seasonally migrate so as to remain within their season of nighttime.
One method that's somewhat unusually Earth like, is to locate upon a planet that already offers or where one can go about creating a relatively stable thermonuclear core, along with the necessary other elements so as to create and sustain a seriously big magnetic field. This nifty field needs to be substantial enough so as to not only trigger certain geological and biochemical events but, also for creating those essential Van Allen belts. As without such Van Allen belts, the atmosphere alone simply isn't going to cut it and, all life as we know it is going to be radiated to death long before Darwin's evolution of genetic alterations kicks in, unless of course there's technology involved and/or a superior knowledge of knowing how to cope and utilize the resources and the materials of potential shielding capacity, so as to extend the lives of whatever is initiated upon Earth (housing/temples or grand monument class dwellings made of extremely thick rock is certainly a good start).
Obviously there's another perfectly good option of remaining under tonnes of sea water or just sufficiently under ground is yet another survivable option, as long as you never wanted to see the light of day.
Is it possible that Venus was terraformed?
One other worthy consideration is for that of finding yet another planet that has a sufficient abundance of other elements but just so happens to exclude whatever it takes as to creating any thermonuclear/magnetic core or, perhaps because of the other elements and of the planet's proximity as being somewhat closer to the sun, this means that the option of creating a considerably greater radiation density shield surround, as potentially formulated into the atmosphere is an even better long term solution. Obviously there are a number draw backs (one of which is not going to be creating snow and ice) from this accelerated greenhouse producing method, one that would require a somewhat different grouping or cultivation of inhabitants, as over time it's going to become a whole lot hotter, especially once your terraforming process has displaced the bulk of whatever is fluid/H2O and perhaps sulphur as an affective radio wave shielding electrolyte into the upper atmosphere, as also acting as the planet's additional solar flare as well as UV reduction, formulating your fortified radiation shield in place of not having those Van Allen belts and, even that could eventually turn out as becoming somewhat marginal for 100% daytime exposure. As yet another backup or alternate plan (B), you make certain that the chosen planet is either already or can be made to rotate sufficiently slowly, so that there's a long season of day/night, thus offering your inhabitants the workable option of migrating about their globe so as to remaining in the added comfort zone as well as for receiving lesser solar radiation, as to be living the majority of their lives within the season of nighttime, that which only presses the need for nocturnal physiology attributes and, as such that's a relatively genetic snap (biolumination to boot).
As your terraforming normally goes, perhaps so far so good and, the best part is that this toasty new environment has become sufficiently different as well as isolated from the other terraformed planet, in that there should never be any unexpected interactions, no mixed blood, no infection of Earthly arrogance and stupidity genes and therefore no need of spicing this cocktail up by introducing the technology of radar/radio to those that obviously need to be protected from the Frankenstein petri dish mistakes that now occupies Earth.
As creator, from time to time, you might return and even contemplate upon going a little foreign exchange, partly well intended just to see what happens and otherwise perhaps just for the entertainment value. Like placing Catholics and Cathars on the same planet ott to be worth a ticket. After all, if you've been traveling through space for years, and more likely hundreds to thousands of years (like from Sirius), cabin fever has got to be at the top of your list. So, what's a little tit for tat of fun and games going to hurt, after all, you created both worlds and manipulated each with livestock to suit the ideals and emotions of what you thought was a proper balance and, being the sort of normal ET that you are, making a few mistakes here or there is certainly not going to take away any significant number of browny points.
Unless you are truly a super duper power, as well as having a lightspeed mothership the size of Texas, it's highly unlikely any terraforming ideas are going to get themselves off the ground by what you can bring along. It's most likely that you'll need to be a little on location creative, be that inventive or perhaps God like if need be, as to working with whatever is at hand. Essentially, your selected space rock needs to have it's own sufficient base of the basic elements and, that of a plausible orientation to some other somewhat stable star, like our sun. It would also be a darn good thing if this solar system that's to be terraformed is sort of out of the way of any "big bang" debris, as you certainly wouldn't want everything going to hell in that hand-basket shortly after you went though so god damn much trouble just to get the livestock you've got balanced out.
I mean, as truly big global petri dishes go, especially those situated half way across the galaxy, you can't just drop everything and come running to rescue every stinking sole, as good Christ all mighty, you'd never get any sleep. Just like in that aquarium, some things will simply have to fend for themselves and, perhaps that's just as much a part of the petri dish experiment as anything, as how truly good can any ET actually be, in that fate and Darwin's evolution couldn't accomplish one better, as long as there were a fighting chance.
This is where I seem to favor upon the terraforming of Venus aspects, as obviously representing a somewhat greater challenge than Earth but, as long as you're in the neighborhood and, having a few more of those spore samples to disperse, what do you have to lose?
Naturally, as to understanding all of this terraforming concept is going to become another one of those stressful events, especially if you're Catholic and just found out that those Cathar relatives are still alive and kicking about on Venus. Of course, as I've already stipulated at least a hundred times before, we could start off with just some near UV communications probing (we could have done that one nearly 13 years ago), at worst establishing the VL2 platform into relaying whatever and, go from there. For all we know these folks are dumber than us (how sad) and willing to follow warlord Bush off the very next cliff. Of course, if they turn out being the least bit Islamic or just Muslim along with a Taliban agenda, we're probably in deep horsepucky.
Never fear because, warlord Bush will save us all, even if he has to blow up half our world and otherwise devastate and pollute the other half.