There seems to be a huge difference in the quantity of asteroids below 1 AU, and those above. Almost as if something changes at exactly 1 AU.<p>Even though Earth is special for harbouring life, is the location of Earth really that significant from the perspective of how many objects could have smaller orbits? The "goldilocks zone" shouldn't determine the density of objects in any particular orbit.<p>Or is the issue that it is easier to detect asteroids further away than it is to detect asteroids closer to the sun?
I like to see a stat: orbital velocity at minimum altitude.<p>Uranus and Neptune have similar surface (OK, cloud-top) gravity to Earth's, but ~2x delta-V to orbit. And Saturn, but 3x. We will need some sort of skyhook apparatus to get back out of the atmosphere, if we visit. Besides fission or fusion power, because dark.