Colonization of the outer Solar System is subject to only 0.01 rem a day. When NASA carried out a study called "HOPE" (Revolutionary Concepts for Human Outer Planet Exploration) regarding the future exploration of the Solar System, the target chosen was Callisto. It might be possible to build a surface base that would produce fuel for further exploration of the Solar System. The Keck Observatory announced in 2006 that the binary Jupiter trojan 617 Patroclus, and possibly many other Jupiter trojans, are likely composed of water ice, with a layer of dust. This suggests that mining water and other volatiles in this region and transporting them
Monument to the Sun time because the planet installations would have to be from a few hundred meters to several tens of kilometers away from the Sun. Beneath the glass are photo-voltage solar modules with lighting elements which turn on at night, and produce show of light. On the chrome ring that surrounds the photo-voltage solar modules on the Sun, are inscribed the names of all of the saints after which present and previous churches on the Zadar peninsula have been named. Next to their names and the date of their feast are the declination and the altitude of the Sun north or south