Moons of Uranus these five, Titania, is 1,578 km in diameter and the eighth-largest moon in the Solar System, and about one-twentieth the mass the Earth's Moon. The orbits of the regular moons are nearly coplanar with Uranus's equator, which is tilted 97.77° to its orbit. Uranus's irregular moons have elliptical and strongly inclined (mostly retrograde) orbits at large distances from the planet. William Herschel discovered the first two moons, Titania and Oberon, in 1787, and the other three ellipsoidal moons were discovered in 1851 by William Lassell (Ariel and Umbriel) and in 1948 by Gerard Kuiper (Miranda). These five have planetary mass,
The Case for Mars Mars. The Mars Direct plan was originally detailed by Zubrin and David Baker in 1990. "The Case for Mars" is, according to Zubrin, a comprehensive condensation for laymen of many years' work and research. Chapters one and four deal with Mars Direct most completely. For Robert Zubrin, the attractiveness of Mars Direct does not rest on a single cost-effective mission. He envisions a series of regular Martian missions with the ultimate goal of colonization, which he details in the seventh through ninth chapters. As initial explorers leave hab-structures on the planet, subsequent missions become easier to undertake. Large subsurface, pressurized