A primary reason is that viruses do not possess a cell membrane or metabolise on their own - characteristics of all living organisms. Examples of common human diseases caused by viruses include the common cold, the flu, chickenpox and cold sores.
In the past spacecraft have taken greatly different amounts of time to make it to Saturn. Pioneer 11 took six and a half years to arrive. Voyager 1 took three years and two months, Voyager 2 took four years, and the Cassini spacecraft took six years and nine months to arrive. The New Horizons spacecraft took a short two years and four months to arrive on the scene.
29.46 years multiply that by 365 to get days Interestingly, Saturn spins very fast, so a Saturn day is only 0.43 of an Earth day. So, in one Saturn year (one Saturn trip around the Sun), there are about 25,000 Saturn days. Source(s): http://en.wikipedia.org/wiki/Planets.