Photovoltaics is an important energy technology

Photovoltaics (PV) is an important energy technology for many reasons. As a solar energy technology, it has numerous environmental benefits. As a domestic source of electricity, it contributes to the nation's energy security. As a relatively young, high-tech industry, it helps to create jobs and strengthen the economy. As it costs increasingly less to produce and use, it becomes more affordable and available.

Few power-generation technologies have as little impact on the environment as photovoltaics. As it quietly generates electricity from light, PV produces no air pollution or hazardous waste. It doesn't require liquid or gaseous fuels to be transported or combusted. And because its energy source - sunlight - is free and abundant, PV systems can guarantee access to electric power.

PV frees us from the cost and uncertainties surrounding energy supplies from politically volatile regions. And in addition to reducing our trade deficit, a robust domestic PV industry creates new jobs and strengthens the U.S. economy.

Photovoltaics is an important energy technology

Photovoltaics (PV) is an important energy technology for many reasons. As a solar energy technology, it has numerous environmental benefits. As a domestic source of electricity, it contributes to the nation's energy security. As a relatively young, high-tech industry, it helps to create jobs and strengthen the economy. As it costs increasingly less to produce and use, it becomes more affordable and available.

Few power-generation technologies have as little impact on the environment as photovoltaics. As it quietly generates electricity from light, PV produces no air pollution or hazardous waste. It doesn't require liquid or gaseous fuels to be transported or combusted. And because its energy source - sunlight - is free and abundant, PV systems can guarantee access to electric power.

PV frees us from the cost and uncertainties surrounding energy supplies from politically volatile regions. And in addition to reducing our trade deficit, a robust domestic PV industry creates new jobs and strengthens the U.S. economy.

Dione

Dione [Die-OH-nee; adjective: Dionean] is a small moon of 1,123 kilometers (698 miles) in diameter orbiting Saturn every 2.7 days at a distance of 377,400 kilometers (234,000 miles), which is roughly the same distance that the Moon orbits around the Earth.

Dionean Geology

Dione's features include heavily cratered terrain with craters as large as 100 kilometers (62 miles) across, moderately cratered plains, lightly cratered plains, and fractured areas. The heavily cratered areas are most common on the trailing hemisphere. Logically, a moon's leading hemisphere should be the more heavily cratered, so it has been theorized that a more recent impact spun Dione around. It has been calculated that bodies as small as those that made 35-kilometer (22-mile) craters could have spun Dione around. However, the fact that Dione seems to have spun exactly 180 degrees is a mystery.

Fractured areas, seen in Voyager images as bright thin wispy lines, have lengths of tens to hundreds of kilometers, often cutting through plains and craters. Cassini flybys starting in 2005 showed "the wisps" as bright canyon ice walls (some of them several hundred meters high), probably caused by subsidence cracking. The walls are bright because darker material falls off them, exposing bright water ice. These fracture cliffs suggest Dione experienced tectonic activity in its past. They could be a mature phase of the so-called tiger stripes on Enceladus.

Very fine ice powder (equivalent to cigarette smoke) from Saturn's E-ring constantly bombards Dione. The dust in the E-ring ultimately comes from Enceladus, which has prominent geyser activity.

Dione's density is 1.48 times that of liquid water, suggesting that about a third of Dione is a dense core (probably silicate rock) and the rest is ice. At Dione's average temperature of -186 degrees Celsius (87 kelvin or -121 degrees Fahrenheit), ice is very hard and behaves like rock.