March 4, 2013
Cassini Spies On Earth’s Twin Planet Venus From Behind Saturn’s Rings
Lee Rannals for redOrbit.com — Your Universe Online
The international Cassini spacecraft, a NASA, European Space Agency (ESA) and Italian Space Agency (ASI) jointly-operated project, has taken some unique pictures of Earth's twin planet from the perspective of Saturn.The Cassini-Huygens mission launched on October 15, 1997, traveling 2.2 billion miles toward Saturn, reaching the distant ringed-planet June 30, 2004. The orbiter includes 18 sophisticated science instruments to help study the planet and its moons.
Now, the sophisticated spacecraft has sent back images of Venus shining in the distance behind Saturn. One image was taken in November, when Cassini sat in the shadow of Saturn, giving scientists a backlit image of the planet and its rings in a viewing geometry known as "high solar phase." This perspective helps dish out details about the rings and Saturn's atmosphere that is unable to be seen in lower solar phase.
Another image released by the international cooperation shows off Venus suspended in Saturn's G ring, appearing as a distance bright light. Saturn's G ring is a thin ring just beyond the main Saturnian rings. The image also gives you a look at the E ring just outside of the G ring, which was created by the spray of the moon Enceladus.
Venus is nicknamed "Earth's twin" because it shares a similar size and mass as Earth, and is also a rocky "terrestrial" planet. Other rocky planets in our solar system include Mercury and Mars, as well as our home planet Earth. Venus has an atmosphere that reaches nearly 900 degrees Fahrenheit, and a surface pressure 100 times that of Earth's.
Cassini has helped scientists unveil the curtain behind what the world is like from the ringed planet and its moons' perspectives. In December, the spacecraft showed off how Saturn's moon Titan has a river valley similar to Earth's Nile River. Scientists believe this river is filled with liquid, because it appears dark along its entire extent in the images.
“Though there are some short, local meanders, the relative straightness of the river valley suggests it follows the trace of at least one fault, similar to other large rivers running into the southern margin of this same Titan sea,” said Jani Radebaugh, a Cassini radar team associate at Brigham Young University.
Cassini also revealed that blocks of hydrocarbon ice might cover the surface of existing lakes and seas of liquid hydrocarbon on Titan. A new model developed by scientists showed that winter ice will float in Titan's methane-and-ethane-rich lakes and seas if the temperature is below the freezing point of methane.
The mission was originally planned to last just four years after arriving at Saturn, but since October the spacecraft has been floating around in space for 15 years and orbiting the ringed-planet for the past eight years. The $3.3-billion international spacecraft continues to give scientists more details about the mysteries of Saturn, its rings and its many moons.
Image Below: Dawn on Saturn is greeted across the vastness of interplanetary space by the morning star, Venus, in this image from NASA's Cassini spacecraft. Credit: NASA/JPL-Caltech/Space Science Institute