NASA’s Cassini spacecraft made its last fly-by of Enceladus on Dec. 19. Since then it has been transmitting to Earth images taken of the ocean moon, including this beauty received Feb. 15:
As NASA’s Cassini probe continues its exploration of Saturn and its moons, it sends home some amazing images of that distant region of our solar system.
Yesterday, NASA released an image showing three of the gas giant’s moons: Tethys, Enceladus, and Mimas. Here it is:
According to NASA:
The view was acquired at a distance of approximately 837,000 miles (1.35 million kilometers) from Enceladus, with an image scale of 5 miles (8 kilometers) per pixel. Tethys was approximately 1.2 million miles (1.9 million kilometers) away with an image scale of 7 miles (11 kilometers) per pixel. Mimas was approximately 1.1 million miles (1.7 million kilometers) away with an image scale of 6 miles (10 kilometers) per pixel.
Tethys’ diameter is about 1,066 kilometers. The cratered moon orbits Saturn from a distance of about 294,600 kilometers. That is about 20 percent farther from Saturn than the Moon is from Earth. Tethys is slightly less dense than liquid water, which suggests that its structure is mostly ice. This frigid moon is tidally locked to Saturn – it does not rotate and only one side of Tethys faces Saturn.
Enceladus is smaller than Tethys, with a diameter of about 500 kilometers. The host of a sub-surface liquid water ocean, Enceladus is covered by water ice and reflects nearly all the sunlight that hits it. That makes it a very cold satellite. The surface temperature on the moon is about -201 degrees Celsius. It orbits Saturn from a mean distance of about 238,000 kilometers, which is about the same distance as Earth’s satellite is from our planet.
Mimas is the smallest of Saturn’s major moons. It is heavily cratered, with a giant crater called Herschel stretching across about one-third of its surface. That feature has led Mimas to sometimes be called the “Death Star moon” because it evokes the fictional planet-destroying spacecraft in the Star Wars films. Mimas’ diameter is about 400 kilometers; it orbits Saturn from a mean distance of about 200,000 kilometers.
NASA’s Cassini probe is in its last year of operation, continuing to explore the Saturn system, and it seems appropriate to look back at some of the amazing images the spacecraft has sent home to Earth.
This one was taken on August 17, 2015, during the probe’s last flyby of Saturn’s moon Dione.
Dione (Di-OH-nee) is a small moon, with a diameter of only about 1,120 kilometers, and it orbits Saturn at about the same distance as the Moon orbits Earth. Covered by ice for which one of Saturn’s rings is the main source, Dione has many craters. Some are as large as 100 kilometers across.
Like Earth’s sole satellite, Dione does not rotate. Only one side of the moon ever faces Saturn.
Giovanni Cassini discovered Dione in 1864. The moon takes its name from the mythological Greek goddess who was said by Homer to be the mother of Aphrodite.
It is difficult to choose the most fantastic space-related photograph of the year. There are, after all, many contenders. We had, for example, many “first-time” pictures of features on the Red Planet, our neighbor Mars. This one shows the west rim of huge Endeavor crater, which has a diameter of about 14 miles. The crater is characterized by geological features that are older than any others Opportunity has investigated during its mission.
Then there was the first image ever obtained of the huge asteroid known as Vesta. NASA’s Dawn mission is in the midst of an exploration of the asteroid belt. This full view of Vesta was taken from a distance of 5,200 kilometers. The asteroid has a mean diameter of about 530 kilometers and is the second-largest object in the asteroid belt, second in size only to the dwarf planet Ceres.
Sticking with the space theme, there are many other amazing images to see, starting with this dramatic one from the MESSENGER probe that shows just a small part of Mercury:
We cannot forget the incredible images obtained by the Hubble Space Telescope, either. This one, obtained by the telescope in Feb. 2011, shows a nebula (a region of space in which stars are being formed) that is about 2,000 light years away from Earth:
But my favorite picture from 2011 is this one, which was obtained by NASA’s Cassini probe. It shows a storm encircling the huge planet. The storm is the most intense, and the largest, ever observed by Cassini. It produces a significant amount of radio noise, which indicates that there is lightning occurring in Saturn’s atmosphere. One odd feature of storms on Saturn is that they occur when a huge amount of energy is released all at once, which is unlike the meteorological pattern on other planets.