Materials Used to Make a Model of the Solar System
A billion years ago, our Moon was closer to Earth than it is now. As a result, it appeared to be a much larger object in the sky. During that ancient era, if human beings had been around to witness such a sight, it would have been possible to see the entire Moon--not merely the one near side face that we see now. A billion years ago, it took our Moon only twenty days to orbit our planet, and Earth's own day was considerably shorter--only eighteen hours long. Stupendous, almost unimaginably enormous tides, that were more than a kilometer in height, would ebb and flow every few hours. However, things changed, as the lunar orbit around our primordial planet grew ever wider and wider. Annually, Earth's Moon moves about 1.6 inches farther out into space. Currently, the lunar rate of rotation, as well as the time it takes to circle our planet, are the same.
When Jupiter was born along with the rest of our Solar System, approximately 4.56 billion years ago, it twinkled like a star. The energy that it emitted--as a result of tumbling surrounding material--made Jupiter's interior searing-hot. In fact, the larger Jupiter grew, the hotter it became. At long last, when the material that it had drawn in from the whirling, swirling surrounding protoplanetary accretion disk--made up of nurturing dust and gas--was depleted, Jupiter may well have attained the enormous diameter of over 10 times what it has today. It also may have reached a truly toasty central temperature of about 50,000 Kelvin. During that long ago era, Jupiter twinkled, glittered, and sparkled like a little star, shining ferociously with a fire that was approximately 1% that of our much more brilliant Sun today.
The more recently imaged plume erupts to a height of 62 miles above Europa's surface, while the one seen in 2014 was estimated to rise almost half as high at 30 miles above its surface. Both erupting plumes are located in an unusually warm region of this icy small world. This relatively toasty area shows some strange features that appear to be cracks in the moon's shell of ice, that were first observed back in the late 1990s by NASA's Galileo spacecraft. Planetary scientists propose that, like Enceladus, this could be a sign of water erupting from a sloshing global ocean of liquid water, swirling around in the moon's interior, that is hidden beneath its crust of surface ice.