Primary evidence for dark matter comes from calculations showing that many galaxies would fly apart, or that they would not have formed or would not move as they do, if they did not contain a large amount of unseen matter. Other lines of evidence include observations in gravitational lensing and in the cosmic microwave background, along with astronomical observations of the observable universe’s current structure, the formation and evolution of galaxies, mass location during galactic collisions, and the motion of galaxies within galaxy clusters. In the standard Lambda-CDM model of cosmology, the total mass–energy of the universe contains 5% ordinary matter and energy, 27% dark matter and 68% of an unknown form of energy known as dark energy. Thus, dark matter constitutes 85%[a] of total mass, while dark energy plus dark matter constitute 95% of total mass–energy content.
"For the smaller craters, it's like if you're filling a bucket, eventually your bucket gets full, but if you keep pouring cups of water into the bucket, you can't tell how many cups of water beyond full you've gone. Looking at the larger craters at the subsurface might give us insight, because that 'bucket' isn't full yet," Dr. Soderblom added. "We developed new operations methods for INMS for Cassini's final flight through Enceladus' plume. We conducted extensive simulations, data analyses, and laboratory tests to identify background sources of hydrogen, allowing us to quantify just how much molecular hydrogen was truly originating from Enceladus itself," explained Dr. Rebecca Perryman in the April 13, 2017 SwRI Press Release. Dr. Perryman is INMS operations technical lead. A Distant, Dusty Moon. Titan experiences changing seasons--just like Earth. In particular, Titan's seasons change around the equinox, when our Sun passes Titan's equator. At this time, huge clouds can form in tropical areas, resulting in violent methane storms. Cassini observed these ferocious methane storms during several of its flybys over Titan.