The first ISS component was launched in 1998, with the first long-term residents arriving on 2 November 2000. Since then, the station has been continuously occupied for 18 years and 357 days. This is the longest continuous human presence in low Earth orbit, having surpassed the previous record of 9 years and 357 days held by Mir. The latest major pressurised module was fitted in 2011, with an experimental inflatable space habitat added in 2016. Development and assembly of the station continues, with several major new Russian elements scheduled for launch starting in 2020. The ISS is the largest human-made body in low Earth orbit and can often be seen with the naked eye from Earth. The ISS consists of pressurised habitation modules, structural trusses, solar arrays, radiators, docking ports, experiment bays and robotic arms. Major ISS modules have been launched by Russian Proton and Soyuz rockets and US Space Shuttles.
The existence of ample amounts of hydrogen in the subsurface ocean of Enceladus indicates that microbes--if any exist there--could use it to obtain energy by mixing with carbon dioxide dissolved in water. This particular chemical reaction, termed methanogenesis, because it manufactures methane as a byproduct, may have been of critical importance in the emergence of life on our planet.
Among the ringed gas giant planet Saturn's amazing collection of 62 diverse, bizarre, and beautiful moons and moonlets, sometimes one of them just seems to stand out in the crowd. Such a moon is little Methone. Looking like a shiny white egg in Space, and composed of very lightweight fluffy stuff, Methone is less dense than any other known moon or asteroid in our Solar System. In March 2013, astronomers announced at the 44th Lunar and Planetary Science Conference held in the Woodlands, Texas, that this strange little 5-kilometer-size moon is one of a batch of Space eggs in orbit around Saturn!
However, Dr. Thomas explained to the press in May 2013 that the ring arcs are much more tenuous than the fully formed rings of Saturn. As a matter of fact, the ring arcs are so delicate and thin that it would take about ten billion years for just 1 meter of blowing icy snow to collect within the craters of Methone.