![]() STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. ![]() The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). "The OPAL program allows us to observe each of the outer planets with Hubble every year, enabling new discoveries and watching how each planet is changing over time," said Simon, principal investigator for OPAL. ![]() The Saturn observations are part of Hubble's Outer Planets Atmospheres Legacy (OPAL) program. NASA's Dragonfly mission will fly over the surface of Titan, touching down in various locations to search for the primal building blocks of life. This mix of chemicals is thought to be similar to that on Earth billions of years ago when life first emerged. Titan, Saturn's largest moon, is the only moon in our solar system with a thick atmosphere, including clouds that rain liquid methane and other hydrocarbons on to the surface, forming rivers, lakes, and seas. Two of these moons, Titan and Enceladus, appear to have oceans beneath their icy crusts that might support life. ![]() Saturn is the second largest planet in the solar system, over 9 times wider than Earth, with more than 50 moons and a spectacular system of rings made primarily of water ice. Since many of the planets discovered around other stars are gas giants as well, astronomers are eager to learn more about how gas giant atmospheres work. Enormous storms, some almost as large as Earth, occasionally erupt from deep within the atmosphere. Like Jupiter, the solar system's largest planet, Saturn is a " gas giant" made mostly of hydrogen and helium, although there may be a rocky core deep inside. Saturn is tilted also, so as the seasons change on that distant world, the change in sunlight could be causing some of the observed atmospheric changes. This variation in solar energy is what drives our seasonal changes. Earth is tilted with respect to the Sun, which alters the amount of sunlight each hemisphere receives as our planet moves in its orbit. It takes around 29 Earth years to orbit the Sun, making each season on Saturn more than seven Earth years long. Saturn is the sixth planet from our Sun and orbits at a distance of about 886 million miles (1.4 billion kilometers) from the Sun. Further observations are needed to tell which is happening. Saturn's winds also vary with altitude, so the change in measured speeds could possibly mean the clouds in 2018 were around 37 miles (~ 60 km) deeper than those measured during the Cassini mission. In 20 they decreased back to the Cassini speeds. In 2018, winds measured near the equator were about 1,000 miles per hour (roughly 1,600 kilometers per hour), higher than those measured by NASA's Cassini spacecraft during 2004-2009, when they were about 800 miles per hour (roughly 1,300 kilometers per hour). The Hubble data show that from 2018 to 2020 the equator got 5 to 10 percent brighter, and the winds changed slightly. Figure 104: Hubble Space Telescope images of Saturn taken in 2018, 2019, and 2020 as the planet's northern hemisphere summer transitions to fall (image credits: NASA/ESA/STScI, A.
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