Overview
In the early 1600s, Galileo turned his primitive telescope to Jupiter and saw tiny points of light with no discernible features. More than 400 years later, today's backyard telescopes can resolve Europa's disk so well, what a difference it makes. Europa is now considered one of the most complex and fascinating worlds in the solar system. Cracks, ridges and chaotic terrain in the moon's icy crust could provide access to one of the largest oceans in the solar system and could be home to aquatic life. NASA's Europa Clipper spacecraft will launch a week later, on October 10, and will conduct detailed reconnaissance of the lunar surface to help plan future missions, including landers and possibly even submarines. The main science goal of Europa Clipper is to determine whether there is a place below Europa's surface that could support life.
Discussion about Europa and the mission
The world Europa has strong evidence for an ocean of liquid water beneath its icy crust, which would likely provide conditions favorable for life. NASA will send a high-performance, radiation-hardened spacecraft called Clipper into a long circular orbit around Jupiter to make repeated flybys of the icy moon. In fact, the plan is to conduct 49 flybys of Europa at closest approach altitudes as low as 16 miles, each pass to a different location to scan nearly the entire moon. With its massive solar array and radar antenna, Europa Clipper will be the largest spacecraft NASA has ever developed for planetary missions. The spacecraft will need large solar arrays to collect enough light to meet its power needs as it operates in the Jupiter system, which is more than five times farther from the sun than Earth is. The spacecraft is approximately 16 feet (5 meters) tall. With the array deployed, the spacecraft spans more than 100 feet and has a dry mass (without propellant in the tanks) of 7,145 pounds. The spacecraft's launch date is currently scheduled for Thursday, October 10, and it will arrive at Jupiter in April 2030.
Image source: NASA/JPL-Caltech
Because Europa is bathed in radiation from Jupiter's magnetic field, the Europa Clipper's payload and other electronics will be enclosed in a thick-walled vault. This strategy of traveling through radiation vault armor to Jupiter was developed and first successfully used by NASA's Juno spacecraft. The vault walls, made of titanium and aluminum, will act as a radiation shield for most high-energy atomic particles, significantly slowing the degradation of the spacecraft's electronics.
In order for Europa to be habitable, it needs the basic building blocks of life, including carbon, hydrogen, oxygen and sulfur. Liquid water is crucial to the complex chemical processes that make life possible on Earth. Many scientists predict that there is an salty sea beneath Europa's surface that contains more water than all of Earth's oceans combined. Although Jupiter's icy moon is far from the sun, Europa gets its life-sustaining energy from Jupiter's powerful gravity, which creates tides that stretch and pull the moon, generating heat. One of the most important measurements from the previous Galileo mission that explored Europa showed how Jupiter's magnetic field is disrupted in the space around Europa. This measurement strongly suggests that a special type of magnetic field is generated (induced) by deep conductive fluids (such as salt water) beneath Europa's surface that interact with Jupiter's strong magnetic field.
Galileo's amazing work
On January 7, 1610, Italian astronomer Galileo Galilei observed Jupiter through his newly improved 20x homemade telescope and noticed three other points of light near Jupiter. He initially thought they were distant stars. After several nights of observation, he noticed that they seemed to be moving in the wrong direction relative to the background stars. They were still located near Jupiter, but their position relative to each other had changed. He later observed the same unusual behavior on a fourth star near the planet. By January 15, Galileo correctly concluded that they were not stars at all but satellites orbiting Jupiter, providing strong evidence for Copernicus' theory that most celestial bodies did not orbit the Earth. In March 1610, Galileo published his observations of Jupiter's moons and other celestial bodies in a book called “The Moons of Jupiter” Sidrius Sinius (Starlight Messenger).
Above: Galileo's two telescopes. Bottom: Page from Galileo's notebooks regarding his observations of Jupiter's moons. Image credits: National Geographic, gabrielevanin.it, University of Michigan Special Collections Library.
As the discoverer of Jupiter's moons, Galileo had the right to name them. He proposed naming them after his patrons, the Medici family, and for much of the 17th century astronomers referred to them as the Medici stars, although Galileo followed their order in his own notes They are called by the Roman numerals I, II, III and IV. Astronomers still refer to these four satellites as the Galilean satellites, in honor of their discoverer. German astronomer Johannes Kepler suggested naming the moons, namely Io, Europa, Ganymede and Callisto, after mythical figures associated with Jupiter, but his idea did not materialize more than 200 years later catch on. It was not until 1892 that American astronomer EE Barnard discovered Jupiter's fifth moon, Amalthea, that scientists discovered more moons around Jupiter. It was much smaller than the Galilean satellites and closer than Io. Jupiter. It was the last satellite in the solar system discovered through visual observation – all subsequent discoveries were made through photography or digital imaging. So far, astronomers have identified 79 moons orbiting Jupiter.
Meteorologist Paul Dorrian
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