On January 7, 1610, Italian astronomer Galileo Galilei peered at Jupiter with his new and improved 20x homemade telescope. He noticed three other points of light near the planet, but at first believed them to be distant stars. Observing them over several nights, he noticed that they appeared to be moving in the wrong direction with respect to the background stars, and that they remained close to Jupiter but changed their positions relative to each other. I noticed. Four days later, he observed a fourth point of light near the planet with the same unusual behavior. By January 15, Galileo correctly concluded that he had discovered four moons orbiting Jupiter, providing strong evidence for the Copernican theory that most celestial bodies do not orbit the Earth.
In March 1610, Galileo published his discoveries of Jupiter’s moons and other astronomical observations in a book titled Siderius Nuncius (The Starry Messenger). As a discoverer, Galileo had naming rights for Jupiter’s moons. He proposed naming them after what his patrons, the Medici family, and astronomers had called the Medician stars throughout the 17th century, but Galileo in his notes called them Roman numerals. I, II, III, IV are called in order. Distance from Jupiter. Astronomers still refer to the four moons as the Galilean satellites in honor of their discoverer.
In 1614, German astronomer Johannes Kepler proposed naming the moons Io, Europa, Ganymede, and Callisto after mythical figures associated with Jupiter, but his idea remained popular for more than 200 years. I didn’t. Scientists did not discover any more moons until 1892, when American astronomer EE Barnard discovered Jupiter’s fifth moon, Amalthea. This moon is much smaller than Galileo’s moon and orbits closer to Jupiter than Io. This was the last satellite of the solar system to be discovered by visual observation, and all subsequent discoveries were made by photography or digital images. As of today, astronomers have identified 95 moons orbiting Jupiter.
Each of the Galilean moons has unique features, such as Io’s volcanoes, Callisto’s cratered surface, and Ganymede’s magnetic field, but scientists are considering the intriguing possibility that they may harbor life. , drawing even more attention to Europa. . During the 1970s, NASA’s Pioneer 10 and 11 and Voyager 1 and 2 spacecraft increasingly took detailed images of large moons, including Europa, during their approaches to Jupiter. These photos show that Europa has the smoothest surface of any object in the solar system, a relatively young crust, and is one of the brightest moons, due to its surface reflectance. It is clear that this indicates that the value is high. These features have led scientists to hypothesize that Europa is covered by an icy crust floating in a salty underground ocean. They further hypothesized that tidal heating caused by Jupiter’s gravity re-forms the surface ice layer through cycles of melting and freezing.
More detailed observations by NASA’s Galileo spacecraft, which orbited Jupiter from 1995 to 2003 and made 11 close encounters with Europa, revealed that long linear features on its surface indicate tidal or tectonic activity. It has become clear that there may be. The reddish-brown material along cracks and in spots on the surface may contain salts and sulfur compounds that have been transported from below the Earth’s crust and denatured by radiation. Observations by the Hubble Space Telescope and reanalysis of images taken by Galileo have revealed the possibility that the plume is erupting from beneath Europa’s crust, lending credence to the hypothesis. The exact composition of this material is unknown, but it may contain clues to whether Europa can welcome life.
Future robotic explorers of Europa may answer some of the unanswered questions about this unique moon of Jupiter. NASA’s Europa Clipper set out on a five-and-a-half year journey to Jupiter in October 2024. Upon arrival in 2030, the spacecraft will enter orbit around the giant planet and conduct 49 flybys of Europa during its four-year mission. Managed by the Jet Propulsion Laboratory in Pasadena, California, and the Johns Hopkins University Applied Physics Laboratory in Baltimore, Maryland, the European Clipper includes imaging systems and radar to better understand the structure of the icy crust. equipment will be installed. Data from Europa Clipper complements information returned by the European Space Agency’s JUICE (Jupiter Icy Moon Explorer) spacecraft. JUICE, launched in April 2023, is scheduled to first be inserted into orbit around Jupiter in 2031, and then into orbit around Ganymede in 2034. The spacecraft will also conduct research on Europa that will complement Europa Clipper’s exploration. The two spacecraft will greatly increase our understanding of Europa and perhaps uncover new mysteries.
