Questions 29-40
The largest of the giant gas planets, Jupiter, with a volume 1,300 times greater than
Earth’s, contains more than twice the mass of all the other planets combined. It is thought
to be a gaseous and fluid planet without solid surfaces, Had it been somewhat more massive,
Jupiter might have attained internal temperatures as high as the ignition point for nuclear
5) reactions, and it would have flamed as a star in its own right. Jupiter and the other giant
planets are of a low-density type quite distinct from the terrestrial planets: they are
composed predominantly of such substances as hydrogen, helium, ammonia, and methane,
unlike terrestrial planets. Much of Jupiter’s interior might be in the form of liquid, metallic
hydrogen, Normally, hydrogen is a gas, but under pressures of millions of kilograms per
10) square centimeter, which exist in the deep interior of Jupiter, the hydrogen atoms might
lock together to form a liquid with the properties of a metal. Some scientists believe that
the innermost core of Jupiter might be rocky, or metallic like the core of Earth.
Jupiter rotates very fast, once every 9.8 hours. As a result, its clouds, which are composed
largely of frozen and liquid ammonia, have been whipped into alternating dark and bright
15) bands that circle the planet at different speeds in different latitudes. Jupiter’s puzzling
Great Red Spot changes size as it hovers in the Southern Hemisphere. Scientists speculate
it might be a gigantic hurricane, which because of its large size (the Earth could easily fit
inside it), lasts for hundreds of years.
Jupiter gives off twice as much heat as it receives from the Sun. Perhaps this is primeval
20) heat or beat generated by the continued gravitational contraction of the planet. Another
starlike characteristic of Jupiter is its sixteen natural satellites, which, like a miniature model
of the Solar System, decrease in density with distance—from rocky moons close to Jupiter
to icy moons farther away. If Jupiter were about 70 times more massive, it would have
become a star, Jupiter is the best-preserved sample of the early solar nebula, and with its
satellites, might contain the most important clues about the origin of the Solar System.
【題組】32. According to the passage, hydrogen can
become a metallic-like liquid when it is
(A) extremely hot
(B) combined with helium
(C) similar atmospheres
(D) metallic cores