Question 1

The Galileo probe was deliberately steered into Jupiter's atmosphere, ending its mission.

Accepted Answer

The Galileo probe was intentionally directed into Jupiter's atmosphere in 2003 to avoid any possibility of it contaminating one of Jupiter's moons, such as Europa, with bacteria from Earth.

Question 2

The equators of all four jovian planets rotate more rapidly than the polar regions.

Accepted Answer

False

Question 3

Changes in the predicted motion of Uranus led to the search for an eighth planet.

Accepted Answer

In the 19th century, discrepancies in the orbit of Uranus led to the prediction of the existence of an eighth planet, which was later confirmed with the discovery of Neptune.

Question 4

William Herschel was the discoverer of Uranus.

Accepted Answer

This statement is true. William Herschel discovered Uranus in 1781 while conducting a survey of the night sky.

Question 5

All four jovian planets are made primarily of hydrogen and oxygen.

Accepted Answer

All four jovian planets (Jupiter, Saturn, Uranus, and Neptune) are primarily made of hydrogen and helium, not hydrogen and oxygen.

Question 6

While Voyagers were probes that flew past in a few days, Galileo and Cassini are orbiters, designed to study Jupiter and Saturn over prolonged periods of time.

Accepted Answer

Galileo and Cassini were indeed orbiters designed to study Jupiter and Saturn, respectively, over extended periods, unlike the Voyager missions which were flyby missions that passed by the planets.

Question 7

Saturn is less dense than water.

Accepted Answer

Saturn has a density of less than 1 gram per cubic centimeter, while the density of water is 1 gram per cubic centimeter. Therefore, Saturn is less dense than water.

Question 8

The axial tilts of Uranus and Neptune are similar.

Accepted Answer

Uranus has a unique axial tilt of about 97.77 degrees, making it appear to rotate on its side, whereas Neptune's axial tilt is about 28.32 degrees, which is more similar to Earth's tilt than to Uranus's extreme tilt.

Question 9

All nine planets in the solar system have been visited by spacecraft.

Accepted Answer

There are only eight recognized planets in the Solar System since Pluto was reclassified as a dwarf planet in 2006, and not all of them have been visited by spacecraft.

Question 10

Jupiter's Great Red Spot is similar to a hurricane on Earth except for its size.

Accepted Answer

Jupiter's Great Red Spot is indeed similar to a hurricane on Earth in terms of being a massive storm system, but it is vastly larger and has been ongoing for centuries.

Question 11

Galileo's early telescopes revealed the four large moons of Jupiter, the rings of Saturn, and its large moon Titan.

Accepted Answer

Galileo's early telescopes revealed the four large moons of Jupiter and the phases of Venus, but he did not discover Saturn's moon Titan nor clearly identify the rings of Saturn. Titan was discovered by Christiaan Huygens in 1655, and while Galileo observed Saturn, he did not recognize its rings as such.

Question 12

When Cassini entered orbit around Saturn, it caused the planet's orbit to change.

Accepted Answer

When Cassini entered orbit around Saturn, its gravitational pull caused slight perturbations in Saturn's orbit. However, the effect was so minor that it was only measurable with precise instruments, and did not significantly affect Saturn's overall orbit around the Sun.

Question 13

The rotation of the magnetic fields of the jovian planets is believed to also give us the rotation rate of the planet's core.

Accepted Answer

The rotation of the magnetic fields of the jovian planets is indeed used to infer the rotation rate of the planet's core because these magnetic fields are thought to be generated by the movement of conducting materials within the core.

Question 14

Like the discovery of Uranus, the finding of Neptune was accidental.

Accepted Answer

The discovery of Neptune was not accidental; it was based on mathematical predictions made to explain the irregular orbit of Uranus. Astronomers Johann Galle and Heinrich d'Arrest located Neptune in 1846 using these predictions.

Question 15

All four jovian planets spin faster than any of the terrestrials.

Accepted Answer

Jovian planets (Jupiter, Saturn, Uranus, and Neptune) have shorter rotational periods compared to terrestrial planets (Mercury, Venus, Earth, and Mars), meaning they spin on their axes more quickly.

Question 16

Most of our detailed knowledge of the jovian planets comes from the Hubble Space Telescope.

Accepted Answer

Most of our detailed knowledge of the jovian planets comes from spacecraft missions sent to study them, such as Voyager, Galileo, Juno, and Cassini, rather than solely from observations made by the Hubble Space Telescope.

Question 17

Differential rotation is when a planet's equatorial and polar regions rotate at different rates.

Accepted Answer

Differential rotation occurs because the equator of a planet typically rotates faster than the polar regions due to the planet's shape and the way mass is distributed, leading to different rotational velocities across latitudes.

Question 18

Jupiter's axial tilt is similar to that of Mercury, while Saturn's is more like ours.

Accepted Answer

Jupiter's axial tilt is about 3 degrees, similar to Mercury's 0.034 degrees, both being relatively small. Saturn's axial tilt is about 26.7 degrees, closer to Earth's 23.5 degrees, making it more similar to ours.

Question 19

There is a clear relationship between the interior and atmospheric rotation rates of the jovian planets.

Accepted Answer

The interior and atmospheric rotation rates of the jovian planets can differ significantly. For example, Jupiter and Saturn have atmospheric bands that rotate at different speeds, which do not necessarily match the rotation rate of the planet's interior. This indicates that the relationship between interior and atmospheric rotation rates is not straightforward or uniform across these planets.

Question 20

A gravitational assist, or slingshot, can be used to either speed up or slow down a spacecraft.

Accepted Answer

A gravitational assist involves a spacecraft using the gravity of a planet or other celestial body to alter its speed and trajectory, allowing it to either gain speed (for reaching distant parts of the solar system more quickly) or slow down (to enter orbit around a planet or moon, or to approach a target more carefully).

Quiz 8: The Jovian Planets: Giants of the Solar System