12 Questions
What is a characteristic of the orbits of terrestrial planets?
They are closely spaced.
Which planet has the largest mass?
Jupiter
What is the surface composition of jovian planets?
Gaseous, no solid surface, mostly hydrogen and helium.
What is the duration of a day on Mercury?
176 Earth days.
What is the effect of Mercury's slow spin on its axis?
The same side of Mercury faces the sun on every other orbit.
How does the gravity of Mercury compare to that of Earth?
It is about 0.4 (two-fifths) the gravity of Earth.
Why is Mercury unable to hold an atmosphere?
It is too small and cannot hold gases
What is the source of the gases in Mercury's atmosphere?
The solar wind that blows by Mercury
Why are there many impact craters on the surface of Mercury?
Because of the meteor collisions on the surface of Mercury
What is the reason for the magnetic field of Mercury being so small?
Because Mercury's core should have cooled off completely
Why did scientists not expect to find a magnetic field around Mercury?
Because Mercury's core should have cooled off completely
What percentage of Earth's magnetic field is Mercury's magnetic field?
1%
Study Notes
Comparing Terrestrial and Jovian Planets
- Terrestrial planets have closely spaced orbits, small mass, small radius, rocky and solid surface, high density, and few or no moons and no rings.
- Jovian planets have widely spaced orbits, very large mass, large radius, gaseous surface, low density, many moons, and rings.
Mercury as a Terrestrial Planet
- Mercury is a terrestrial planet with a rocky surface, small mass (1/20th the mass of Earth), and a small radius (slightly larger than the Moon).
- Mercury's gravity is about 0.4 (two-fifths) the gravity of Earth.
- Mercury is too small to hold an atmosphere, and the hydrogen and helium gases are captured temporarily from the Solar wind that blows by Mercury.
Orbit and Motion of Mercury
- Mercury's orbit is noticeably elliptical, and its orbit constantly shifts, never repeating the same path around the Sun.
- Mercury spins on its axis every 58.6 days, which means it spins exactly three times every two trips around the Sun.
- A day on Mercury (from noon to noon) lasts 176 Earth days (about 6 Earth months), with 3 months of daylight and 3 months of darkness.
Magnetic Field of Mercury
- Scientists did not expect to find a magnetic field around Mercury, but Mariner 10 measured a small magnetic field around Mercury, only about 1% of Earth's magnetic field.
- Despite being small and spinning slowly, Mercury has a magnetic field, which was a surprise to scientists.
Surface Features of Mercury
- The surface of Mercury is packed with many impact craters due to past meteor collisions.
- When a meteor hits Mercury, it strikes harder than any other planet due to its high orbit speed.
Compare and contrast the characteristics of terrestrial and jovian planets, including their masses, radii, orbits, moons, and surface features.
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