Valles Marineris is a
A) large valley on the Moon.
B) vast plain on Mars.
C) huge series of cliffs on Mercury.
D) large canyon on Mars.
E) large canyon on Venus.
Question 2
The Dynamo Theory holds that
A) lightning plays a major role in generating our magnetic fields.
B) any other planet of similar density will also have a strong magnetic field.
C) the Earth's core, like Mercury's, is now a solid, rigid bar magnet.
D) magnetic fields are generated by rapidly spinning, fluid magnetic interiors.
E) the Earth's magnetic field must switch polarities every few million years.