Today,we'll talk about another planet,Mar
Mars is one of the planets in the solar syste
It is the forth planet from the su
It is named for the Roman god of wa
because it appears fairly red in the night sky.
Mars is a relatively small plane
with about half the diameter of Eart
The force of gravity on the surface of Mar
is about one-third of that on Eart
Mars has twice the diamete
and twice the surface gravity of Earth.
The surface area of Ma
is almost exactly the sam
as the surface area of the dry land on Eart内容来自 听力课堂网：http://www.tingclass.net/show-9179-287773-1.html