Lecture #26: Extraterrestrial Volcanism and Faults
Be familiar with the bolded terms.
Several planets and moons in our Solar System show evidence of volcanism and quakes.
There are now eight recognized planets in the Solar System, which are listed from closest
to farthest from the
(Abbott, 2008: Figure 17.4, p. 469; Table 17.2, p. 470;
know the order of the
planets from the Sun
Recently, astronomers decided that
really isn't a planet.
The American and Russian space programs have allowed us to view the planets and some
of their moons in greater detail.
Mercury is the closest known planet to the Sun.
The planet is slightly larger than the
Like the Moon, Mercury has many craters and essentially lacks an atmosphere.
Mercury’s low mass and close proximity to the Sun are probably responsible for its
virtually nonexistent atmosphere.
Because of its short distance from the Sun and lack of
a heat-retaining atmosphere, surface temperatures range from –177°C at night to 427°C
during the day (Busch 2000, p. 14).
The landscape of Mercury may be divided into highlands and lowland plains (Vilas 1999,
The highlands are heavily cratered.
The lowland plains have fewer craters
and consist of
plains that result from eruptions billions of years ago.
structures have only been recently discovered on Mercury.
up to 500 km
long and 2 km high cross part of Mercury’s surface.
The faults may have resulted from
contractions in the planet’s diameter as the mantle and core cooled (Vilas 1999, pp. 88–
Venus, the second planet from the Sun, is slightly smaller than Earth.
The planet is
covered with a thick atmosphere consisting almost entirely of
has about 92 times the surface pressures of Earth (Busch 2000, p. 15). The carbon dioxide
that results in surface temperatures above 400°C, or hot
enough to melt lead (Busch 2000, p. 15; Abbott, p. 293).
Volcanism on Earth releases
large amounts of carbon dioxide. However, rather than being retained by the Earth's
atmosphere, the compound is largely absorbed by ocean water, converted into carbonates
to form rocks (such as
) or stored as organic carbon in organisms (Saunders
1999, p. 98).
Because Venus has no oceans or life, the carbon dioxide accumulates in