(1) What happens to the habitable zone of a planet around a star
*on the main sequence* as the star grows older?

 - (c) Moves outward as the star gets brighter

(2) The gas which contributes most to the greenhouse effect on the
Earth is?

 - (a) H20

Although the exact contribution of H20 changes with varying water vapour 
concentration, averaged over the Earth it is the dominant contributor.

(3) In terms of the total mass of the solar system, the planets plus
everything else excluding the Sun represents

 - (c) about 1\% of the mass

Slightly tricky one. Since the list of possibilities is a logarithmic one 
you should look at the ratios between the answer and the possibilities 
rather than the difference. Since Sun is about 0.2% of the mass the ratio 
to 1% is about a factor of 5, the ratio to 0.01% is about a factor of 15, 
in which means the remaining material. 0.01% corresponds to the mass of 
comets. I've decided in this case to give a mark for 0.01% as well as 
some people worked out the linear difference. In the future though, when 
given a logarithmic list of numbers look for the ratios.

(4) Uranus's axial tilt is evidence of what?

- (a) Possibly an impact event early in its evolution

(5) During the differentiation process that occurs in the formation
of planets, the physical processes leading to the release of heat are
approximately

 - (d) Gravitational energy -> kinetic infall energy -> heating

(6) The approximate increase in temperature due to the greenhouse 
effect on Earth is about

- (a) 35 K

Slightly tricky question - I quoted 290 K as the average surface temp in the 
notes, and the radiation balance model gives an estimated temp of 254 K, so 
that is 36 K difference.  Some sources cite a slightly high average surface 
temp making the difference around 40 K, but that is still closer to 35 K 
than 50K.

(7) The large amount of volcanic activity on Jupiter's moon Io is 
primarily caused by

- (c) Tidal effects from Jupiter

Internal friction (Io is constantly stretched in different directions) 
releases extremely large amounts of energy.

(8) The pressure on the surface of Venus is approximately the same 
as

- (d) being under half a mile of water

(9) The martian polar ice caps are believed to be *largely*

- (a) water ice

The 2003 hypothesis is that the ice caps are mainly frozen water covered 
with a sheet of CO2. Yes there is CO2 ice there, but we think the water ice 
is the predominant component.

(10) The atmospheric composition of Mars is largely

- (a) CO2

The atmosphere is very thin though.