Astronomy 110 Homework #5

Due  October 9th, 2012

Name:_________________________________

In the table below, I have listed certain common molecules found in the nucleus of a comet, and the temperatures at which the transition from ice to gas occurs (note that in space, the ices are exposed directly to the vacuum of space, and thus there are no liquid forms of these molecules on comets---just ices or gases).

 Substance Vaporization (Ice to Gas) Temperature in a vacuum Methane (CH4) 59 K = -214 C Carbon Dioxide (CO2) 125 K = -148 C Ammonia (NH4) 148 K = -125 C Sulfur Dioxide (SO2) 160 K = -113 C Water (H2O) 231 K = -42 C

1.) Describe which of these ices would be vaporized (changed from ice) to gaseous form at

a) the distance of Jupiter (R=5.2 AU) (7pts)

b) the distance of Mars (R=1.88 AU) (7pts)

c) the distance of the Earth (R=1.0 AU) (7pts)

Hint: to figure out the mean temperature at the distance of a particular planet, use the following equation: Tplanet = 290/R1/2 K. Where R1/2 is the square root of the distance in AU. For Saturn, R = 9.54 AU. The square root of 9.54 is 3.09 (that is 3.09 x 3.09 = 9.54). Thus, the mean temperature at the distance of Saturn is Tplanet = 290/(9.54)1/2 K = 290/3.09 = 94 K (only methane would still be a gas at this distance, all others would be in ice form). If you get stuck see me, or ask your lab TA. If your calculator does not have a square root function key, you can go to the following website to calculate the square root of a number.

2. Which of these molecules would still be in a gaseous form at the distance of Pluto (R=39.5 AU)? (4 pts)