Astronomy 120: Fall 2008
Homework 7: Due in October 24/27 recitation
Name ___________________________ Section _______
A guided question about the mass of planetary atmospheres. This
may sound like a tough thing to do, but it really isn't too bad.
- What is the mass of the Earth's atmosphere?
Here's one way to proceed:
- The pressure of the atmosphere at sea level is 1 bar, which
is approximately 1 kg / cm2 (this is 14.7 lbs per square inch).
- That means that the mass of the atmosphere above each square cm of the
Earth is 1 kg
- The radius of the Earth is 6,330 km. Since the area of a sphere is
4πr2, you can calculate the area of the entire Earth's
surface in km2.
- Finally, you know that 1 km2 is
so you can find the total mass of the Earth's atmosphere.
- Use the same reasoning to find the mass of Mars's atmosphere -
you can find the radius of Mars in Table E, and the atmospheric pressure in
- On to Venus!
- Find the mass of Venus's atmosphere as above.
- You should find that Venus's atmosphere is much more massive
than the Earth's. Why do you think this is so (that is, why is the surface
pressure so much higher)? A short (5-10 line) answer should be sufficient.
From your reading and from lecture, you've learned that Mars is our best hope
for finding evidence of life beyond the Earth in our solar system. From what
you have learned, and from further investigation, discuss the question of
life on Mars in a short (10-15 lines or so) essay. Did Mars ever have any kind of life? If so, did it have simple
(bacterial) life only, or perhaps more complex forms? Do you think there is
life currently on Mars?