QUESTION:
How much does Mars itself weigh?

ANSWER from Ted Roush on April 14, 1997:
Mars has a mass of 641,800,000,000,000,000,000,000 kilograms.
The Earth has a mass of 5,979,000,000,000,000,000,000,000 kilograms.
If we divide these two numbers, then we find that Mars has about 1/10 
(a tenth) the mass of the Earth.