First calm down. Failure is a natural part of life, so get used to it (everyone fails some). The key is to reduce our failures using some strategy or system. Calm, confident students get higher scores on tests and homework (even though they still guess). Don't "blank out" on me, here.
We can also learn a lot from out failures. Ben Franklin wrote, "I didn't fail the test, I just found 100 ways to do it wrong." And he was quite an inventor. If you want some research, find out how many elections Abraham Lincoln LOST before he was elected President.
Now, if you are allowed to use Wikipedia.org, there is a very nice article about "Atmosphere of Earth" that you should read carefully (also you might have a text book or notes that gives the information).
Now, get confident (When the going gets tough, the tough get going.)