Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

[Q]: Question: What is the term for the gases that surround a planet? Answer: the atmosphere
[A]: An atmosphere is the gases that surround a planet. The early Earth had no atmosphere. Conditions were so hot that gases were not stable.

[Q]: Question: The metacarpophalangeal joints in the finger are examples of what kind of joints? Answer: condyloid
[A]: Figure 38.30 The metacarpophalangeal joints in the finger are examples of condyloid joints. (credit: modification of work by Gray's Anatomy).

[Q]: Question: Glucose, galactose, and fructose are all what? Answer: hexoses
[A]:
Figure 3.5 Glucose, galactose, and fructose are all hexoses. They are structural isomers, meaning they have the same chemical formula (C6H12O6) but a different arrangement of atoms.