What is the article about?
Oxygen
What is its symbol?
O
it's numeral?
Eight
is it abundant?
Yes
how does it rank?
third
What is more abundant?
hydrogen and helium
What makes up O2?
two atoms of oxygen
What seems to be lowering earths levels of O2?
fossil-fuel burning
Does O2 exist inside our planet?
Yes
How is O2 released by plants? What process?
photosynthesis
What is O3?
ozone
Where is this found?
high-altitude
Is it found near the face of the planet?
Yes
What is this called?
a pollutant
Does smog cause this?
Yes
What can erode space vehicles?
atomic oxygen
At what level?
higher low earth orbit altitudes