Modern_rocko t1_jb92xq5 wrote
Reply to comment by ChickenChimneyChanga in TIL the largest moon in our solar system, Ganymede, is larger than the planet of Mercury by Jugales
I thought oxygen was only present as a byproduct of organic materials ?
Cohibaluxe t1_jb9eanb wrote
Oxygen is the third most abundant material in the universe. It’s made at the end of the helium fusion process in massive stars, and our sun is 0.9% oxygen by mass.
There’s oxygen on Mars and Venus too, but in insufficient quantities to support the oxygen cycle. The fact that we have the oxygen cycle (part of that being photosynthesis) is why Earth has a much higher amount of oxygen, but it’s not the only source of it.
bearsnchairs t1_jba05j3 wrote
Molecular oxygen, O2 is seen as a marker for biological activity. Molecule oxygen is pretty reactive and over long time scales it will react with mostly anything and form oxides. If it builds up enough for you to detect it, there must be a source to counteract the sink.
Fun fact, oxygen is the most abundant element in earth’s crust.
FibroBitch96 t1_jb986eg wrote
That is not true
herbw t1_jbavcuq wrote
Exactly! H, He, Li, most abundant. O is way down the line.
JeffFromSchool t1_jbcqsec wrote
Oxygen is actually the third most abundant element in the Milky Way
jschild t1_jb9fsv3 wrote
Significant Oxygen only is, because oxygen is so reactive that it bonds with other elements pretty fast. Trace amounts are ok, but if you see a planet with 10-20% oxygen (and the atmosphere isn't super thin), it's almost certainly going to be life.
Modern_rocko t1_jb9g9zf wrote
That must have been where my mind was at - thanks for the clarification!
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