At one time, we thought that all living things on earth could not survive without oxygen. But is this really the case? Is oxygen really necessary for life? Is it possible that life can depend on other elements instead of oxygen?

I think it is very likely that there is some such evidence on earth.

Oxygen is not necessary.

In 2020, an important discovery in the scientific community was the discovery of a creature that can get energy without breathing oxygen, which is the "small leaf moth" parasitic on fish.

Scientists sequenced the gene and detected the DNA sequence of this creature, and the result was very unexpected. This creature does not contain any mitochondria. Mitochondria are the places where cells breathe aerobically, and the DNA in mitochondria is responsible for the genes that control respiration.

In other words, this creature doesn't breathe, at least not through oxygen.

Scientists don't know why this creature has a retrogressive tendency in the process of evolution, and slowly loses nerve cells, muscles and so on. Even give up breathing, so this shows that breathing may really be "one-off" for living things, and it is not necessary.

What do creatures breathe before there is no oxygen?

The earth was not rich in oxygen at the beginning of its birth, and even at the beginning of life germination, the oxygen on the earth was not completely gathered. The earth was born about 4.5 billion years ago, and the primitive atmosphere was very chaotic. However, the scientific community generally believes that oxygen began to accumulate in the atmosphere 2.5 billion years ago, and life began to appear 3.5 billion years ago.

So, in this 10 billion years without oxygen, how do creatures breathe and survive?

In the salt lakes in the Chilean desert and the Australian coast, there is such evidence-stromatolites. They are recognized as the oldest life in this area, and they are organic sedimentary structures formed by the co-deposition of the most primitive prokaryotes on the earth and chemicals in seawater. The living environment of these microorganisms is basically an area with extremely low oxygen content or no oxygen at all. If oxygen is necessary for life, how do these lives survive?

In the environment where these microorganisms live in large numbers, scientists find that the surrounding water is rich in hydrogen sulfide and arsenic, so they think that these microorganisms are likely to feed on hydrogen sulfide or arsenic and decompose organic matter in an oxygen-free environment to obtain energy.

The primitive life of the earth also tells us that oxygen is not necessary for life. Without oxygen, life may germinate.

Can extraterrestrial life rely on breathing hydrogen or helium?

If extraterrestrial life really exists, then I think it is also possible. The structure of alien life may be very different from that of life on earth, so we can't expect to judge aliens by the cognition of people on earth.

Otherwise, why do we never think that aliens look exactly like humans, but have their own unique appearance?

We think oxygen is the key to life on earth, because we can't live without oxygen now. But for other creatures on earth, oxygen is also dispensable. For example, for the small leaf roller moth, anaerobic survival is not impossible for the primitive life of the earth.

So I think that even in the space without oxygen, there may be other forms of life.

Just as Venus's atmosphere is 97% carbon dioxide and 3% nitrogen, when scientists found phosphine in Venus's atmosphere, they did not hesitate to think that there was probably life in Venus's atmosphere. And this life must have no oxygen to breathe.

Therefore, I think that when looking for extraterrestrial life, we should be more open and should not be imprisoned by the original cognition.

Summary:

Is oxygen necessary for life? Perhaps it is indispensable for human beings and most creatures on earth. Without oxygen, there would be no life.

However, there are also creatures on the earth that can survive without oxygen breathing, and the primitive life of the earth was also formed under anaerobic conditions. So oxygen is very important to life, but it is not necessary.

This year, scientists found traces of phosphine on Venus, believing that there is likely to be life on Venus. However, Venus' atmosphere is 97% carbon dioxide and 3% nitrogen. If Venus has life, then they certainly don't depend on oxygen to survive.