Oxygen in planet is not a sign of life, says study

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Representational Image
Representational Image

New Delhi : While most scientists across the globe believe that oxygen plays a key role for the existence of life; a new study contradicts the age-old thinking. The study claims that presence of oxygen and organic compounds on planets don't necessarily mean they can host life.

In the hunt for life in the solar system, far and wide, scientists have often believed that the presence of oxygen in a planet's atmosphere is the surest sign that life may exist there.

Researchers at the Johns Hopkins University in the US successfully created both organic compounds and oxygen, absent of life. The interesting findings have been published in the journal ACS Earth and Space Chemistry. The findings serve as a cautionary tale for researchers who suggest the presence of oxygen and organic compounds on distant worlds is evidence of life there.

"Our experiments produced oxygen and organic molecules that could serve as the building blocks of life in the lab, proving that the presence of both doesn't definitively indicate life," said Chao He, assistant research scientist at the Johns Hopkins University.

"Researchers need to more carefully consider how these molecules are produced," said He

Experts say that oxygen makes up 20 per cent of Earth's atmosphere and is considered one of the most robust biosignature gases in Earth's atmosphere. The team tested nine different gas mixtures, consistent with predictions for super-Earth and mini-Neptune type exoplanet atmospheres.

Such exoplanets are the most abundant type of planet in our Milky Way galaxy, researchers said.

Each mixture had a specific composition of gases such as carbon dioxide, water, ammonia, and methane, and each was heated at temperatures ranging from about 26 to 371 degrees Celsius.

The researchers exposed the mixture to one of two types of energy, meant to mimic energy that triggers chemical reactions in planetary atmospheres: plasma from an alternating current glow discharge or light from an ultraviolet lamp.

It must be known that plasma is a source of energy stronger than UV light which can simulate electrical activities like lightning and/or energetic particles, and UV light is the main driver of chemical reactions in planetary atmospheres such as those on Earth, Saturn and Pluto.

After conducting the experiments continuously for three days, corresponding to the amount of time gas would be exposed to energy sources in space, the researchers measured and identified resulting gasses with a mass spectrometer, an instrument that sorts chemical substances by their mass to charge ratio.

Researchers finally observed multiple scenarios that produced both oxygen and organic molecules that could build sugars and amino acids, the raw materials which could begin life, such as formaldehyde and hydrogen cyanide.

"People used to suggest that oxygen and organics being present together indicates life, but we produced them abiotically in multiple simulations.

"This suggests that even the co-presence of commonly accepted biosignatures could be a false positive for life," He said.