An international team of astronomers has found a potential sign of life in the Venus' atmosphere. Instantly, the discovery brings the brightest planet in the night sky back in the news. The study says that there may be strange bacteria residing in the hothouse planet's sulphuric acid-laden clouds.

According to a report in Monday's journal Nature Astronomy, two telescopes in Hawaii and Chile found the chemical signature of phosphine in the thick Venutian clouds, a noxious gas that is related only to life on Earth.

Several outside experts including the authors of the study themselves acknowledged that this was exciting, but said that it was far from being the first signs of life on another planet. They said it doesn't meet the "extraordinary claims require extraordinary proof" criterion set by the late Carl Sagan, who in 1967 speculated about the possibility of life in the Venus clouds.

However, the researchers made it clear that it's not a straight forward observation of life on Venus. But, the astronomical observations confirmed the highly surprising existence of chemical phosphine at the top of the acidic clouds that cover the planet.

Phosphine is a basic molecule, formed by bacteria by an industrial process on Earth. As a result, it is believed by scientists to be possible "biosignatures" of life on Earth-sized planets whose atmospheres can be observed through telescopes. Oxygen is another on the list of molecules.

Janusz Petkowski, Co-author and Massachusetts Institute of Technology researchers said that, "This means either this is life, or it’s some sort of physical or chemical process that we do not expect to happen on rocky planets."

Study co-author Sara Seager, an MIT planetary scientist said, "Researchers exhaustively went through every possibility and ruled all of them out: volcanoes, lightning strikes, small meteorites falling into the atmosphere. Not a single process we looked at could produce phosphine in high enough quantities to explain our team’s findings.”

Clements said that, "Phosphine is present in ooze at the bottom of the wetlands, the guts of some animals such as badgers and maybe most unpleasantly associated with piles of penguin guano."

He further added that, "Venus is hell. Venus is a kind of Earth's evil twin. Clearly, something has gone wrong, very wrong, with Venus. It's the victim of a runaway greenhouse effect."

Since 1989, the National Aeronautics and Space Administration (NASA) has not sent anything to Venus, though Russia, Europe, and Japan have dispatched probes. Two future Venus missions are being considered by the US space agency. DAVINCI+ is one of them and it will reach the Venutian atmosphere as early as 2026. Many scientists say that, "Life on Venus is certainly a possibility but more evidence is needed."