Earth’s ocean might turn PURPLE one day – and scientists say it used to be a totally different colour too

THE Earth’s ocean could one day turn purple – and scientists say it used to be a totally different colour.

The Earth’s seas have been predominantly blue for around the last 600 million years.

Tropical island beach with granite rocks and turquoise water. — The ocean was once green, say scientists. Some waters on modern Earth still have a greenish hueCredit: Getty

But experts insist that the ocean’s hue is far from stable – as it is wholly dependent on water chemistry and its influence on the organisms that live underwater.

For example, high volcanic activity and low oxygen levels in the atmosphere could lead to increased sulphur levels – meaning more purple sulphur bacteria and therefore turning the ocean purple.

Equally, the seas could also theoretically turn red under intense tropical climates.

Such conditions see rocks decay, producing red oxidised iron – which is then transported into the oceans via rivers.

Red oceans could also be theoretically be caused by an increase in red algae.

These already thrive in areas with an intense concentration of nitrogen, such as near sewers.

A study by Japanese researchers, published in the Nature journal, has also made the argument that the Earth’s oceans used to be green, rather than blue.

They landed on the conclusion after first analysing the waters around the Japanese volcanic island of Iwo Jima – and the blue-green algae within them.

Plus, the seas could once again turn green if the phytoplankton population continues to increase – driven by rising temperatures.

The strange revelation comes after it was revealed that an ocean full of alien life could be hiding on an icy moon system not far from earth.

Alien-hunters given 3D space map showing exactly where scientists think extraterrestrials may be hiding on nearby worlds

The moon, named Miranda, orbits the planet Uranus – just 1.7 billion miles away in our very own solar system.

It is now believed to have a hidden ocean, trapped under a layer of ice, according to a recent study.

The presence of water on the moon means it could harbour alien life.

No extra-terrestrial life has ever been discovered by scientists, but it could include intelligent, non-human beings.

The ocean could be as large as 62 miles deep, underneath an icy crust that’s 19 miles thick.

Planetary scientist Tom Nordheim, who did the study along with fellow scientists Caleb Strom and Alex Patthoff, expressed his astonishment at the findings.

He said: “To find evidence of an ocean inside a small object like Miranda is incredibly surprising.

“It helps build on the story that some of these moons at Uranus may be really interesting – that there may be several ocean worlds around one of the most distant planets in our solar system, which is both exciting and bizarre.”