A sea of ​​milk seen for the first time from space

For centuries, there has been written and oral evidence of the existence of a phenomenon known as the sea of ​​milk. It was never filmed until now

Francisco Jose Torcal Milla, University of Zaragoza

Earth observation satellites collected images of a sea of ​​bioluminescent milk south of Java (Indonesia), with an extension of more than 100,000 km², and this was later confirmed by sailors on a boat that sailed the same night, the same sea .

What is the reason for this phenomenon? Is it just the reflection of the moon on the surface of the water? What does it have to do with the search for life on planets outside the solar system?

The sea of ​​milk in the great stories

In Jules Verne’s classic 20,000 leagues under water can be read:

“Nautilus, floating on the surface of the water, found itself in the middle of a whitish sea, which may be said to be milky. The strange effect was not due to the rays of the moon, for the moon had scarcely risen above the horizon. The whole sky, though illuminated by star radiation, appeared black in contrast to the whiteness of the waters. Conseil could not believe his eyes and questioned me about the causes of the unusual phenomenon. This is what is called a sea of ​​milk, I replied […]”.

The milky seas, also mentioned by the writer Herman Melville in his work Moby DickThey have been observed by dozens of sailors over the centuries, but until recently there was only written and oral evidence of their existence.

A team led by researcher Steven Miller from the Department of Atmospheric Sciences at Colorado State University (USA) discovered the phenomenon by analyzing satellite images taken south of Java Island between July and September 2019. Some of the images show what could be be a sea of ​​milk, a finding later confirmed by the crew of the yacht Ganesha.

On August 2, 2019, the yacht Ganesha (named after the Hindu god of wisdom and new beginnings) entered a patch of foamy water in the Indian Ocean region (between Lombok and the Cocos Islands) while on its course to circumnavigate the globe .

The crew observed a sea of ​​milk for about eight hours, between 9pm and 5am, over an area of ​​more than 100,000 km² and recorded it both in the logbook and in emails sent to family and friends.

Ganesha’s crew captured the glow of the milky sea with a GoPro camera (left) and a smartphone (middle). The image on the right has been color-corrected to match the crew’s memory. The crew of Ganesha / Stephen D. Miller

In recent work, Steven Miller confirms this phenomenon based on interviews with crew members, digital photographs, video footage of the yacht, and satellite imagery.

Satellite image of the Sea of ​​Milk in Java. Stephen Miller, Leon Schommer and Naomi McKinnon, Australian National University, CC BY

How does the sea of ​​milk originate?

Although not proven, the sea of ​​milk is thought to be due to a communication process between millions of luminescent bacteria (Vibrio fischeri) is present in ocean water called quorum sensing.

The discovery that bacteria could communicate with each other changed the perception of their behavior. They do this by releasing certain signaling molecules into the environment, in this case water, some of them luminescent. This allows them to coordinate to perform actions together as a population.

Fireflies aren’t the only ones that glow

There are two natural processes capable of generating light: bioluminescence and biofluorescence.

  • Bioluminescence: it is the process by which some animal species are able to generate light through a chemical reaction (this is the case with bacteria).
  • Biofluorescence: is the process by which light of invisible wavelengths is converted to light of visible wavelengths by absorption/emission of photons.

Light worm or firefly (Lampyris noctiluca). Wofl~commonswiki / Wikimedia Commons, CC BY-SA

Corals in the Red Sea. Jörg Wiedenmann

There are many living things capable of producing light, such as bacteria, fungi, protozoa, cnidaria, intestinal worms, worms (annelids and nematodes), molluscs, cephalopods, crustaceans, insects, echinoderms and fish. Although perhaps the most famous bioluminescent animal is the firefly or glowworm, which is increasingly rare in nature.

Corals also emit light, but in this case it is fluorescence, that is, the conversion of ultraviolet light into visible light through a process of absorption and emission of photons.

Fluorescence has also recently been demonstrated in almost all amphibian species.

The light of extraterrestrial life

Many astronomers are interested in this discovery because it could be a possible way to find life, both bioluminescent and biofluorescent, on other planets by observing the light emitted by their signals.

Cornell University in Ithaca (USA) researcher Lisa Kaltenegger investigated in one of her studies the number of biofluorescent organisms that would be needed to be able to observe their light from Earth using the next generation of giant telescopes such as the Extremely Large Telescope (Cerro Armazones, Chile), which is scheduled to start operating in 2027.

The Sea of ​​Milk, a phenomenon turned into fiction by some writers and observed by dozens of sailors over the centuries, has finally been photographed thanks to technology and subsequently confirmed. Now, who knows if it will be observed outside the solar system and what it will be able to discover about us.The conversation

Francisco José Torcal Milla, Professor of the Department of Applied Physics, University of Zaragoza

This article was originally published on The Conversation. Read the original.

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