Ocean under the ice of Enceladus may contain phosphorus – and therefore life

(ORDO NEWS) — In a new article, based on data previously collected by the Cassini space probe, a model of the geochemical composition of Enceladus is obtained.

She showed that the subglacial ocean of this satellite of Saturn can contain a lot of phosphorus, a chemical element that plays a key role in abiogenesis, that is, the origin of life.

Both the question of the origin of life on the young Earth, and the assumption of extraterrestrial forms of life, still arouse great interest of researchers and science lovers.

It is important to note that both these topics are closely related, since abiogenesis (the emergence of the first living cell from non-living material) can follow universal patterns and occur on different planets according to a common scenario.

When searching for extraterrestrial life, not only exoplanets (orbiting around other stars) are promising, but also some bodies of the solar system.

Scientists do not exclude that Mars, the atmosphere of Venus and some large satellites of gas giants, such as Titan with its dense atmosphere and moon-ice balls containing liquid water, can (or could) be habitable in one form or another.

An example is Europa, orbiting Jupiter, and Enceladus, one of the satellites of the planet Saturn. The second gas giant is remarkable not only for its system of colossal rings, but also for the largest “collection” of 82 satellites, some of which are quite large.

Enceladus has a diameter of about 500 kilometers, making it Saturn’s sixth largest moon. The surface of the satellite reflects sunlight well, that is, it is quite bright – this is due to a thick layer of water ice on its surface, under which a huge ocean of liquid water is hidden.

Volcanoes erupt at its bottom, and in some places peculiar “geysers” break out through the ice, streams of water under high pressure: it is estimated that their speed reaches almost 1300 kilometers per hour.

The hypothetical possibility of the existence of life in the ocean of Enceladus has been discussed for a long time, and now the authors of a new article in the Proceedings of the National Academy of Sciences have given it even more credibility.

Ocean under the ice of Enceladus may contain phosphorus and therefore life 2
The ocean under the ice of Enceladus

The work was done on data obtained by the Cassini spacecraft, which NASA launched in 1997. The purpose of that mission was to study Saturn and its satellites: it ended back in 2017 with a dramatic fall of the probe into the dense atmosphere of this gas giant.

But before that happened, the device managed to collect a lot of data about Saturn, its rings and amazing satellites – including Enceladus.

It turned out that this celestial body contains all the main ingredients included in the “recipe” of a living cell: carbon, nitrogen (including in the form of an ammonium ion), oxygen and, of course, liquid water.

A new study has drawn attention to another “biological” chemical element – phosphorus. It is part of nucleic acids ( DNA and RNA) and is necessary for the synthesis of ATP “battery molecules” that provide energy for the metabolism of any living cell.

So, the authors used the Cassini data to build thermodynamic and kinetic models, with the help of which they estimated the possible geochemical composition of Enceladus – including the content of phosphorus in its ocean.

According to their findings, the distant space ocean contains a large amount of this element – its concentration is at least comparable to that of the Earth’s oceans , but may be more.

It is assumed that phosphorus is dissolved in water and is represented mainly by orthophosphate, a derivative of phosphoric acid.

Areas of the ocean with low pH and high concentrations of dissolved carbon dioxide should contain more phosphorus.

It is the presence of this acid-forming carbon monoxide that makes the abundance of phosphorus in Enceladus’ ocean likely. In addition, the concentration of phosphorus depends on the content of silicon and ammonium ions in the water.

On Earth, phosphorus is not found in its pure form, and its compounds are usually formed during the weathering of rocks – in the case of Enceladus, they, according to the authors, enter the waters of the dark and cold ocean during the destruction of rocks (probably chondrite) at its bottom.

By the way, the presence of a solid stone core under the ice and water covers was shown using the same Cassini probe.

“We don’t know exactly what the rocky part of Enceladus is made of, but we can make good guesses about this due to what we know about other objects in the solar system,” commented colleagues Geoff Collins, a planetary scientist from Wheaton College (USA).

At the same time, it is important to note that the new study does not provide direct evidence for the presence of this chemical element on Enceladus.

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