When the ancient Greeks and Romans looked south, they saw vast, unconquerable expanses of sea. Some constellations in the southern sky seemed to rise and set from the “great deep.” They are called the “watery constellations” to this day.

The best known is Aquarius, the Water Bearer. You can see him just after dark by looking toward the southern horizon. Aquarius’s body consists of a large oval of relatively faint stars. On his shoulder is a small, symmetrical group of four stars called the “Water Jar.”

Below Aquarius is the constellation Piscis Austrinus, the Southern Fish. The water from Aquarius’ jar flows as a faint stream of stars toward the Fomalhaut, the bright star we discussed last week.

Except for Fomalhaut, the stars of the Southern Fish are pretty faint. The Greek poet-astronomer Aratus (ca. 270 BCE) barely gives it a mention in his “Phenomena”:

“Below Aegeoceros (Capricorn), below the blast of the south wind, swims a fish, facing Cetus, alone and apart. From the former fishes (Pisces), and him men call the Southern Fish.”

Still, the constellation is an ancient one. It predates the ancient Greeks and traces its roots to the ancient Egyptians and, after them, the Syrians.

They called the constellation Oxyrhynchus, i.e., “sharp-nosed,” which presumably describes the fish’s head.

Piscis features in a classic tale about the Egyptian god Osiris, the God of Light, and an unmentionable part of his anatomy.

Seth, the God of Darkness and Osiris’s brother, murdered Osiris. Seth knew that the magical goddess Isis, the sister/wife of Osiris, could breathe life back into her dead husband so long as he stayed in one piece.

“No problem,” thought Seth. He cut the body into 13 pieces and scattered them far and wide.

Isis was undaunted. She tracked down 12 of the body parts and put Osiris back together. However, the body’s unmentionable part was missing. It had fallen into the Nile River and had been swallowed whole by the Southern Fish.

Isis fashioned a replacement out of wood and breathed life into the God of Light. The Southern Fish was now imbued with part of Osiris’s power. Consequently, the Egyptians worshipped it as a god.

As astronomer and poet Hyginus writes in the first century BCE, “For that reason, many Syrians abstain from fish and pay tribute to gilded fish as household gods.”

The fish eventually ended up in the sky to facilitate that worship and ensure that the story would live forever. And, of course, it has, at least in places like this one.

Another fishy origin story comes to us from Ctesias of Cnidus, a 5th century BCE physician and historian with an excellent reputation as a physician but a less admirable standing as a historian.

Much of his constellation writing has now been lost, save for a few fragments and second-hand accounts. Ctesias’s Piscis story was recorded by the Greek polymath Eratosthenes of Cyrene in his comprehensive history of constellation origin myths called “Katasterismoi,” meaning “Placings Among the Stars.”

“Katasterismoi” is also lost. However, an unknown author, sometimes called Pseudo-Eratosthenes, wrote a summary of the work during the first century CE.

In the Cnidus story recounted by Pseudo-Eratosthenes, Piscis saved the life of the Syria earth-mother Derketo, a fertility deity famed for her libidinous nature.

Derketo fell into a lake at Bambyce near the Euphrates River. She was saved by a large fish, now honored in the sky as the fish-god Piscis Austrinus.

As a result, Derketo’s temples honored Piscis with ponds of sacred fish. Also, the fish’s bravery provides another justification for the fish-eating prohibition.

Derketo punished fish eaters with severe illness. But the temple priests safely consumed fish as a ritual act of fish-god eating.

I know. The priestly practice sounds pretty strange until one considers the Christian tradition of consuming — symbolically or literally, depending on the particular religious belief — the body and blood of Jesus Christ.

But there’s one more twist to the story. In a variant tale told by Greek writer Diodorus Siculus (first-century BCE), Derketo deliberately threw herself into a lake near Ascalon in Palestine. She attempted suicide because of a shameful love affair with Caystrus, a young and handsome Syrian mortal.

As a result of the affair, she gave birth to a daughter. Derketo killed her lover, abandoned her child, and jumped in the lake. While underwater, Derketo transformed into a half-woman, half-fish mermaid.

Fomalhaut, the star that forms the mouth of the Southern Fish, gets its name from the Arabic expression “Fam al Hut,” which means, you guessed it, the “Mouth of the Fish.”

The ancient Philistines worshipped Fomalhaut as their fish-god Dagon at their temple near Gaza. According to the Bible, the Israelite hero Sampson destroyed that temple.

Sadly, all the stories above leave three unanswered questions. Why is Aquarius pouring water into a fish’s mouth? Why is the fish drinking it? Do fish get thirsty?

We must look to another ancient story with a Biblical connection for answers.

In ancient times, Aquarius was called Deucalion. He was the son of Prometheus, the Titan who created humans out of clay. As a result, he felt a special love for his creations.

As the generations passed, humans became brazen in their disrespect for Mother Earth and the other forces of nature that the ancients believed were gods.

Zeus, the king of the gods, decided to wipe humanity from the planet. A flood is always a good way to go.

Is the story beginning to sound familiar? Here, I do not intend to doubt the veracity of the Noah story in the Bible. I merely note that it reflects even older stories appearing in several cultures worldwide.

People experienced floods. They needed to explain them.

Prometheus got wind of Zeus’ plan and told Deucalion to build … an ark. Okay, it was more like a sea chest, just large enough to fit Deucalion and his wife.

Zeus squeezed the water from the clouds. The rains fell in torrents for nine days and nights until the world was covered with a great flood. Only the innocent fish escaped destruction.

When the rains ceased, Deucalion and his wife drifted until they landed on Mount Parnassus, the only place above water.

Zeus saw that Deucalion and his wife were just and loving people and agreed to help them repopulate the Earth.

To do so, he told them to throw the bones of their mother over their shoulders.

The riddle was a test of their piety. Only righteous people could realize that the Earth was their mother. So they picked up stones from the ground and threw them over their shoulders.

Humans sprang up where the rocks fell. Only people made from stone could survive the task of rebuilding the human race.

As the sun rose again on a rich and fertile Earth, plants and animals emerged from Mother Earth’s soil.

To this day, the sunrise from Mount Parnassus, with the beauty of central Greece spread out before it, is among the most glorious in the world.

When Deucalion died, the gods rewarded him by turning him into stars. He became the constellation Aquarius, the Water Bearer. Deucalion pours water from his jar to warn us that disrespect for Mother Nature could again lead to disaster.

So why is Aquarius pouring water into the fish’s mouth? On this matter, the ancient storytellers are silent.

As we begin to experience the effects of climate change, here is what the ancient storytellers might say if they were alive today:

“Aquarius, whom we knew as Deucalion, is the father of us all. He must be angry that we have again descended into disrespect for nature. So he pours a new flood of waters upon the Earth from his inexhaustible jar. Only the kindness of the Southern Fish, which drinks up the water, hovers between humanity and sure destruction.

“Love your Mother. Protect her and do not squander her bounty,” the old, dead poets might say, “lest your savior, the innocent fish, become disgusted by your ways and swim away into the boundless depths of night.”

I hope it’s clear this weekend. Saturn and Jupiter are visible in the southern sky, and I’ll be at some public program showing people their beauty.

But after the public has drifted away, I will perhaps stand and look at the Water Bearer and the Southern Fish and think about our relationship with our changing planet, mother to us all.