Life on the Ocean Wave

The control room’s atmosphere was suffocatingly tense. The command was sent. The room feel silent. Anxious glances and hopeful smiles were traded as several excruciating minutes slowly passed. The tension was finally broken by a gasp drawing the attention of the room’s nervous eyes. A reading began to scan across the large central screen. The news was good. The submarine’s engines had successfully fired. The room erupted with relieved cheers, whoops of joy and punches of the air.

Hugs were exchanged, and tears were wiped from disbelieving eyes. All those years of gruelling hard work had hinged upon this one moment. And now, the meticulous planning and endless testing, had proved its worth.

A second reading began to appear upon the central screen. Preliminary checks indicated that the submarine had survived its perilous journey. It was ready for its mission. Engine power was increased. The ballast tanks were opened. The hydroplanes were adjusted and the craft began to disappear beneath the icy waves.

Back in the command centre eager eyes studied the murky images sent back by the on-board cameras. The army of eyes stared intently as ghostly shapes and shadows loomed in and out of view.

The images depicted a bizarre, alien world unfamiliar to human eyes. No one could predict what these images might reveal. The submarine’s radar indicated the ocean floor was approaching. If there was life to be found, this was most likely where.

As the ocean floor rose up to greet the craft, the propellers began kicking up mud and silt that had lain undisturbed for millennia. As the clouds dissipated the crowded room stood silent and motionless. From the fading clouds shapes began to emerge. Gasps of shock accompanied sharp intakes of breath. As the image cleared it revealed a field of plant-like creatures attached to the ocean floor. The control room once again erupted into ecstatic cheers and excited screams. The unbridled jubilation was well-placed. The room, and the world watching, had just witnessed the most incredible discovery in human history: life, found by NASA, using a remotely controlled submarine a billion miles from earth exploring the freezing oceans of Saturn’s largest moon: Titan.

It’s astounding to think that the scene described above may actually take place within the next decade or so. There are several locations within our solar system, over than Earth, where liquid oceans exists. Any of these may contain life. These worlds, and their potential exploration, was the focus of the latest episode of the BBC’s flagship science programme, Horizon.

Titan is fifty percent larger than Earth’s moon. At -180C it’s clearly too cold to host liquid water, but there are still oceans. Oceans of liquid methane.

In 2005 a probe named Huygens descended through the dense, cloudy atmosphere to provide our first ever glimpse of Titan’s landscape. Previously, the moon had been shrouded in a dense, hazy atmosphere. Huygens revealed a landscape more Earth-like than had ever been seen before. The surface was covered in large bodies of open liquid oceans. There were rivers, coastlines, lakes and seas. The revelations inspired speculations that life may well inhabit those frigid oceans.

It would be life completely distinct from that on Earth, with a completely different chemistry. It would be an example of a second genesis, featuring lifeforms occupying branches of a second tree of life.

But it wasn’t just the landscape that revealed tantalising clues to Titan’s potential for life.

Life on Earth produces seasonal changes in carbon dioxide levels. It’s absorbed by plants during the summer and released again during winter. It was predicted that life on Titan might produce a similar seasonal pattern in hydrogen. If so, hydrogen levels would be significantly lower near the surface than higher in the atmosphere.

As Huygens descended it sent back some intriguing readings. Hydrogen levels remained steady until close to the surface, where they dropped abruptly. Could this be owed to the behaviour predicted? Or could there be another, more prosaic, reason?

The intriguing readings convinced NASA to assemble a team tasked with designing a craft capable of exploring Titan’s alien oceans. After much experimentation and exploration of computer models, they settled upon a submarine design capable of plumbing the frozen depths. If ongoing tests are successful, launch may be only a decade or so away. If life exists elsewhere in the Solar System, it’s thought this is our best chance of finding it.

Horizon also discussed Enceladus. Enceladus is Saturn’s sixth largest moon. The Cassini craft that carried the Huygens probe captured photographed of giant jets of water spraying out from between large cracks in the moon’s icy crust. We now know that, beneath this thick layer of ice, is a briny, water ocean 10km deep. It would be too dark for photosynthesis to take place. But evidence of geysers raises the possibility of life eking out an existence around hydrothermal vents, just like on Earth. There are several proposals vying for funding to investigate, with a scheduled launch date of 2021. Will they detect the tell-tale chemical signature of life?

Lastly, Horizon considered Ganymede. Ganymede is Jupiter’s, and indeed the Solar System’s, largest moon. Beneath its icy crust exists a vast, salty ocean containing more water than all of Earth’s oceans. Beneath the 150km of ice exists an ocean reaching down 100km. Ten times the depth of Earth’s oceans. A probe tasked with exploring Ganymede is scheduled to launch in 2022.

It’s astounding to consider the very real possibility that life could inhabit these alien worlds, lurking beneath those thick icy crusts or frigid methane seas. And it’s even more awe-inspiring to acknowledge that, if such life exists, it may be discovered within only a decade or so. What a time to live – whether on Earth or elsewhere.

Horizon: Oceans of the Solar System is currently available on the BBC iPlayer.