Dawn of the Deep

“I want to walk through it.”

“Go walk through it. I’ll get a video.”

It’s the end of a busy day working on the seabed when Megan and I see the huge school of bait fish. I take three steps, my suit weighted down to simulate partial gravity. Suddenly I’m the centre of a snow globe.

I watch the white fish swarm round my helmet, this way then back again. For a moment I command them, an honorary marine life form, emulating the callsign my crewmates have given me: Dawn of the Deep.

I’m underwater, but thanks to my helmet I have a bubble of air surrounding my head. I can breathe freely and talk freely.

“Aaaaaah!” I sing, walking back towards Megan. The fish disperse.

The helmet’s air supply comes through 600 feet of umbilical hose that snakes back to Aquarius Reef Base, the underwater habitat where we’re living during the mission. Managing the umbilicals, which also carry our communications, is a job all by itself.

Thankfully we have technicians and support divers keeping an eye on them to make sure they don’t wrap around coral, ourselves, or each other.

It takes a village to run one of these missions. For each of the six crew members in the habitat there’s around a dozen research and support team members, most of them back at mission control six miles away on shore.

Yet even with all this support, we are cut off. Physiologically. Unlike a recreational SCUBA dive, we can’t go to the surface if there’s an issue. After 24 hours at depth, our bodies are saturated with nitrogen.

If we went straight to the surface, we could get decompression sickness, which could lead to serious injury or death. Anything that might happen, we have to handle it underwater.

Talking to the astronauts who have done this mission, they say that there are many similarities between living in space and living in an undersea habitat. You’re living in a small environment, under physical and psychological pressure, unable to immediately abort the mission.

This makes habitat diving a great way for NASA and other space agencies to see how people handle new protocols and equipment before they’re used on the International Space Station.

Living in an underwater habitat

It’s Mission Day 9 when crewmate Noel and I splash down to begin our stay in the habitat. Our first night underwater is spectacular. Outside the bow window we watch the night species take over from the daytime species.

This is something you won’t see as a SCUBA diver. Living in the habitat, you get to watch the underwater world go by.

Dinner is less spectacular. Camp food, a staple down here because you can cook it using only hot water. We douse most of our food in hot sauce. The pressure down here dulls our sense of taste.

As the mission goes on, the craving for salad will become intense. I’m adamant that when we get Sentinel in the water, we try to have some plant life on board. It’s nice to see (and eat!) greenery.

Twenty-four hours after splashdown, our bodies have absorbed as much inert gas as they will at this pressure. We’re fully saturated, and are now officially aquanauts.

Saturation diving is a legacy of the Conshelf and Sealab missions of the 1960s, which proved that after a certain point a diver can stay at a given depth indefinitely without adding to the decompression time needed when they resurface.

NASA now takes advantage of this knowledge, sending astronauts and scientists to live under the sea as part of their training and simulating the kind of protocols, living arrangements, and group dynamics they will encounter in space.

It seems that there’s an issue with comms when Noel and I arrive in the habitat. It’s taking 15 minutes for messages to reach the research and support teams at mission control, and another 15 minutes for their replies to get to us.

This comms delay isn’t a malfunction though. Since Mission Day 5, all communications have been subject to a simulated delay, to mimic the lag caused by the distance between Earth and Mars. It’s another way NASA is using this mission to lay the ground for future exploration.

Taking data, growing coral

Mission Day 11. A full 4-hour extravehicular activity (EVA), aka a simulated spacewalk. The technicians help us suit up.

The Kirby Morgan Stainless Steel 37 diving helmet weighs 32lbs (15kg) and needs to be sealed tightly to keep water out and so it turns when your head turns.

I’m alongside Megan McArthur Behnken, who is Commander for the second half of our mission. We exit the habitat via the moon pool, which is basically a hole in the bottom that acts as our doorway to the sea. The pressure in the habitat keeps out the water.

We hop off the deck onto the sandy bottom and walk the five minutes to the deepest part of the reef, around 25-30 metres below the ocean’s surface. The temperature is lower here.

Today we’re looking for three species of coral: Agaracites agaricia, Agaricites humilis, and Orbicella faveolata. Our job is to find them, tag them, and send the pictures and readings back to the science team, who’ll then decide which corals to sample.

The earliest habitat missions, in the 1960s, focused their study on people. How long can they stay down there? What does it do to a human body?

But it didn’t take long before researchers were using the advantages of habitat diving to learn more about the marine ecosystem, first with the Tektite habitat (1969 and 1970) and then La Chalupa in the 1970s.

DEEP is developing its Sentinel System for subsea habitation with research applications squarely in mind. You can get so much more work done when you’re staying down there and don’t have to worry about decompression times. Sentinel will be modular and re-deployable, allowing it to be used around the world and scale according to the project.

Megan and I finish tagging potential coral samples. Or, to be more accurate, we use up all our tags.

As we head back to the habitat, pulling the sled with our tools behind us, we see what looks like a giant TV aerial decorated in little white flags on the seabed. It’s the coral nursery tree that our crewmates built during the first half of the mission.

White cards hang from its ‘branches’. On each one is a coral seedling being grown for eventual replanting as part of a collaboration with the Coral Restoration Foundation.

We take some pictures and measurements to assess the seedlings’ ability to photosynthesise, then head back to the habitat.

Twelve months later, I’m back here, a support diver on the next mission. I’m watching the next crew harvest these same coral, ready for planting in the reef. With a little nudge, the cycle of life underwater goes on.

Images courtesy of NASA.