Discovering the Lost City was the most exciting moment of my career, and it was all down to chance. 
Twenty years ago I was out on an expedition mapping the seafloor. We were there taking photos and I just happened to be on watch. It was a real example of serendipity — we weren’t in search of anything special, we just stumbled across it.
Hercules captured this image of a deep-sea jelly fish, possibly Poralia rufescens, undulating several meters above the seafloor just south of the IMAX vent at Lost City. Atlantic Ocean, Mid-Atlantic Ridge. © NOAA/OAR/OER, The Lost City 2005 Expedition.
We weren’t sure what we were looking at to begin with, it tested our scientific understanding and knowledge at first, because we hadn’t seen anything like this before. First we saw corals, and then we saw these huge white structures, hydrothermal geysers, which emit hot water into the ocean. 
Some of the geysers and structures looked like cathedrals — that’s why my colleagues called it the Lost City. It was such a fitting name because we were on the research ship Atlantis, mapping a mountain called the Atlantis Massif, which is bound by the over 4000m deep Atlantis Fracture Zone.
The beauty of the Lost City is hard to describe — I just never lose my awe for the area. I can look at video footage of it for hours. It’s hard to believe that there’s colour even at a depth of 800 meters, everything has colour, the corals and even the crabs. I mean, it’s dark down there, why do things need colour?
The mauve stinger jellyfish, or Pelagia noctiluca, grows up to 10 centimeters in diameter. When a calm sea is disturbed by a passing boat or dolphin at night, this jellyfish is able to produce flashes of light. © Greenpeace, Azores deep sea life survey.
I still get excited about the chance to go back to the Lost City. It’s like going back to that special place you love to go on holiday. 
I’ve been out there four times, since we discovered it 20 years ago. I’d love to visit more but it’s expensive to visit the deep sea. Scientific expeditions cost money, so it’s taking us years to find out more about the Lost City. 
We haven’t found many areas like the Lost City, it’s the only one in the Atlantic. We still don’t know how these systems have formed or how they’ve been able to sustain themselves for thousands of years. We know and understand so little about the seafloor, so it makes you wonder how many other surprises are out there.
Arbonate spires in the Lost City vent field. Atlantic Ocean, Mid-Atlantic Ridge. © NOAA/OAR/OER, The Lost City 2005 Expedition.
Every time we get down there we come away with more questions. Does it hold information on how our earth formed? Is it the building blocks of life? We just don’t know… yet!
We’ll have a better understanding in a few years, but even then we can’t say ‘wait for 10 years, and then you can go and destroy it’. With science you’re never done. 
I am very protective of the Lost City. Even as a scientist, just breaking off a small sample of it for research hurts, because you want to protect it.
There are no rules about visiting Lost City. There is no government, no policies, no permission required from anyone to go there and do whatever you want. It doesn’t belong to me, it doesn’t belong to anybody, I just continue to discover it. Nobody owns places like this.  
The Madeira rockfish, or Scorpeana Maderensis, can change pattern and color from almost white to deep red, in an attempt to imitate the background. © Greenpeace, Azores deep sea life survey.
Right now the Deep Sea Mining industry is carelessly drawing lines on the seafloor and buying it up — as if it’s just up for grabs.
It’s costly to go out and mine or dredge the deep sea, but it’ll be very tempting as minerals become rarer. We can’t set a precedent that anyone can send diggers down and do what they want with our oceans.
If diggers go in, they’ll likely create huge amounts of dust and noise, and we don’t know what the impact will be. We don’t know what it will do to ocean chemistry. We don’t know what we’re destroying or disturbing. And because we don’t know, surely we should be careful?
Protecting natural wonders on the seafloor would be the first step towards safeguarding our oceans. It’s not just the Lost City that needs protecting. If we can understand what’s going on in our natural laboratory, we can learn more about how life on earth started and perhaps even more about other planets.
Join Gretchen in calling for a strong Global Ocean Treaty, which would protect places like the Lost City, by putting the most vulnerable and important parts of our seas off-limits to destructive industries. Sign the petition here: www.greenpeace.org/protecttheoceans
Professor Gretchen Früh-Green is a senior research scientist in the Department of Earth Sciences at the ETH-Zurich, Switzerland, who discovered the Lost City in 2000.