"Our dredge must have fallen right over its top. This anchored the ship for over an hour but it finally broke off at the base," said expedition leader Dr Ray Binns, of CSIRO Exploration & Mining.
Black smokers are chimney-like structures created by underwater geysers. The waters swept up from deep within Earth's crust are rich in dissolved minerals, which are deposited as tall funnels.
They were only discovered in the late 1970s but have been the subject of intense study ever since. Scientists are intrigued by the lifeforms that can thrive around the smokers and the vast hydrothermal systems in which they are found.
These are extreme environments with no light, where the lifeforms must use the minerals from the vents to make the chemical energy they need to survive.
Not surprisingly, mining companies are also interested in the opportunities for tapping these systems for new resources.
Venting chimney
This particular chimney was recovered at a depth of two kilometres in the Bismarck Sea and is laced with gold. It was caught accidentally in the dredge frame of the Research Vessel Franklin, which was being operated by Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO).
"Our dredge must have fallen right over its top. This anchored the ship for over an hour but it finally broke off at the base," said expedition leader Dr Ray Binns, of CSIRO Exploration & Mining.
"Luckily for us it got wedged into the dredge frame on its point of balance, so it stayed there while we winched it all the way up to the ship.
"It proved to be 2.7 metres long, 80 cm in diameter at the base, and weighed at least 800 kg in water, closer to a tonne in air.
"It must have been an actively venting chimney, for live snails dropped into the dredge bag, and fluid dripping from it was quite acidic. But there was no characteristic smell of rotten eggs (from hydrogen sulphide gas) often found with smaller chimneys.
Black smokers were discovered in the late 1970s
Preliminary investigation revealed the catch to be teeming with bacteria and archaea, which are microscopic organisms commonly found in extreme environments. One of the main goals of the expedition is to identify particular microbes that can be harnessed to process minerals on dry land, and so develop more efficient and cleaner ways to win metals.
Earliest lifeforms
"We believe that microbes such as these deep sea bugs may enable Australia's miners to exploit lower grade ore deposits, extract metals more cheaply, clean up waste streams and may even improve mine safety," said project designer Dr Dave Dekker.
Microbiologist Dr Peter Franzmann of CSIRO Land & Water said that the mineral-mining bugs are possibly relatives of some of the earliest forms of life to emerge on the planet, more than three billion years ago.
"Back then, conditions were similar to what we now see in these seafloor hydrothermal vents - high temperatures, lots of volcanic activity, darkness, with the nutrients to sustain life pouring out of the Earth itself."
Black smoker chimneys are generally made from sulphides of iron, copper and zinc. This "very fragile" specimen consists mainly of the mineral known as sphalerite, which is zinc sulphide.
The sulphides are precipitated when the very hot mineral-rich waters erupting up from below mix with the cold water of the ocean. It is the precipitates that make the vent water appear black in colour and give the chimneys their name.