A team of researchers has embarked on a journey to map a series of vast mountain ranges lying up to five kilometres beneath the sea surface in what they say is one of the least-understood regions in Australia.
Located around Christmas and Cocos Islands, the vast undersea seamounts are barely understood and scientists believe they could be home to unknown deep-sea species.
The mountains are part of a new 740,000-square-kilometre marine park declared earlier this year.
CSIRO research ship RV Investigator departed from Darwin Harbour on Friday morning for the 35-day expedition with 53 crew members aboard.
Voyage Chief Scientist Tim O'Hara, who researches animals who live and thrive in the deep sea, said the area was one of the few places in Australia that scientists know nothing about.
"We know the region is covered with massive seamounts formed during the dinosaur era and we know the region sits at a critical juncture between the Pacific and Indian Oceans," he said.
Museums Victoria Research Institute collection manager Melanie Mackenzie said it was an exciting opportunity to show Australians more of their marine resources.
"So many people might scuba dive down to 30 metres, but no one gets to go this far down," she said.
Researchers return to the deep
It's not the first time RV Investigator has scoured the depths around Christmas and Cocos Islands.
Last year the same ship conducted a similar expedition in the region, using technology to map out vast mountains up to 70 kilometres wide and trenches up to five kilometres deep.
This mission will use a high-tech sonar system to survey the topography of the sea floor, as well as cameras and nets researchers hope will help them discover new species.
Ms Mackenzie said the team will be exploring depths of four and five kilometres and expect there to be some interesting creatures compared to those found closer to the surface.
"Down there you've got a lot of really blobby things, and a lot of really fangy things," she said.
Last year scientists on the first expedition found an undersea volcano which they described as looking like the 'Eye of Sauron', a nod to the fiery antagonist in the Lord of the Rings series.
They also named a number of other mountains nearby after other locations in Sauron's kingdom of Mordor.
Where the Pacific and Indian oceans meet
Any new creatures found on the journey will be added to the Museum Victoria State Collection.
Among the wildlife found in the region are whale sharks and certain species of turtles and manta rays.
The waters around Christmas and Cocos Islands are also home to an unusually high number of unique "hybrid" fish, according to Parks Australia.
Scientists believe they evolved because of interbreeding between animals in the Pacific and Indian Ocean.
"We are really excited about the prospect of discovering new species, perhaps even new branches of the tree of life, which until now have remained hidden beneath the waves in this unexplored region," Dr O'Hara said.
"We know nothing about what animals live on the sea floor... this is a real voyage of discovery."
The waters around Christmas Island and Cocos Island, which lie north west of the West Australian coast, were designated as marine parks in March this year.
