By Rebecca Morelle
Science Correspondent, BBC News
An American explorer has found plastic waste on the seafloor while breaking the record for the deepest ever dive.
Victor Vescovo descended nearly 11km (seven miles) to the deepest place in the ocean – the Pacific Ocean’s Mariana Trench.
He spent four hours exploring the bottom of the trench in his submersible, built to withstand the immense pressure of the deep.
He found sea creatures, but also found a plastic bag and sweet wrappers.
It is the third time humans have reached the ocean’s extreme depths.
The first dive to the bottom of the Mariana Trench took place in 1960 by US Navy lieutenant Don Walsh and Swiss engineer Jacques Piccard in a vessel called the bathyscaphe Trieste.
Movie director James Cameron then made a solo plunge half a century later in 2012 in his bright green sub.
The latest descent, which reached 10,927m (35,849ft) beneath the waves, is now the deepest by 11m – making Victor Vescovo the new record holder.
In total, Mr Vescovo and his team made five dives to the bottom of the trench during the expedition. Robotic landers were also deployed to explore the remote terrain.
Mr Vescovo said: “It is almost indescribable how excited all of us are about achieving what we just did.
“This submarine and its mother ship, along with its extraordinarily talented expedition team, took marine technology to a ridiculously higher new level by diving – rapidly and repeatedly – into the deepest, harshest, area of the ocean.”
Witnessing the dive from the Pacific was Don Walsh. He told BBC News: “I salute Victor Vescovo and his outstanding team for the successful completion of their historic explorations into the Mariana Trench.
“Six decades ago, Jacques Piccard and I were the first to visit that deepest place in the world’s oceans.
“Now in the winter of my life, it was a great honour to be invited on this expedition to a place of my youth.”
The team believes it has discovered four new species of prawn-like crustaceans called amphipods, saw a creature called a spoon worm 7,000m-down and a pink snailfish at 8,000m.
They also discovered brightly coloured rocky outcrops, possibly created by microbes on the seabed, and collected samples of rock from the seafloor.
Humanity’s impact on the planet was also evident with the discovery of plastic pollution. It’s something that other expeditions using landers have seen before.
Millions of tonnes of plastic enter the oceans each year, but little is known about where a lot of it ends up.
The scientists now plan to test the creatures they collected to see if they contain microplastics – a recent study found this was a widespread problem, even for animals living in the deep.
The dive forms part of the Five Deeps expedition – an attempt to explore the deepest points in each of the world’s five oceans.
It has been funded by Mr Vescovo, a private equity investor, who before turning his attention to the ocean’s extreme depths also climbed the highest peaks on the planet’s seven continents.