Vanessa O'Brien: British-American explorer becomes first woman to reach Earth's highest and lowest points

A British-American explorer has become the first woman to reach the Earth's highest and lowest points.

Vanessa O'Brien dived 10.925km (6.78m) to reach the Challenger Deep at the bottom of the western Pacific Ocean.

The 55-year-old successfully completed the 11-hour voyage by submersible on 12 June - having previously scaled the peak of Mount Everest - at 8.848km (5.5m) high - in 2012.

Ms O'Brien is now officially the first woman to have travelled to both extremes - and she has been entered into the Guinness World Records.

It took Ms O'Brien four hours to get to the southern end of the Mariana Trench for the second challenge, where she spent another three hours helping to map the ocean floor and collecting water samples.

She endured eight tonnes of pressure - the equivalent of 20 jumbo jets stacked on top of one another.

Ms O'Brien told Sky News: "It's almost two kilometres deeper than Everest is tall.

"Sometimes people can't conceptualise that - that there's something deeper in the ocean than there is taller."

Describing the conditions, she added: "There's no light down there. It's extreme darkness. The pressure is extremely high. It's a little bit eerie if you have a good imagination."

She said she wanted to take on the double feat to draw attention to a project called Seabed 2030, which aims to map all of the ocean floor over the next 10 years.

The explorer said: "Currently 80% of the world's seabeds are unmapped. So we actually know more about the surface of the moon and Mars than we do about our own oceans, which is almost unbelievable."

Ms O'Brien's team was predominately female and included astronaut Kathy Sullivan - who completed the same journey days before her - and lead surveyor and honorary commander Durdana Ansari, who presented her with a Royal Navy ensign to take on the journey.

She told Sky News: "I find women are very good at endurance sports. And that's primarily because a lot of endurance sports have to do with having focus and concentration.

"Men sometimes can have short attention spans, they can get bored easily and have their minds wander.

"Women are very, very organised. They're good at communication, building teams and making decisions within those teams. That tends to gel really well on an expedition."

She said that at least half of the challenge is a mental one, adding: "It's about that willpower. It's about having that desire to complete what you have set out to do. Rather than the physicality of what you're doing."

Ms O'Brien became the first British or American woman to summit K2, the second-highest peak in the world, in 2017 - and has climbed the highest peak in every continent faster than any woman, taking just 295 days to do so.

A Fellow of the Royal Geographical Society, she has also skied to both the North and South Pole - and climbed five peaks over eight kilometres (five metres) high.

Asked what her next challenge would be, Ms O'Brien ruled out space and said she would be keen to continue her work with oceans.