"Nothing is impossible" has been the constant mantra of record-breaking Swiss explorer Bertrand Piccard, who along with compatriot Andre Borschberg has again made history with the first round-the-world solar flight.

Piccard on July 26 completed the final leg of the marathon tour aboard the fully sun-powered plane, Solar Impulse 2, landing in Abu Dhabi and completing a journey that began in March last year.

The 58-year-old is scion of a dynasty of trailblazers -- Piccard's grandfather Auguste was the first man to climb to the stratosphere in a balloon and his father Jacques was the first to reach the deepest point of the world's oceans.

Born on March 1, 1958 in the picturesque lakeside Swiss city of Lausanne, he was greatly inspired by his illustrious forebears and was fascinated by challenge from a very early age.

He has said a defining moment in his life was the lift-off of Apollo 11 on July 16, 1969, which landed the first humans on the moon.

The 11-year-old Piccard got to witness the historic moment live from Cape Canaveral, Florida, since Wernher von Braun, the inventor of the Apollo rockets, was a family friend.

"The moment was a turning point in my life," he says on his website.

"There and then I thought: 'These astronauts, who are now setting off for the moon, have a dream, and that dream is greater than the fear of failure. These heroes dare to do the impossible. They are doing something that no human being has done before them. That is true pioneering spirit'."

- 'Everyone has dreams' -

From a very early age, Piccard was fascinated by human behaviour in extreme situations, and got a degree in psychiatry from the University of Lausanne.

He also obtained licences to fly balloons, aeroplanes, gliders and motorised gliders and became one of the pioneers of hang gliding and microlight flying in Europe during the 1970s.

On March 1, 1999 Piccard and fellow adventurer Brian Jones set off from Switzerland on the first non-stop balloon circumnavigation of the globe without using any fuel.

The two men, in close touch with a team of meteorologists on the ground, caught rides in a series of jet streams that saw them land in Egypt after a flight lasting nearly 20 days.

"Everyone has dreams," Piccard said. "The only thing is that there are those who know they are achievable and do everything they can to make them come true and there are those who don't believe so."

Before Solar Impulse 2 completed its historic trip of more than 42,000 kilometre (26,000 miles), the first Solar Impulse plane proved its ability to store enough power in lithium batteries during the day to keep aloft at night.

The initial plane was put through its paces in Europe, crossed the Mediterranean to reach Morocco and traversed the United States in 2013 without using a drop of fossil fuel.

Now it has been upstaged by its successor.

The two pilots alternated at the controls of the single-seat plane, with Piccard flying across the Atlantic last month in a 6,765-kilometre journey.

Borschberg meanwhile covered the 8,924-kilometre flight from Japan to Hawaii last year in 118 hours, breaking the previous record for the longest uninterrupted journey in aviation history.

Piccard told AFP last week the plane could fly continuously. "The pilot is the limit," he said.

- Enter the unknown -

Always keen on pushing the limits, Piccard has previously said that what he likes "about the life of an explorer is you are in the unknown; you are out of your habits".

"You are obliged to produce new answers to what life is bringing to you. These are the moments that wake you up from the automatic," he said.

Piccard, who studied medicine and psychiatry, is also passionate about spirituality and hypnosis and has written several books, including a self-help guide to achieving a better and more balanced life.

His other pet obsession is environmental protection, and he told AFP he hoped the Solar Impulse achievements would prove that broader use of sustainable energy is possible.

"Renewable energy is no longer restricted to a small ecological niche," he said, insisting it now provided "an extraordinary development for industry, for job creation, for conquering new markets while protecting the environment at the same time".

Piccard, who is married with three daughters, hopes the Solar Impulse 2 will help drive home this message across the world.

"What we need to do now is convince the political and the industrial world that this is the direction we need to go in," he said.