Update: Explorer Ranulph Fiennes' epic challenge

British explorer Sir Ranulph Fiennes has started to climb the world's second highest mountain, Mount Aconcagua, in Argentina.

It's part of his record-breaking challenge to raise money for the charity Marie-Curie.

Mount Aconcagua is the highest mountain in South America, standing 6,959m high.

Check out the video to see which other mountains Sir Ranulph has left to conquer.