Complex sentence: He ventured to the South Pole on December 8,2005, and on January 15,2006, he began a journey to the North Pole, which he and Mike Horn concluded on March 23.
Split into simpler sentences: He ventured to the South Pole on December 8,2005. On January 15,2006, he began a journey to the North Pole, which he and Mike Horn successfully concluded on March 23.