For five days now, Ben Saunders has been crossing Antarctica alone. If he completes the trek, he will be the first person to do it without support or assistance.

Anyone seeking adventure in Antarctica must do it hearing echoes of Shackleton’s legend. But Saunders is also shadowed by the memory of his friend Henry Worsley, who planned the route and almost completed his own trek last year. After crossing more than 900 miles on foot, he became ill just 30 miles short of the end and died days later in a hospital. Worsley was himself a descendant of Frank Worsley, who captained the Endurance and navigated the expedition’s survivors to South Georgia Island.

Saunders’ journey started last Wednesday, when a small ski plane dropped him off on Berkner Island, an icy dome surrounded by a frozen shelf on the continent’s west side. He skied for nearly an hour before setting up his tent. When he woke up on Thursday, he saw nothing. Clouds and snow made the world invisible all day, so for nine hours he skied blind, using a compass at his waist to stay on course. On Friday, he crossed from the island, which sits on bedrock, to the Ronne Ice Shelf, under which there is only ocean. I️t was still nearly impossible to see anything, and the snow remained rough and uneven. Hauling a 300-pound sled felt like “dragging a washing machine across a ploughed field for eight hours in a day.”

Things improved yesterday. Although Saunders was woken hours before sunrise by howling wind, he unburied his sled and set out on a path now scoured smooth by the “hoolie” (a Scottish word for a strong gale). Mountains came into view in the distance, at last providing a point of reference on the horizon.

Today started windy again, but by late afternoon the air became still and the sun emerged. It’s already getting dark here in Somerville, but at the other end of the world the days are very long now. In such a blank and featureless world, the warmth of the sun must feel miraculous.