The felt-tip pen that saved Buzz Aldrin and Neil Armstrong from becoming the first permanent lunar colonists is now up for auction in New York. Sotheby's estimates the dented silver plastic Duro Rocket pen - used by the second man on the moon to fix a broken circuit breaker during the Apollo 11 mission in July 1969 - will fetch between $800,000 and $1.2 million. The lucky bidder will also receive the broken piece of circuit breaker, because nothing says 'souvenir' like the thing that almost stranded two guys on the moon.

Aldrin noticed the small black switch on the floor of the lunar module's cabin while preparing to sleep after their first moonwalk. In his 2009 autobiography Magnificent Desolation, he wrote: 'My heart jolted a bit … The broken switch had snapped off from the engine-arm circuit breaker, the one vital breaker needed to send electrical power to the ascent engine that would lift Neil and me off the moon.' In a letter of provenance, Aldrin jokes, 'I think Neil broke the switch off and Neil thinks that I broke the switch off.' By 2016, however, he was more willing to take the blame, noting that he had apparently bumped it with his heavy backpack.

Mission Control initially hoped to reroute the power but ultimately informed the astronauts bluntly: 'There is no way to reroute the power.' Aldrin then remembered the black felt-tip pen he had brought as part of his 'personal preference kit' - not on the official list of items taken to the moon. 'I gingerly pressed the pen against the engine arm circuit breaker,' he wrote. 'Slowly, almost reluctantly, I eased the pressure on my hand and lifted the pen's tip. The pen did the trick; the circuit breaker held. We could return to Earth after all!'

Aldrin, now 96, is one of four surviving moonwalkers from the Apollo era. NASA plans to return to the lunar surface as early as 2028, and China aims for a crewed landing by 2030. Aldrin, however, has long advocated for skipping the moon reunion and heading straight to Mars. In 2013 he wrote in the New York Times: 'A second “race to the moon” is a dead end … US resources are better spent on moving toward establishing a human presence on Mars.' The pen and broken circuit breaker, which Aldrin still had as of 2016, may soon pass to a new owner - hopefully one who appreciates that sometimes the best tool is the one you forgot to pack.