Heritage's Space Exploration auction is now just a couple of weeks away and the company has released full details of the catalogue for excited collectors to pore over.

One of the lots is a fascinating piece for both medal and space specialists: the Distinguished Flying Cross and flown mustard seeds of astronaut Ed White.

Born in 1930, Edward H White II was the first American to 'walk' in space as part of the Gemini 4 mission of June 3-7 1965. The experience was not lost on him, and he was quoted as saying "This is the saddest moment of my life." on his return to the craft.

The medal is in its original case with matching lapel pin and chest ribbon; it is engraved on the reverse: "Edward H White II" and comes with acopy of the Air Force Special Order GB-136 listing those astronauts awarded DFCs at that time; an official photo taken at the ceremony; and a signed letter of transmittal for the photo from Air Force Chief of Staff John McConnell.

Ed White Distinguished Flying Cross mustard seeds

The mustard seeds, are a symbol of White's religious faith and were in a pocket of White's spacesuit while he walked in space. In the Bible's New Testament, there are several examples of Jesus using the mustard seed as a model of the growth of the Kingdom of God from an extremely tiny seed to the largest of all garden plants, as well as an example of the tiny amount of faith needed to accomplish much.

White, along with Roger Chafee and Gus Grissom, died in a fire during the testing of what was later designated Apollo 1. Had he not died in 1967, just two years after his pioneering spaceflight, he might have been one of the first men on the moon. That makes this lot a particularly strong investment.

The medal and mustard seeds are expected to sell for $16,000-20,000 in Heritage's auction which concludes after internet bidding with a live session Dallas, Texas on June 3.