Do metals fuse together in space?

In theory, yes – it’s an effect called ‘cold welding’ by which the metallic bonds that hold atoms together in each object effectively ‘bridge the gap’ between them to create a single solid object. In practice, this rarely happens on Earth because most metals form a protective oxide layer where their surface is exposed to the atmosphere. Slight bumps and irregularities in metallic surfaces also prevent this from happening. Even when metals are taken into space, the oxide layer remains – but, of course, if you deliberately polished it off then, yes, the two metals would fuse together, and that’s something satellite and spacecraft designers need to bear in mind.

Answered by Giles Sparrow.