Vacuum

In space vacuum, two clean pieces of the same metal can fuse on contact without heat. On Earth, oxide films and grime block this bond; in vacuum, bare atoms meet directly and act as one solid. This is cold welding, so spacecraft parts need coatings or anodizing.

Tardigrades survived 10 days exposed to the Vacuum of Space and cosmic Radiation in a 2007 ESA experiment. Some even endured solar UV; after rehydration on Earth, they revived and laid eggs—the first animal shown to survive such exposure.

In 2008, UCLA showed in Nature that peeling Scotch tape in a vacuum emits nanosecond X-ray bursts. The tape's adhesive side charges positive, outer side negative — a ~40,000 V gap. Accelerated electrons strike across and emit X-rays. They photographed finger bones with it.