Short answer In a vacuum, clean surfaces of the same metal can bond on contact without any heat. Spacecraft designers have to watch out for it.
Galileo, the probe sent to Jupiter. Its big antenna never fully opened.
In air, metal surfaces are coated with thin oxide layers and grease. That's why they don't stick when they touch.
Cold weldingMetal bonding from contact alone, with no heat
When clean surfaces of the same metal touch in a vacuum, the atoms can't tell they belong to different pieces and just become one lump.
Metal sticks to metal with no glue?
It was first recognized as a general phenomenon in the 1940s. Some mechanical problems in early satellites were blamed on it.
In 1991, Galileo's big antenna never fully deployed. A European Space Agency paper cites this as a documented case of cold welding.
In space, being clean is the problem
Sources
Photo credits
- Galileo spacecraft leaves the Orbiter.jpg, Don Davis, Public domain (source)
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