What happens to balloons that float off into space?

After helium filled balloons escape, or are released, they rise up into the atmosphere at around two metres per second. They will rise to about 28,000 feet (8.5 kilometres) in about 90 minutes. The pressure and temperature both drop as the altitude increases; the temperature at this height is a very cool minus 40°C.

By now the balloon has reached its elastic limits and, at about 700% of its original un-inflated size, it bursts. The shatter that happens in these conditions is referred to as a “brittle fracture.” This shattering effect is similar to the smashing of glass, and the balloon splinters into many tiny pieces, about the size of a 5- or 10-cent piece, and then floats back to the ground, spreading over a large area.

Organic break down of these “shattered” balloons happens at a much faster rate than a whole latex balloon, especially one that has been thrown into the rubbish and disposed of as landfill.