Humans are very vulnerable in space and can't survive without a
space suit or space ship. But there was one stowaway from Earth
that survived everything that space could throw at it.
Surveyor 3
In 1967 an unmanned spacecraft called Surveyor 3 landed on the
moon. It was supposed to be unmanned, but it did carry some life
from Earth. A common bacterium called Streptococcus mitis had
hitched a ride. This fact would never have been discovered except
that some time later Apollo 12 landed right next door and returned
some parts of Surveyor 3 to the Earth for study.
Truly amazing: grown up
bacteria!
What they found was truly amazing: living bacterial spores that
were woken up and grew into perfectly normal bacteria. This was
after three years in a perfect vacuum enduring freezing, frying and
bombardment with ultra high levels of radiation.
Pete Conrad, the commander of Apollo 12, summed it up, he said,
"I always thought the most significant thing that we ever found on
the moon was that little bacteria who came back and lived and
nobody ever said anything about it."
Today it is even believed that life may have originally come to
the Earth from deep space aboard a meteorite. This has led to the
theory of Panspermia which is the theory that we may all turn out
to be descended from germs from space! But that's another
story!