Eventually, of course, the subject of procreation was raised.
The Martians took their guests deep into their underground
complex, into a room with red paneling covered in dials,
switches and other controls.  "Right," said one of the Martians,
adjusting  various controls.  "I think we should make a boy who
will grow up to be tall, fair, an engineer, a good sportsman with
a good sense of humor but a bit shy".
    He checked his settings, punched a blue button and a few seconds
later a panel in the wall opened and a basket containing a Martian
baby slid into view.  Everyone, Martians and humans gathered around
and gasped in wonder at the new born child.
    Then the Martians asked how this was  accomplished on Earth.
"Well," said the Expedition Leader. "If Miss  Johnson would care
to assist in the demonstration, I should be only too pleased to show
you how it is done".  The lady astronaut was more than willing and,
together, they stripped each other and proceeded to have sex.
When they finished and were redressing one Martian raised a quizzical
eyebrow and asked when the issue could be expected.
    "Oh sorry," said the leader. "It takes nine months".
"Nine months!" exclaimed the Martian.
"Well, why all the hurry at the end?"