Is there oxygen on Mars?

[Mark Feit]

Forwarded-by: Martin Bondy <martin_bondy at yahoo.com>
Forwarded-by: Ken Glasser <glasserk at acm.org> and his father

Two astronauts land on Mars.  Their mission: to check whether there is
oxygen on the planet.

"Give me the box of matches," says one.  "Either it burns and there is
oxygen, or nothing happens."  He takes the box, and is ready to strike
a match when, out of the blue, a Martian appears waving all his
arms... "No, no, don't!"

The two guys look at each other, worried.  Could there be an unknown
explosive gas on Mars?  Still, he takes another match... and... a
crowd of hysterical Martians is coming, all waving their arms: "No,
no, don't do that!"

One of the astronauts says, "This looks serious.  What are they afraid
of?  Nonetheless, we're here for Science, to know if man can breathe
on Mars".

So he strikes a match, which flames up, burns down, and.... nothing
happens.

So he turns to the Martians and asks, "Why did you want to prevent us
from striking a match?"

The leader of the Martians says, "Today is Shabbos!"