Makes sense to me

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!", says the Martian.

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

One naut says "It looks serious. What are they afraid of? But - we're here for science, to know if man can breathe on Mars".

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

"Why did you want to prevent us from striking a match?"

The leader of the Martians replies, "Its Shabbos!"