I have always loved this little poem.  And so, with the great invention of the internet I am glad to be able to post it for others to enjoy.  I was able to find a little link, by another admirer which provides some information.  I recall that this was published in Analog (which I was fond of reading).  Unfortunately, this is all the information I have been able to find.  If you have a copy of the magazine or more accurate information, please send it along.

	Once upon a planet dreary
	Came a rocket engine cheery
	On a flight to test a theory
	On Mars's frigid desert floor!

	Did life arise spontaneous
	Or some alien's trash extraneous
	Seed the globe that now contains us?
	Quoth the Lander, "Either-or."

I hope you enjoy it as much as I.