Pet Rocks

A Mars rover surveyed the planet’s topography to help plan for a colony that would build and launch an interstellar generation ship.

A wormhole opened up, and a heavily armed alien warship orbited Earth, signaling the United Earth Space Agency:

“Humans, stop what you’re doing at once, or face total annihilation!”

“Stop what?”

“That rock you call Mars belongs to us.”

“By what right do you make this claim, alien?”

“I gifted it to my daughter.”

“How’s that possible? No one can own an entire planet.”

“Of course, humans, we’ve monitored your culture. Your children have pet rocks, don’t they?”