Makes me think of this short story I read recently.
Imagine if another race of beings have also sent a probe to Mars. Our rovers and their rovers, roving around. Constantly missing each other. But we keep finding little funny things like bits that have fallen off the other rover, or unexplained track marks.
"Where are we going daddy?"
"Well, sweetie, we're going to the Pathfinder Festival!"
"What's that daddy?"
"It's where all us colonists get together and celebrate the ones who helped us establish The Colonies, almost 1500 years ago."
"Are they still around?"
"No, honey, they died a long long time ago. But their bodies are preserved, so you can still see them."
"Eww! That sounds yucky!"
"Oh it's not, sweetie. They're not made of flesh and bone like you or I, honey."
"Whoa! Is that them, daddy? Are those the Pathfinders?"
"Yes baby, that's them."
"They sure are! Look at that one! He's almost the size as our car!"
"WHOAH! Who's that?"
"That's Curiosity, sweetie. She was one one of the last ones to come here."
"What're those people doing?"
"They're leaving gifts for her! See, every year, we place little pieces of Earth next to the Pathfinders."
"Well see, the Pathfinders came from Earth, all those years ago. They loved Earth very much, but it was their duty to explore this planet, and make it safe for us. It was very lonely on Mars, back then, and the Pathfinders missed their homes very very much. So we leave little pieces of their home here for them!"
"I'm really glad the Pathfinders came."
"Me too, sweetie. Me too."