This chapter contains the prompt! 

Yup. There was a hole, and it was bloody big as well. The ground radar displayed the cavity in all its glory.

Fortunately, since its roof had been pierced, the mysterious hollow had stayed in situ. They really didn't need mobile underground hazards. Not only were they a bloody menace, but they were scientifically impossible. There was a logical explanation for all this. There had to be.

They only had to find it.

"The unidentified object is exactly circular, with a circumference of 20 meters. That gives us 6.36942675159 for the diameter."

"Just round it up, will you, Dr. Katal?" Floyd said. He'd given up on the first name. There were some people he didn't want to be on a first-name basis with, and sweet little Leela was one of them.

"I never round things up."

Of course not.

"The thingumajig looks like a ball cut in half. Top is there, bottom has been sliced off," Bones said, tapping his finger at the plas-glass screen.

"Don't do that. It leaves stains," Leelawati said.

Bones sighed. But he withdrew his finger.

"The camera scan revealed nothing of further relevance. Apart from an unidentifiable object in the corner." Leelawati's tone conveyed very clearly what she thought of the camera's observational capabilities.

Nothing.

"What's this here?" Floyd would have tapped the screen, but caught himself at the last moment. "There's something on one wall."

"It's unidentifiable as well. This equipment is flawed."

"Looks like we have to ditch the camera and spy with our own little eyes," Bones said.

Floyd sighed. No our. His. The Boy Friday of the mission had just got himself another job.

"Gotcha. I'll suit up."

***

The Mars atmosphere muffled the boosters' roar, but they worked just fine and deposited Floyd on the sandy floor of the cave, bubble, cavity, or whatever the stupid thing was. From above seeped a diffuse tangerine glow into the place's murky interior. It was late in the day. Normally not the ideal time for explorations, but even Leelawati for once didn't insist on procedures. She was curious, she only didn't want to admit it.

"Floyd to Base. Am on site. Now proceeding to investigate object. Tape and camera activated."

"Base to Floyd. Copied," Bones said.

Protocol observed, Floyd let the beam of his power-torch travel over the smooth walls of the cavity. They lit up in a flare of glitter, which caused the self-adjustable visor of his helmet to enter shading mode, leaving him standing in a black sinkhole.

"Oh, screw this."

It took a moment for his eyes to adjust, but eventually Floyd pointed the torch at the floor and pressed his gloved fingers against the wall. Smooth, not quite like glass, but definitely not rock.

He pointed his scanner at the wall. Readings flickered over the screen.

"Igneous rock detected."

That was a big fat help.

"Which igneous rock?"

"Correlation Obsidian 95 percent. Mica minerals four percent."

Okay, that was possible. Obsidian was basically volcanic glass formed when lava cooled rapidly with minimal crystal growth. Mars had plenty of volcanos, and a huge one was just around the corner. The minerals might be responsible for the flare, though the flare had been rather on the bright side.

But lava bubbles, glittery or not, don't move. He switched off the little voice at the back of his brain. It wasn't telling him anything new.

Having dimmed his power-torch, Floyd turned around and lumbered for the other end of the cavity where the first unknown object lay on the ground.

Now, that was odd.

He was right here, quite close to the damn thing—and he still couldn't work out what he was seeing.

He blinked.

Ah, the dang visor. He raised his hands and pushed the button that deactivated the shading mode.

The chamber was suddenly a lot lighter. He looked down.

A human skeleton lay at his feet.

Floyd couldn't help it. He jumped back.

Of course, this being Mars, he sort of floated, knotted his legs in the process and landed on his butt with a thump. A little cloud of dust rose, floated, and quietly settled again.

"Base to Floyd, what are you doing?"

"This isn't possible." The voice in his ear sounded hoarse, alien, totally unlike his.

"Navigator DeNeville, please adhere to protocol," another voice drilled into his head.

Oh gawd, there was a human skeleton in the chamber and the woman gave him protocol.

His gaze slipped back to the bones, brown and stained they reminded him of twigs. He wasn't the biggest expert on human remains, but the broad pelvis made him think his unwelcome find might have been female.

Perhaps, she too didn't adhere to protocol.

He sniggered.

You're hysterical. Cool it, man.

There was a human skeleton that couldn't be there on the floor of a cavity that moved.

"Navigator DeNeville?"

He breathed in and out. Twice. He felt a bit better. Not much, though.

"Floyd to Base. There's a female skeleton in the cave. At least I think it's female."

Silence roared in his ear.

"Base to Floyd. Repeat that for me."

"Floyd to Base. Confirmed. We have what I think is a female skeleton in our cavity. Which seems to be made of volcanic material, but it's a bit weird."

"Base to Navigator DeNeville. Observation of first object acknowledged. What about the other one? The unidentified phenomenon on the wall."

Leelawati sounded as cool as one of her baby cucumbers she was growing in the new greenhouse.

"I'll check." Sod the protocol.

He turned his back on the remains that shouldn't...couldn't be there, and stepped up to the curving side of the cave.

He squinted.

No, he wasn't imagining things.

There was a writing on the wall. Four words. Or letters. Or glyphs. Or something. The problem was, he couldn't read any of it.

"Floyd to Base. I'll show you what I found." He raised the camera and pointed it at the nonsensical scribbles in front of his helmet.

"What's that?" Bones asked. In the background, Leelawati gave him aggro over protocol.

"Language is my best guess. Just don't ask me which one."

Something flashed.

No, not something. The words flashed, shimmied and shivered. Then, they melted and rearranged themselves into a different shape.

There were still four...whatevers in front of him. But they weren't the same thing he'd observed a few instants ago.

"Did you catch that?"

The answer was a while in coming.

"Yes," Bones said. "Floyd, get the heck out of there. This isn't normal."

"You're not telling me anything new."

"Base to Floyd. Evacuate chamber." Leelawati's voice, was tight, urgent, concerned for once.

He didn't need another invitation. Floyd fired the boosters and rose at the darkening skies. As he ascended, the ray of his torch slid over the sad muddle of bones on the floor. They, at least, hadn't moved. 

(1151/4479 words)

https://youtu.be/YXF29tCeh0c

OMG, we're talking dinosaurs in space. But this stuff is hilarious! And the spaceship super cool. Okay, you need to speak German if you want to watch the films, but I believe there's a version with subtitles.

This chapter is dedicated to @lyttlejoe who is the fastest and most amazing writer on Wattpad. Long may you post!