The ground above thundered with another violent quake, shaking loose cascades of dust and rock. The cavern trembled as if Mars itself were groaning under the weight of its own secrets.
"Everyone move!" Commander Hayes barked. "The fissure's collapsing—we can't stay here."
They scrambled toward the slope they had fallen from, only to find it sealed. Tons of red stone had crumbled down, burying the way back in an unbroken wall. The Odyssey was cut off.
Daniel's heart sank. "We're trapped…"
Dr. Marquez pressed her gloved palm against the wall, shaking her head. "There's no digging through that. Not without heavy equipment."
For a moment, silence pressed in on them, broken only by the faint hum of the crystal. Then Okafor pointed to the far side of the cavern, where a narrow tunnel split off into the darkness.
"There," he said. "That's our only option."
Hayes hesitated. The tunnel was jagged, unstable, its ceiling jagged with sharp stone that seemed ready to collapse. But there was no choice.
"Alright," he said. "Lights on. Stay close. And for God's sake, don't touch the walls."
The crew moved into the passage, their helmet beams slicing through the dark. The air grew colder as they descended, the silence broken only by the crunch of their boots and the occasional drip of unseen condensation.
Daniel kept glancing back at the crystal. Even as they moved, it seemed to pulse faintly, its glow trailing like a heartbeat that refused to be left behind. It was as if it wanted them to follow.
The tunnel widened unexpectedly, opening into a chamber unlike anything they had seen before.
This was no natural cave. The walls were smooth, polished, etched with faint symbols that glowed as their lights passed over them. The designs spiraled in patterns that made no sense—yet felt intentional, deliberate.
Marquez whispered, almost reverently, "This is… architecture. Intelligent design. Mars didn't make this."
At the center of the chamber rose a massive stone arch, half-buried in dust but unmistakably crafted. Its surface bore the same sigils as the crystal, pulsing faintly in sync with its glow.
Daniel stepped closer, awe written across his face. "It's like… a doorway."
Before Hayes could stop him, the crystal in Daniel's pack gave a sudden flare. Light shot across the chamber, lancing into the arch. The symbols blazed, the entire structure humming with a low vibration that rattled their bones.
The air shimmered. The arch stirred.
And for the first time, the crew realized: this wasn't just a tunnel deeper into Mars.
It was a threshold.
A gate.