Emboldened by curiosity after his initial shock, Montreaux edged closer to the precipice and looked down. Contrary to his initial impression, instead of a sheer drop, the crater sloped away from him, not as gently as the debris field behind him, but certainly not vertical either. He found himself comparing it to a tough ski slope: potentially deadly if he’d had skis on and it was covered in snow, but quite possible to clamber down given the circumstances. What did impress, however, was not the incline of the slope but its scale. Whereas on Earth he would have expected the drop to end after at the most a few hundred metres, the wall of the Hellas Basin did not. It continued on its way down, gradually levelling out as it neared the bottom like the inside of a soup bowl, until he imagined it must merge with the crater floor kilometres below. He had to ‘imagine’ where it met the bottom for two reasons, he surmised. Firstly, he calculated that with the depth of the crater and gradient of the slope, the intersection of ‘floor’ and ‘wall’ of the crater had to be at least fifteen kilometres away from him, and his ability to define accurate shapes at such distances without visual aid was quite low. This was in no way helped by his second reason, which was that as far as the eye could see, all the rocks and debris looked the same.
Looking to his left and right, he saw that from a distance, the crater rim looked like an unbroken ring of mountains, imprisoning the plain below.
The slope was made up of a mixture of varying sizes of rock and Martian soil. Almost everything was the same colour, a pale shade of orangey-brown. Occasionally a particular rock would be slightly darker or lighter, but there were few obvious geological variances, at least to his untrained eyes.
He looked over at Danny, who was kneeling at the edge examining a small spherical rock about the size of a baseball.
“Impressive, isn’t it?” he said.
The Russian looked up across the plain and nodded slowly before standing. He wrapped his fingers around the stone and bounced it in his palm a few times, getting a feel for its weight and balance. Without a word he stretched his arm back fully before sweeping it forwards in a flash, releasing the stone mid-swing. They watched the stone fly forwards at least a hundred metres before gravity started to bring it down to the ground.
The low gravity made for an impressive pitch indeed.
Because of the incline, the stone continued to fall for about three hundred metres before finally striking a large flat rock jutting out from the cliff-face. A small cloud of pale orange debris was thrown up from the rock as the stone bounced off and disappeared below.
“See if you can beat that,” he grinned and looked at Montreaux.
But Montreaux wasn’t listening. He was still looking down at the flat rock that the stone had struck; the dust had now settled and despite its distance, it was obvious that there was a striking difference in colour between the surface dust that had been disturbed and the rock beneath. It was jet black.
“Captain Marchenko, pass me the binoculars, please.”
He focussed the electronic device on the stone below. After several long minutes, he passed the binoculars back.
“Look at the flat rock you just hit,” he said, seriously.
Danny’s first instinct was to be sarcastic. He felt like saying that he was sorry he’d damaged a Martian rock, but that there were billions more identical ones where that came from. Instead, he took the binoculars and steadied the image on the flat rock.
“What do you think it is?” He didn’t move his eyes from the binoculars, but instead zoomed in further to examine the small patch of jet black stone that had been uncovered. They had spent days picking up rocks and digging test holes in the soil near their base, and had never seen anything like it.
Montreaux had already been thinking about his answer, and had remembered some basic facts from his early days at school. “Well, on Earth, a black colour in stone often comes from carbon.”
Marchenko pulled his eyes away from the binoculars and looked at the American.
“Carbon? From plants and animals?”
“Yes, I think, although I don’t know if it can be naturally occurring too.” He thought about this for a moment. “In any case, we’ll never know until we get down there to look at it. We’ll need a sample to take back to Dr Richardson.”
“Wow! That was one lucky throw!”
“It certainly was. Now, I propose that we climb down together, but first, we need fresh air, I only have half an hour’s worth left.”
They climbed down the cliff in parallel, connected by a thin strand of synthetic rope for safety. It was by no means a dangerous climb, and on Earth could certainly have been attempted with barely a second’s thought. But on Mars, the combination of reduced gravity and airtight suits made for a nervous descent for both men.
As they came within twenty metres of the flat stone, Montreaux paused and turned his upper body round to face it. He tugged sharply on the safety line to get Danny’s attention and pointed down at their goal.
“It’s definitely not your standard Martian rock formation, is it?” he said, out of breath.
“There’s something out of place about it, definitely. Something –”
“Not natural,” Montreaux finished his sentence for him, “I agree.”
From where they now sat, the stone betrayed not only its huge dimensions, but also its unexpected shape and orientation. It was about six metres wide and rectangular, protruding at least ten metres from the cliff-face.
Although it was difficult to tell with any accuracy from where they were sitting, the stone looked to be completely flat amidst the chaos of debris deposited around them.
“It looks almost like a,” Danny searched for the word. “Like a jetty, where you moor a boat on a riverbank.”
The two astronauts looked at each other and then continued to descend in silence. Montreaux checked the small LCD display on his forearm to ensure that his suit camera was capturing the whole event.
The Russian reached the stone first. He stood up to his full height and looked at Montreaux, who had continued past the stone and was now investigating below.
“This is incredible,” he said. “The stone comes right out of the cliff, it’s about a metre and a half thick, below is filled up with soil and other rocks, but apart from that you can clearly see the shape of the stone.” His voice was filled with awe. “This stone has to be artificial. The edge is perfectly flat all around, and wait.” His gloves had a built in rubber wiper along the seam of the thumb, for his own visor in case of sandstorms. He used it to scrape the stone clean. “Yes, that’s incredible! There’s a thick coat of dirt and dust, but underneath it’s the same jet black stone, and it’s so smooth!”
Danny was using his gloves to expand the impact crater that his small projectile had created.
“Same up here; it’s perfectly smooth. And whatever it is, it’s –”
Montreaux waited for him to finish his sentence, but the words didn’t come.
“Yes?” he pressed.
“Oh, my God,” Danny said, followed by a short burst of Russian that Montreaux didn’t understand. “Yves, get up here and look at this!”
Despite his usual friendly carefree attitude, Marchenko never referred to Montreaux using his Christian name. That was a break in protocol that only Dr Richardson enjoyed. Montreaux almost fell over himself reaching the top of the stone to join the Russian.
“What?” he said, urgently, glancing sideways at the stone.
He pointed to the patch of black surface he had uncovered. His hand was shaking visibly.
Captain Montreaux did not need it spelled out. What had stunned Danny had the same effect on him. His knees grew weak, and he sank down slowly until he could touch the stone. He ran his gloved fingers across it until they slotted neatly into a groove, about two centimetres deep and ten wide that ran in a perfectly straight line from under one edge of the cleaned area, near the wall of the crater out towards its centre. Danny’s gloved fingers had left small furrows where he had done his best to clear out most of the sand. After about sixty centimetres, the groove split in two in a perfect V. At the edges of the cleared area, he could make out the lines of two more possible grooves. He stood up and tilted his head as he examined the stone. The grooves made the shape of a V, pointing towards the crater wall, with a line emerging from its apex and disappearing into the cliff.