The red earth creaked under their boots as Lena, David and Nicholas slowly walked towards the north exit of the dome. The landscape behind the thick layer of armoured glass shimmered with a palette of rust, orange and grey, and the rarefied sky took on the colour of spilled coffee with milk. Mars seemed to be silent, but every inhabitant of the colony knew how illusory this sense of silence could be. That morning, when Lena entered the lab, the monitor screen flashed an unknown code. Other engineering teams also reported disruptions in communications-transmissions interrupted by noise, sudden flashes in the drone tracking system. The most senior engineers shrugged their shoulders, saying it was a solar storm. Lena was sure it was something more. After lessons, she gathered David and Nicholas in the room. Lena had a gift for persuasion-a rather, as they laughed, she was unstoppable when she wanted something. Together they analysed parts of the coded signals. The diagrams showed regular repetitions, among them a pattern similar to the signature of biological radio messages-something that Martian automatons could not produce. They were among the youngest inhabitants of the base, but they felt they had a right to seek answers. They made a plan: they would leave just after sunset, when the guards were busy changing watch. Lena programmed the reconnaissance drone, Nicholas pulled out maps of the exclusion zones and David secured extra batteries and a handheld decoder. As Martian twilight fell, they secretly sneaked through the service airlocks. It wasn't until they were a few hundred metres from the base that they felt how really thin the line was that protected them from the void. The receiver indications vibrated. Lena stopped and looked at her friends: the signal was getting more and more intense. Somewhere beyond the dune where the colony maps ended, a barely discernible pulse of light flashed. Everyone held their breath. Did they have the right to go on? Just then, the silent transmission turned into a clear, crystalline sound, like a voice repeating their own names. They stood still, listening to the echo of Mars, knowing that there was no turning back from that moment....