Sci-fi One shot idea

Year 2604. After surviving a major global war, environmental collapse and an alien invasion, Earth is rule by aristocracy, at the top of which is the monarch King Thayone. Terran humans have returned to the stars using technology taken from their alien invaders, allowing them to build new interstellar capable exploratory ships. The HMS Icarus as part of the Earth Exploratory Corp has dropped out of Jump space in relatively close system called Alarus, hidden in the same G-cloud that contains Alpha Centauri and Altair. Deep space probes detected a terrestrial world relative close to the Yellow star – Alarus II.

Most expected it to be a hot desert world. Icarus crew sent down lander shuttle to investigate an sensor anomaly on the planet. What the found astounded them. A derelict ship buried in the sand. A dead pilot of alien origin but vaguely humanoid. Equipment a readouts that are vaguely familiar but still alien. Sensors showed that not all the ship was filled with sand. There is a hold completely sealed beneath the sand. The five man crew of the lander shuttle is not equipped to investigate but the order came down to investigate as far as they could. What will they find? Why are these aliens vaguely familar? They are not invaders humans are far too familiar with. So who?