Donnchadh and Gwalcmai, along with the other fourteen teams selected for planetary infiltration, had been put into deep sleep shortly after liftoff from their planet.
2005, Bob Ticer, Visiting the Strange Planet Called Earth, →ISBN, page 13:
The Kironian had remained in deep sleep until alerted by a high-pitched squeaky sound. When the Kironian woke, everything seemed as though it had just left Kiron.
2008, Cavin Wright, The Golden Prize, →ISBN, page 17:
There is also the possibility that our aliens perfected cryogenics and simply went into deep sleep until the environment improved.