Lava is a block found under the surface of some planets and also some asteroids. It will not affect the player if they are in a ship, even if the core touches the Lava nor will it affect the player when it is in their Inventory. It can be found in the side of planets in caves that are 'Cut' from the edge, they emit a red glow making them easy to find when in caves.
Older Versions: It will kill the player instantly whether they walk on it or jump on it making it rather a dangerous light source.
Newer Versions: Lava will damage the player by about 2 bars, after the player dies it will say that the 'Planet' killed them, they will lose a sum of credits and they will spawn at the last Undeathinator module.