Lake Breach Floods Eroded Surface of Early Mars, Study Says
A dead body left on Mars would dry out and mummify so well it would make the ancient Egyptians jealous. The first few stages (algor mortis [body cools], livor mortis [blood pools], and rigor mortis [muscles stiffen]) would still take place. But there could be no other overt signs of decomposition.
Giant Balls of Mush Made From Ammonia and Water Form in the Atmospheres of Uranus and Neptune