The predecessor of Phoenix probe was the probe Mars Polar Lander, which was developed within the tightening conception of NASA focused on the development of simpler and cheaper means. It was planned to land on Mars in December 1999, but just during the landing maneuver it failed and crashed. The problem was the landing way itself, which used breaking jets and legs to sit on the surface. This way of landing was successful for the last time at the Viking probes in the 70s of the 20th century, following missions landed using inflatings bags. Due to the size and weight of the probe this was not possible and also the development of a landing system capable to handle the landing of bigger probes and later also with human crew was necessary. The failure of Polar Lander was moreover predecessed a few months ago by the failure of orbiter called Mars Climate Orbiter, which had also to serve as the retranslation station to the Polar Lander and shortly after injection into the Mars orbit lost signal. The Phoenix probe is in fact reworked Polar Lander, which should finally land successfully and analyze the promising ice samples around the pole, where the signs of life could be hidden.

The expected time of landing is on 25th May 2008 at 7:38 p.m. EDT, which is 26th May 2008 at 01:38 Central European Summer Time. The signal from Mars flies 15 minutes, so the confirmation of the successful landing could come at 7:53 p.m. EDT, which is 01:53 CEST.