The launch of a Delta rocket carrying the Phoenix lander to Mars has been pushed back 24 hours to early Saturday morning because of weather concerns at the Kennedy Space Center, agency officials announced today.

Phoenix is scheduled to land at Mars’ north pole to undertake a science mission looking for organic materials that would be requisite for life to have been present on Earth’s closest neighbor.

Phoenix is poised to begin its mission as twin rovers Spirit and Opportunity are battling to survive a severe wind storm that has obscured sun light so severely that the rovers’ solar panels can scarcely collect enough light to keep heaters going long enough to prevent over-night freeIng of the probes.

Spirit and Opportunity, designed to operate for 90 days, are now in the fourth year of their mission.

NASA has approved August 7 as the target launch date for Shuttle Endeavour on STS-118. Today’s announcement follows a two-day flight readiness review.