NASA says they heard no signals from the Phoenix lander this week during 30 communications passes over the probe's icy landing site, an expected outcome because the craft was never designed to survive the dark and cold Martian winter.

The HiRISE high-resolution camera on NASA's Mars Reconnaissance Orbiter snapped this enhanced color image of the Phoenix landing site on Jan. 6, 2010. Credit: NASA/JPL-Caltech/University of Arizona

The Odyssey orbiter circling Mars listened for potential radio signals from Phoenix 30 times over three days this week. NASA announced late Thursday that Odyssey did not detect any communications from Phoenix.

"After all their tries so far, they haven't recovered it yet," said Peter Smith, the Phoenix mission's principal investigator at the University of Arizona.

Officials cautioned the odds of hearing anything from Phoenix were very slim because the lander was not designed to weather the bone-chilling temperatures and months of darkness during winter on Mars' northern polar plains.

NASA last communicated with Phoenix in November 2008, when the lander's solar panels stopped producing enough electricity to power communications and scientific equipment.

Images from the Mars Reconnaissance Orbiter show Phoenix encased in a dry ice field. The ice is now retreating as spring arrives at the landing site.

"That picture shows the reason we're not seeing it yet," Smith said in an interview on Thursday.

Artist's concept of Phoenix on the Martian surface. Credit: University of Arizona

Odyssey's antenna will again turn toward Phoenix in February and March for more communications attempts. The sun will be higher in the sky by then, increasing the odds the lost spacecraft could receive enough sunlight for electricity.

"We think the odds are very low that Phoenix has survived the winter environment," said Chad Edwards, chief telecommunications engineer for Mars prorgrams at the Jet Propulsion Laboratory. "But if it has, the available energy to it will be increasing over the next few months."

Phoenix will be in constant sunlight by April, but NASA says the lander will still be unlikely to wake up then.

If Phoenix is alive, it would transmit UHF radio signals on two antennas for two hours each day, according to Edwards.

The probe landed on Mars in May 2008 and operated on the ground for about five months, two months longer than originally planned. Phoenix verified the existence water ice just below the surface at the landing site.

Smith said the Phoenix science team is no longer receiving funding, but researchers are seeking money from NASA research programs and government grants to restart data analysis.

"We went through it as much as we were able to do before we lost funding, Smith said.

Phoenix also returned more than 25,000 pictures from the Red Planet, ranging from panoramic stereo images to snapshots with a microscopic camera.