ON DECKSince its safe landing on the Red Planet May 25, the Mars Phoenix Lander has been sending images, including this view of its deck, which is about 1 meter high. It contains the American flag and a mini-DVD with more than 250,000 names of Earthlings, along with science fiction and art inspired by exploration of the Red Planet. JPL/NASA, U. of Arizona

After its successful May 25 landing on Mars, the Mars Phoenix Lander remained in good health on the Red Planet’s northern plains. But plans to unlatch and flex the craft’s robotic arm — designed to dig for possible ice under the hard soil — are now delayed for at least another day because a radio transmitter on a spacecraft flying overhead failed to deliver commands to the Lander.

The UHF transmitter on the Mars Reconnaissance Orbiter, one of two craft that relays commands from Earth to the Lander, suddenly stopped operating Tuesday morning, Fuk Li, the Mars Exploration program manager at NASA’s Jet Propulsion Laboratory, told reporters at a 2 p.m. EDT briefing May 27.

Engineers are now trying to revive the transmitter, which may possibly have failed due to a cosmic ray hit. If the radio can’t be quickly fixed, researchers can switch to a transmitter on another orbiting spacecraft, Mars Odyssey, which has been sharing communication duties with Reconnaissance Orbiter. Odyssey will “do double duty” if necessary in communicating between Earth and Phoenix, Li said.

Mars Reconnaissance Orbiter did send new images to Earth of the landed Phoenix, including views of the region in which the craft’s robotic arm will scoop up soil samples. The craft landed about 20 kilometers away from a crater called Heimdall and in a flat region consisting of material that was thrown out of the crater during its formation, says Phoenix principal investigator Peter Smith of the University of Arizona in Tucson. Low-lying hills, about 250 meters high, are about 15 kilometers away.

“It looks like we have lots of good opportunities here” to dig into trenches, or into polygonal formations in the soil that may have been created by the repeated contraction and expansion of underlying ice, Smith noted. “This is a place we’re going to get to know very well over the next three months,” he added.

Researchers also released the first weather report from the landing site, provided by a Canadian meteorology station mounted on the Lander’s mast. Temperatures ranged from a low of -80° Celsius in the early morning to high of -30° C in the afternoon. That’s warmer than it will be come August, when the sun sets below the landing site at the planet’s arctic circle.

The average pressure was 8.55 millibars, less than 1 percent the pressure at sea level on Earth. The wind is blowing from the northeast at about 20 kilometers per hour with little dust obliterating the view. Future reports will include measurements of humidity and visibility as more weather instruments are switched on.

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