PASADENA, Calif., July 2 (UPI) -- The U.S. space agency says the next sample of Martian soil to be analyzed by the Phoenix Mars Lander might be its last.

A team of National Aeronautics and Space Administration engineers and scientists who assessed the spacecraft's Thermal and Evolved-Gas Analyzer, or TEGA, after a short circuit was discovered last month has concluded another short circuit could occur when the oven is again used.

"Since there is no way to assess the probability of another short circuit occurring, we are taking the most conservative approach and treating the next sample to TEGA as possibly our last," said Peter Smith, Phoenix's principal investigator.

Although mission teams will "stand down" until Saturday evening to mark the Fourth of July holiday, skeleton crews -- including ones at the Jet Propulsion Laboratory in Pasadena, Calif., which manages the Phoenix mission -- will monitor the spacecraft and its instruments, NASA said.

"The stand down is a chance for our team to rest, but Phoenix won't get a holiday," Smith said, noting the spacecraft will be operating from preprogrammed science commands, taking atmospheric readings, panoramas and other images.

Supercomputer helps osteoporosis diagnoses

LAUSANNE, Switzerland, July 2 (UPI) -- Swiss scientists announced an achievement in supercomputing simulations they say could vastly improve osteoporosis diagnosis and treatment.

Osteoporosis -- reduced bone mass that causes an increased susceptibility to fracture -- is typically diagnosed after it has progressed beyond repair.

Using an IBM Blue Gene supercomputer, researchers at the Swiss Federal Institute of Technology and the IBM Zurich Research Lab said they demonstrated, within a few minutes, the most extensive simulations of human bone structures ever conducted.

The scientists said their achievement could lead to the development of better clinical tools to diagnose and treat osteoporosis -- the most widespread bone disease known, which has healthcare costs second only to those associated with the treatment of cancer.

"With these simulations, researchers can provide a kind of dynamic 'heat map' of the strength of the bone, showing exactly where the bone structure is damaged and at what load a bone is likely to fracture," IBM said in a statement. "Such powerful simulations could be routinely adopted in future computer tomography, greatly enhancing clinicians' ability to analyze the risk of fractures and hence to improve treatment."

NASA begins new type of astronomy

BERKELEY, Calif., July 2 (UPI) -- The U.S. space agency says its Solar Terrestrial Relations Observatories, or STEREO, have detected particles from the edge of the solar system.

The National Aeronautics and Space Administration announced last year's event Monday, saying it marked the beginning of a new type of astronomy.

"The two STEREO spacecraft were launched in 2006 into Earth's orbit around the sun to obtain stereo pictures of the sun's surface and measure magnetic fields and ion fluxes associated with solar explosions," NASA said. "From June to October 2007, sensors aboard both STEREO spacecraft detected energetic neutral atoms originating from the same spot in the sky, where the sun plunges through the interstellar medium."

Mapping the region by means of neutral, or uncharged, atoms instead of light "heralds a new kind of astronomy using neutral atoms," said University of California-Berkeley Professor Robert Lin, lead scientist for the suprathermal electron sensors aboard the STEREO spacecraft.

"This is the first mapping of energetic neutral particles from the edge of the heliosphere," Lin said. The heliosphere is a bubble in space produced by the solar wind. It stretches from the sun to beyond the orbit of Pluto.

The complex research is reported in the journal Nature.

An Alzheimer's disease target identified

PHILADELPHIA, July 2 (UPI) -- U.S. scientists say the protein neprilysin can reduce plaque formation and neuron death associated with Alzheimer's disease, but at the expense of lifespan.

Thomas Jefferson University researchers said the buildup of amyloid-beta protein plaques within the brain is a hallmark of Alzheimer's. Normally, enzymes remove the plaques, and deficiencies in those enzymes are one potential disease cause.

The scientists said neprilysin, or NEP, a major amyloid degrader, decreases naturally with age and might be the reason the elderly are more at risk for Alzheimer's.

While studies using mice suggest enhancing NEP production has potential, the possible adverse effects of such therapy were unknown.

The new research with transgenic fruit flies expressing human NEP found a "good news-bad news" scenario. On the positive side, NEP expression did reduce plaque deposits and neuron damage in the flies. On the other hand, NEP also reduced the activity of important neural proteins called CREB proteins and shortened the flies' average lifespan.

The researchers said their finding illustrates caution is needed when considering Alzheimer's treatments, and that it's critical to better understand normal aging when dealing with Alzheimer's or other age-related conditions.

The study appears online in the Journal of Biological Chemistry.