GREENBELT, Md., July 3 (UPI) -- The U.S. space agency says it has determined Mercury's smooth plains were produced by volcanoes and its magnetic field is produced in the planet's core.

National Aeronautics and Space Administration scientists have argued about the origins of Mercury's smooth plains and the source of its magnetic field for more than 30 years. Those mysteries have now been solved by data from the January flyby of the planet by the Mercury Surface, Space Environment, Geochemistry and Ranging spacecraft called Messenger.

NASA scientists said they also studied the chemical composition of Mercury's surface, analyzed the composition of the planet's thin atmosphere, sampled charged particles (ions) captured near the planet and demonstrated new links between both sets of observations and materials on Mercury's surface.

The scientists also determined Mercury's core makes up at least 60 percent of its mass -- a figure twice as large as any other known terrestrial planet.

The results of the study of data produced by Messenger, led by Sean Solomon of the Carnegie Institute, are reported in a series of 11 papers published in a special section of Science magazine.

BOSTON, July 3 (UPI) -- U.S. scientists say they've used nanotechnology to transform an old drug derived from mold into a potential non-toxic therapy for a wide range of cancers.

Children's Hospital Boston researchers said the first oral, broad-spectrum angiogenesis inhibitor they created shows promising anti-cancer results in mice.

Since it's a non-toxic oral medication, the scientists say the drug -- called Lodamin -- might be useful as a preventive therapy for patients at high risk for cancer or as a chronic maintenance therapy for a variety of cancers, preventing tumors from forming or recurring by blocking the growth of blood vessels to feed them.

Lodamin may also be useful in other diseases that involve aberrant blood-vessel growth, such as age-related macular degeneration and arthritis, they said.

Developed by Ofra Benny and the late Dr. Judah Folkman, Lodamin is a slow-release reformulation of TNP-470, a drug developed nearly two decades ago by Dr. Donald Ingber. It was one of the first angiogenesis inhibitors to undergo clinical testing.

The scientists said Lodamin appears to retain TNP-470's potency and broad spectrum of activity, but with no detectable neurotoxicity and greatly enhanced oral availability.

The research is reported online in the journal Nature Biotechnology.

CLAYTON, Australia, July 3 (UPI) -- Australian scientists say they have started three-year clinical trials to find a successful vaccine against footrot in sheep.

The trials, funded by $663,000 from the Australian Wool Innovation organization, are taking place at Monash University and the University of Sydney.

The trials are the culmination of eight years of collaborative work on the pathogenic bacterium which causes footrot, Dichelobacter nodosus, said Professor Julian Rood who is leading the study. We have determined the bacterium's complete DNA sequence, which was then analyzed to identify proteins that are potentially exposed on the surface of the causative bacterium and therefore more likely to elicit an immune response.

The approach, called reverse vaccinology, identified 90 proteins in the footrot bacterium that are potential antigens for a new cross-protective vaccine.

This funding will allow us to pinpoint those proteins that will target the disease in a vaccine application, Rood said.

Footrot is a highly contagious disease that attacks the feet of sheep causing severe lameness and loss of body condition. It is prevalent in many countries around the world and, in Australia, the financial impact of the disease on the wool and livestock industry is estimated at $100 million a year.

PHILADELPHIA, July 3 (UPI) -- U.S. scientists say they've used tiny proteins called zinc fingers to modify T-cell receptor genes in a study that may lead to a new type of AIDS treatment.

Researchers at the University of Pennsylvania School of Medicine and colleagues at Sangamo BioSciences Inc. of Richmond, Calif., said their goal is to use modified T cells from an HIV-infected person for that person's own treatment. They showed that, by using the zinc fingers, they could reduce the viral load of immune-deficient mice transplanted with engineered T cells.

The researchers, led by Dr. Elena Perez, an assistant professor of pediatrics, and Dr. Carl June, a professor of pathology and laboratory medicine at Penn, are planning a clinical trial in humans in which T cells from HIV patients would have their CCR5 gene -- necessary for the AIDS virus to enter immune system cells -- deliberately knocked out.

The modified T cells could then be infused back into the patients to re-establish their immune system and decrease their viral load.

The research is reported online in the journal Nature Biotechnology.