The protesters were taking advantage of an Arizona law that allows people to carry unconcealed guns, Phoenix Police Department spokesman Andy Hill said. Police made no arrests.

A fundamental ingredient for life has been discovered in a comet sample, supporting the idea that such icy objects seeded early Earth with the stuff needed to whip up living organisms.

New research firms up past suggestions of glycine, the simplest amino acid used to make proteins, inside samples from the comet Wild 2.

"This is the first time an amino acid has been found in a comet," said lead researcher Jamie Elsila of NASA's Goddard Space Flight Center in Greenbelt, Md. "Our discovery supports the theory that some of life's ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts."

NASA launched an inflatable spacecraft heat shield that showed such a device could be used to slow and protect a space capsule as it enters the atmosphere at hypersonic speeds. The material - several layers of silicone-coated Kevlar - could be used to insulate a crew and cargo from the searing temperatures of re-entry.

About a dozen people carrying guns, including one with a military-style rifle, milled among protesters outside the convention center where President Barack Obama was giving a speech Monday - the latest incident in which protesters have openly displayed firearms near the president.

Gun-rights advocates say they're exercising their constitutional right to bear arms and protest, while those who argue for more gun control say it could be a disaster waiting to happen.

Boston T. Party (Ken Royce) in the 2nd Hour - But first...Obama comes to Phoenix (again) and is greeted with peaceful armed people. I bet everyone is polite today :) But then,... there are always the agent provocateurs. This is one good reason for so many video cameras and our doing the radio show live from the event.