New miniature sensors designed to warn of chemical dangers here on Earth might one day be worn like badges on space suits to alert astronauts or Martian colonists to dangerous chemicals or elevated radiation levels. Mars is a wild frontier, with potential dangers that scientists know little about. The Red Planet lacks an ozone layer, which on Earth blocks out lethal doses of solar ultraviolet radiation. This and other forms of radiation change daily and seasonally, but researchers do not yet know how significant or dangerous the problem is. And there are also likely unknown chemicals in Martian soil, NASA scientists say. Future spacesuits will be designed to protect humans against the various risks.