NASA is preparing a robotic probe for launch this weekend to search for life's habitats on Mars, but it is the health of people on Earth that is of immediate concern.
The Mars Science Laboratory, nicknamed Curiosity, is powered by the radioactive plutonium isotope Pu-238, which generates heat as it naturally decays. The heat is tapped to produce electricity for the rover's systems and science instruments.
NASA says the chance plutonium will escape into Earth's atmosphere is very remote, given the perfect track record of the Atlas 5 rocket that will be used to launch Curiosity into space.
In addition, the 10 pounds (4.5 kilograms) of plutonium inside the probe is laced into ceramic pellets, designed to break apart into pieces, like a coffee mug, rather than disperse as dust into the air. The plutonium also is encased in a capsule of iridium and wrapped in carbon fibers to absorb heat.
Overall, the chance plutonium will be released during launch is 1 in 420, Randall Scott, director of NASA's Radiological Control Center at the Kennedy Space Center, told Discovery News.
During liftoff, 30 radiation detectors placed throughout the region surrounding the Cape Canaveral Air Force Station launch site, will be taking air samples and reporting measurements real-time to Scott's team.
"Most people will not notice the monitors," added NASA's Steve Brisbin, who is coordinating among the half-dozen federal, state and local government agencies responsible for public safety during launch.
"They're at fire stations and secured behind fence lines at municipal facility," Brisbin told Discovery News.
Curiosity's plutonium is inside what is called a radioisotope thermoelectric generator, or RTG. Similar devices have been used on spacecraft since the early days of the space program, including the Apollo moon missions, the Mars Viking landers and the Voyager probes, now heading into interstellar space. The Saturn-orbiting Cassini spacecraft is nuclear powered, as is NASA's Pluto-bound New Horizons probe.
Unlike NASA's previous solar-powered Mars rovers Spirit and Opportunity, the nuclear-powered Curiosity will be able to travel at night and operate multiple science instruments simultaneously.
The launch is scheduled for 10:02 a.m. EST on Saturday. Arrival at Mars is expected in August 2012.