Plutonium-238 and RTG’s use on “Curiosity” and other NASA robots

Raquel I. Quiñones Acosta

Physics laws, ideas and discoveries started out as simple curiosity of a person or group of persons. A perfect match for my curiosity launched to Mars these past days (November 26, 2011) from Kennedy Space Center, FL. “Curiosity” as the Mars new rover was named, has been set to arrive Mars soil on August 6, 2012. The huge robot weighs five times what the rovers Spirit and Opportunity did. Its mission is to find out whether Mars has or had some sort of life. Studies made, arise the thought of Mars soils possibilities to have microbial life. Something as simple as a salt mixture can create a habitable place for microbial life to take part. This because the levels of deliquescence inside the salt mixtures increase, becoming a source for life on Mars soils as it has been proven to happen on the Atacama Desert and other Mars alike soils on Earth by NASA’s scientists Christopher P. McKay  and Alfonso Dávila among others.  This mission as many other NASA missions has the capability of arising new important discoveries for our generation and the generations to come. 

Curiosity will have the capability to be a field geologist and a laboratory simultaneously. Another interesting fact would be the energy source for the rover. As the other NASA rovers, Curiosity will have solar panels to provide energy and a plutonium battery to maintain all parts of the robot working properly. NASA has employed plutonium material batteries to keep the robots warm and collect data for a longer period of time. Plutonium material batteries can make the robots work for years; and even after 10 years the battery produces 92% of its initial energy, making them a powerful tool on our engineering world. According to Michael Banks from Physics World; Curiosity will have enough energy to fire a laser with a 1067 nm wavelength and a power of 10 MW to deposit 15 mJ of energy onto a millimeter spot of rock to break it down.  Then the robot will have the capacity of analyzing the data to determine chemical composition. 

Focusing on the batteries as the source of energy, basic physics terms explain that a normal battery transforms chemical energy into electric energy. Plutonium material batteries are nuclear batteries that use thermal energy to produce electrical energy. Plutonium-238 has been used for decades in radioisotope thermal generators (RTG’s) and the heat energy or electrical energy produced by them maintains the products working for longer considerable periods of time. Plutonium-238 produces 1 kilowatt of energy per 2 kilograms of mass. In the case of the rover Curiosity this type of battery is indispensable for its proper functioning, but yet very expensive. Still alpha particles responsible for the energy on RTG’s are one of the highest energy sources employed by humanity on the military, space and heart pacemakers, because of the mentioned ability of longer-lasting useful life. Alpha particles are responsible for the high energy nuclear reactions necessary for the robots, landers, rovers and other devices prepared for space studies to last long enough for discoveries farther away from the sun than our planet Earth. Probably physicist Ernest Rutherford never imagined that his studies on alpha particles would have such a large and amazing impact on our actual studies for the search of life on other planets.