NASA’s Solar Probe

What NASA claimed for years it couldn’t do—use solar power as an energy source on a space probe going beyond the orbit of Mars—it plans to do on Friday.

That’s when NASA intends to launch a space probe it has named Juno to Jupiter. Juno is to make 33 passes of Jupiter while all along getting power from three solar panels.

“It is quite interesting that NASA is going to use solar to travel to Jupiter—they once claimed it was not possible,” comments Bruce Gagnon, coordinator of the Global Network Against Weapons & Nuclear Power in Space. “I think it just goes to show that they needlessly put people and the planet in grave danger during past plutonium launches. It surely shows that our claims they could use solar in deep space were not wrong as NASA claimed during the Galileo, Ulysses, and Cassini launches.”

Galileo was a space probe sent to Jupiter in 1989, Ulysses a space probe sent to orbit the Sun in 1990 and Cassini a space probe sent to Saturn in 1997—with all getting their onboard electric power from plutonium-fueled radioisotope thermoelectric generators.

For all three shots, NASA insisted that nuclear power was necessary because solar energy would not work. This claim was also made in court papers when the Galileo mission to Jupiter was challenged in federal court on the basis of the plutonium on board constituting a huge danger if released in an accident.

“NASA’s upcoming mission to Jupiter can’t get much greener than this: a solar-powered, windmill-shaped spacecraft,” began an Associated Press story this week on the Juno mission.

It noted that “Juno is equipped with three tractor-trailer-size solar panels for its 2 billion-mile journey into the outer solar system.” Even when it gets to Jupiter, “nearly 500 million miles from the Sun,” its panels will be providing electricity. NASA, in the past, has claimed that there wasn’t enough sunlight far out in space to be utilized to generate electricity.

However, the AP story suggested the use of solar on Juno wasn’t exactly the first choice. It describes Scott Bolton, the principal investigator for the mission for the Southwest Research Institute, a NASA contractor, as maintaining “the choice of solar was a practical one…No plutonium-powered generators were available to him and his San Antonio-based team nearly a decade ago, so they opted for solar panels rather than develop a new nuclear source.”

Indeed, between November 25 and December 15 NASA plans to revert to its use of nuclear power in space launching a rover to be deployed on Mars fueled with 10.6 pounds of plutonium. That’s more plutonium than ever used on a rover. NASA has sent solar-powered rovers to Mars but claims in its Final Environmental Impact Statement for the Mars Science Laboratory Mission a “solar-powered rover…would not be capable of operating over the full range of scientifically desirable landing site latitudes” on this mission.

Said Gagnon this week: “Sadly our deep concern about space nuclear devices remains in place as we next face the launch of 10.6 pounds of plutonium this winter on the Mars rover mission. We are already organizing to oppose the Mars rover plutonium mission. We’ve been proven to be right that solar will work in deep space. Hopefully we won’t next be shown to be right about a plutonium launch disaster.”

If there is an accident before the rover is well on its way to Mars and plutonium is released on Earth, the cost of decontamination of areas affected by the plutonium could be, according to the NASA Environmental Impact Statement, $267 million for each square mile of farmland, $478 million for each square mile of forests and $1.5 billion for each square mile of “mixed-use urban areas.”

The mission itself is said by NASA to have a cost of $2.5 billion.

The “the probability of an accident with a release of plutonium” is 1-in-220 “overall,” says the NASA document. It says a large swath of Earth could be impacted by the plutonium on the rover, which NASA calls Curiosity. Its section on “Impacts of Radiological Releases” says “the affected environment” could include “the regional area near the Cape Canaveral Air Force Station and the global area.”

“Launch area accidents would initially release material into the regional area, defined…to be within …62 miles of the launch pad,” it says. This is an area from Cape Canaveral west to Orlando.  But “since some of the accidents result in the release of very fine particles less than a micron in diameter, a portion of such releases could be transported beyond…62 miles,” it goes on. These particles could become “well-mixed in the troposphere”—the atmosphere five to nine miles high—“and have been assumed to potentially affect persons living within a latitude band from approximately 23-degrees north to 30-degrees north.” That’s a swath through the Caribbean, across North Africa and the Mideast, then India and China, Hawaii and other Pacific islands, Mexico, and southern Texas.

Then, as the rocket carrying Curiosity aloft gains altitude, the impacts of an accident in which plutonium is released would be even greater. The plutonium could affect people “anywhere between 28-degrees north and 28-degrees south latitude,” says the document.  That’s a band around the mid-section of the Earth including much of South America, Africa and Australia.

Furthermore, the isotope of plutonium used as fuel on space probes is especially hot. It is Plutonium-238 as distinct from Plutonium-239, the same isotope of plutonium used in atomic bombs.

Plutonium-238 has a far shorter half-life–87.8 years—as compared to Plutonium-239 with a half-life of 24,500 years. An isotope’s half-life is the period in which half of its radioactivity is expended.

As Dr. Arjun Makhijani, a nuclear physicist and president the Institute for Energy and Environmental Research, has explained, Plutonium-238 “is about 270 times more radioactive than Plutonium-239 per unit of weight.” Thus in radioactivity, the 10.6 pounds of Plutonium238 that is to be used on the Mars Science Laboratory Mission would be the equivalent of 2,862 pounds of Plutonium-239. The atomic bomb dropped on Nagasaki was fueled with 15 pounds of Plutonium-239.

The significantly shorter half-life of Plutonium-238 results in it being extremely hot. This heat is translated in a radioisotope thermoelectric generator to electricity.

The pathway of greatest health concern is breathing in a plutonium particle. A millionth of a gram of plutonium can be a fatal dose. As the NASA Environmental Impact Statement says: “Particles smaller than about 5 microns would be transported to and remain in the trachea, bronchi, or deep lung regions.” The plutonium particles “would continuously irradiate lung tissue.”

The NASA Environmental Impact Statement lists “secondary social costs associated with the decontamination and mitigation activities” as: “Temporary or longer term relocation of residents; temporary or longer term loss of employment; destruction or quarantine of agricultural products including citrus crops; land use restrictions which could affect real estate values, tourism and recreational activities; restriction or bans on commercial fishing; and public health effects and medical care.”

Meanwhile, as to Juno, Aviation Week and Space Technology reports: “The unique spacecraft will set a record by running on solar power rather than nuclear radioisotope thermoelectric generators previously used to operate spacecraft that far from the Sun.”

Juno—66-feet wide—will be powered by solar panels built by a Boeing subsidiary, Spectrolab. The panels can convert 28 percent of the sunlight that reaches them to electricity. They’ll also produce heat to keep Juno’s instruments warm. This mission’s cost is $1.1 billion.

Accidents have happened in the U.S. space nuclear program. Of the 26 space missions that have used plutonium which are listed in the NASA Environmental Impact Statement for the Mars Science Laboratory Mission, three underwent accidents, admits the document.

The worst occurred in 1964 and involved, it notes, the SNAP-9A plutonium system aboard a satellite that failed to achieve orbit and dropped to Earth, disintegrating as it fell. The 2.1 pounds of plutonium fuel dispersed widely over the Earth, and Dr. John Gofman, professor of medical physics at the University of California at Berkeley, long linked this accident to an increase in global lung cancer. With the SNAP-9A accident, NASA switched to solar energy on satellites. Now all satellites—and the International Space Station—are solar-powered.

Karl Grossman, professor of journalism at the State University of New York/College of New York, is the author of the book, The Wrong Stuff: The Space’s Program’s Nuclear Threat to Our Planet (Common Courage Press) and wrote and presented the TV program Nukes In Space: The Nuclearization and Weaponization of the Heavens (

Karl Grossman, professor of journalism at State University of New York/College at Old Westbury, and is the author of the book, The Wrong Stuff: The Space’s Program’s Nuclear Threat to Our Planet, and the Beyond Nuclear handbook, The U.S. Space Force and the dangers of nuclear power and nuclear war in space. Grossman is an associate of the media watch group Fairness and Accuracy in Reporting (FAIR). He is a contributor to Hopeless: Barack Obama and the Politics of Illusion.