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I understand Curiosity is powered by plutonium decay. I was wondering if that kind of battery leaks.

If humans ever go to Mars, and they want to meet with Curiosity, would they need to take extra precautions?

(I understand that present-day settlers would need protection from cosmic and solar radiation anyway, due to the thin atmosphere on Mars. So for the purposes of this question please assume that we have spent 2,000 years or so terraforming Mars to give it an Earth-like atmosphere. Alternatively, imagine Curiosity finds a way to return to Earth. I'm just wondering if Curiosity's plutonium battery leaks a significant amount of radiation or not.)

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    $\begingroup$ There is a picture of the battery and a short video here on popsci.com. $\endgroup$
    – joeytwiddle
    Commented Aug 17, 2016 at 9:50
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    $\begingroup$ "imagine Curiosity finds a way to return to Earth" lol, bit of V'Ger there... $\endgroup$
    – Lightness Races in Orbit
    Commented Aug 17, 2016 at 15:47
  • $\begingroup$ You're imagining they would survive all the radiation getting to Mars, which they probably wouldn't. $\endgroup$
    – developerwjk
    Commented Aug 17, 2016 at 22:03
  • $\begingroup$ More to the point. The cosmic rays on the Martian surface would make the RTG look like a glowing exit sign. $\endgroup$
    – Aron
    Commented Aug 18, 2016 at 4:38

2 Answers 2

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At first glance, the RTG does not pose a risk.

  • It is powered by Pu-238, which is primarily an alpha emitter throughout its decay chain. Alpha particles can be stopped by a sheet of paper. An astronaut is perfectly safe in his suit, even if the RTG were disassembled and the Pu lying around unprotected.

  • The RTG is built to survive a launch failure, i.e. it will remain intact if the launcher explodes underneath it.

  • When the RTG is intact, no radiation leaks out. The Pu is sealed in several layers of metal.

  • If they wanted to move the RTG into a pressurized building and work on it, they'd need to check for leaks with a simple Geiger counter.

The story is a bit more complicated than that, though. In addition to alpha, an RTG produces a small amount of gamma radiation. This NASA report gives a detailed analysis of the gamma radiation produced by an RTG. I'm having trouble converting this data into an answer to the question 'would standing next to an RTG have damaging consequences for a human?'

From the New Horizons environmental impact statement:

PuO2 emits much less gamma and neutron radiation than Sr-90 and Cm-244. Because gamma and neutron radiation are more penetrating than the alpha particles emitted by Pu-238, extensive shielding (not required with PuO2) would be required during production and handling, as well as onboard the spacecraft to protect sensitive components.

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    $\begingroup$ Also, if the RTG leaked radiation, this would probably affect the sensors and cameras and render the entire rover pointless. $\endgroup$
    – Jörg W Mittag
    Commented Aug 17, 2016 at 10:25
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    $\begingroup$ I haven't looked this up, but I'm pretty sure that some gamma rays are also emitted in the plutonium decay chain. These are probably nastier than alphas... $\endgroup$
    – DarioP
    Commented Aug 17, 2016 at 11:22
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    $\begingroup$ @DarioP: no. That's the nice thing about Pu-238: the entire decay series is via Alpha emission. $\endgroup$
    – Hobbes
    Commented Aug 17, 2016 at 11:38
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    $\begingroup$ @Yakk So to answer OPs question, if humans ever go to Mars they have to take extra precautions when EATING the abandoned Curiosity rover to make sure they don't ingest the remaining Pu-238. Gotcha! $\endgroup$
    – Keeta - reinstate Monica
    Commented Aug 17, 2016 at 13:22
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    $\begingroup$ @Keeta Well, maybe. In dust form, it is about as toxic as nerve gas, and it is more toxic injected than breathed than eaten. Try to keep the amount of plutonium 238 you eat to a moderate amount, basically. Don't cut open the robot, reshape the plutonium into a frying pan, and cook eggs with it. Avoid excessive licking of the plutonium core. That kind of percautions. (It is probably more toxic than this flippant comment indicates, do not taunt happy fun plutonium cores, they are not bouncy balls). $\endgroup$
    – Yakk
    Commented Aug 17, 2016 at 13:25
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Any Martian explorer stupid enough to not take some obvious necessary precaution (which would be unnecessary in this case) shouldn't have been on Mars in the first place. The initial colonists better be damned smart people, they'll need every bit of it.

As well, they will all be radiation experts. The journey to Mars is fraught with radiation perils both from cosmic rays and solar events; and the surface of Mars won't be a picnic either for unshielded humans. Habitations will likely be underground for that reason.

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  • $\begingroup$ This was posted as an answer, but it does not attempt to answer the question. It should possibly be an edit, a comment, another question, or deleted altogether. $\endgroup$
    – cat
    Commented Aug 18, 2016 at 1:06
  • $\begingroup$ Did you actually read the question? $\endgroup$
    – cat
    Commented Aug 18, 2016 at 1:11
  • $\begingroup$ Hi Phil. This answer doesn't give any context or reference its claims. It offers some insight into the matter of the question, but only if you make a bit of a leap of logic to figure there are many other sources of radiation and colonists will understand it well enough to manage any source. Most if it is opinion that has little to do with the question. It needs to be more explicit about the comparison between the RTG and other radiation sources, and the shielding involved in habitats. $\endgroup$
    – kim holder
    Commented Aug 18, 2016 at 3:37

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