Does NASA's New Horizons flyby probe to Pluto have instruments to measure Pluto's (or Charon's) magnetic field, if any?

I'm a bit confused by the Wikipedia article which says that New Horizons, during its flyby of Jupiter, on one hand:

Travelling through the planet's magnetosphere New Horizons collected valuable particle readings.[45] "Bubbles" of plasma which are believed to be formed from material ejected by the moon Io were noticed in the magnetotail.[47]

But then on the other hand:

An objective to measure any magnetic field of Pluto was dropped. A magnetometer instrument could not be implemented within a reasonable mass budget and schedule, and SWAP and PEPSSI could do an indirect job detecting some magnetic field around Pluto.

And how true is this story which I read or heard somewhere? That when New Horizons was being built and launched, no one really believed that Pluto could have a magnetic field. But since then planetary science has advanced and it is now plausible that it might have a magnetic field, because of tidal forces between Pluto and Charon which might make both objects somewhat fluid and possibly generating magnetic fields.


1 Answer 1


I believe, I don't know if there is evidence of it however, that Pluto does not have an active core. An active core as I'm sure your aware produces the magnetic field, without a magnetic field neither Pluto nor Charon have a magnetosphere. If there was sufficient or any evidence at all to suggest otherwise, I believe it would have become a priority.

Theoretical models of Pluto are based typically on it's orbital speed, which suggest there is no field. However as you have stated we have witnessed tidal stresses producing activity, such as Io, which should be frozen like rock however is the most geological active body we know of it the solar system. One major difference, is we don't have images of neither Plutos nor Charons surfaces, if we had images of a smooth surface we could suffice the surface at least is active through tidal forces. Being all cratered and looking ~5 billion years old indicates the opposite. There just isn't any data as yet to say otherwise, and certainly wasn't when New Horizons was being designed.

As for what the craft could detect with it's instruments, the most indicative feature would be optical imagery and the dwarfs' surfaces. In essence, all of it's instruments could be used; ALICE for detecting atmospheric properties could certainly indicate a magnetic field, whether it's able to hold onto any material spewing from it's surface for example and any ionization of any atmosphere, which in turn is what PEPSSI does. The other great tool would be Ralph, mapping thermal imagery of the dwarfs. If there is indication of internal heating unexpected from gravitational compression of the core, or veins of thermal radiation could also help determine any activity in turn producing the magnetic field.

I hope this was what you were asking.

  • $\begingroup$ Perhaps you could provide some links or authoritative references to support your answer? NB dwarfs is the plural of dwarf unless you are Tolkien. $\endgroup$
    – ProfRob
    Jan 24, 2015 at 10:22
  • $\begingroup$ @RobJeffries, thank you for grammar correction. $\endgroup$ Jan 24, 2015 at 13:23
  • $\begingroup$ @RobJeffries, New Horizons lists the instruments. Tidal force explains the working of tidal forces. Io explains volcanism on Io. Information was initially provided from Neil Degrasse Tyson in Cosmos, Brian Cox in Wonders of the Solar System and The Universe. Anything else I can cite for you? $\endgroup$ Jan 24, 2015 at 13:29

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