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While we are still waiting for the official Discovery finalists announcement, and it's perhaps a bit premature to be discussing the proposals, I've been thinking about the exciting MAGIC mission to orbit Callisto, for which it has been suggested a very limited payload, consisting of a Magnetometer, an Altimeter, a set of Cameras, and of course the spacecraft's comm system. enter image description here

I was wondering whether if, in addition to this mission's objectives related to internal structure and topography, such a limited set of instruments could tell us anything about the chemical composition of the surface, perhaps inferring it from roughness and radiance maps.

The principal investigator, David E Smith, has been heavily involved over the last few decades on previous missions that have carried Laser Altimeters, such as Messenger, MGS, and LRO, but all of them were also equipped with many other instruments, for instance 5 spectrometers in the case of MESSENGER, designed with that task in mind.

So, can some sort of mineralogy map of Callisto be produced with MAGIC's only 3 instruments?

As a side note, could we also learn anything about Callisto's thin atmosphere only by radio occultations?

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  • $\begingroup$ I don't understand what you are asking for. The MAGIC mission's purpose is to do high resolution feature mapping, not a mineralogical or atmospheric survey. $\endgroup$
    – GdD
    Commented Feb 7, 2020 at 8:44
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    $\begingroup$ @uhoh en.wikipedia.org/wiki/Discovery_Program#Discovery_15_and_16 $\endgroup$
    – gerrit
    Commented Feb 7, 2020 at 9:10
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    $\begingroup$ Sorry, I should have explained the context a bit, and also make clear that I am well aware that the focus of this mission is interior structure and topographic maps, and that the instruments are perfect for those tasks. I am asking whether information of chemical composition or atmosphere could be obtained indirectly, as a bonus. $\endgroup$
    – Venus was her name
    Commented Feb 7, 2020 at 9:18
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    $\begingroup$ Great question! You might consider asking about radio occultations and Callisto's atmosphere as a separate question since the answers will be different. Just a thought. $\endgroup$
    – uhoh
    Commented Feb 7, 2020 at 10:06

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The scientific instruments on board will not be able to detect minerals on Callisto.

Cameras will record physical features of the surfaces, such as: craters, geological faults, folds and color variations. The color variations will indicate change in mineralogy, but nothing else.

Altimeters only measure altitude.

The magnetometer will measure variations in magnetic field. However it will not be able to differentiate between minerals on Callisto. Not all metals are magnetic. Iron, cobalt and nickel are strongly magnetic, whereas tungsten, platinum, aluminum and magnesium are weakly magnetic and gold, copper and silver are not magnetic.

To ascertain what minerals are on the surface, a spectroscope will be needed.

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    $\begingroup$ If one of the proposed cameras have a filter wheel with a gazillion filters it might be useable to at least infer something about mineralogy, There's also a possibility that one of the cameras can operate as an imaging spectrograph and it wasn't mentioned in that one page brief. $\endgroup$
    – uhoh
    Commented Feb 10, 2020 at 21:39

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