The UI will of course need to handle globes it doesn't understand so the following is possibly going off on a tangent a bit, but I wanted to share it anyway in case it's useful to anyone. :)

GeoHack can show maps of the moon (e.g. https://tools.wmflabs.org/geohack/geohack.php?pagename=Hooke_%28lunar_crater%29&params=41.2_N_54.9_E_globe:Moon_type:landmark), as well as various other non-earth things (I assume everything listed in https://en.wikipedia.org/wiki/Category:GeoTemplates). It uses a single image for each globe and I guess it just positions the coordinates relative to the dimensions of the image.

It appears the WDQS UI is using Leaflet. Leaflet can do image overlays and there's no reason why a single image (like the ones GeoHack uses) couldn't be set to overlay the entire globe. I know very little about map projections and stuff like that, but it seemed like it shouldn't be that hard to replace tiles with a full-globe overlay and I was also curious, so I played around and eventually came up with the following little HTML/JS thing:

<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet/v0.7.7/leaflet.css" />
<script src="http://cdn.leafletjs.com/leaflet/v0.7.7/leaflet.js"></script>

<div id="mapid" style="min-height: 600px; height: 100%"></div>

<script type="text/javascript">
var bounds = L.latLngBounds([[-90, -180], [90, 180]]); // the image overlays the whole globe

var map = L.map('mapid', {
    maxZoom: 3,
    minZoom: 2,
    center: [0, 0],
    zoom: 3,
    crs: L.CRS.EPSG4326 // magic stuff that makes it 2x1
});

var objects = Array(
    // Moon
    { lat: 41.2, lon: 54.9, name: 'Hooke' }, // https://tools.wmflabs.org/geohack/geohack.php?pagename=Hooke_%28lunar_crater%29&params=41.2_N_54.9_E_globe:Moon_type:landmark
    { lat: 4.1, lon: 132.9, name: 'Green' }, // https://tools.wmflabs.org/geohack/geohack.php?pagename=Green_%28lunar_crater%29&params=4.1_N_132.9_E_globe:Moon_type:landmark
    { lat: 28.1, lon: 109.1, name: 'Espin' }, // https://tools.wmflabs.org/geohack/geohack.php?pagename=Espin_%28crater%29&params=28.1_N_109.1_E_globe:Moon_type:landmark
    { lat: 86.1, lon: -61.8, name: 'Gore' } // https://tools.wmflabs.org/geohack/geohack.php?pagename=Gore_%28crater%29&params=86.1_N_61.8_W_globe:Moon_type:landmark

    // Mars
//  { lat: 34.67, lon: 144.23, name: 'Fenagh' }, // https://tools.wmflabs.org/geohack/geohack.php?pagename=Fenagh_%28crater%29&params=34.67_N_215.77_W_globe:Mars_type:landmark
//  { lat: 33.7, lon: -81.9, name: 'Nipigon' } // https://tools.wmflabs.org/geohack/geohack.php?pagename=Nipigon_%28crater%29&params=33.7_N_81.9_W_globe:Mars_type:landmark

    // Europa
//  { lat: -25.2, lon: 88.6, name: 'Pwyll' } // https://tools.wmflabs.org/geohack/geohack.php?pagename=Pwyll_%28crater%29&params=25.2_S_271.4_W_type:landmark_globe:europa
);

objects.forEach(function (obj) {
    var marker = L.marker([obj.lat, obj.lon]).addTo(map);
    marker.bindPopup(obj.name);
});

var url = 'https://upload.wikimedia.org/wikipedia/commons/d/db/Moonmap_from_clementine_data.png'; // Moon
//var url = 'https://upload.wikimedia.org/wikipedia/commons/b/b7/Mars_G%C3%A9olocalisation.jpg'; // Mars
//var url = 'https://upload.wikimedia.org/wikipedia/commons/7/74/Jupiter_II-Europa_map_NASA_JPL_Voyager.jpg'; // Europa

L.imageOverlay(url, bounds).addTo(map);

map.setMaxBounds(bounds);
</script>

The markers appear to be in the same locations on the images as those on GeoHack, so as far as I can tell (and to my surprise :P), it seems to work.

Displaying non-Earth maps would be very interesting (and cool) but for starters I think the map display shouldn't fail at least on non-Earth entities. Then we could proceed to thinking about integrating non-earth maps like Geohack does, maybe.

Maps of the Moon would be very cool, but I guess it is not that simple. What if the query result for example contains earth and moon coordinates?

@Jonas It seems to me like a query by coordinate should always filter by the reference globe. That's currently not possible using the simply "truthy" statement mapping, though.

@Smalyshev: Agreed, that's what I meant by my first line. :) Should I make a new ticket for displaying maps of other globes?

@Jonas: For supporting multiple maps, the most obvious option to me would be: When there are non-earth coordinates in the results, change "Map" in the display menu to "Map (Earth)" and add similar options (e.g. "Map (Moon)") for the other supported globes which are in the results.

Change 278720 had a related patch set uploaded (by Jonas Kress (WMDE)):
Evaluate globe in coordinates

https://gerrit.wikimedia.org/r/278720

I think for starters we should just not display any coordinates with globes on Earth map and not enable maps if there are only such coordinates. In the future, once we figure out how to do it, maps of the Moon etc. (a-la Geohack?) would be extremely cool, of course. But not a short-term requirement.

Change 278720 merged by jenkins-bot:
Evaluate globe in coordinates

https://gerrit.wikimedia.org/r/278720