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From pictures I've seen, all rocky planets in our solar system are some shade of grey, brown, and red. Ignoring stuff like atmosphere and oceans and plant life of course.

I was thinking of a world that had a stark white moon. But could such a thing exist? The only 'white' moon I know of is Triton, and that world is covered in ice. I highly doubt a planet in the 'Goldilocks zone' could have a frozen moon.

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  • $\begingroup$ I'm not so certain about your last sentence. The Moon temperatures range from -153ºC to 133ºC because it's tidally locked. If it were spinning much more quickly (say, 24h or less), I think average temperatures would range from -30ºC to 0ºC, which means that a completely frozen Moon would be possible, if there were enough water in it. And for sure it's in the Sun's Goldilocks zone. $\endgroup$ – Rekesoft Nov 2 '17 at 11:00
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There are various compounds in nature which are white.

One of these is Titanium Dioxide

Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO2. When used as a pigment, it is called titanium white.

Another of these is Lead Carbonate, or white lead

White lead is the basic lead carbonate, 2PbCO3·Pb(OH)2. It is a complex salt, containing both carbonate and hydroxide ions. White lead occurs naturally as a mineral, in which context it is known as hydrocerussite, a hydrate of cerussite. It was formerly used as an ingredient for lead paint and a cosmetic called Venetian Ceruse, because of its opacity and the satiny smooth mixture it made with dryable oils. However, it tended to cause lead poisoning, and its use has been banned in most countries.

Now, to have a white looking moon, you don't need the entire body to be made of this material, but just to have the surface layer being covered with it. Which helps if your material is not that abundant.

Parking aside the issue of abundance, you need to cope with depositing of other dust, which will be most likely not be as white as the background.

So, it is possible though not highly likely. And even then, without a mechanism constantly refreshing the white surface, it won't last long.

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    $\begingroup$ There's a zamboni $\endgroup$ – Carl Oct 31 '17 at 20:59
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The obvious answers are ice and clouds which could easily give a planet or moon a white appearance. If you require some other type of white surface then quartz can be white and is very common. Crushed coral can also produce white beaches. But your biggest problems will be if you want the place to be inhabited. In this situation you probably need seas or oceans to some extent which would are certainty not white, as well as vegetation coverage which would also not be white.

Probably the best bet would be to arrange the water content of your world to be low, have it fairly close to the sun and have a larger proportion of that water there was high in the atmosphere creating white clouds, a bit like Venus but at a much reduced pressure and without the toxic components caused by volcanism.

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There are white rocks on earth, many of them in fact, I used to work in the white river formation and the rock is so white you can get a sunburn from reflected light alone. It contains a lot of calcium minerals and volcanic ash.

enter image description here

here is what it looks like close up, keep in mind this is a color photograph. enter image description here There are many white rocks so it is not unbelievable to say your moon just happens to have an abundance of them.

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  • $\begingroup$ As so often happens on this site, "Is [fnord] possible?" "Why, yes, check nature!" $\endgroup$ – Ghotir Nov 1 '17 at 17:33
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Building on @Slarty 's answer, ice and clouds could very well give a planet a stark white appearance. Its worth noting that a star's light shining on the surface of a planet could amplify the white of the surface.

The problem arises if you want your planet to be habitable. Seeing as you've mentioned the Goldilocks zone in the question, I'll be assuming you want it to be habitable.

Thankfully, we have a real world example to help us here. Saturn's moon, Titan, has a completely ice and water covered surface. Research suggests that there are large oceans under the surface, that might be very similar to those of Earth's. The temperatures near the ocean bed are generally stable enough to support organic life.

Dense white clouds could also be a sign of a thick atmosphere, holding in heat and essential UV radiation to make life possible.

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