by Chris Peterson » Fri Aug 31, 2012 2:14 pm
500pesos wrote:Why is the moon so uniformly grey?
In fact, there are
distinct color variations across the Moon, but they are subtle in terms of what we see on Earth. The lunar surface is primarily basalt, which is equally low color here on Earth. Without water, or an atmosphere, the Moon has never experienced most of the mineralization processes that have produced so much color on Earth. Without complex tectonics and weathering processes, there is no turnover of deep and surface material on the Moon. And what variation does occur mineralogically across the surface is disguised by a surface layer of dust from billions of years of meteorite impacts (the regolith), as well as space weathering from the bombardment of high energy particles. And of course, unlike Earth, there are no biological processes to alter the geology and add colors.
Which is weird because we know it is composed of the same minerals that compose Earth...
No, it is made of similar elemental abundances. Mineralogically the two bodies are very, very different.
(btw. is this also a colour photo?
Yes.
Other question: what is the temperature on the moon (day-time/night-time)? Is it close to Earth's, or there are much sharper contrasts because the moon has no atmosphere? Like, in this picture, which is taken during daytime, is it scorching hot outside?
Without an atmosphere, all the surface heating and cooling is radiative (moderated to a degree by internal conduction, but the regolith has poor thermal conduction). In direct overhead sunlight, the surface heats up to about 120°C. Towards the end of night, it has cooled to about -150°C. The swing remains large as you move towards the poles, and the average drops.
[quote="500pesos"]Why is the moon so uniformly grey?[/quote]
In fact, there are [url=http://apod.nasa.gov/apod/ap060907.html]distinct color variations[/url] across the Moon, but they are subtle in terms of what we see on Earth. The lunar surface is primarily basalt, which is equally low color here on Earth. Without water, or an atmosphere, the Moon has never experienced most of the mineralization processes that have produced so much color on Earth. Without complex tectonics and weathering processes, there is no turnover of deep and surface material on the Moon. And what variation does occur mineralogically across the surface is disguised by a surface layer of dust from billions of years of meteorite impacts (the regolith), as well as space weathering from the bombardment of high energy particles. And of course, unlike Earth, there are no biological processes to alter the geology and add colors.
[quote]Which is weird because we know it is composed of the same minerals that compose Earth...[/quote]
No, it is made of similar elemental abundances. Mineralogically the two bodies are very, very different.
[quote](btw. is this also a colour photo?[/quote]
Yes.
[quote]Other question: what is the temperature on the moon (day-time/night-time)? Is it close to Earth's, or there are much sharper contrasts because the moon has no atmosphere? Like, in this picture, which is taken during daytime, is it scorching hot outside?[/quote]
Without an atmosphere, all the surface heating and cooling is radiative (moderated to a degree by internal conduction, but the regolith has poor thermal conduction). In direct overhead sunlight, the surface heats up to about 120°C. Towards the end of night, it has cooled to about -150°C. The swing remains large as you move towards the poles, and the average drops.