Why is Mars Red?火星點解是紅色?



We learn from our science class during our secondary school that Mars is a red planet, and it is red, because it is full of rusty iron on the surface of the planet.

I just watch the follow video, and found it very interesting:


The iron got rusty because of the rain/water and the oxygen in the air, causing the iron oxidized.

But if you look closely at the surface of Mars, you’ll see that it can actually be many different colours. Some regions appear bright orange, whilst others look more brown or even black. But if you average everything out, you get Mars’ familiar red colour.

What  I am most  curios about Mars is:

If I could stand on the surface of Mars and look around, is



1.the sky on Mars  red too?

(The dust in the atmosphere scatters the red photons, makes the sky appear red. We have something similar when there’s pollution or smoke in the air.)

2. the sunsets blue?

(The dust absorbs and deflects the red light, so you see more of the blue photons streaming from the Sun.) 



Further…………so,  Mars is further away from the sun than the earth, I wonder how bright is daylight on Mars?

ANSWER from Jim Murphy on July 18, 1997:
The brightness of the sun on Mars, were there to be a clear day, is about
half the brightness of a similar day here on Earth.  I arrive at the value
of one-half simply by knowing that the brightness of an object decreases by
the square of the distance, and since mars is on average 1.5 times as far
from the Sun as earth, 1.5 times 1.5 is 2.25, and 1 divided by 2.25 is 0.44,
or 44 percent as bright.

Now, just because the apparent brightness is half, that does not necessarily
mean that the scene will be half as bright on Mars.  Mars' less massive
atmosphere will mean less scattering of light, and thus the clear martian
sky would not be as blue as here on earth, and all the scattered light which
we see here on Earth, which makes the sun appear a bit less of a flashlight
beam than it is would all conspire to make the Martian sky appear darker.




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