Thomas J. Wdowiak is an Athena scientist who takes time out of his busy schedule to show kids how to do fun
science experiments at home. When he isn't teaching at the University of Alabama at Birmingham or training
at the Jet Propulsion Lab in California, he writes for the local newspaper in Birmingham in the "Just for
Kids" section. He goes by "Tommy Test Tubes," a nickname given to him when he was a kid. Now "Tommy Test
Tubes" contributes his experience and knowledge to the Athena web page with a new column. If you have a
question for Tom, click here.
Why is Mars Red?
Asking why Mars is red is a question that can be asked along with "why does the Moon have
dark areas?" That's because the answers involve the same thing, the element iron. It also
involves an important difference between Mars and the Moon: Mars has an atmosphere and the
Iron is pretty interesting cosmic stuff. That's because it's the last element a star can make
and still generate energy. This only happens at the end of the lifetimes of certain stars,
particularly the "heavyweights".
The simplest element is hydrogen;
it's no. 1. This means it has only one piece of a kind of matter, called a proton, in the
center and consequently usually has a piece of matter, called an electron, in the outer part.
Protons are said to have positive (+) charge, and electrons are said to have negative (-)
charge. The rule is that "opposites attract". Also, protons are 1836 times "heavier" than
electrons. Sometimes, you can find hydrogen atoms with companions to the proton, a piece of
matter called a neutron, which is said to be electrically neutral (neither "+" nor "-").
In the Sun, and other similar stars, the centers of hydrogen atoms are joined together to
make a center of another kind of atom. This atom is helium, no. 2, and it has two protons and
generally two neutrons in the center and usually two electrons in the outer part. This
process of joining centers of atoms together is called fusion. Stars do it, and each time it
happens energy is released. This energy becomes starlight (or sunshine in the case of the
This continues until 26 protons (and a bunch of neutrons) have been joined together, and
element no. 26 is produced. This element is iron. Adding a 27th proton does not release any
energy (it actually consumes energy!), so this doesn't happen. As a result, iron accumulates
inside the stars in which this is going on. Elements beyond no. 26 do get made, but the
energy has to come from some process other than fusion.
Iron is pretty abundant stuff. It gets into a lot of things, like planets and even you
(remember the iron in your blood). And it has 26 (+) protons and generally 26 (-) electrons.
Actually, this is the situation when it is said to be metallic, you know, "shiny". The kind
of stuff a lot of things, like cars and refrigerators, are made of. You can even find certain
meteorites made of metallic iron, but this only happens about 5% of the time.
Iron atoms easily lose two or three of their electrons. This happens when they encounter
other elements like oxygen (which is no. 8). Oxygen really sucks away electrons. When this
happens it's called "oxidation".
When metallic iron loses two or three electrons to some other element, it stops being shiny
and the iron atom joins with the atom or atoms of the other element to form a molecule (what
two or more atoms joined together is called).
Iron-containing molecules where the iron atoms lose two electrons tend to be black or green
in color. When three electrons leave the iron atoms, the color is yellowish-orange, and in
many cases bright red. We say it's more oxidized when 3 electrons are involved than just 2.
The answer to the question of why Mars is red (and why there are dark areas on the Moon) is
first because both worlds contain iron, like Earth contains iron. Secondly, the iron on the
surface of Mars is more oxidized than the iron on the Moon, which is why Mars looks red and
you see dark places on the Moon (remember, it's often called the "man on the Moon"). Why is
iron on Mars more oxidized? Because it has an atmosphere that contains carbon dioxide (CO2)
and water (H2O), both of which can be a source of oxygen for oxidizing iron. The Moon on the
other hand, has a surface in a vacuum -- no atmosphere, no oxygen to make the iron red.
Here's an experiment you can do: If you can find a piece of rusty iron, carefully
remove the red rust with some medium grade sand paper. Just before it gets to be shiny, if
you look closely, you will see a thin black layer between the red rust and the shiny metal.
That experience will acquaint you with the three forms of iron we've been talking about. When
you're doing this, think about the "red planet" and the "man on the Moon".
Back to Tommy Test Tubes Archive