wondered about the Red Planet. Easily seen from Earth with the
naked eye, ancient astronomers have charted its course across the
heavens with regularity. By the 19th century, with the development
of powerful enough telescopes, scientists began to observe the
planet's surface and speculate about the possibility of life existing
there.
However, it was not until the Space Age that research began to truly
shine light on the planet's deeper mysteries. Thanks to numerous
space probes, orbiters and robot rovers, scientists have learned much
about the planet's surface , its history, and the many similarities it
has to Earth. Nowhere is this more apparent than in the composition
of the planet itself.
Like Earth, the interior of Mars has undergone a process known as
differentiation. This is where a planet, due to its physical or chemical
compositions, forms into layers, with denser materials concentrated
at the center and less dense materials closer to the surface. In Mars'
case, this translates to a core that is between 1700 and 1850 km
(1050 – 1150 mi) in radius and composed primarily of iron, nickel
and sulfur.
This core is surrounded by a silicate mantle that clearly experienced
tectonic and volcanic activity in the past, but which now appears to
be dormant. Besides silicon and oxygen, the most abundant elements
in the Martian crust are iron, magnesium, aluminum, calcium, and
potassium. Oxidation of the iron dust is what gives the surface its
reddish hue.
Beyond this, the similarities between Earth and Mars' internal
composition ends. Here on Earth, the core is entirely fluid, made up
of molten metal and is in constant motion. The rotation of Earth's
inner core spins in a direction different from the outer core and the
interaction of the two is what gives Earth it's magnetic field. This in
turn protects the surface of our planet from harmful solar radiation.
The Martian core, by contrast, is largely solid and does not move. As
a result, the planet lacks a magnetic field and is constantly
bombarded by radiation. It is speculated that this is one of the
reasons why the surface has become lifeless in recent eons, despite
the evidence of liquid, flowing water at one time.
Composite image showing the size difference between Earth and
Mars. Credit: NASA/Mars Exploration
Despite there being no magnetic field at present, there is evidence
that Mars had a magnetic field at one time. According to data
obtained by the Mars Global Surveyor, parts of the planet's crust
have been magnetized in the past. It also found evidence that would
suggest that this magnetic field underwent polar reversals.
This observed paleomagnetism of minerals found on the Martian
surface has properties that are similar to magnetic fields detected on
some of Earth's ocean floors. These findings led to a re-examination
of a theory that was originally proposed in 1999 which postulated
that Mars experienced plate tectonic activity four billion years ago.
This activity has since ceased to function, causing the planet's
magnetic field to fade away.
Much like the core, the mantle is also dormant, with no tectonic
plate action to reshape the surface or assist in removing carbon from
the atmosphere. The average thickness of the planet's crust is about
50 km (31 mi), with a maximum thickness of 125 km (78 mi). By
contrast, Earth's crust averages 40 km (25 mi) and is only one third
as thick as Mars's, relative to the sizes of the two planets.
The crust is mainly basalt from the volcanic activity that occurred
billions of years ago. Given the lightness of the dust and the high
speed of the Martian winds, features on the surface can be
obliterated in a relatively short time frame.
Much of Mars' composition is attributed to its position relative to the
Sun.
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