The Atmosphere of Mars Lost in Space
(written by Cory Van Auken)
Mars has been thrust into the spotlight as of late due to recent exciting discoveries. Evidence of liquid water, a block buster
motion picture, and ample speculation about the possibility of terra forming Mars have highlighted certain similarities
between us and our red neighbor. However, there are striking differences between our worlds, ultimately rendering Mars
an uninhabitable barren landscape.
Our planet hosts an astounding diversity of life, an abundance of liquid water, and a wonderfully dynamic atmosphere.
Nitrogen (78%) and oxygen (21%) make up the bulk of Earth’s atmosphere, while Mars possesses an atmosphere 100times thinner than Earth’s, made up of almost entirely carbon dioxide (93%). Why is the atmosphere of Mars so thin?
Thanks to NASA’s Maven spacecraft scientist have collected enough data to detail the story of Mars and its lost
atmosphere. Scientists believe Mars lost the majority of its atmosphere to intense solar winds. Currently, Mars loses 100
grams of atmosphere per second, which is 1,000 times less than it lost some 4.2 billion years ago. A short time after the
formation of our solar system intense solar winds stripped away the bulk of its once thick atmosphere. Lakes and rivers
dried up (geologic evidence suggests both existed on the surface at one time in its history) and the surface morphed into
the cold dry world it is today. Why did Earth escape this doomed fate?
Solar wind is an intense stream of energized charged particles protons and electrons. These intense streams of plasma
flow out from the sun at speeds of 1 million mph at temperatures of 1,000 ◦C. As these particles bombard the atmospheres
of planetary bodies they strip it away. To understand why this phenomenon has not stripped away the atmosphere on
Earth we must delve under the surface and into the core of our planet.
Solar winds can be diverted around planets by the existence of a magnetic field.
The Earth possesses a powerful magnetic field, and as a result deflects the majority
of these harmful solar winds protecting the atmosphere from being siphoned off into
space. Magnetic fields are created by the movement of charged particles, and the
earth has an incredible system to do this. Earth possesses a solid iron core which
fractionated out and sank to the center during its early stages of development.
Intense pressure keeps this iron alloy in a solid state. However, surrounding this
solid iron core is an outer shell of liquid iron and nickel alloy. The heat is incredibly
intense, and while the pressure is astounding, it’s not enough for the layer to
solidifying. This results in a molten metal outer core. Because the earth rotates on its axis at a fairly brisk pace (about
1,000 mph), it creates convection currents in the outer core. As these charged particles move around they create an
intense magnetic field, subsequently protecting the atmosphere by deflecting oncoming solar wind.
Mars has a magnetic field 40 times weaker than that of Earth’s. Mars and Earth spin on their axes at a surprisingly similar
velocity, so the lack of magnetism is not from lack of movement. Instead, Mars lacks a substantial liquid core, and the lack
of convection results in an almost non-existent magnetic field. As solar wind bombards the red planet there is little
protection and the atmosphere is stripped away.
While our Earth and Mars possess many similarities their geology differs. Because of Earth’s dynamic inner core a
substantial magnetic field is created and the majority of solar wind is diverted, saving our atmosphere from continuous
stripping. Mars lacks the magnetic field to protect its atmosphere from these damaging solar winds and is thus
continuously losing its already thin atmosphere.
Further Reading:
http://arstechnica.com/science/2015/11/how-mars-lost-its-atmosphere-and-became-a-cold-dry-world/
http://www.space.com/31044-mars-terraforming-nasa-maven-mission.html