Mars - A Natural Atmospheric Laboratory

A less well known, but equally important reason for studying the planet Mars, is that it is a perfect laboratory for investigating climate and weather.

Unlike the Earth, Mars has no oceans and no ocean currents to complicate its weather phenomena. Also, Mars seems to have only a single global atmospheric circulation cell in each hemisphere, one in the North and one in the South, whereas the Earth has three such global circulation cells in each polar hemisphere. The relative simplicity of the Martian atmosphere can yield important clues to the fundamental dynamics of the Earth's atmosphere.

Primary atmospheric circulation cells on Earth and Mars

Figure 3: The Earth has three primary atmospheric circulation cells in the Northern and Southern hemisphere whereas Mars seems to have only one. The red arrows indicate zones of low atmospheric pressure and the blue arrows indicate zones of high atmospheric pressure. Note: The scale has been greatly exaggerated to show the wind circulation.

The energy from the Sun is responsible for all weather phenomena, both on Mars and on the Earth. What make Mars even more suited to Earth-Mars comparison is that the length of the day on Mars is almost exactly the same as the length of the day on Earth and by a remarkable coincidence, the rotational axis of Mars is tilted at approximately 25° to its orbital plane, amazingly close the 23° tilt of the Earth's to its orbital plane. The result is that Mars has seasons, with the notable difference that a Martian year is nearly two Earth years in duration.

Rotational Axis of Mars

Figure 4: The rotational axis of Mars is tilted 25.2 degrees away from the perpendicular to the ecliptic causing seasons in the same way that seasons are produced on Earth.

Rotational Axis of Earth

Figure 5: The rotational axis of the Earth is tilted 23.4 degrees away from the perpendicular to the ecliptic.

Mars also appears to have been a much wetter and warmer place in the past. What caused this dramatic drought? What lessons are there to be learned that could help us understand the Earth's fragile environment?

Scientists believe that the answers to these and other related questions will have profound consequences for understanding the atmosphere on Earth, perhaps even giving us the knowledge and insight needed to avoid potential global planetary disasters on our home planet.