Mars and Venus Weather vs. Earth: A Comparative Study

Introduction: Earth's Nearest Planetary Neighbors

Mars and Venus are Earth's closest planetary neighbors, and it might be assumed their weather is similar to Earth's — but nothing could be further from the truth. The weather on both Mars and Venus differs dramatically from Earth's and cannot support life as we know it. However, there are also some startling similarities between Earth's weather and the weather on these neighboring planets.

Mars: Atmosphere and Temperature

Earth is the third planet from the sun, and Mars is the fourth. One of the biggest differences between Earth and Mars is Mars' atmosphere. As the BBC Weather website notes, "Mars' atmosphere is very different to ours, and weighs less than 1% of Earth's, as it is made up principally of carbon dioxide with small amounts of other gases, including neon, water, nitrogen, argon, and oxygen" ("Mars"). Because oxygen makes up such a small fraction of the Martian atmosphere, humans would be unable to breathe the air without some form of breathing apparatus.

The temperatures on Mars are cooler than those on Earth, which makes sense given that the planet is farther from the sun and receives less solar warmth — roughly half the solar energy Earth receives (Brillo). There is a greenhouse effect on Mars due to its high concentration of carbon dioxide, which helps keep the planet somewhat warmer, but it is far less significant than Earth's greenhouse effect. As Brillo writes, "As on Earth, the gas has a greenhouse effect. But the Martian atmosphere is too thin to achieve much in the way of global warming" (Brillo). Average temperatures on Mars range from -140°C (-220°F) to 20°C (68°F). Such extreme temperature swings would make sustained habitation on Mars nearly impossible without climate-controlled environments.

Mars Weather Patterns, Storms, and Seasons

Mars weather resembles Earth's weather in many respects. Clouds form on the planet occasionally, usually composed of ice crystals or carbon dioxide. The ice crystals originate from Mars' polar ice caps, but since Mars is essentially a desert, these crystals rarely fall back to the surface as rain. Storms are also quite common on Mars, and scientists have even observed and photographed cyclones and other major storm disturbances on the planet, much as we see on Earth.

Mars is also famous for its magnificent dust storms. Scientists believe these massive storms can produce wind gusts reaching 300 miles per hour, while normal winds on Mars average as little as 15 miles per hour or less. Brillo notes, "These dust storms often take place regionally, but in some years they seem to combine to form a dust-laden tempest that can cover the whole planet" (Brillo). Over geological time, these winds have sculpted the planet's surface and created vast sand dunes across portions of Mars.

One thing Mars weather does not have is rain. The planet appears to be bone dry, although there is evidence of former water channels on its surface. No one knows what happened to that water, and tests by the Mars rovers and other instruments have found no evidence of liquid water on the planet. Water cannot exist in liquid form on Mars because the atmospheric pressure and temperature only allow water to exist as ice or vapor. Unlike Earth, which is covered in oceans and experiences healthy rainfall and snowfall, the only thing that can fall on Mars is solid carbon dioxide — the primary component of the polar ice caps (Brillo). Earth's atmosphere is thus conducive to rain and, therefore, to life, while Mars' atmosphere is not conducive to liquid water, an essential ingredient for life on any planet.

Mars tilts on an axis similar to Earth's and rotates around the sun in a comparable manner, giving it four seasons just as Earth has. The seasons are also reversed between Mars' northern and southern hemispheres, just as on Earth. However, because Mars' orbit around the sun takes much longer, each Martian season lasts roughly twice as long as a season on Earth. Martian days, by contrast, are only about 40 minutes longer than Earth's.

Venus: Atmosphere and Surface Conditions

Venus is the second planet from the sun, and its proximity to the sun makes it far hotter than Earth. Remarkably, Venus — perpetually shrouded in clouds — is even hotter than Mercury, the planet closest to the sun. Surface temperatures on Venus can exceed 903°F, hot enough to melt lead ("Venus"). Venus' atmosphere is extraordinarily dense and composed mostly of carbon dioxide, which creates massive surface pressure approximately 100 times greater than what we experience on Earth.

As with Earth's atmosphere, Venus' atmosphere contains trace gases and compounds in addition to its dominant carbon dioxide. The BBC Weather website explains, "Venus' atmosphere has had some other gases detected — hydrochloric and hydrofluoric acid were discovered in 1967, carbon monoxide was noticed in 1968, water in 1972, and sulphuric acid was found six years later. In addition, small amounts of oxygen, argon, and neon have been detected too" ("Venus"). This atmosphere would be impossible for humans to breathe unaided, and any visit to Venus would require breathing apparatus as well as climate-control technology capable of withstanding the planet's extreme temperatures and violent storms.

Conclusion: A World Away in Weather

Both Mars and Venus — Earth's closest planetary neighbors in terms of distance — are a world away in terms of weather and atmosphere. Mars is a desert planet of extremes: exceedingly cold and enormously windy. Venus is a planet perpetually blanketed in clouds and intensely hot. Both planets share certain weather-related phenomena with Earth, but the differences are far more striking. As scientists continue studying the weather on these planets, they will deepen their understanding of each planet's atmosphere, storm systems, and other meteorological events. Eventually, they may discover ways for humans to survive on, or at least visit, these remarkable planets right next door.

References

Borenstein, Seth. "Like Earth, Venus Has Bursts of Lightning." Discovery.com. 2008.

Brillo. "Martian Weather." Ozgate.com. 2008.

Editors. "The Planets — Mars." BBC.com. 2008.

Editors. "The Planets — Venus." BBC.com. 2008.

Editors. "Venus Express." ESA.int. 2008.