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This drawing represents several features of the atmosphere on Mars including: dust storms, an atmospheric pressure much lower than found on Earth, and a composition primarily of carbon dioxide.
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Lower Atmosphere

The atmosphere of Mars is much thinner than that of Earth, with a surface pressure averaging 1/100th that at the surface of the Earth. Surface temperatures range from -113oC at the winter pole to 0oC on the dayside during summer.

Although the length of the Martian day (24 hours and 37 minutes) and the tilt of its axis (25 degrees) are similar to those on Earth (24 hours and 23.5 degrees), the orbit of the planet about the Sun affects the lengths of the seasons the most. The atmosphere is composed mainly of carbon dioxide (95.3%), nitrogen (2.7%), and argon (1.6%), with small amounts of other gases. Oxygen, which is so important to us on earth, makes up only 0.13% of the atmosphere at Mars. There is only one-fourth as much water vapor in the atmosphere.

Although small, this is thought to be enough to allow water ice to be frozen into the surface of the planet. With so little water, clouds are rarely seen in the Martian sky. The possible role in the past of liquid water in forming the dry river beds which we can see is still unknown, particularly because water ice is not plentiful on the surface of the planet.

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The Martian Ionosphere

The Martian ionosphere is a layer of gas that is very high up above Mars and is composed of ions and electrons. It extends from about 75 miles up to several hundred miles up above the surface. It is shown...more

The Martian Magnetosphere

An important new result from the Mars Global Surveyor (MGS) mission is the definite confirmation of the presence of a magnetic field near Mars. The magnetic field leads to the formation of a magnetosphere,...more

Mars Global Surveyor Measures Water Clouds

You might think that clouds in the sky have to be made of water like those of Earth, but this is not always so. Clouds might be made of carbon dioxide or ammonia. Just take a peek at the planets Jupiter...more

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The Mars Global Surveyor reached Mars in September of 1997. But it didn't make it into its final mapping orbit until February 1999. What took so long? Surveyor needed to reach a near-circular, low-altitude...more

The South Pole of Mars

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Mars Express - Beagle 2 Lander

The European Space Agency (ESA) launched a mission to Mars called "Mars Express" in June of 2003. The Mars Express spacecraft has two parts: an orbiter that will circle the Red Planet for at least one...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF