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Our Glaciers: Then and Now activity kit helps you see the changes taking place in glaciers around the world. See all our activity kits and classroom activities.
This graph illustrates one way in which the altimeter instrument studies the planet.
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Image from: NASA/JPL

Mars Global Surveyor Measures Martian Global Hemispheres

Mars Global Surveyor carries an instrument which measures the altitudes of things. The instrument is called an altimeter, or "altitude-meter".

The graph to the left shows Mars Global Surveyor's measurement of the size of the bluff which separates the southern and northern hemispheres of Mars. The red line shows the lower, northern plains, then the abrupt bluff which separates the northern plains from the highlands of the south. The height of the bluff is shown in both kilometers and in miles. It can be seen from the picture that the southern hemisphere as a whole is much more elevated than the northern hemisphere. The southern hemisphere is also much older than the nothern hemisphere. The different sizes of the two hemispheres is suggestive that Mars has a giant southern continent. More about the peculiar surface topography of Mars can be found in the discussion of the Martian global surface, and a nice picture of the giant, continent sized southern hemisphere can be found in the discussion of the Tharsis Ridge.


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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