Since the end of Mars' last ice age roughly 370,000 years ago, about 21,000 cubic miles of ice has accumulated primarily around the planet's north pole, an analysis of radar images taken by NASA's Mars Reconnaissance Orbiter shows.
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That's the equivalent of about 2 feet of ice distributed evenly over the entire surface of the planet.
The study, published in this week's Science, is the first to put a hard number on the amount of ice shifting around the planet, information that will help researchers piece together Mars' climate history.
Climate studies are key to figuring out when Mars -- the planet most like Earth in the solar system -- may have been best suited for life to evolve and where to look for evidence.
"We have a volume of ice (that transfers after an ice age) that can now be used to direct climate models. Previously those models ... started with guesses," Smith said.
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It's also the first time scientists have directly tied a particular layer of Martian ice with a specific period of time.
"Eventually we'd like to be able to do this for every layer so this is the fist step in the right direction," Smith said.
Understanding the history and climate evolution of Mars helps scientists figure out which processes, such as dust storms, are important in determining the surface temperature and conditions, notes Christine Hvidberg, an associate professor with the University of Copenhagen's Center for Ice and Climate.
"It is also important to realize that Mars is actually undergoing changes at present ... This is an important step toward understanding the climate on Mars," Hvidberg said.