The ice began its retreat about 370,000 years ago, said the study in the journal Science, led by Isaac Smith , a postdoctoral researcher at Southwest Research Institute in Boulder, Colorado. That would be enough to spread a 2 foot thick layer of ice across the entire surface of our solar-system neighbor, a rocky planet that is about half the size of Earth.
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NASAClimatic cycles of ice and dust build the Martian polar caps, season by season and year by year.
For one thing, he says “the polar caps would be smaller”, because Martian poles actually warm up during an ice age.
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.
The geology of the upper layers shows that ice has been accumulating relatively rapidly at the poles, indicating that Mars is emerging from its ice age. It’s a outcome of the red planet’s proximity to Jupiter and the latter’s gravitational effects, as well as the lack of a moon as big as Earth’s. Moreover, as ice erodes, spiral troughs and other distinct features can result within the ice, and the scientists found that the motions of these spiral troughs could sometimes abruptly increase in slope, reverse direction or get completely buried, evidence of ice accumulation and thus changes in climate.
Mars may experience more pronounced climate change cycles because its tilt alters by as much as 60 degrees on time scales of hundreds of thousands to millions of years.
The problem, of course, is that Mars still doesn’t have an atmosphere that could keep liquid water on the surface in large quantities. Mars’ axis is now tilted 25 degrees, but it wobbles between from 10 to 40 degrees. “Now they have more to run on”, Smith said. That ice will stay there until it becomes unstable, at the end of the ice age. That happens for two reasons: first, Mars doesn’t have a moon as big as ours to stabilize its orbit; second, it’s much closer to Jupiter, and Jupiter’s gravity affects Mars’ rotation.
Unlike Earth, ice ages on Mars occur when its poles are warmer than average and frozen water is more stable at lower latitudes.
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“If we were to look at Mars 150,000 years in the future or 400,000 years in the past, it would look very different to us”, Smith said.
