This is Scientific American 60-Second Science. I'm Lee Billings. Got a minute?
Long before the Space Age, humans looking at Mars thought they saw evidence for the presence of water, in the form of giant canals built by some very advanced, very thirsty civilization.
Those 19th-century notions proved to be the products of poor telescopes and wishful thinking: the canals were an optical illusion.
But 20th and 21st century observers have definitely found water on Mars.
Telescopes spied water in ice caps at the Red Planet's poles, as well as signs of an ancient ocean covering the northern hemisphere.
The Viking landers saw water frost on rocks, the Phoenix lander found water ice buried centimeters beneath the soil, and the Curiosity rover has rolled through an ancient riverbed.
Most mysteriously, orbiters overhead have glimpsed the outlines of what seem to be belts of buried glaciers girdling the globe at high latitudes.
Some researchers thought the dust-covered glaciers might be mostly made of mud, or of carbon dioxide ice.
But a new study from researchers at the University of Copenhagen reinforces the consensus view that the glaciers are made of water ice, and a lot of it.
The findings are in the journal Geophysical Research Letters.
The researchers paired a decade's worth of radar measurements with models of how glacial ice flows on Earth to calculate the approximate thickness and size of all the Martian glaciers.
The glaciers contain nearly 150 billion cubic meters of water ice, enough ice to cover Mars a meter deep, and more than enough to someday sustain human colonists.
Though of course they'd need to find a way to melt and move all that water around.
Who knows, maybe they'd build canals.
Thanks for the minute, for Scientific American 60-Second Science. I'm Lee Billings.