After three weeks of catastrophic floods in Pakistan, two million people are homeless and one-fifth of the country is underwater. These satellite photographs, taken a year apart, help show the extent of the disaster—click to see them full-size.

This one was taken on August 14, 2009:

The Satellite Pics of Pakistan's Devastating FloodsS

And this one was taken on August 15, 2010 (this past Sunday):

The Satellite Pics of Pakistan's Devastating FloodsS

Using infrared and visible light, the photos provide a clear contrast between water (blue), vegetation (green) bare ground (brown) and clouds (light blue-green). Though neither picture shows the entire area of Pakistan, the extent of flooding is obvious.

Over the weekend, United Nations Secretary-General Ban Ki-Moon said he'd seen no disaster like the floods. Nearly 1,500 people are already dead, and at least one case of cholera has been reported, raising fears of disease. The Pakistani government has also expressed concern about the possibility of a political "vacuum" that could aid militants and insurgent groups.

[NASA; The Upshot]