A stunning high-resolution satellite image of the Mississippi River that was taken over a period of about three weeks has been posted online by the European Space Agency (ESA).
The roughly 2,300-mile river flows from the north of the U.S. to the south, starting in Lake Itasca in Minnesota and ending in the Gulf of Mexico. It's the second-longest river in the country.
The following image shows the Mississippi River between the states of Louisiana and Mississippi and was featured as ESA's 'Earth observation image of the week' on October 14.
The picture is a composition of three radar observations taken 12 days apart that show changes in crop and land conditions over time. A higher-resolution version can be found here.
Andrew Shepherd, a professor of Earth observation at the University of Leeds in the U.K., told Newsweek: "One image is taken on 7 April (red), one is taken on 19 April (green) and one is taken on 1 May (blue). Areas that have not changed over that time period are merged into white. Other colours show the changes during the interval.
"The easiest things to interpret are ships along the river as they turn from red to green to blue as they move. Other features like fields don't move, but they do change over the time period as crops grow and so they appear in a mixed colour, for example yellow."
The left side of the image shows countless fields represented by various colors of differing brightness, with the Catahoula Lake seen on the far left. The Mississippi River itself is the thick, winding line on the right side.
Bodies of water in the image appear black since water tends to reflect radar signals away from the satellite.
Zooming in on the image reveals that the blackness of the Mississippi river is scattered with small colored dashes. These are boats on the river's shipping routes that happened to be traveling at the time the radar observations were made.
The images might at first seem a strange way of representing Earth's surface as the colors aren't representative of how our planet really looks, but it's a very useful method of documenting change over time, Shepherd said.
"These radar images are really powerful as they combine high spatial resolution with the ability to see through clouds and at night, so they are 24/7 sensors unlike photographs. When you combine them together like this you can see how the Earth's surface changes over time which has lots of different uses.
"In this image we can see crops growing and objects moving, for example. But you can use the same approach to study any other changes in the Earth's surface, like forest fires, flooding, or changing snow cover for example."
In total, parts or all of 31 states and two Canadian provinces drain into the Mississippi River, creating a drainage basin that is around 1.25 million square miles in size according to the U.S. Environmental Protection Agency (EPA).
The basin is home to a variety of agricultural activity, including soybean and cotton farming.
Update, 10/21/22, 9:00 a.m. ET: This article has been updated with a higher-resolution image.
Uncommon Knowledge
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Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
