Siachen Glacier

An astronaut aboard the International Space Station captured this image of the Siachen Glacier on the spine of the Karakoram mountains in central Asia. This remote part of the world—where territories of Pakistan, India, and China all meet—is uninhabited and lies well above the tree line.

Siachen is the second-longest glacier within Earth’s midlatitudes, which exclude, for example, the continental glaciers of Antarctica and Greenland. It measures 75 kilometers (47 miles) long and is 3.5 kilometers (2.2 miles) wide at the top-center of this image.

The image shows four smaller tributary glaciers flowing into the main Siachen Glacier. The many dark, parallel lines in the glacier and its tributaries are moraines, which give a sense of the southward flow of the glacier. The darkest and most prominent moraine results from the merging of moraines from the Teram Shehr Glacier and its neighbor immediately to the north. Early afternoon sunlight casts shadows from small cumulus clouds onto the glaciers’ surfaces.

The high-resolution version of the image reveals several smaller features on the glaciers’ surfaces and illustrates the magnification achievable with a long camera lens from orbit. Details of crevasses and individual moraine lines become visible, as do lakelets and winding streams. Two small white spots on the Siachen Glacier (lower-right) appear to be blocks of ice embedded in one of the wide moraines.

The volume of Karakoram glaciers has expanded slightly in recent decades, unlike most glaciers on Earth that have decreased in volume. These gains—known as the “Karakoram anomaly”—are yet to be fully explained, and scientists question how long they will persist.

Astronaut photograph ISS069-E-60266 was acquired on August 15, 2023, with a Nikon D5 digital camera using a focal length of 1150 millimeters. The image was provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit at Johnson Space Center. The image was taken by a member of the Expedition 69 crew. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed. The International Space Station Program supports the laboratory as part of the ISS National Lab to help astronauts take pictures of Earth that will be of the greatest value to scientists and the public and to make those images freely available on the Internet. Additional images taken by astronauts and cosmonauts can be viewed at the NASA/JSC Gateway to Astronaut Photography of Earth. Caption by Justin Wilkinson, Texas State University, JETS Contract at NASA-JSC.