L-band radar data from the NISAR (NASA-ISRO Synthetic Aperture Radar) satellite orbiting Earth between the United States and India was used to produce an image of Nunatak Zaterjavshijsja, a mountain peak in East Antarctica, jutting out in the middle of an ice stream flowing northeast toward the ocean. The blockage causes stresses in the ice, severely fracturing the surrounding surfaces with deep cracks, called crevasses, which show up as sharp green lines in the image. Produced in August 2025, the image has been nicknamed “the hummingbird” by NISAR scientists.

The colors show differences in the way polarized microwave signals, vibrating in different directions, interact with and reflect off the ice. Over Antarctica, NISAR transmits horizontally polarized radar waves toward Earth. The orientation of the returning signals, whether horizontal, vertical, or both, provides clues about the object or surface that reflected them.

Signals returning with a horizontal polarization probably bounced off a more regular surface, such as smooth ice. Those signals appear magenta in the image. Signals returning with vertical polarization may have been refracted by partially penetrating the ice or scattered at different angles by reflecting off irregular surfaces, such as crevice faces. These observations, called volume spread, are shown in green.

White represents areas where the magenta and green signals are strongly scattered, a possible indication that there is an equal combination of surface and volume scattering.

Figure A is an annotated version of the image.

Managed by Caltech, NASA’s Jet Propulsion Laboratory leads the U.S. component of the project and provided the satellite’s L-band SAR and antenna reflector. The spacecraft bus and its S-band SAR were provided by the Indian Space Research Organization. The NISAR satellite is the first to carry two SAR instruments at different wavelengths, collecting data using the spacecraft’s giant drum-shaped reflector, which measures 39 feet (12 meters) across, the largest radar antenna reflector NASA has ever sent into space.

For more information about NISAR, visit:

https://science.nasa.gov/mission/nisar/