Description
Data from the Earth-orbiting U.S.-India NISAR (NASA-ISRO Synthetic Aperture Radar) satellite’s L-band radar was used to produce an image of Nunatak Zaterjavshijsja — a mountaintop in East Antarctica — poking out amid a stream of ice flowing northeast to the ocean. The obstruction causes stresses in the ice, heavily fracturing the surrounding surfaces with deep cracks, called crevasses, which show 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, which vibrate in different directions, interact with and reflect from the ice. Over Antarctica, NISAR transmits radar waves toward Earth with a horizontal polarization. The orientation of the signals that return, either horizontal, vertical, or both, provide clues about the object or surface that reflected them.
Signals that come back with a horizontal polarization likely bounced off a more regular surface, such as smooth ice. Those signals appear magenta in the image. Signals that return with vertical polarization may have refracted as they partially penetrated the ice or scattered at different angles as they reflected off irregular surfaces, like the faces of crevasses. Called volume scattering, these observations are displayed in green.
The white represents areas in which both magenta and green signals scatter back strongly, a possible indication that there is an equal blend of surface and volume scattering.
Figure A is an annotated version of image.
Managed by Caltech, NASA’s Jet Propulsion Laboratory leads the United States 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 Organisation. 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) wide — the largest radar antenna reflector NASA has ever sent into space.
To learn more about NISAR, visit:
Facts Only
* Data from the Earth-orbiting U.S.-India NISAR L-band radar was used to image Nunatak Zaterjavshijsja in East Antarctica.
* The obstruction causes stresses in the ice, heavily fracturing surrounding surfaces with deep cracks called crevasses.
* Crevasses appear as sharp green lines in the image.
* Horizontal polarization signals likely reflect off a more regular surface like smooth ice and appear magenta.
* Vertical polarization signals may result from refraction or scattering off irregular surfaces, such as crevasses, and appear green (volume scattering).
* White areas indicate strong scattering from both magenta and green signals, suggesting an equal blend of surface and volume scattering.
* The NISAR satellite uses a giant drum-shaped reflector measuring 39 feet wide.
* The U.S. component was managed by Caltech/NASA, providing the L-band SAR and antenna reflector.
* The spacecraft bus and S-band SAR were provided by the Indian Space Research Organisation.
Executive Summary
Full Take
The image analysis reveals a system where physical processes—ice deformation and wave reflection—are mapped onto spectral colors, creating a layered interpretation of physical reality. The shift from magenta (smooth surface) to green (volume scattering/crevasses) introduces a visual taxonomy for subsurface structure that goes beyond simple topography. This mapping implies that the appearance of an Antarctic feature is not just a matter of shape but a composite reflection of material state and geometric irregularity, forcing an interpretation where 'shape' is secondary to 'interaction.' The fact that scientists nicknamed the image "the hummingbird" suggests an immediate human recognition of dynamic, ephemeral motion captured through these complex wave interactions. The layered signaling (magenta for surface regularity versus green for internal volume scattering) establishes a framework where what is visible on the surface necessitates accounting for what lies beneath and within the material itself. This pattern challenges simplistic visual observation by embedding physical mechanisms directly into the data presentation.
Bridge questions: How do different scientific disciplines interpret the meaning of magenta versus green in geophysical imaging? What assumptions about surface vs. volume scattering are inherent in this specific polarization framework? What alternative visualization methods could reveal these subsurface stresses more directly than signal scattering patterns?
Sentinel — Human
The text reads as a clear explanation of scientific findings, effectively translating complex radar physics into accessible observations while correctly attributing the source of the data.