Frequently Asked Questions

Early hypotheses in the 1950s and 60s assumed its circularity was an astrobleme. However, detailed ground field campaigns led by Guillaume Matton and colleagues analyzed mineral thin sections under polarizing microscopes and transmission electron microscopy. They found zero planar deformation features (PDFs) in quartz, no high-pressure silica polymorphs like coesite or stishovite, and no shatter cones. Radiometric argon-argon dating established the alkaline igneous ring dikes were emplaced around 100 million years ago during continental rifting.

Optical sensors (such as Landsat 9 OLI or Sentinel-2 MSI) are passive systems that collect reflected solar radiation in visible, near-infrared, and short-wave infrared wavelengths. They require daylight and are blocked by clouds. SAR (such as Sentinel-1 or TerraSAR-X) is an active sensor that generates its own coherent microwave electromagnetic pulses and records the timing and intensity of the backscattered signal, penetrating clouds, rain, smoke, and operating identically in total darkness.

Scientists apply mathematical spectral indices, most notably the Normalized Difference Water Index (NDWI) and Modified NDWI (MNDWI). Water strongly absorbs short-wave infrared (SWIR) while reflecting green light. Dry soil and salt crusts reflect strongly in SWIR. By calculating (Green - SWIR) / (Green + SWIR), every pixel on a 10-meter to 30-meter grid is classified as either water or land, enabling automated software to compute surface areas across time-series databases spanning 1972 to the present.

Most scientific Earth-observation satellites orbit in Sun-Synchronous Low Earth Orbit (LEO) at altitudes between 680 and 800 kilometers above mean sea level. This specific orbital inclination (typically ~98 degrees) ensures the satellite crosses the equator at the exact same local solar time on every pass (for example, 10:00 AM local time), providing consistent sun angles and shadow lengths for comparative time-lapse science.

Yes. Known as paleochannel mapping, spaceborne radar and thermal inertia imaging regularly discover fossil river networks buried under the Sahara, the Taklamakan Desert, and the Australian Outback. These ancient river systems flowed during the African Humid Period (5,000 to 11,000 years ago) and Pleistocene pluvials. Radar penetrates the dry overlying sands, revealing coarser gravels and compacted sediments that once lined ancient riverbeds.

Spatial resolution is defined by Ground Sample Distance (GSD)—the real-world ground area represented by a single pixel. For open-access scientific satellites, Sentinel-2 offers 10-meter GSD in visible bands, Landsat offers 15-meter panchromatic and 30-meter multispectral, while commercial constellations can resolve down to 30 cm per pixel, allowing detection of individual vehicles and narrow fault scarps.

Missions like GRACE (Gravity Recovery and Climate Experiment) and GOCE use pairs of satellites flying in tandem with microwave or laser ranging systems measuring the distance between each craft to micron accuracy. As the lead satellite passes over a denser rock mass, it speeds up slightly, followed by the trailing satellite. When an asteroid shatters continental crust—as at Chicxulub—it lowers the crustal bulk density, producing a measurable negative gravitational gradient.