As Hormuz chokes global oil markets, satellite images reveal vast oil spills

The same waters that carry about a fifth of global oil and gas flows, and remain critical to India's crude supplies, are now stained with oil slicks visible from space.

In Short

• Satellite images showed suspected oil slicks across four Gulf locations
• A May 6 spill near Kharg Island covered over 120 square kilometres
• Radar and true-colour imagery were used to verify likely oil traces

Even as the world scrambles for oil after the blockade of the Hormuz corridor, satellite images show a grim irony. On one hand, the crisis is pushing up oil prices, making everything from fuel to food more expensive. On the other, oil is spilling into the very waters that carry it, spreading across the sea instead of reaching homes, factories and markets.

In Hormuz, oil is not only trapped in tankers. It is actually floating across the waters.

Multiple oil slicks are visible from space after US-Iran strikes hit oil facilities and ships in the Hormuz corridor. At least one of them spread across more than 120 square kilometres, large enough to cover a capital-sized city on the map.

Satellite imagery from the European Space Agency’s Sentinel programme was used to assess the spread of the slicks across the waters. At least four stretches of water across the wider Gulf and Strait of Hormuz corridor were visually checked for suspected oil slicks following media reports of strikes on oil facilities and tankers since the beginning of the West Asia conflict.

Oil-like stains were visible on March 5 near the Kuwait coast, April 10 around Lavan Island, April 22 off Qeshm Island and, most recently, May 6 near Kharg Island. Together, the images suggest a scattered trail of surface staining across waters close to major tanker routes and oil infrastructure in the Gulf region.

The slicks are not just an environmental problem. They can hit people in different ways. For Gulf communities that live off these waters, the damage is even more direct. For fishermen, coastal families and marine life, oil on the sea is not a distant crisis. It can mean lost income, poisoned waters and a fragile ecosystem pushed closer to the edge.

The same waters that carry about a fifth of global oil and gas flows, and remain critical to India’s crude supplies, are now stained with oil slicks visible from space.

One image from May 6 shows an oil spill covering a span of more than 120 square kilometres in waters near Iran’s Kharg Island. In true-colour imagery, at least one vessel is visible off the island’s western coast, while two others to the east appear to be engaged in possible refuelling activity.

Another satellite image, captured on April 10, shows oil slicks spreading around Iran’s Lavan Island, days after Iranian state media reported that an oil facility near the island’s coast had been hit on April 7. The slick also appeared to reach Shidvar Island, a coral island east of Lavan Island known for its turtles, seabirds and fragile marine habitat.

These spills are difficult to confirm from satellite images by visual inspection alone. The colour or texture of seawater can change for several reasons, including suspended sediment, algae, sunlight reflection, wave conditions or changes in the surface film or viscosity of the water. A dark patch on the sea, therefore, does not automatically mean an oil spill.

To test whether the floating slicks were likely oil, India Today first examined true-colour Sentinel-2 imagery for visual clues, including long, dark surface streaks consistent with an oil layer. The assessment was then solidified using Sentinel-1 radar imagery, processed independently in Google Earth Engine through a custom detection workflow.

The radar script looked for parts of the sea that had suddenly become unusually smooth. Normally, seawater has tiny wind-driven ripples. But when oil floats on top, it can flatten those ripples, almost like a thin film spreading over the surface. In Sentinel-1 radar images, such smoother patches often appear darker than the surrounding water.

To detect them, the image was first cleaned to reduce radar noise. The script then separated the unusually dark patches from normal seawater and turned them into a binary layer, or mask, showing where the suspected oil slick was spread. This helped estimate the approximate area covered by the spill.

Dead shrimp blanket Mirbat beach

Another unusual event coincided with the oil-spill trail. In southern Oman’s Dhofar Governorate, beaches in the wilayat of Mirbat saw large quantities of dead shrimp wash ashore, staining stretches of the coast red. The discolouration was also visible in Sentinel-2 imagery. While the incident does not by itself establish a link to the oil slicks seen elsewhere in the Gulf, its timing adds to concerns over possible stress on the region’s marine ecosystem.

The shrimp deaths can be attributed to low oxygen levels in the water, which can suffocate marine species, as well as strong sea currents that may have pushed the shrimp into shallow coastal waters, where they were more exposed to stress, predation and mass beaching.

But it remains difficult to independently rule out a pollution link. The visible impact appeared to be largely confined to shrimp, with no clear evidence at the time of a wider die-off involving other marine species. Still, the episode adds another layer of concern over ecological stress in waters already showing signs of oil-like surface slicks.

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