“Invisible oil” escaped the view of satellites that were tasked with measuring the extent of the Deepwater Horizon spill in the Gulf of Mexico in 2010, according to a new study. In the Science Advances article, researchers argue that updated techniques need to be deployed alongside satellite measurements to track future oil spills below the water’s surface.

BP’s Deepwater Horizon rig spewed more than 200 million gallons into the Gulf in 2010. At the time, satellite readings were used to determine which areas in the Gulf were off-limits to fishing, but the dangers posed by the spilled oil to fish and the humans who eat them spread beyond those boundaries. In places where oil from the spill was no longer visible from space, it still persisted in concentrations that were enough to be toxic. The extent of the spill could have been as much as 30 percent larger than previous estimates, according to study authors.

New computer models can now more accurately predict how a spill will spread. Used in tandem with satellite remote sensing and measurements taken at the site of the spill, these advancements can make for a faster and more effective cleanup in the event of another disaster.

“there will be another oil spill like that.”

“Eventually, there will be another oil spill like that,” cautions Claire Paris-Limouzy, an author of the report and a biological oceanographer at the University of Miami. “I’m definitely concerned,” she says, pointing to offshore oil drilling at deeper and deeper depths.

Paris-Limouzy and her colleagues looked at water and sediment samples, satellite and aerial images, and modeled how oil droplets might have moved through the water over time — factoring in currents, temperature, how the oil degrades, and other factors. Although the spill took place almost 10 years ago, some of the data wasn’t released until recently. Putting the different sources of information together allowed the researchers to have a more comprehensive view of what was going on in the Gulf immediately after the spill. Their technique, they hope, will change the way authorities respond to future spills. “The less uncertainty you have about where the oil will go, the better the response will be,” says Paris.

Satellites face some obvious challenges when it comes to peering into the depths of the sea. “There was no one satellite able to observe all the time, everywhere, and the spill was big,” says Ira Leifer, a researcher at the University of California, Santa Barbara. Leifer was a member of a technical group tasked with putting together official estimates of the flow of oil from the spill, but he was not involved in this study. Leifer says the study confirms what a decade of observations, medical records, and anecdotes had implied: “the impact of this spill was larger than generally publicized,” he says.

Satellites have gotten more advanced since Deepwater Horizon, and they’re still a necessary go-to for assessing oil spills, Leifer and other experts tell The Verge. Leifer says satellites are important for studying areas that aren’t easy for humans to get to, and getting their data is often cheaper than deploying a team to take measurements in the field. And most marine oil spills occur on the surface from boats, making it easier to assess from above.

“You can leverage the power of satellites.”

The study doesn’t discount how important satellite data is when it comes to cleaning up a spill. It just says that researchers shouldn’t stop there. Leifer points out that satellite remote sensing can better inform efforts to gather data on the ground — or in this case, on the water — especially when resources are scarce. “You can leverage the power of satellites to wisely use your resources, it builds the foundation,” he says.

The horrific damage from Deepwater Horizon, one of the most catastrophic oil spills on record, catalyzed efforts to hold oil companies accountable for their effects on the environment. BP, which a US federal judge ruled was responsible for “gross negligence” and “willful misconduct” for the spill, announced yesterday that it wants to take efforts to eliminate the greenhouse gas emissions from the fossil fuels it produces. The details of how, exactly, it would do that have yet to be released.