That time can reveal the dips and peaks, or topography, of the ocean surface to within centimeters, scientists say. "So, we may be able to detect another 25,000 on top of the 5,000 already known," the Scripps Institution of Oceanography researcher explained. To create the seafloor map, which covers the world's oceans, the scientists relied on measurements taken from high-resolution altimeters onboard the European Space Agency's (ESA) CryoSat-2 satellite and NASA's Jason-1 satellite, along with information resulting from new data-processing methods. (Photo Credit: Ministry of the Interior, Taiwan) 
 
 The gravity model reveals an extinct spreading ridge buried under sediment in the Gulf of Mexico, and the boundary between continental and oceanic crust (COB). Previously unseen features in the map include newly exposed continental connections across South America and Africa, and new evidence for seafloor spreading ridges at the Gulf of Mexico that were active 150 million years ago and are now buried by mile-thick layers of sediment. Developed using a scientific model that captures gravity measurements of the ocean seafloor, the new map extracts data from the European Space Agency’s (ESA) CryoSat-2 satellite, which primarily captures polar ice data but also operates continuously over the oceans, and Jason-1, NASA’s satellite that was redirected to map the gravity field during the last year of its 12-year mission. Interpolation of ocean-floor shape by satellite 
 
 Image copyright ESA 
 
 Most ocean maps are derived from satellite altimeter measurements 
 
 Satellites infer ocean-floor features from the shape of the sea surface 
 
 They detect surface height anomalies driven by variations in local gravity 
 
 The gravity from the extra mass of mountains makes the water pile up 
 
 In lower-mass regions, such as over trenches, the sea-surface will dip 
 
 Limited high-resolution ship data has calibrated the satellites' maps 
 
 Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos
– Underscoring how much of the Earth remains mysterious, scientists have located "thousands" of previously unknown underwater mountains, known as "seamounts," reports LiveScience. The discovery, announced in this month's Science journal, was a joint effort between a European Space Agency satellite and one from NASA that used high-tech imagery and gravity mapping to find the peaks, which rise a mile or more off the seafloor, the BBC reports. And because they're still analyzing the data, researchers think there may be even more of the topographical treasures. "We may be able to detect another 25,000 on top of the 5,000 already known," says one of the scientists involved with the project. The ocean's deepest parts remain a mystery—as evidenced by the logistical issues during the search for still-missing Malaysia Airlines Flight 370, as the BBC notes—but the Jason-1 and CryoSat-2 satellites worked together to bounce radar signals off the Earth to detect topographic "dips and peaks." The discovery is important to conservation scientists—"wildlife tends to congregate" near the mounts' peaks, notes the BBC—as well as to researchers who study seafloor makeup to determine water current and heat-transfer patterns. So how come we've never spotted the mountains before? A release from the Scripps Institution of Oceanography cites "drastically improved remote sensing instruments" and new data combined with old. "You may generally think that the great age of exploration is truly over; we've been to all the remotest corners of continents, and perhaps one might think also of the ocean basins," a University of Sydney professor tells the BBC. "But sadly this is not true—we know much more about the topography of Mars than we know about the seafloor." (Tons of plastic in the ocean seems to have disappeared, and that's probably not a good thing.)