By Will DunhamWASHINGTON, April 15 (Reuters) – There is a lot of evidence from orbiting satellites and surface rovers indicating that liquid water was present long ago on the surface of Mars in the form of ponds, lakes and rivers. But the idea that Mars once had a huge and long-lived ocean on its northern plains has remained a matter of debate.Scientists have now detected what might be the contours of this putative ocean on Earth’s planetary neighbor, using data collected by a NASA probe that orbited Mars for a decade. Their research indicates the presence of the Martian equivalent of the continental shelf that defines the boundaries of Earth’s oceans.AdvertisementAdvertisementThey compared it to a huge “bathtub ring” showing where water may have once met land on Mars. Because Mars does not possess continents and lacks the geological process called plate tectonics that led to the formation of Earth’s continents, the researchers are calling the Martian landforms a coastal shelf.Like Earth and the solar system’s other planets, Mars formed roughly 4.5 billion years ago. Early in its history, Mars was warmer and wetter than the cold and arid place it is today.”The Martian ocean could have existed when the planet had an active hydrological cycle, with flowing rivers and lakes, nearly 3.7 billion years ago, and it likely disappeared as the planet became dry. Exactly where the water went remains highly debated,” said University of Texas planetary scientist Abdallah Zaki, lead author of the research published on Wednesday in th …
