\n \u201cThe question is: If there was an ocean on Mars and it dried up, what signs would it have left?\u201d said Michael Lamb, senior author of the study published last week in the journal Nature<\/a>. \u201cWhat we\u2019ve looked for is a band that would wrap around where the shoreline would have been, like a flat bench \u2014 because that\u2019s essentially what we see on Earth, which we know as the continental shelf.\u201d\n <\/p>\n \n Lamb, a professor of geology at the California Institute of Technology, and lead author Abdallah Zaki, a distinguished postdoctoral researcher at the University of Texas at Austin, ran computer simulations to dry up the oceans on Earth and see what geological traces they would leave behind. The continental shelf emerged as the most distinct feature, enduring through time and changing sea levels.\n <\/p>\n \n The research team then searched for an analog on Mars using data from NASA\u2019s Mars Orbiter Laser Altimeter or MOLA, a probe that mapped the planet\u2019s surface features from orbit using laser. \u201cWe looked for a similar feature on Mars and found some evidence that it could be there,\u201d Lamb said. \u201cIt doesn\u2019t look exactly like the continental shelf on Earth, however, so there\u2019s some evidence in support of it, but not all the pieces of the puzzle.\u201d\n <\/p>\n \n The idea that an ocean might have once existed on Mars originated in the 1970s, when the Viking 1 and Viking 2 missions launched by NASA detected what some researchers believed was a shoreline \u2014 a much narrower band than the newly proposed coastal shelf \u2014 and a depression in the planet\u2019s northern hemisphere that was suggestive of an ancient seabed.\n <\/p>\n \n However, this older evidence was never considered conclusive: \u201cThe shoreline has some issues,\u201d Lamb said. \u201cIt doesn\u2019t trace constant elevation as you might expect for a shoreline, but it waves up and down.\u201d\n <\/p>\n \n One way to explain this elevation change, he noted, is volcanic eruptions that might have shifted Mars\u2019 crust and deformed the shorelines. \u201cBut it\u2019s hard to prove that that\u2019s what happened, and so it remains debated whether those are in fact shoreline features or not,\u201d Lamb said\n <\/p>\n \n Another issue is that shorelines are very thin. \u201cIf you want to look for long-lived oceans, then there must be something bigger than a shoreline, and we think that\u2019s the coastal shelf,\u201d said Zaki, who conducted the research with Lamb when he was a postdoctoral scholar<\/a> at Caltech.\n <\/p>\n \n The coastal shelf is an improvement on the shoreline data in several ways, according to the new study. The sloping feature is easier to see and much larger, at about 200 to 400 meters wide (650 to 1,300 feet), making it relatively resistant to erosion over billion of years. The formation would have resulted from rivers carrying sediments into the ocean, as well as changing sea levels. \u201cOn Earth, the continental shelf is the largest sedimentary sink on the planet, due to the material brought by rivers and some added sediment deposition from waves and currents,\u201d Zaki added.\n <\/p>\n \n Zhurong, a Chinese rover that landed on Mars in 2021, detected evidence of ancient beaches<\/a> within underground sedimentary layers in the planet\u2019s northern plains, the same area where Zaki and Lamb think they have found traces of a coastal shelf. Geological remnants of river deltas<\/a> further bolster that idea.\n <\/p>\n \n Mars still holds some water, mostly in its ice caps, but there might be much more underground \u2014 enough to fill an ocean, according to data from NASA\u2019s InSight lander<\/a>. The red planet lost most of its water as its atmosphere thinned over time, allowing water molecules to escape into space. By some recent estimates, the planet could have had surface water until as recently as 2 billion years ago<\/a>.\n <\/p>\n \n The \u201cbathtub ring\u201d could be spotted soon. The European Space Agency\u2019s rover Rosalind Franklin, expected to launch in late 2028 for a landing on Mars in 2030, will explore the northern hemisphere with the ability to probe both the surface and underground. \u201cIt will give us a definitive answer,\u201d Zaki said.\n <\/p>\n \n Confirming an ancient ocean on Mars would help deepen our understanding of the red planet and could help illuminate why it changed so dramatically over time and whether it ever hosted any kind of life.\n <\/p>\n \n \u201cThere are lots of indicators that Mars had liquid water on its surface, but what we really don\u2019t know is how long that liquid water was stable,\u201d Lamb said. \u201cThe climate of Mars is now very cold and dry, so it\u2019s changed substantially from the past and it remains a scientific challenge to understand how and why Mars was warm and wet and for how long, and what happened to cause the planet to have such a catastrophic change to its current state.\u201d\n <\/p>\n \n The study offers an intriguing new approach to the question of whether Martian oceans once existed, according to James W. Head, a professor of Earth, environmental and planetary sciences at Brown University who was not involved with the study. However, he added in an email, due to the lack of plate tectonics on Mars, the formation of such a sharp boundary \u2014 the coastal shelf \u2014 is debatable. Further observations are required to see if this analog to Earth\u2019s continental shelf is a reliable marker. \u201cIn the final analysis, two problems remain,\u201d he concluded. \u201cWhere did so much water come from? And where did it all go? Neither has yet been adequately accounted for.\u201d\n <\/p>\n \n Brian Hynek, a professor in the department of geological sciences at the University of Colorado Boulder, agrees that while the study bolsters the evidence for a past ocean, the appearance of Earth\u2019s continental shelves is partly due to the role of plate tectonics, which Mars never had. \u201cThis, plus expected differences in ocean tides and currents, leads to a bit of an apples to oranges comparison,\u201d Hynek said in an email. He was not part of the new research.\n <\/p>\n \n Lamb acknowledges the differences in formation between the Martian coastal shelf and Earth\u2019s continental shelf but maintains that some of the elements that operated to make the shelf on Earth \u2014 rivers, waves and sea level changes \u2014 also likely were present on Mars.\n <\/p>\n \n Bryony Horgan, a professor of Earth, atmospheric and planetary sciences at Purdue University in West Lafayette, Indiana, said in an email that whether or not Mars ever had a large ocean is a critical question because it has major significance for the ancient climate, geology and habitability of the red planet. \u201cBut it remains one of the longest lived controversies in Mars science, to the point where many younger scientists are hesitant to even discuss the hypothesis,\u201d Horgan said.\n <\/p>\n \n The controversy stems from the fact that Mars seems to have had temperate climate periods with rain that deeply altered the rocks, as well as widespread rivers and lakes that persisted for potentially millions of years. \u201cIt\u2019s hard to imagine such a well-developed water cycle existing without a large ocean filling the deepest and largest basin in the northern lowlands, but we have yet to see rigorous direct evidence of such an ocean, so the debate rages on,\u201d added Horgan, who also did not participate in the latest work.\n <\/p>\n \n Using Earth as a comparison is a good approach, and ESA\u2019s Rosalind Franklin rover will help settle the debate, she concluded. \u201cI appreciate that the study generates a very testable hypothesis \u2014 we can now go investigate in detail the mineralogy and geology of the landscapes above, within, and below the proposed marine shelf to see if they support the presence of an ancient ocean.\u201d\n <\/p>\n![\"Today,](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/04\/pia04304-mars.jpg\")
<\/p>\n![\"This](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/04\/15-032.jpg\")
<\/p>\n![\"An](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/04\/exomars-rover-20260417132922822.jpg\")
<\/p>\n![\"The](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2026\/04\/w_860.jpeg\")
<\/p>\n