\n Mars was once much wetter<\/p>\n NASA\/USGS<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n Geological features on Mars suggest the planet once boasted rivers and broad coastlines around a vast ocean. The discovery provides the most direct evidence yet for the Red Planet\u2019s former blue vistas.<\/p>\n \u201cThe presence of liquid water [on Mars] is a broad topic that includes rains, rivers, lakes, as well as oceans,\u201d says Ezat Heydari, a geochemist at Jackson State University in Mississippi who wasn\u2019t involved in the research. \u201cIn my opinion, this paper addresses the most important one: the ocean.\u201d<\/p>\n A research team including planetary geologist Ignatius Indi and geoscientist Fritz Schlunegger, both at the University of Bern in Switzerland, made the discovery by analysing data gathered from different probes orbiting Mars, including NASA\u2019s Mars Reconnaissance and the European Space Agency\u2019s Mars Express and ExoMars Trace Gas Orbiter. The ExoMars vessel is equipped with a specialised camera, the Bernese Mars, which can take high-resolution colour images. It was instrumental to the new work.<\/p>\n <\/p>\n \u201cThese images allow us to distinguish subtle differences in surface materials that are invisible in black-and-white images,\u201d says Indi. When combined with topographic data from the other probes, these tools become \u201cgeological time machines\u201d that paint a clearer picture of how the Martian landscape formed, he says.<\/p>\n To apply the imagery to the question of putative past water sources on Mars, the researchers focused on Valles Marineris, a channel more than 4000 kilometres long that cuts along the Martian equator. They paid particular attention to a south-eastern region of the channel called Coprates Chasma. Its deep features are around 3.3 billion years old.<\/p>\n By combining the new imagery with geomorphological analyses, the researchers identified many structures comparable to those that form on Earth where rivers pour into oceans or where alpine lakes materialise at the base of mountains.<\/p>\n \u201cThe Nile delta is a classic example,\u201d says Schlunegger. If you removed the Mediterranean waters just beyond the terminus of the Nile, he says, you would see structures very similar to those detected on Mars.<\/p>\n \n Silty deposits left by ancient water on Mars<\/p>\n Argadestya et al. 2026, CaSSIS<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n The new data also enabled the researchers to trace ancient coastlines around a former ocean, allowing them to measure its approximate size. They concluded that it was about as large as Earth\u2019s Arctic Ocean. This would have been the largest ocean on Mars.<\/p>\n \u201cOur research suggests that around 3 billion years ago, Mars may have hosted long-lasting bodies of surface water inside Valles Marineris, the largest canyon in the Solar System,\u201d says Indi. \u201cEven more exciting, these water bodies may have been connected to a much larger ocean that once covered parts of Mars\u2019 northern lowlands.\u201d<\/p>\n Previous research has given many scholars reason to believe Mars once held water, but this work has primarily been indirect. One study found Martian minerals that appear to have interacted with water in the distant past. Another found signs that ancient asteroid impacts triggered massive Martian tsunamis. While much evidence has hinted at a past humid world, definitive data is difficult to come by.<\/p>\n \u201cThe idea that Mars once had large oceans remains controversial \u2013 in part because, if they existed, their record is not fresh because they are so old,\u201d says Michael Manga, a geoscientist at the University of California, Berkeley who wasn\u2019t involved in the research.<\/p>\n The discovery has tantalising implications for the search for extraterrestrial life, but also offers a cautionary tale that Earth\u2019s most indispensable resource might one day similarly disappear.<\/p>\n \u201cThe paper\u2026 addresses an issue that is in the mind of anyone who conducts research on the evolution of the planet Mars,\u201d says Heydari. \u201cOceans on Mars would have acted just like oceans on Earth, and they are vital to the health of the planet.\u201d<\/p>\n Experience the astronomical highlights of Chile. Visit some of the world\u2019s most technologically advanced observatories and stargaze beneath some of the clearest skies on earth.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<\/section>\n Topics:<\/p>\n<\/section><\/div>\n![\"Silty](\"https:\/\/images.newscientist.com\/wp-content\/uploads\/2026\/01\/19125750\/SEI_281392052.jpg\")
<\/div>![\"New](\"https:\/\/images.newscientist.com\/wp-content\/uploads\/2024\/11\/28003449\/shutterstock_1102540808-scaled.jpg\")
\n <\/picture>\nThe world capital of astronomy: Chile<\/h3>\n