Mars Rover's Stunning Discovery Suggests Red Planet Was Once A Blue Planet

New data and analysis are rewriting the biography of the Red Planet as evidences suggest that Mars could have held more water (and potential life) than previously thought, where it once hosted a vibrant, blue world dominated by a massive northern ocean.

Recent breakthroughs, including a study published in Nature, have mapped ancient shoreline features that point to a colossal body of water once covering the Martian northern hemisphere. By analyzing high-resolution images (from Mars probes, such as ESA's Mars Express and ExoMars Trace Gas Orbiter, and NASA's Mars Reconnaissance Orbiter) of fan-shaped deltas in the Coprates Chasma region, researchers identified "scarp-fronted deposits" that mirror river mouths on Earth.

These geological signatures indicate that around 3.4 billion years ago, a connected oceanic system existed on a planetary scale, rather than just isolated lakes. This so-called deep blue period occurred much later in Martian history, thus potentially extending the window during which the planet may have been hospitable to life.

Meanwhile, NASA’s Curiosity rover has been busy uncovering other evidence on the ground, such as the discovery of rare mineral patterns and boxwork lattice formations within Gale Crater. These web-like structures form when minerals crystallize in underground fractures where salty liquid water once flowed.

Perhaps more intriguingly is the rover’s encounter with a field of bright, yellow crystals composed of pure elemental sulfur—a find that project scientist Ashwin Vasavada compared to finding "an oasis in the desert." Pure sulfur hints at a complex, possibly warm, underground water system that persisted even after the surface oceans vanished.

These findings are but part of a growing body of evidence, including a 2025 study also published in Nature, which suggests that Mars wasn't just wet, but also unexpectedly warm. Researchers have identified minerals like kaolinite and spinel in the Martian soil—substances that form only in environments with intense rainfall or active hot springs.

That said, if Mars remained a blue planet for much longer than we thought, the window for life to emerge and evolve was significantly wider. Researchers are now eyeing these ancient paleoshorelines as the holy grail for future sample-return missions. These sites likely acted as giant sediment traps, potentially burying and preserving organic molecules within the mud of a long-lost sea.