Dunes glowing gold against a background of blue shine out on the surface of Mars in an incredible image from a long-serving Nasa satellite.
The false-colour image shows colder areas in blue – so there’s not actually a huge ocean on the Martian surface.
The image shows Mars's northern polar cap, where the dunes cover an area as big as Texas, although the area in the image is 19 miles wide.
Nasa said: “In this false-color image, areas with cooler temperatures are recorded in bluer tints, while warmer features are depicted in yellows and oranges.
“Thus, the dark, sun-warmed dunes glow with a golden color.”
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It combines images taken from December 2002 to November 2004 by the Thermal Emission Imaging System instrument on the Mars Odyssey orbiter.
It is part of a special set of images marking the 20th anniversary of Odyssey, the longest-working Mars spacecraft in history.
The spacecraft was launched 20 years ago on 7 April, making it the oldest spacecraft still working at the red planet.
The orbiter, which takes its name from Arthur C Clarke’s classic sci-fi novel 2001: A Space Odyssey (Clarke blessed its use before launch), was sent to map the composition of the Martian surface, providing a window to the past so scientists could piece together how the planet evolved.
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Geological features including the work of water and wind have been frozen in time on Mars for about 4 billion years.
There are giant wave-shaped features in sedimentary layers of Gale crater, often called “megaripples” or antidunes, that are about 30 feet high and spaced about 450 feet apart.
Researchers say this suggests that almost unimaginably huge floods washed across the crater about 4 billion years ago – and hints that life might have existed there too.
Data collected by Nasa’s Curiosity Rover, published in 2020, shows the gigantic ripples were likely left by a giant flood.
Scientists believe the flood may have been set off by a meteor impact which melted ice on the surface of the planet.
The impact may have allowed life to briefly flourish on the surface, the researchers say.
“We identified megafloods for the first time using detailed sedimentological data observed by the rover Curiosity,” said Alberto G. Fairén, a visiting astrobiologist at Cornell University.
“Early Mars was an extremely active planet from a geological point of view. The planet had the conditions needed to support the presence of liquid water on the surface – and on Earth, where there’s water, there’s life.
“So early Mars was a habitable planet. Was it inhabited? That’s a question that the next rover Perseverance … will help to answer.”
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