Flyover of Mars crater shows details of an ancient lake

Scientists at the European Space Agency, in conjunction with NASA, have created a realistic computer simulation that takes you on a flight over what was once a lake on Mars. 

Since 2004, the ESA's Mars Express spacecraft has been orbiting Mars and mapping the surface in high-resolution detail. So far, about 90 per cent of the planet has been covered. These images have been combined with images from NASA's Mars Reconnaissance Orbiter to produce 3D terrain maps that allow you to fly over real Martian landscapes as though you are really there.

Space scientists use maps like these to choose the landing sites for rovers that are sent to Mars. This particular site is Jezero Crater, a 45-kilometre-wide circular depression with features indicating that it was a lake about three billion years ago.

Back then Mars had a thicker atmosphere and warmer temperatures so liquid water could exist on the surface. The images provide an overview of the entire area, including meandering river channels that once fed water into and out of the lake. 

The image is so clear, you can almost hear the sound of rushing water and waves lapping against the shoreline. This is not the first time channels have been seen on Mars, but it is a clear indication of how significant quantities of water moved on the surface of our neighbouring planet in the distant past.

This was the reason that Jezero Crater was chosen as the landing site of NASA's Perseverance rover, which touched down on the crater floor in 2021. The rover has been taking samples from what looks like a delta formed by the river that flowed into the basin. These samples will be returned to Earth by a joint ESA Nasa mission in the 2030s to look for signs of life.

Looking down on what is now a cold, dry desert shows how dramatically climate change can affect a planet. If you placed a glass of water in Jezero Crater today, it would instantly boil away — even though the temperature is below freezing. That's because Mars has lost most of its atmosphere since those warm wet days, and there is no longer enough air pressure to keep water in liquid form.

There is a possibility of some liquid water underground or beneath the polar ice, but the only water you will find on Mars today is in permafrost or at the polar ice caps.

As the United Nations warns about fresh water shortages on Earth this week at the Water Conference in New York, there is a need for better water management on this planet, including across borders to ensure a healthy supply for all. 

The Earth is not so much losing water; rather, the proportion of freshwater to salt and ice is changing. Since the last ice age, polar caps and glaciers — a major source of fresh water — have shrunk dramatically. As temperatures rise and droughts become more common, more fresh water is lost and becomes salty in the oceans.

Mars stands as a stark reminder that fresh water can disappear from the surface of a planet over long time scales. We have an obligation to protect our most precious resource while life on this planet still thrives.