New evidence for oceans on Mars

NASA scientists have discovered new evidence that huge oceans covered much of ancient Mars, boosting the chances that there was once life.

Mars' northern plainsThe red planet is now a huge desert except for ice below ground and around its poles. But an orbiting spacecraft reveals evidence for two vast seas over a third of the planet just a few billion years ago.

One, ten times the size of the Mediterranean, covered the northern plains of Mars. The other was twice as big – around 20 times the size of the Med.

The evidence was gathered by an instrument on NASA’s Mars Odyssey probe that detects gamma rays emitted by rocks. By checking the distribution of potassium, thorium and iron, the space scientists were able to fix a likely location for shorelines marking the edges of ancient oceans.

They found a greater concentration of the elements in the lowlands and believe they were carried there from the higher lands by flowing water.

It follows other research reported last month that concluded that there was still water flowing on Mars as recently as two billion years ago. Direct evidence of water-ice just below the surface was found by NASA’s Phoenix lander in the northern plains earlier this year. The probe has now shut down after losing power.

The Gamma Ray Spectrometer, operated by William Boynton’s team at the University of Arizona’s Lunar and Planetary Laboratory, can detect elements buried more than a foot, or a third of a meter, below the martian surface.

The instrument was previously used to make the dramatic discovery in 2002 that there is abundant water-ice near the surface of Mars at high latitudes and around the poles.

Professor Victor Baker, of the University of Arizona, believes that volcanic eruptions a few million years ago unleashed floods far greater than Brazil’s Amazon River.

They filled the northern lowlands of Mars, forming seas and lakes that triggered relatively warmer and wetter conditions lasting tens of thousands of years.

Geologist James Dohm, who led the latest study, said: “We compared data on potassium, thorium and iron above and below a shoreline believed to mark an ancient ocean that covered a third of Mars’ surface, and an inner shoreline believed to mark a younger, smaller ocean.”

The latest research will be published in a special issue of the journal Planetary and Space Science.

Photo: An image of the northern plains of Mars from another probe, Mars Global Surveyor. Credit: NASA/JPL/Malin Space Science Systems.

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Paul Sutherland

Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.
Paul Sutherland

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Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.

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