RIVER DELTAS AT SIMILAR ALTITUDES HINT AT AN ANCIENT OCEAN
A huge ocean may formerly have covered nearly one-third of the Martian surface two scientists from the University of Colorado at Boulder suggest.
In Nature Geoscience today, Gaetano di Achille and Bryan Hynek report how they analysed data that imply Mars was once covered by a huge ocean of water. Their evidence is a range of dry river deltas and valleys all at a similar elevation, meaning that the rivers fed into a single, great, body of water. This supports the idea that what are now the northern lowlands of Mars could have supported an ocean and therefore a water/atmosphere cycle much like Earth's.
Twenty years ago scientists scrutinising pictures of the Martian surface claimed to recognize extensive shorelines and networks of river valleys and outflow channels feeding in the same direction. Other scientists using thermal physics considered that such networks were likely carved by the workings of a complete water cycle, fuelled by an ocean of water.
So much water on Mars for many hundreds of millions of years may have helped originate, develop and sustain life forms, fossils of which could remain to be discovered by visiting space scientists. Where is the water now? How much remains on Mars? Might a useful fraction remain frozen in the subsoil?