University of California, Berkeley | 2018 Mar 19
A new scenario seeking to explain how Mars’ putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million years earlier and were not as deep as once thought.The early ocean known as Arabia (left, blue) would have looked like this when it formed
4 billion years ago on Mars, while the Deuteronilus ocean, about 3.6 billion years old,
had a smaller shoreline. Both coexisted with the massive volcanic province Tharsis,
located on the unseen side of the planet, which may have helped support the existence
of liquid water. The water is now gone, perhaps frozen underground and partially lost
to space, while the ancient seabed is known as the northern plains.
Credit: Robert Citron images, UC Berkeley.
The proposal by geophysicists at the University of California, Berkeley, links the existence of oceans early in Mars history to the rise of the solar system’s largest volcanic system, Tharsis, and highlights the key role played by global warming in allowing liquid water to exist on Mars. ...
Those claiming that Mars never had oceans of liquid water often point to the fact that estimates of the size of the oceans don’t jibe with estimates of how much water could be hidden today as permafrost underground and how much could have escaped into space. These are the main options, given that the polar ice caps don’t contain enough water to fill an ocean.
The new model proposes that the oceans formed before or at the same time as Mars’ largest volcanic feature, Tharsis, instead of after Tharsis formed 3.7 billion years ago. Because Tharsis was smaller at that time, it did not distort the planet as much as it did later, in particular the plains that cover most of the northern hemisphere and are the presumed ancient seabed. The absence of crustal deformation from Tharsis means the seas would have been shallower, holding about half the water of earlier estimates. ...
Timing of Oceans on Mars from Shoreline Deformation - Robert I. Citron, Michael Manga, Douglas J. Hemingway
- Nature (online 19 Mar 2018) DOI: 10.1038/nature26144