A team of geophysicists have developed a new theory explaining how eruptions from some of the biggest volcanoes in the Solar System could have led to oceans on Mars.
Tharsis, a region in equatorial Mars stretching about 5,000 kilometers across, is home to some of the biggest volcanoes on the planet. The largest one, Olympus Mons, is about 22 kilometers high and almost two and a half times taller than Mount Everest.
A paper published in Nature on Monday ties the formation of Tharsis to the rise of oceans on Mars. Michael Manga, senior author of the paper and a professor of earth and planetary science at the University of California, Berkeley, said: “Volcanoes may be important in creating the conditions for Mars to be wet."
Over the eons the volcanoes would have helped form deep oceans on Mars. However, further eruptions altered the planet's crust to make shallower seas.
“If you took the oldest and youngest ocean and spread the water over the entire planet, the water would be at least 280 and 85 meters deep,” he explained to The Register.
Some scientists have previously opposed the idea of oceans on Mars by arguing that the polar ice caps don’t contain enough water, it has no atmosphere to keep liquid oceans, and that potential shorelines show uneven levels of water.
But in the new model, the oceans either formed earlier or at the same time as Tharsis some 3.7 billion years ago. It means that the volcanic structure would have been smaller and its crust would have been less deformed, so it wouldn’t have been able to hold as much water as previously thought.
"The assumption was that Tharsis formed quickly and early, rather than gradually, and that the oceans came later," Manga said. "We're saying that the oceans predate and accompany the lava outpourings that made Tharsis."
The volcanoes in the Tharsis region would have also ejected gases into the atmosphere to create a greenhouse effect, allowing liquid water to remain in the oceans. The eruptions could have also brought water found underground up to the surface and contributed to the development of seas.
Manga said the shorelines would have been even, as expected for a standing body of water. But as Tharsis continued to deform over time from volcanic activity, its possible that the ancient seabed depressed the land so that ocean levels dipped, changing the shoreline.
The lines in the Arabia shoreline leftover from the oldest ocean are higher than the ones in the Deuteronilus shoreline from the youngest ocean that was created after Tharsis caved in.
The model is hypothetical, and researchers will have to find more concrete evidence to back up their claims. NASA is expected to launch InSight, a lander module, to Mars later this summer. The researchers hope that the seismometer onboard will be able to detect a presence of subsurface ice leftover in its crust from an ancient ocean. ®