The formation of an enormous volcanic mass on Mars called Tharsis may help explain the discrepancy in Mars’ shoreline elevation, according to a study published Monday by UC Berkeley researchers.
When a body of water forms, its accompanying shorelines should be flat, according to Michael Manga, co-author of the study, campus professor of earth and planetary science and director of the Center for Integrative Planetary Science. The shorelines on Mars today, however, vary in height by several kilometers, a fact that some have used to dispute the idea that the shorelines are in fact shorelines.
The study offers a solution by suggesting that Tharsis created such a large bulge on the surface of Mars that it distorted the shape of the entire planet, including shorelines that were once level.
Douglas Hemingway, co-author of the study and campus postdoctoral fellow, compared the shell of Mars to an elastic ball.
“If you push on the elastic ball, it creates a bulge outside where you’re pushing (and) can change the shape of the shoreline even away from where Tharsis is,” Hemingway said.
Another solution offered by an earlier study tried to explain the discrepancy in shoreline elevation. A 2007 paper co-authored by Manga suggested that true polar wander, or a change in the spin axis of a planet, explained the differences. Later evidence showed that there was only a true polar wander of about 20 degrees, suggesting that the effect of the phenomenon was smaller than believed.
Hemingway notes that true polar wander is still a factor, but the new study hypothesizes that the formation of Tharsis plays a larger role in altering shoreline heights. According to Hemingway, the study’s model suggests that about 80 percent of Tharsis formed after the early ocean known as Arabia formed. This model would suggest it formed about 4 billion years ago, which provides a timestamp for the history of large bodies of water on Mars.
If these shorelines did in fact correspond to oceans, they may not have been “stable,” according to Robert Citron, lead author of the study and campus graduate student in planetary science.
“Climate models (predicted) a cold Mars, too cold to support an ocean,” Citron said. “So the oceans could instead have potentially formed intermittently during periods … of volcanic growth.”
Hemingway said part of the significance of the study is that it provides a link between volcanic activity and the appearance of water on Mars. He believes this is useful in understanding the history of water on Mars and, by extension, Mars’ climate and habitability.
This May, NASA will launch another mission to Mars called InSight, which could provide more answers to questions about Mars’ shorelines and the existence of water. The lander will use a seismometer to record waves produced by marsquakes and create an image of the interior of Mars, and maybe even find frozen or liquid water under the surface.
“I think it’s pretty amazing with these sort of remote observations (that) we can say something about the timing and history of water on a planet,” Hemingway said.