You’re an anaerobic microbe sunbathing on a Martian beach billions of years ago listening to the small waves hit the shoreline as you take in the perchlorates in the Martian regolith. This is because while Mars is warm and wet, it still lacks sufficient oxygen, so anaerobic life like yourself doesn’t need oxygen to survive. You’re chilling for several hours and eventually notice the water hasn’t touched you. You remember over-hearing some otherworldly fellows who briefly landed and discussed the landscape didn’t look well formed, so they left.
Anaerobic microbes may or may not have existed on Mars billions of years ago (the “otherworldly fellows” might have, though), but scientists have strong evidence that flowing liquid water existed on the surface of ancient Mars. However, there’s been a longstanding debate regarding whether tides helped shape the landscape in Gale Crater and Utopia Planitia, which have been explored by NASA’s Curiosity Rover and China’s Zhurong Rover, respectively. The findings were recently published in the Journal of Geophysical Research: Planets and could provide key insights into how tides played a role in landscape formation on ancient Mars billions of years ago. While Gale Crater is hypothesized to have been a lake on ancient Mars, Utopia Planitia is hypothesized to have been a vast ocean during that time.
For the study, the researchers used a series of computer models to simulate the speed and movement of tides on ancient Mars to ascertain if they could be responsible for depositing sedimentary rocks previously observed by the aforementioned rovers. This is because tides on Earth are responsible for sustaining life and climate regulation through driving ocean currents, resulting in circulating vital nutrients and mixing oxygen in deep ocean waters.
In the end, and after incorporating the one-third gravity of Mars, the researchers found that the maximum tide speed at both rover locations, which are located on vastly different locations on the Red Planet, was calculated to be approximately 0.01 meters per second (0.03 feet per second). For context, the tide speeds on Earth vary on location. For example, the open ocean is estimated to have tides as fast as 0.05 meters per second (0.16 feet per second), whereas coastlines can experience tidal speeds between 0.5-1.0 meters per second (1.64-3.28 feet per second).
The study notes, “Our research suggests that tides should rarely be considered a primary factor when analyzing sedimentary structures on Mars in the future. They may be considered a secondary driver of sediment suspension and transport, but the sediment transport capacity of Martian tides was too small across most of the ocean and coastal areas for it to be considered a primary driver of sediment transport. However, there are uncertainties that should be considered when interpreting these results, especially around the size of an ancient Martian ocean.”
Tides on Earth are possible from the gravitational influence between the Earth and the Moon, as both are tidally locked, which is why the Moon always has one side facing the Earth. This ultimately comes down to the Moon being a large enough companion to exert this gravitational tug-of-war being approximately one-quarter the diameter of the Earth. In contrast, while Mars has two moons, Phobos and Deimos, they are both far too small to exert any significant gravitational influence on Mars. Phobos is approximately 300 times smaller than Mars with Deimos being even smaller. Therefore, Mars relies on what’s known as solar tides, which is when the Sun’s gravitational influence is exerted on a planetary body. Solar tides are experienced on Earth when the Earth, Moon, and Sun are aligned (spring tides), or when the Moon is at a 90-degree angle relative to the Earth and Sun (neap tides).
What new insight into tides on ancient Mars will researchers make in the coming years and decades?
As always, keep doing science & keep looking up!
