Novel maps from the red planet offer the strongest evidence yet of a previous climate of extended warmth and wetness on Mars, as well as a massive ancient ocean.
Was Mars, the fourth planet from the sun, always a sterile and dead world? Was Mars always this barren and lifeless? Or is there a chance that Mars was much more hospitable than we think? A few decades ago, experts would have maintained that Mars was always dry and inhospitable. However, this is not the case. Recent topography maps indicate an ancient northern ocean existed on Mars. Interestingly, the maps offer the strongest evidence yet of a previous climate of extended warmth and wetness on the planet rather than today’s harsh, frozen landscape.
A key point of emphasis in this study comes from the fact that a large ocean means that life has a greater chance of surviving, explains Benjamin Cardenas, assistant professor of geosciences at Penn State, who authored the study published recently in the Journal of Geophysical Research: Planets. “It also tells us about the ancient climate and its evolution. Scientists know that for this much liquid water to exist at once, it had to have been warm, and the atmosphere had to be thick enough. Cardenas explained that there had been long-standing questions about whether Mars had an ocean in its low-elevation northern hemisphere. Using topographic data, the team discovered hundreds of thousands of square kilometers of sedimentary accumulation, at least 900 meters thick, along an ancient shoreline approximately 3.5 billion years old.
Mars’ stratigraphy and sedimentary record
Cardenas explained the most novel part of this paper was how we analyzed Mars through its stratigraphy and sedimentary record. On Earth, sediments deposited over time provide insight into the history of waterways. “We call that stratigraphy, the idea that water transports sediment, and you can measure the changes on Earth by understanding how sediment piles up. That’s what we’ve done here — but it’s Mars,” Cardenas revealed. A team of scientists mapped data from NASA and the Mars Orbiter Laser Altimeter using software developed by the US Geological Survey. They found over 6,500 km of fluvial ridges and grouped them into 20 systems, which they believe were once part of a Martian shoreline that had been eroded.
It was possible to understand how the region’s paleogeography evolved by analyzing rock formations such as thicknesses of ridge systems, elevations, locations, and sedimentary flows. As Cardenas explains, Aeolis Dorsa contains the largest number of fluvial ridges on the planet and was once part of the ocean. In Aeolis Dorsa, the rocks tell us a lot about what the ocean was like thousands of years ago. During that time, it was dynamic. There was a significant rise in sea level. There was a rapid deposition of rocks along the basins. It was a time of great change.
Ancient life on Mars?
The stratigraphic records of Earth’s evolving climate and life can be found in ancient sedimentary basins, according to Cardenas. So it would be most logical to begin looking for life on Mars in an ocean the size of the one that once covered Aeolis Dorsa. Cardenas said one of the major missions of the Mars Curiosity rover is to search for evidence of life. It has always searched for water, for signs of habitable life. There has never been a more significant one than this. The body of water was fed by sediments originating in the highlands, which may have contained nutrients. A tide would have gently brought and drained water if tides existed on ancient Mars. A place like this is the kind of place where ancient Martian life could have emerged.
Researchers have determined that Mars has other ancient waterways that Cardenas and his colleagues have mapped. According to an upcoming study in the Journal of Sedimentary Research, several outcrops visited by the Curiosity rover are likely to be sedimentary strata from ancient river bars. In another paper published in Nature Geoscience, a method for observing stratigraphy beneath the Gulf of Mexico’s seafloor is applied to a model of Martian basin erosion. Research indicates the fluvial ridges found throughout Mars are the remains of ancient rivers eroded from large basins like Aeolis Dorsa.
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