“Great Lakes of the Red Planet” –One a Potential Landing Site for NASAs 2020 Mars Mission

 

 

Jezero Crater, a potential landing site for NASA’s Mars 2020 rover mission to look for signs of past life, is one of 24 paleolakes that held vast amounts of water across the Red Planet featured in a new study by NASA scientists and University of Texas researchers. The mission is designed to search for evidence of possible ancient life on Mars and to gather and store geological samples that a future NASA mission could one day bring back to Earth laboratories.

NASA is prepared to announce which of four final contenders it has selected as the landing site for its Mars 2020 rover, which is due to touch down on the Red Planet in 2021, and we’ll all find out more on Monday (Nov. 19) via live stream on NASA TV.

 

 

Today, most of the water on Mars is locked away in frozen ice caps. But billions of years ago it flowed freely across the surface, forming rushing rivers that emptied into craters, forming lakes and seas. New research led by The University of Texas at Austin has found evidence that sometimes the lakes would take on so much water that they overflowed and burst from the sides of their basins, creating catastrophic floods that carved canyons very rapidly, perhaps in a matter of weeks.

A false-color topographic map (blue marks low elevations) at the top of the page shows the area around Jezero Crater. Flowing water would have gathered any biologic or organic material from a wide area and deposited it at the crater, making it a logical landing site for the Mars rover mission.

The findings suggest that catastrophic geologic processes may have had a major role in shaping the landscape of Mars and other worlds without plate tectonics, said lead author Tim Goudge, a postdoctoral researcher at the UT Jackson School of Geosciences who will be starting as an assistant professor at the school in 2019.

“These breached lakes are fairly common and some of them are quite large, some as large as the Caspian Sea,” said Goudge. “So we think this style of catastrophic overflow flooding and rapid incision of outlet canyons was probably quite important on early Mars’ surface.”

The research was published Nov. 16 in the journal Geology. Co-authors include NASA scientist Caleb Fassett and Jackson School Professor and Associate Dean of Research David Mohrig.

From studying rock formations from satellite images, scientists know that hundreds of craters across the surface of Mars were once filled with water. More than 200 of these “paleolakes” have outlet canyons tens to hundreds of kilometers long and several kilometers wide carved by water flowing from the ancient lakes.

However, until this study, it was unknown whether the canyons were gradually carved over millions of years or carved rapidly by single floods.

Using high-resolution photos taken by NASA’s Mars Reconnaissance Orbiter satellite, the researchers examined the topography of the outlets and the crater rims and found a correlation between the size of the outlet and the volume of water expected to be released during a large flooding event. If the outlet had instead been gradually whittled away over time, the relationship between water volume and outlet size likely wouldn’t hold, Goudge said.

In total, the researchers examined 24 paleolakes and their outlet canyons across the Red Planet. One of the paleolakes examined in the study, Jezero Crater, is a potential landing site for NASA’s Mars 2020 rover mission to look for signs of past life. Goudge and Fassett proposed the crater as a landing site based on prior studies that found it held water for long periods in Mars’ past.

The ancient lake at the Jezero crater was first identified in 2005 by Fassett, then a professor at Mount Holyoke College. Fassett identified two channels on the northern and western sides of the crater that appear to have supplied it with water. That water eventually overtopped the crater wall on the southern side and flowed out through a third large channel. It’s not clear how long the system was active, but seems to have dried out around 3.5 to 3.8 billion years ago.

 

While massive floods flowing from Martian craters might sound like a scene in a science fiction novel, a similar process occurs on Earth when lakes dammed by glaciers break through their icy barriers. The researchers found that the similarity is more than superficial. As long as gravity is accounted for, floods create outlets with similar shapes whether on Earth or Mars.

“This tells us that things that are different between the planets are not as important as the basic physics of the overflow process and the size of the basin,” Goudge said. “You can learn more about this process by comparing different planets as opposed to just thinking about what’s occurring on Earth or what’s occurring on Mars.”

It’s clear that Mars was once much wetter than it is now, but it’s not clear that the Martian climate was warm enough to sustain liquid water at the surface for long periods. Some researchers have suggested that if the early Martian climate was cold, chemical alteration on Mars may have been driven largely by water percolating in the warmer subsurface crust. That period of subsurface activity was followed some time later by pulses of water on the surface — potentially sourced by either snowmelt or rainfall — during transient periods of warm temperatures. That second round of events was largely responsible for the mechanical erosion on the Martian surface.

The events at Jezero seem to be consistent with that idea, the researchers say. The fact that Jezero crater records the history of two separate water events makes it an interesting target for future study. In fact, Jezero is high on scientists’ list of possible landing sites for NASA’s Mars 2020 rover. If life had emerged in either of the two water-related events, signs of it may well have been preserved at Jezero.

“River and lake deposits on Earth are some of the best preservers of biologic signatures,” Goudge said. “At Jezero, you’re gathering all this material from this huge watershed and dumping into one place. So if there perhaps was any biologic or organic material in the watershed, you might have transported some of that to the basin.”

Although big floods on Mars and Earth are governed by the same mechanics, they fit into different geological paradigms. On Earth, the slow-and-steady motion of tectonic plates dramatically changes the planet’s surface over millions of years. In contrast, the lack of plate tectonics on Mars means that cataclysmic events — like floods and asteroid impacts — quickly create changes that can amount to near permanent changes in the landscape.

“The landscape on Earth doesn’t preserve large lakes for a very long time,” Fassett said. “But on Mars … these canyons have been there for 3.7 billion years, a very long time, and it gives us insight into what the deep time surface water was like on Mars.”

The image at the top of the page shows Jezero crater, a paleolake and potential landing site for NASA’s Mars 2020 rover mission to look for past life. The outlet canyon carved by overflow flooding is visible in the upper right side of the crater. Ancient rivers carved the inlets on the right side of the crater. NASA Tim Goudge

The Daily Galaxy via University of Texas at Austin and Brown University

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