A new study from The University of Texas at Austin is helping scientists piece together the ancient climate of Mars by revealing how much rainfall and snowmelt filled its lake beds and river valleys 3.5 billion to 4 billion years ago.
The study, published in the journal Geology, represents the first time that researchers have quantified the precipitation that must have been present across the planet, and it comes out as the Mars 2020 Perseverance rover is making its way to the red planet to land in one of the lake beds crucial to this new research.
The ancient climate of Mars is something of an enigma to scientists. To geologists, the existence of riverbeds and paleolakes — eons-old lake basins — paints a picture of a planet with significant rainfall or snowmelt. But scientists who specialize in computer climate models of the planet have been unable to reproduce an ancient climate with large amounts of liquid water present for long enough to account for the observed geology.
“This is extremely important because 3.5 to 4 billion years ago Mars was covered with water. It had lots of rain or snowmelt to fill those channels and lakes,” said lead author Gaia Stucky de Quay, a postdoctoral fellow at UT’s Jackson School of Geosciences. “Now it’s completely dry. We’re trying to understand how much water was there and where did it all go.”
Although scientists have found large amounts of frozen water on Mars, no significant amount of liquid water currently exists.
In the study, researchers found that precipitation must have been between 13 and 520 feet (4 to 159 meters) in a single episode to fill the lakes and, in some cases, provide enough water to overflow and breach the lake basins. Although the range is large, it can be used to help understand which climate models are accurate, Stucky de Quay said.
“It’s a huge cognitive dissonance,” she said. “Climate models have trouble accounting for that amount of liquid water at that time. It’s like, liquid water is not possible, but it happened. This is the knowledge gap that our work is trying to fill in.”
The scientists looked at 96 open-basin and closed-basin lakes and their watersheds, all thought to have formed between 3.5 billion and 4 billion years ago. Open lakes are those that have ruptured by overflowing water; closed ones, on the other hand, are intact. Using satellite images and topography, they measured lake and watershed areas, and lake volumes, and accounted for potential evaporation to figure out how much water was needed to fill the lakes.
By looking at ancient closed and open lakes, and the river valleys that fed them, the team was able to determine a minimum and maximum precipitation. The closed lakes offer a glimpse at the maximum amount of water that could have fallen in a single event without breaching the side of the lake basin. The open lakes show the minimum amount of water required to overtop the lake basin, causing the water to rupture a side and rush out.
In 13 cases, researchers discovered coupled basins — containing one closed and one open basin that were fed by the same river valleys — which offered key evidence of both maximum and minimum precipitation in one single event.
Another great unknown is how long the rainfall or snowmelt episode must have lasted: days, years or thousands of years. That’s the next step of the research, Stucky de Quay said.
As this research is published, NASA recently launched Mars 2020 Perseverance Rover to visit Jezero crater, which contains one of the open lake beds used in the study. Co-author Tim Goudge, an assistant professor in the UT Jackson School Department of Geological Sciences, was the lead scientific advocate for the landing site. He said the data collected by the crater could be significant for determining how much water was on Mars and whether there are signs of past life.
“Gaia’s study takes previously identified closed and open lake basins, but applies a clever new approach to constrain how much precipitation these lakes experienced,” Goudge said. “Not only do these results help us to refine our understanding of the ancient Mars climate, but they also will be a great resource for putting results from the Mars 2020 Perseverance Rover into a more global context.”
Reference: “Precipitation and aridity constraints from paleolakes on early Mars” by Gaia Stucky de Quay, Timothy A. Goudge and Caleb I. Fassett, 13 August 2020, Geology.
This study was supported by a grant through NASA’s Mars Data Analysis Program.
Eons ago Mar’s Moon was struck by an asteroid or comet, it crashed to the surface creating Valles Marinara. Temp dropped, rivers/lakes dried up. Life perishes or goes underground.
No, and spelling is wrong. Mars has tow extant moons (Phobos and Deimos.) And Valles Marineris seems to be caused by the mantle plume that caused the three large volcanoes next to it.
First rule of mentioning spelling mistakes, check the spelling of the same sentence: “Mars has tow extant moons” = Mars has two extant moons.
If Mars, Earth and Asteroid belt was one large planet that broke up eons ago, and reformed into what we have now, would that help explain where the missing water on both Earth and Mars went. That would also help explain our moon etc etc. If we where at one time a planet the size of Jupiter and for some reason split apart, and recondensed into the 2 planets and asteroid belt that now exist, I think that would describe the anomalies that we have on both planets and some of the mysterious items or structures found on the moon and Mars that really have no other explaintions.
But it wasn’t a break up, the different bodies – as well as among asteroids themselves – have different element compositions.
Isn’t that a centuries old idea? In any case, it dies with sampling of these bodies – for Mars, earliest with the martian meteorites that were ejected by large impacts and found here on Earth.
Also, you need to give references to “the mysterious items or structures found”. We can’t know what you mean, and there are many crackpots out there looking at images and ‘seeing’ things (i.e. rocks).
You take random samples from the earth today, different locations different depth yoh end up with different compositions, you should not be so closed minded
In the picture, we can clearly see that there are craters from asteroids. This can explain the ‘lake’ pictures. The impact of the asteroid must have created the lake. We can infer this because Mars’s atmosphere is not as dense as Earth’s. This means that the ‘lake’ must have come from an asteroid. This might have caused Earth to have water.
Good idea, well described!
But on the other hand, why would a meteorite have so much water? Asteroid belt chondrites are on average 10 % water by mass, c.f. how the inner system like Earth is just 0.05 % water by mass (but still, large oceans).
I think geologists see that Mars has had plenty water, especially early on before the atmosphere was lost, so did not need extraneous sources. The source of inner planet water is still an open question though [ https://en.wikipedia.org/wiki/Origin_of_water_on_Earth ]. “It was long thought that Earth’s water did not originate from the planet’s region of the protoplanetary disk. Instead, it was hypothesized water and other volatiles must have been delivered to Earth from the outer Solar System later in its history. Recent research, however, indicates that hydrogen inside the Earth played a role in the formation of the ocean. The two ideas are not mutually exclusive, as there is also evidence water was delivered to Earth by impacts from icy planetesimals similar in composition to asteroids in the outer edges of the asteroid belt.”
I did not give a scale or volume reference: “why would a meteorite have so much water?”
Hypervelocity impactors, those that hit with typical orbital speeds (large and/or thin atmosphere as here) which is about 10 times or more higher than the sound velocity in rock and so generates shock waves, typically gouge a crater 20 times the diameter of the object and often as deep as it.