Nav: Home

Rivers raged on Mars late into its history

March 27, 2019

Long ago on Mars, water carved deep riverbeds into the planet's surface--but we still don't know what kind of weather fed them. Scientists aren't sure, because their understanding of the Martian climate billions of years ago remains incomplete.

A new study by University of Chicago scientists catalogued these rivers to conclude that significant river runoff persisted on Mars later into its history than previously thought. According to the study, published March 27 in Science Advances, the runoff was intense--rivers on Mars were wider than those on Earth today--and occurred at hundreds of locations on the red planet.

This complicates the picture for scientists trying to model the ancient Martian climate, said lead study author Edwin Kite, assistant professor of geophysical sciences and an expert in both the history of Mars and climates of other worlds. "It's already hard to explain rivers or lakes based on the information we have," he said. "This makes a difficult problem even more difficult."

But, he said, the constraints could be useful in winnowing the many theories researchers have proposed to explain the climate.

Mars is crisscrossed with the distinctive tracks of long-dead rivers. NASA's spacecraft have taken photos of hundreds of these rivers from orbit, and when the Mars rover Curiosity landed in 2012, it sent back images of pebbles that were rounded--tumbled for a long time in the bottom of a river.

It's a puzzle why ancient Mars had liquid water. Mars has an extremely thin atmosphere today, and early in the planet's history, it was also only receiving a third of the sunlight of present-day Earth, which shouldn't be enough heat to maintain liquid water "Indeed, even on ancient Mars, when it was wet enough for rivers some of the time, the rest of the data looks like Mars was extremely cold and dry most of the time," Kite said.

Seeking a better understanding of Martian precipitation, Kite and his colleagues analyzed photographs and elevation models for more than 200 ancient Martian riverbeds spanning over a billion years. These riverbeds are a rich source of clues about the water running through them and the climate that produced it. For example, the width and steepness of the riverbeds and the size of the gravel tell scientists about the force of the water flow, and the quantity of the gravel constrains the volume of water coming through.

Their analysis shows clear evidence for persistent, strong runoff that occurred well into the last stage of the wet climate, Kite said.

The results provide guidance for those trying to reconstruct the Martian climate, Kite said. For example, the size of the rivers implies the water was flowing continuously, not just at high noon, so climate modelers need to account for a strong greenhouse effect to keep the planet warm enough for average daytime temperatures above the freezing point of water.

The rivers also show strong flow up to the last geological minute before the wet climate dries up. "You would expect them to wane gradually over time, but that's not what we see," Kite said. The rivers get shorter--hundreds of kilometers rather than thousands--but discharge is still strong. "The wettest day of the year is still very wet."

It's possible the climate had a sort of "on/off" switch, Kite speculated, which tipped back and forth between dry and wet cycles.

"Our work answers some existing questions but raises a new one. Which is wrong: the climate models, the atmosphere evolution models, or our basic understanding of inner solar system chronology?" he said.
UChicago Planetary GIS/Data Specialist David Mayer, now at the United States Geologic Survey Astrogeology Program, and then-visiting student Gaia Stucky de Quay from Imperial College London, co-authored the study, as well as scientists with the Smithsonian Institution, the Natural History Museum in London and the Centre National de la Recherche Scientifique in Paris. The study used University of Chicago Research Computing Center resources.

University of Chicago

Related Mars Articles:

Getting mac and cheese to Mars
Washington State University scientists have developed a way to triple the shelf life of ready-to-eat macaroni and cheese, a development that could have benefits for everything from space travel to military use.
A material way to make Mars habitable
New research suggest that regions of the Martian surface could be made habitable with a material -- silica aerogel -- that mimics Earth's atmospheric greenhouse effect.
Life on Mars?
Researchers from Hungary have discovered embedded organic material in a Martian meteorite found in the late 1970s.
New evidence of deep groundwater on Mars
Researchers at the USC Arid Climate and Water Research Center (AWARE) have published a study that suggests deep groundwater could still be active on Mars and could originate surface streams in some near-equatorial areas on Mars.
Why we won't get to Mars without teamwork
If humanity hopes to make it to Mars anytime soon, we need to understand not just technology, but the psychological dynamic of a small group of astronauts trapped in a confined space for months with no escape, according to a paper published in American Psychologist, the flagship journal of the American Psychological Association.
Mars: Not as dry as it seems
Two new Oxford University papers have shed light on why there is no life on Mars.
More evidence of water on Mars
River deposits exist across the surface of Mars and record a surface environment from over 3.5 billion years ago that was able to support liquid water at the surface.
How hard did it rain on Mars?
Heavy rain on Mars reshaped the planet's impact craters and carved out river-like channels in its surface billions of years ago, according to a new study published in Icarus.
Does Mars have rings? Not right now, but maybe one day
Purdue researchers developed a model that suggests that debris that was pushed into space from an asteroid or other body slamming into Mars around 4.3 billion years ago and alternates between becoming a planetary ring and clumping up to form a moon.
Digging deeper into Mars
Scientists continue to unravel the mystery of life on Mars by investigating evidence of water in the planet's soil.
More Mars News and Mars Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.