Rivers on Mars raged for more than a billion years, according to new study

Extract from ABC News

Updated about 3 hours ago

Photo: A preserved river channel on Mars with colour overlaid to show different elevations (blue is low, yellow is high). (Supplied: NASA/JPL/University of Arizona, University of Chicago)

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Mars had large rivers of liquid water long after its atmosphere was stripped away into space billions of years ago, a new study suggests.

Key points:

• The study found evidence of an intense run-off which fed rivers for more than a billion years
• The results indicate ancient Mars rivers were wider than rivers on Earth today
• The findings challenge current understanding of the evolution of planets' climates

Researchers have previously observed the distinctive tracks of long-dead rivers criss-crossing Mars, indicating a climate which was a far cry from the dry and dusty planet we know today.
Seeking a better understanding of the evolution of Mars' climate, scientists examined photographs and elevation models of more than 200 ancient Martian riverbeds.
Their analysis found evidence for intense run-off that "was not short-lived or a local anomaly" and fed rivers for more than a billion years.

Five years on Mars

NASA's Curiosity rover has already taught us a lot, but scientists say there's more to come.

The study's results indicate that rivers on Mars were wider than Earth rivers today, for the same catchment area.
By around 3.7 billion years ago, solar winds had stripped away most of the planet's atmosphere — but the new research says the rivers flowed far longer afterwards than previously thought, occurring at hundreds of different locations on the planet.
The results are helpful for scientists who are trying to piece together the Martian climate, according to lead study author Edwin Kite, an assistant professor of geophysical sciences at the University of Chicago and an expert in both the history of Mars and climates of other worlds.
For example, the size of the rivers indicates the water was flowing continuously — so there must have been a strong greenhouse effect to keep Mars warm enough that liquid water could flow.
"You would expect them to wane gradually over time, but that's not what we see," Mr Kite said.

Photo: The study finds rivers flowed on Mars for much longer than first thought. (Reuters: NASA)

Mr Kite said it was possible the climate had some sort of "on/off" switch which tipped back and forth between dry and wet cycles.
The existence of the rivers challenges current models of planetary climate evolution.
He said the study answers some existing questions but also indicates that either climate models, atmosphere evolution models, or scientists' basic understanding of inner solar system chronology was wrong.

"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."