Mars valleys traced back to precipitation

June 28, 2018

The surface of Mars bears imprints of structures that resemble fluvial steam networks on Earth. Scientists therefore assume that there must have been once enough water on the red planet to feed water streams that incised their path into the soil. For years, however, scientists have been debating the source from which this water must have originated: was it rainwater that caused streams and rivers to swell? Or did water ice in the soil melt due to volcanic activity, and seep out to form rivers? Each of these scenarios leads to a completely different conclusion about the climatic history of the red planet.

A new study now suggests that the branching structure of the former river networks on Mars has striking similarities with terrestrial arid landscapes. This has been demonstrated in a recent paper published in Science Advances by physicist Hansjörg Seybold from the group of James Kirchner, ETH professor at the Institute for Terrestrial Ecosystems, and planetary specialist Edwin Kite from the University of Chicago.

Valleys eroded mainly by rainwater

Using statistics from all mapped river valleys on Mars, the researchers conclude that the contours still visible today must have been created by superficial run-off of (rain)water. Consequently, the influence of groundwater seepage from the soil can be excluded as a dominant process for shaping these features.

The distribution of the branching angles of the valleys on Mars is very similar to those found in arid landscapes on Earth. According to lead author Seybold, this implies that there must have been a similar hydrological environment with sporadic heavy rainfall events on Mars over a prolonged period of time and that this rainwater may have run off quickly over the surface shaping the valley networks. This is how river valleys develop in arid regions on Earth. For example, in Arizona, researchers observed the same valley network patterns in a landscape where astronauts are training for future Mars missions. Valleys in arid regions fork at a narrow angle.

The branching angles on Mars are comparatively low. Seybold therefore rules out the influence of groundwater sapping as the major channel forming process on Mars. River networks that are formed by re-emerging groundwater, as found, for example, in Florida, tend to have much wider branching angles between the two tributaries and do not match the narrow angles of streams in arid areas.

Conditions such as those found in terrestrial arid landscapes today probably prevailed on Mars for only a relatively short period about 3.6 to 3.8 billion years ago. In that period, the atmosphere on Mars may have been much denser than it is today. "Recent research shows that there must have been much more water on Mars than previously assumed," says Seybold.

Evaporation made it rain

One hypothesis suggests that the northern third of Mars was covered by an ocean at that time. Water evaporated, condensed around the high volcanoes of the highlands to the south of the ocean and led to heavy precipitation. As a result, rivers formed, which left traces that can still be observed on Mars today.

The big question is where the water has disappeared to over time. "It's likely that most of it evaporated into space. But it could still be found in the vicinity of Mars," says the physicist., " but this is a question for a future space mission".
-end-
Reference

Seybold HJ, Kite E, Kirchner JW. Branching geometry of valley networks on Mars and Earth and its implications for early Martian climate. Science Advances 2018; 4:eaar6692. DOI: 10.1126/sciadv.aar6692

ETH Zurich

Related Mars Articles from Brightsurf:

Water on ancient Mars
A meteorite that originated on Mars billions of years ago reveals details of ancient impact events on the red planet.

Surprise on Mars
NASA's InSight mission provides data from the surface of Mars.

Going nuclear on the moon and Mars
It might sound like science fiction, but scientists are preparing to build colonies on the moon and, eventually, Mars.

Mars: Where mud flows like lava
An international research team including recreated martian conditions in a low-pressure chamber to observe the flow of mud.

What's Mars made of?
Earth-based experiments on iron-sulfur alloys thought to comprise the core of Mars reveal details about the planet's seismic properties for the first time.

The seismicity of Mars
Fifteen months after the successful landing of the NASA InSight mission on Mars, first scientific analyses of ETH Zurich researchers and their partners reveal that the planet is seismically active.

Journey to the center of Mars
While InSight's seismometer has been patiently waiting for the next big marsquake to illuminate its interior and define its crust-mantle-core structure, two scientists, have built a new compositional model for Mars.

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.

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.

Read More: Mars News and Mars Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.