Precipitation explains Mars' fluvial patterns, astronomers claim

While most scientists agree on Mars' watery past, planetary scientists are less sure about where the water came from.

Some have suggested volcanic activity melted subsurface ice, forming Martian streams and rivers. But new research suggests precipitation better explains the Red Planet's fluvial patterns.

When research statistically analyzed the shapes, structures and distribution of river and stream valleys on the Martian surface, they found the patterns most resembled those found among arid landscapes on Earth.

The research -- published this week in the Astrophysical Journal -- suggests superficial runoff formed Mars' river valleys.

"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," researchers at ETH Zurich explained in a news release. "This is how river valleys develop in arid regions on Earth."

In Arizona, where astronauts are training for future manned Mars missions, scientists have observed fluvial patterns nearly identical to those found on Mars.

Fluvial patterns formed by emerging groundwater tend to have very wide branching angles, as evidenced by rivers and streams found in Florida. Martian fluvial patterns feature narrow branching angles.

The evidence that water was once abundant on Mars is overwhelming, and now, scientists have a good idea of where it came from. One main question remains, however: Where did it all go?

"It's likely that most of it evaporated into space," said physicist Hansjörg Seybold. "But it could still be found in the vicinity of Mars."