How Groundwater Shaped Mars

Scientists
think a
massive ocean once covered one-third of Mars, and recent photographs
suggest that pockets of water may still be hidden beneath the planet's surface.
Water is crucial for life as we know it, so signs of underground water now —
and more extensive amounts of water in the past — both suggest Mars was or
might still be habitable, at least to microorganisms.

Postma said
such reservoirs of water probably carved out canyons, rapidly depositing
step-like layers of sediment in Martian impact craters across the planet.

"When we examined photographs
of Mars, we saw that some deltas had steps of material," Postma told SPACE.com.
He noted that such formations are seen on Earth only where water rapidly
deposits delta sediment, such as parts of the Sahara Desert's Lake Chad.

"Based
on our models, these structures might have been caused by catastrophic events
that filled the craters in one go," he said. Instead of taking millions of
years to form, Postma said the fans probably formed in decades.

Ancient
torrents of water spilling out of Martian ground with the output of the
Mississippi River, for example, could have formed some of the dozen step-like
sediment fans the researchers observed in about 13 years.

"Another
puzzling feature is that you don't see a drainage network along the crater's
side," Postma said — yet another clue that fans' formations were rapid and
not the product of rainy runoff. "Craters are thought to be very porous,
so the water can sink through. Another possibility is that the water just
evaporated into the Martian atmosphere."