Did Mars Once Have an Ocean? New Research Suggests Yes

Billions of years in the past, water flowed throughout Mars. Most scientists agree the pink planet had rivers. But did these rivers movement into an ocean? New analysis from the University of Arkansas discovered sturdy proof in Mars’ geology of an ocean within the planet’s northern hemisphere.

“We don’t know of any lifeforms on Earth, or anywhere in the universe, that don’t require liquid water. So the more liquid water we have on Mars, a simple argument could be made that you have a higher chance of life,” mentioned Cory Hughes, a U of A geosciences Ph.D. pupil and the research’s lead writer.

To higher perceive the geology of Mars’ historical rivers, the researchers in contrast river rocks on Earth to rocks on Mars, together with sandstone created by a river that flowed throughout Northwest Arkansas 300 million years in the past.

Hughes studied Mars extensively earlier than coming to Arkansas. He determined to pursue a Ph.D. on the U of A so he might work with John Shaw, affiliate professor of geosciences and an professional on Earth’s deltas. By studying extra about our planet, Hughes might higher perceive Mars.

The outcomes have been published within the journal Geophysical Research Letters.

HOW RIVERS FLOW

Imagine a river with no human-built levees to constrain its course. The river would shift continuously, like a ribbon snaking throughout the panorama. Rivers carry sediment, or strong materials like silt, clay and rocks. The sediment eats away at one aspect, inflicting the river to curve in that path, whereas depositing sand and tremendous filth on the other aspect.

The area that defines how far a river shifts backward and forward over time is named the channel belt.

A river slows down because it approaches an ocean — an enormous, comparatively nonetheless physique of water. As a river’s movement velocity decreases, it will possibly carry much less sediment. The strong matter begins to fall out of suspension, making a river delta. And with much less sediment to erode its banks, the river’s motion from side-to-side decreases. In different phrases, the channel belt narrows as a river approaches an ocean.

This part the place the channel belt narrows, and the riverbed drops under sea degree, is named the backwater zone.

The backwater zone of a river flowing into an ocean is lengthy. In the case of the Mississippi River, for instance, the backwater zone begins close to Baton Rouge, 230 miles from the shoreline.

Looking at Mars from orbit, Hughes discovered geological proof of historical river backwater zones.

“This is a large-scale process taking place, which is why we’re able to see it from space on Mars,” Hughes mentioned.

The presence of deltas with lengthy backwater zones offers sturdy proof that enormous rivers as soon as flowed on Mars and emptied into an ocean earlier than the floor of the planet dried up billions of years in the past.

“These are very mature deltas,” Hughes mentioned. “This is a strong point in favor of an ancient ocean, or at the very least a large sea.”

ANCIENT HISTORY REVEALED

How can scientists know the contours of a river that dried up billions of years in the past?

As rivers movement, gravity pulls the coarsest grain to the underside of the riverbed. If the river finally dries up, that coarse sediment is buried. Over time, because of warmth and strain, the sediment turns into sandstone.

On Earth, shifting tectonic plates will push that rock to the floor, after which wind and rain will erode every thing however the coarse channel mattress, abandoning a ridge the place a channel was. This course of is called topographic inversion. When a ridge prime is comprised of sandstone that was on the backside of a river, it’s referred to as an inverted channel belt or an inverted ridge.

Mars doesn’t have tectonic plates, so its inverted ridges have been probably fashioned when finer deposits across the sandstone eroded. Those inverted ridges present the proof of long-vanished rivers.

Not lengthy after Hughes arrived, Shaw invited him to go to the Wedington Sandstone, a rock formation discovered throughout Northwest Arkansas. The two realized the stone cliffs have been a part of a branching community of inverted ridges fashioned by a 300-million-year-old river that when ran from modern-day Indiana to a sea that coated central Arkansas.

Scientists have identified in regards to the means of topographic inversion for 30 to 40 years. But in Northwest Arkansas, Hughes and Shaw found the one identified instance of an inverted river delta on planet Earth.

“I literally came here to study this without knowing it was in the backyard,” Hughes mentioned. “No better word can describe that besides serendipity.”

Stratigraphic Evidence of Backwater Morphodynamics and Lowland River Deltas in the Northern Hemisphere of Mars, Geophysical Research Letters (open entry)

Astrobiology