The Latest from Mars: Dried up Riverbed May Have Flowed into an Ancient Ocean

by Shannon Hall on July 22, 2013

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An artist's rendition of what water on Mars may have looked like. Source Credit: NASA

An artist’s rendition of what water on Mars may have looked like. Image Credit: NASA

When it comes to Mars, the hot topic of study is water – a prerequisite for life.

While liquid water is currently not stable on the surface of Mars, there is extensive evidence that it may have been in the past. Astronomers have discovered dried up riverbeds, lake deltas, and evidence of widespread glaciers – to name but a few examples.

However, evidence for a massive standing body of water, such as an ocean, is hard to come by. Early climate models struggle to create circumstances under which liquid water would be stable at all. Nonetheless, an ocean spanning the northern lowlands (approximately one third of the planet) has been long hypothesized.

Scientists at Caltech may have just now confirmed this long-held hope in finding recent evidence for a vast Martian ocean.

The region under investigation is known as Aeolis Dorsa – a plain located at the border between the northern lowlands and the southern highlands. This plain contains many ridges, which are interpreted as ancient river channels.

“These ‘inverted’ channels are now elevated because the coarse sand and gravel carried by the channels is more resistant to erosion than the surrounding mud and silt making up the floodplain material,” Dr. Roman DiBiase, lead author on the study, told Universe Today.

Satellite images of Aeolis Dorsa were collected using the HiRISE camera aboard the Mars Reconnaissance Orbiter.  The resolution was so precise scientists could distinguish features as small as 25 centimeters – an impressive feat even when compared to images of the Earth.

For certain locations “repeat pictures taken with a slight offset enable the creation of stereo-images from which we can determine the relative elevations of features on the planet’s surface,” explains DiBiase. This impressive technique led to high-resolution topographic models, allowing the team to analyze the geometry and patterns of these inverted channels in unprecedented detail.

Not only do the channels spread out toward the end, they also slope steeply downward, forming a delta – a sedimentary deposit that forms where rivers flow into lakes or oceans.

While deltas have been identified on Mars before, all lie within distinct topographic boundaries, such as an impact crater. This is the most compelling evidence for a delta leading into an unconfined region – an ocean.

Final proof of a Martian ocean will advance our knowledge of the intricate interplay between water, climate, and life. “The history of water on Mars has implications not only for the evolution of Martian climate, but also for learning about the early evolution of Earth and Earth’s climate,” explains DiBiase.

As always, further research is needed. Perhaps in the nearby future the Mars Reconnaissance Orbiter and Curiosity will compliment each other quite well – the orbiter taking images from above while Curiosity plays in the dirt, gathering samples in the riverbed.

The study was published in the Journal of Geophysical Research and may be found here.

About 

Shannon Hall is an aspiring science journalist and is an editorial intern at Sky & Telescope magazine. She holds two bachelor's degrees from Whitman College in astrophysics and philosophy, and recently received her master's degree in astrophysics from the University of Wyoming.

torque xtr July 22, 2013 at 3:42 PM

a driller with a microscope and isotope analyser to the shoreline is the mission that certainly will find much…

Or, a scooping probe to one of those deltas…

IVAN3MAN_AT_LARGE July 22, 2013 at 10:51 PM

Yo Shannon, that link at the end of your article leads to “404 Not Found”.

Never fear, Ivan’s here; the research paper can be found here.

Grimbold July 23, 2013 at 12:44 AM

A lander at Hellas Planitia would be awesome too. If Mars ever had an ocean, HP would have been a vast inland sea. As it is, it has the lowest elevations and therefore the highest atmospheric pressures, and perhaps these are high enough that on a hot summer day there can be liquid water there even today.

Jeffrey Scott Boerst July 23, 2013 at 9:57 AM

An ex-girlfriend of mine once had a scooping probe on one of her deltas…. never saw the woman again…

Torbjörn Larsson July 23, 2013 at 10:36 AM

It will be interesting to see how the climate evolution of Mars shakes down, especially after Maven (en route) and ExoMars (2016) has explored it.

The paper hypothesize [p 1300] that the Aeolis Dorsa delta deposits are coeval with deposits that have been crater count dated to Noachian times, ~ 4.1 – 3.7 Ga bp [ http://en.wikipedia.org/wiki/Noachian ].

That is possible according to a preliminary interpretation of isotope observations by Curiosity correlated with martian meteorites recently presented at the 44th Lunar and Planetary Science Conference. To predict the martian meteorites isotopes that constrains to little change over geological times on certain volatile elements, consistent with models predicting the atmospheric isotopes that constrains to early catastrophic loss, they suggest that very little original atmosphere survived accretion and outgassing past 4 Ga, or roughly the early Noachian @ ~ 4.1 – 3.9 Ga bp:

“If the escape modeling is correct, minor gases like N, Ne, and Ar were totally removed following atmospheric collapse near 4 Ga and then replaced by later outgassing of the martian interior.”

That leaves, arguably, time enough for life to arise, in an environment that, arguably, contained an ocean amenable for that. On Earth, sterilized by the Theia & Tellus late accretion event @ ~ 4.5 – 4.4 Ga bp, trace fossils are now first observed in the 3.9 – 3.8 Ga bp Isau BIFs, meaning life took less than ~ 0.5 – 0.7 Ga to appear.

Whether life advanced enough to populate crustal refugia is an open question, but odds are it did.

lcrowell July 23, 2013 at 3:11 PM

Planetary geology is pretty far from my area of study. It is my conjecture that this sea was probably similar to an epi-cretonic sea such as the Mediterranean Sea. I had thought for some time that Valles Marineris was some early small tectonic-like formation on Mars. It almost looks like some sort of rift valley that suggests some halted evolution for tectonic activity. However, I remember reading something about this which refuted that hypothesis.

LC

Aqua4U July 23, 2013 at 4:51 PM

Mars.. is so very interesting. I’ll wager that we will eventually find definitive proof that those oceans held primitive life. And I’ll also wager that MUCH of what we see and have assumed was caused by flowing waters was instead caused by dust, dirt and pebbles held/suspended in a state of liquifaction during planet wide ‘dust’ storms. “Blueberries” appear to have been created when impact and or volcanic related heat percolated soils, then again there are other rounded B-B’s which appear to have been created by erosional tumbling. Also notable is the ubiquitous ’rounded off’ appearance of practically ALL of the rock faces, which for lack of a better term appear to have been ‘sand blasted’….

For all practical porpoises, Mars looks like an aged and out-gassed gigantic cometary body!

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