“For years, many scientists had thought that plate tectonics existed nowhere in our solar system but on Earth. Now, a UCLA scientist has discovered that the geological phenomenon, which involves the movement of huge crustal plates beneath a planet’s surface, also exists on Mars.”
View of central segment of Mars’ Valles Marineris, in which an older circular basin created by an impact is offset for about 93 miles (150 kilometers) by a fault. (Credit: Image from Google Mars created by MOLA Science Team)
I’ve been seeing stuff about this all day. And if I’m honest, I’m not convinced. Not by a long shot.
The idea that there was once plate tectonics on mars does make some amount of sense: its hard for there to be volcanoes such as Olympus Mons if there was not mantle pluming etc, but I don’t think their evidence is sound.
One plate boundary with 150km of sinistral displacement on the whole of the planet doesn’t point towards a system of plate tectonics.
How would stress be relieved further down the line? There isn’t any evidence for subduction or spreading, so how does the stress of a tectonic system become equilibrated? And the idea of the plates being ‘buried’ is tenuous to say the least.
As I say, I’m not trying to say they’re idea is wrong, but I think more work needs to be done.
Especially before people get too excited without thinking about it in an critical way…
This research has already been sensationalised far beyond what it deserves, since when has the research of a single author, already criticised by his own students and with such limited lines of evidence been deserving of the term ‘discovery’. Be good to see some response papers in the coming months, as well as the authors promised follow up paper to address some of the remaining questions.
To follow the points above though, I’m going to post a few of my own thoughts on this discussion.
The volcanism on Mars is often attributed to a combination of mantle pluming (or hot spots), and crustal melting triggered by impacts. Mantle plumes relation to plate tectonics is debatable, so whether it can be considered an active (or previously active process) on Mars without allowing the possibility of tectonics isn’t clear. I personally feel that pluming and plate tectonics are inherently linked (that’s another whole discussion I won’t go into), at least on Earth and can see no good reason why this shouldn’t be the case on Mars, considering the similar starting chondritic composition of both planets. There is some good evidence of plume related volcanism, huge >1000km lava flows though these show a surface morphology more similar to portions of the 1783 Laki eruption than the larger Continental Flood Basalt deposits on Earth (Thordarson et al 2000). The volcanism is generally basaltic but the lower atmospheric pressure of Mars allows it to develop into Plinian type volcanoes, which are generally rare on Earth for this viscous magma type. (Carr, 2006) Lower gravity allows larger magma chambers to develop and eruptions of Mars are generally of a scale vastly in excess of what we see on Earth. This might negate the need for intense hot spots (mantle plumes) to ascribe to the formation of the larger flood lavas, and therefore no need for tectonic processes.
Yin’s paper identifies only the one active tectonic boundary (pictured above) and suggests that it is likely there is only the two plates on Mars. He also identifies the likelihood that linear chains of volcanoes observed on the Martian surface can be attributed to tectonic processes (similar to continental and ocean island arcs on Earth). These are formed on Earth above subducting slabs where the dehydration and release of volatiles from the downgoing crustal slab encourages melting of the surrounding mantle and produces volcanic activity in an arc usually about 110km above the subducting slab. So whilst this might seem to provide more evidence for tectonics, if it is to follow an earthlike process then there needs to be active subduction to supply these volcanic arcs. And to maintain a crustal balance, there needs to be some process of crustal generation – seafloor spreading ridges here on Earth. To attribute the discovery of this whole suite of tectonic processes to an apparent 150km displacement on a single “fault” is quite a remarkable stretch, though the author has considered this problem: “maybe Mars has a different form of plate tectonics,” Yin said.
Overall it is an interesting piece of research, rather undeserving of the attention in its current state. It’s a shame that once again a minor publication has been blown well out of proportion in the media before any serious discussion can be made on its reliability, and only helps to alienate the general public from science when these false discoveries are later retracted (see the faster-than-light-neutrinos and the arsenic based life-form for a few recent examples).
Folding at Playa de Valea, near Foz. Asturias. Spain
Folding in deformed marble/schist, Pyrenees.
Crenulation Cleavage in deformed Limestone. Planezes, Pyrenees.
Sepentinites from Apsiou Village, Limassol, Cyprus.
Conjugate Shear zone convergence in Lower Carboniferous Limestone. Mumbles Head, Gower, Wales.
Late Variscan Orogeny deformation. Cleavage deflection occurs as the two shear zones propagate past one another - they form contemporaneously and alter the sense of shear experienced and therefore rotate the cleavage formed in the centre of convergence. In the photo above the left (Easterly) portions of the two shear zones show relatively shallow cleavage orientations becoming steeper in the centre of convergence (right hand side) where they are rotated toward the shear sense of the crosscutting shear zone. Both of these shear zones remained active throughout the convergence.
Cleavage forms in the long axis of a strain ellipse and is progressively rotated toward the orientation of the maximum compressive strength, sigma1. They can be used to interpret sense of shear, the lower shear zone above shows top-to-the-right rotation, a dextral shear sense.