The fault system — dubbed the “Tantalus Fossae” — is a system of lengthy troughs lying along the eastern flank of a vast, low-lying volcano known as Alba Mons. The fossae formed around 3.6–3.2 billion years ago as the summit of the volcano rose in elevation, causing the surrounding surface of the Red Planet to crack open. As pairs of parallel faults opened up, the rock between them would drop down, forming a trough that geologists refer to as a “graben”.
As the Tantalus Fossae formed on the eastern side of Alba Mons, similar graben structures also developed on the other side of the volcano.
Researchers have named these the Alba Fossae.
Together, the two fossae form an incomplete ring around the volcano, stretching over more than 620 miles.
The grabens, meanwhile, stretch up to 6.2 miles in width and can be some 1,150 feet deep.
In the Mars Express images, the grabens, which have been dubbed “claw marks”, can be seen running from the northeast to the southwest — that is, from the bottom right to the top left of each image.
Because the grabens formed one after the other, rather than all at the same time, geologists have been able to reconstruct a timeline for the faulting.
The new images, for example, also capture a large impact crater that is crosscut by the grabens — indicating that the crater must predate the faults and the uplift that produced them.
However, a slightly smaller crater also visible in the shots is superimposed on top of the faults, meaning that it, in contrast, has to be younger.
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The Mars Express Orbiter had been circling and mapping out the Red Planet since 2003.
The mission is providing scientists with information on Mars’ surface geology, the composition and circulation patterns of the thin atmosphere, and is even probing beneath the crust of our neighbouring world.
The new images of the Tantalus Fossae were taken by the orbiter’s High Resolution Stereo Camera, which is capable of producing images with a resolution of 7.5 feet/pixel of 0.9 square miles of terrain from an altitude of around 155 miles.
The camera has imaged the majority of Mars’ surface — revealing diverse features from wind-sculpted ridges and impact craters to ancient lava pools and long-dried-out river channels.