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ESA’s Mars Express Zeroes in on Phlegra Montes

ESA’s Mars Express orbiter has obtained a spectacular color image of the southernmost portion of Phlegra Montes, a mountain range in the Cebrenia quadrangle of Mars.
This image was acquired by ESA’s Mars Express on October 8, 2014. Image credit: ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO.
This image was acquired by ESA’s Mars Express on October 8, 2014. Image credit: ESA / DLR / FU Berlin / CC BY-SA 3.0 IGO.

Phlegra Montes is a complex system of isolated hills, ridges and small basins that spans over 1,400 km from the Elysium volcanic region at about 30ºN and deep into the northern lowlands at about 50°N.
It is is thought to hide large quantities of water-ice and its age is estimated to be 3.65–3.91 billion years.
The mountains themselves are probably not volcanic in origin, but have been raised by ancient tectonic forces that squeezed different regions of the surface together.
The new image from the High Resolution Stereo Camera on ESA’s Mars Express shows the southernmost tip of Phlegra Montes centred on 31ºN / 160ºE.
Based on radar data from NASA’s Mars Reconnaissance Orbiter combined with studies of the region’s geology from other orbiters, scientists believe that extensive glaciers covered this region several hundred million years ago. And it is thought that ice is still there today, perhaps only 20 m below the surface.
The tilt of the Mars’ polar axis is believed to have varied considerably over time, leading to significantly changing climatic conditions. This allowed the development of glaciers at what are today the mid-latitudes of Mars.
This context image shows the strip of the southernmost portion of Phlegra Montes on Mars imaged by the Mars Express. Image credit: NASA / MGS / MOLA Science Team.
This context image shows the strip of the southernmost portion of Phlegra Montes on Mars imaged by the Mars Express. Image credit: NASA / MGS / MOLA Science Team.
Features visible in the mountain range providing strong evidence for glacial activity include aprons of rocky debris surrounding many of the hills.
Similar features are seen in glacial regions on our planet, where material has gradually slumped downhill through the presence of subsurface ice.
Additional features in the region include small valleys cutting through the hills and appearing to flow into regions of lower elevation, in particular towards the centre of the image.
The hummocky terrain provides a distinct contrast to the smooth plains that dominate the upper portion of this image.
The material here is thought to be volcanic in origin, perhaps originating from the Hecates Tholus volcano in Elysium some 450 km to the west, some time after the formation of Phlegra Montes.
Upon closer inspection, wrinkle ridges can be seen in the lava plain. These features arise from the cooling and contraction of lava owing to compressive tectonic forces following its eruption onto the surface.

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