Mars - The Tharsis volcanic province - Arsia Mons

The Tharsis volcanic province covers an area corresponding to 25% of the Martian surface , a diameter (ground surface) of about 8,000 km. It is characterized by an extensive volcanism and tectonic activity .

Various hypotheses for its formation and evolution :

- An uprising of the lithosphere caused in the mantle or the crust of Mars by a thermal  , chemical, or dynamic anomaly , would have led to a fracturing of the lithosphere and later the establishment of the volcanism and the giants shield volcanoes.

- The topography of the Tharsis Province could have been produced by construction, rather than by raising another hypothesis. Elastic and heterogeneous lithosphere has been subject to fracturing , and a volcanism concentrate on that area .

Anyway, the volcanism was active until a currently 100 to 250 Ma, which is the recent geological worldwide , estimated at 4.6 billion years.

Volcanic Tharsis Province / MARS - doc . ESA / DLR / FU Berlin (G. Neukum ) - Original Image by NASA data

The Tharsis Mountains are a chain of volcanoes, located on the Tharsis bulge . The three main summits are Acraeus Mons, 18,225 m. , Pavonis Mons, 14,058 m. and Arsia Mons, 17,761 m.

Ascraeus Mons is the second highest summit in March , after Olympus Mons , the volcano of superlatives , with 21,229 m. , located northwest of Tharsis Mountains .

Throughout, the high density of volcanoes corresponds to a basaltic composition , consistent with that of Martian meteorites fallen on Earth.

New data show a change in density during the construction of the chain of volcanoes . At first, we deal with andesitic lava , lighter , and related to the presence of water, then with  basaltic lava heavier.

The age is going from Arsia Mons volcano, the oldest , Pavonis Mons and finally Acraeus  Mons, the youngest. ( M.Beuthe / Royal Observatory of Belgium / Journal of Geophysical Research)

Tharsis mountains , February 22, 1980 . From bottom to top , the mountains Arsia , Pavonis and Ascraeus - Image reconstructed from a mozaïque of images captured by the Viking probe

Arsia Mons - photo NASA - JPL -Caltech - Arizona State University

Perspective view of Arsia Mons - doc . reconstituted by combining images from the Viking probe and elevation data / Planetary remote sensing, Martian landscapes .

Arsia Mons is a large shield volcano, 460 km wide , with a caldera of 110 km. diameter , overlooking the Tharsis bulge of 9-11000 meters. It peaks at 17,761 meters, compared to the baseline of Mars . Its sides have an average inclination of 5 ° , with side lobes inclined  from 1 to 4°.

Topography of the lava flows in Daedalia Planum - Doc ESA - http://www.esa.int/Our_Activities/Space_Science/Mars_Express/Lava_flows_in_Daedalia_Planum

His flows are on the same scale : a publication of the ESA on images taken by the Mars Express probe on November 28, 2013 revealed the existence of two distinct flows of lava which flooded an area of ​​Daedalia Planum , located about 1000 km . southeast of the volcano.

Daedalia Planum, a plain SE of Arsia Mons - doc . ESA

Daedalia Planum and his lava flows in perspective - doc . ESA

These flows are of different ages , such as craters impacts shows.

The oldest , fractured , contains more impact craters , and larger than the younger.

The latest flow has various features including pressure ridges and a lava channel . Older flow has in its lower part a smoother surface , due to the accumulation of sediments. Impact craters show signs of modification, the largest of which is not affected by the lava flow , but whose ejecta formed during the impact is partially covered with lava.

Sources :

- Evolution of the Tharsis volcanic Province - by Sean C.Solomon - MIT - link

- ESA - Space sciences - Lava flows in Daedalia Planum - link