C.M. Rodrigue, 2007 Geography, CSULB Mars: Third Order Landscapes Geography 494-01 S/07 Dr. Christine M. Rodrigue

C.M. Rodrigue, 2007Geography, CSULB

Mars: Third Order Landscapes

Geography 494-01

S/07

Dr. Christine M. Rodrigue



The “Orders of Relief” for Martian Landscapes The first order was the great crustal dichotomy:

Northern lowlands: ~ 1/3 Southern highlands: ~2/3

The second order is tonight’s focus: Tharsis and Elysium rises The largest craters: Hellas, Argyre, Isidis, Utopia Valles Marineris The polar ice caps



The “Orders of Relief” for Martian Landscapes The third order is in order now:

In many ways, this is a cross-cutting category It addresses the “geological column” or relative ages of all

Martian landscapes in terms of the three regional units that gave the three-part sequences of Mars’ evolution their names:

The Noachian Era The Hesperian Era The Amazonian Era



The “Orders of Relief” for Martian Landscapes The third order is “in order” now:

The three eras and their namesakes: Noachian Era is named for Noachis Terra, one of the oldest

terrains on Mars The Hesperian Era is named for Hesperia Planum The Amazonian Era is named for the smooth Amazonis

Planitia These three regions are subregions of the northern lowlands and

the southern highlands at or smaller in scale and less conspicuous than such features as Utopia Planitia, Valles Marineris, the northern ice cap, or the Tharsis rise



The “Orders of Relief” for Martian Landscapes The third order is “in order” now:

So, the third order of relief is actually rather a vague level spatially (at or somewhat smaller than the second order of relief) but a clear, if contested, temporal concept

I needed to talk about these eras and decided to use their regional namesakes to give them a “place” in the class

If I were a geologist instead of a geographer, I might have organized the class temporally, as a kind of historical narrative, with regions the incidental side effect of the discussion

With that caveat…



Debates over Era Lengths


Mars: Third Order Landscapes Noachis Terra


Mars: Third Order Landscapes Noachian Era

Oldest: ~4.6 – 3.8 or 3.9 billion BP (or is it 3.5 billion?) Earliest accretion, melting, differentiation of the planet Era of bombardment (Earth’s Hadean times)

Intensely cratered with wide range of crater sizes Some geomorphic erosion of craters

Establishment of and shutting down of planetary magnetic field Some geological activity:

Valley networks Volcanic activity (low viscosity flows, small pateræ) Oceans?

Examples: Noachis Terra Arabia Terra Terra Sirenum


Mars: Third Order Landscapes Hesperia Planum


Mars: Third Order Landscapes Hesperian Era

Intermediate ages: Most commonly from ~3.8 – 2.9 billion BP (or even 1.8 billion BP) Era in which the bulk of Tharsis and Elysium rises developed Intense geological activity:

Shield vulcanism Folding Faulting and formation of linear grabens in extensional zones Gigantic outwash floods far past Noachian valley networks

Era in which climate dried out, dustiness, water evaporating, freezing, sinking into permafrost

Examples: Hesperia Planum Terra Tyrrhena Aonia Terra Margaritifer Terra


Mars: Third Order Landscapes Amazonis Planitia


Mars: Third Order Landscapes Amazonian Era

Youngest: Most commonly from ~3.8 – 2.9 billion BP (or even 1.8 billion BP) to

present Much more peaceful geologically:

Some vulcanism Some subsurface water releases and gullying Some meteoroids continue to smack down May even be obliquity-related ice ages Extent and recency of these energetically debated

Examples: Amazonia Planitia Utopia Planitia Chryse Planitia Acidalia Planitia

Documents

C.M. Rodrigue, 2007 Geography, CSULB Mars: Third Order Landscapes Geography 494-01 S/07 Dr. Christine M. Rodrigue