Mars: The Basics and Geology
How many planets is Mars away from the Sun?
- fourth planet from the Sun
What has been suggested to have been accomplished by early basaltic material being weathered, eroded, and redistributed by winds?
It has blanketed Mars with red soil/dust that gives geochemical signature that matches these Martian basaltic breccias
How is the crustal thickness of Mars determined?
Mars Global Surveyor data to range from as little as 3 km to as much as 90 km, with an average of 50 km
What are Pateras?
large structures of low relief, often with central volcanoes and flows of vast extent, but also what appear to by pyroclastics
When was the Tharsis uplift believed to have originated and terminated?
originated before 3.7 Ga, terminating perhaps in 2.3 Ga, as hot mantle material rose by convection
Why is it not surprising that Mars has a lower density that mercury?
Mars probably formed much farther from the Sun in a region of lower temperature (thus, lighter) condensates
What does Mars have its own of?
Milakovitch cycles
why is Olympus Mons so big?
the lack of plate tectonics on mars, such that single "mantle plume" operating over a long span of time would generate a singe enormous volcano
Which terrestrial planet is Mars?
the last of the inner/terrestrial planets.
what is the argument for glacial activity on Mars? (3 points)
the polar ice caps are largely H2O ice,so it should be possible; there is a peculiar spiral form to the polar ice caps, suggestive of some kind of dynamic; deposits who overlap
What do the highlands represent?
the preserved ancient crustal surface, almost certainly older than 4.0 Ga
what is another consequence of the restoration after mass imbalance cause by the Tharsis uplift?
the stream-dissected terrain south of the escarpment, currently irregularly distributed, now take on a latitudinal pattern
characterize Mars atmoshpere.
thin; with a pressure of only 6 mb (compared to Earth at 1000 mb), dominated by CO (at 95%, with lesser N, H20 at 0.03%, O2, and Ar)
what is included on Tharsis Uplift?
Olympus Mons, the largest single volcano in the Solar system at 27 km height and 600 km diameter
What are the names of the two major crustal upwarps?
Tharsis and Elysium
What is a possibility that the eruption of material that formed the Tharsis Uplift created?
a mass imbalance that was stabilized by the shifting/rotation of the crust-mantle system independent of the core, to place the near-surface excess mass on the rotational equator
what would have controlled the precipitation that cause the network of valleys south of the Tharsis Uprift?
adiabatic cooling of air masses rising as they crossed to the southern highlands; growth of ice masses would have resulted as well
what shows that Mars has a warming climate?
after two Martian years, the Mars Global Surveyor noticed that the CO2 that had been lossed had not been redeposited
Discuss Mars' magentic field.
almost nonexistent; less than 0.01%; it is a weak remnant field in the Martian crust from a warmer period in Mars' history when it would have had an active field
Explain how Martian basalts differ from terrestrial basalts.
appear to be enriched in K ad Na (volatiles) and Fe, and depleted in Al compared to terrestrial basalts
2 meteorites are believed to be representative of an 'average' martian crust consisting of what?
basaltic breccias, with fragments of basaltic volcanic rocks in a matrix of basaltic material that may represent melt sheet materials
How much does Mars obliquity vary? Why?
between 15 and 35; its small satellites do not stabilize Mars obliquity the way the larger Moon stabilized Earth's
What is the fundamental division on Mars?
between the North and South hemispheres, with a diametric but non-equatorial separation, plus other features of note
How do others argue that these features once though to be formed by liquid water came to be?
blocks of dry ice, detaching from a blanket of CO2 frost, would ride down a cushion of vaporizing CO2 as 'hover ice' to create these gullies plowing up ridges of sediment at their sides
What is Mar's density?
3.93 g/cm3 (5.52 g/cm3 for Earth)
what percentage is Mars further from the Sun than Earth?
50%
What is Mars diameter?
6,790 km, just slight more than 1/2 of Earth's
What are the 5 geological provinces of Mars?
1. Densely cratered highlands 2. Northern Plains 3. Global Escarpment 4. Crustal Upwarps 5. Polar Regions
What are the two tectonic features on Mars?
1. Mare Ridges/Wrinkle ridges 2. Canyons
What are the three volcanic features on Mars?
1. Shield Volcanoes 2. Volcanic Plains 3. Patera
describe Mars mantle.
1300-1800 km thick, and is understood to be convecting
What is the surface temperature of Mars?
150-300 K (-123-27 degrees C)
This mass imbalance moved the equitorial position by how much?
20-25 degrees latitude
when were the last eruptions on Olympus Mons?
200 my to even as little as 10 My since the last eruptions
How often does Mars rotate on its axis? How often does it rotate around the sun?
24 1/2 hours, in 1.88 years
What is the incline of Mars axis of rotation?
24 degrees
Name a significant canyon on mars. Describe it. (3 points)
Valles Marineris on Tharis dome; it is 4000 km long by 700 km wide by 7 km deep, comparable in scale and configuration to the East African Rift
Incision of valley networks before the mass imbalance caused by the Tharsis uplift would have been primarily driven by what?
a belt of precipitation approx. 14 degrees latitude wide, centered on 24 degrees south latitude
What does suspended dust in the Martian atmosphere do?
causes the atmosphere to heat up very rapidly, temperature rising by 7 degrees C just after sunrise; this captured heat triggers growth of vortices that may grow rapidly, and cover vast areas
Describe the Martian polar caps.
consist of water ice and also some dry ice in winter, when polar temperatures reach 130K v. freezing point of carbon dioxide of 148 k
what effect does the freezing of CO2 have on atmospheric circulation?
consists of a single Hadley cell where surface movement is from the summer (H) to winter (L) hemisphere
What is the global escarpment?
contact between the older southern and younger northern hemisphere that effectively encircles Mars, with a few interruptions
what are fault structures/grabens related to on Mars?
crustal extension as upwarps occurred
Describe the Northern plains (2.points)
dominate the northern hemisphere and are separated from the southern highlands by an escarpment that is 2-3 km high
what are the tectonic features associated with patera?
extensional tectonic features
What did the Mars Global Surveyor mission notice about the south polar icecap? Describe in some detail.
features on teh south polar ice cap had changed; was rapid retreat of the faces of scarps and pits in the layered CO2 ice at rates averaging 3m per Mars year, and int eh extreme reaching 8 m per mars year
What may the fluctuation in CO2 ice cover be responsible for?
features once attributed to flow of liquid water; dunes are cut by gullies, which are noteworthy for having raised edges, and pits rather than sediment deposits at their down-slope end, and also their remarkable straight path
How is the composition of Mars crust known?
from SNC meteorites, recent orbiters, and landers
Why are the differences between Martian basalts and terrestrial basalts expected?
given the Mars is supposed to have formed farther from the Sun and should be more volatile-rich
describe the upwarps.
have shield volcanoes, lava flows, calderas, and radial fracture systems; basaltic composition seems likely
What are the arguments against glacial movement on Mars? (3 points)
if it is CO2 ice it would be too brittle to flow/be plastic; even if H2O, the caps are too thin at the Martian gravitational field to weak for them to flow under their own weight; the spiral troughs would seal or open
How may have these ejecta deposits be described to have happened?
impact melts ice, adn the liqiud mixes with ejecta to form a slurry
Is the structure of Mars comparabel to Earth?
in gross terms
Where are the two major crustal upwarps located?
in the Northern plains
What does removal of CO2 by freezing do to the Martian atmosphere?
it causes a drop in atmospheric pressure over the winter pole
What are the modifications to the global escarpment? (2 points)
it is dissected by stream erosion and mass movement/slumping, and there are isolated blocks/mesa just north of it in what is called fretted terrain
What can be concluded from the fact that its surface rocks are less dense than the planet's average?
it likely has an iron core (perhaps, with S, O) of 1500-2000 km radius, that is now solid
What is an argument to how the global escarpment was produced?
it was produced by a large scale impact
What are the features that make up the northern plains?
mare-type basalts, other volcanic features, some stream-borne sediments, and evidence of Aeolian activity
Explain Patera's explosive activity
may constitute a form of phreatic eruption as ice goes to steam due to the approach of magma/lava
What are there several of in the densely cratered highlands
multiring impact basins; including Hellas at 2000 km
Explain how the Valles Marineris was produced. Which two processes have substantially modified it?
produced by extensional tectonics, but has been substantially modified by two processes: mass movements and fluvial erosion
What comprises the densely cratered highlands?
southern hemisphere, of Mars; similar to the ancient cratered terrains of the moon and Mercury
How are mare ridges produced?
the buckling of cooling lavas in volcanic plains
What is unusual about martian cratering?
the character of the ejecta; although some craters show classic rays and secondary cratering, many show evidence of the flow of ejecta, suggesting the involvement of water; ejecta radius of 1.5 to 2x the crater radius (typical values of 0.7 for the Moon, and 0.5 for Mercury)
what are some intrigueing ideas about what rampart craters might allow or reveal
the distribution of such craters might allow mapping of groundice/groundwater variation, and that the smallest size of ramapart crater might reveal the minimum depth to H2O
describe Rampart or splash craters.
wherein the ejecta moved as heavy mudflows, with lobate flow fronts having steep or rampart faces, rather than airborne rays
What did the Mars Global Surveyor note?
wind storms with wind speeds as high as 580 km/h, almost 5x the minimum for a hurricane on Earth