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Lecture 1

GEO 330 Lecture Notes - Lecture 1: Giovanni Schiaparelli, Christiaan Huygens, Radio Science


Department
Geosciences
Course Code
GEO 330
Professor
Timothy Glotch
Lecture
1

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The bright regions of Mars are dusty while the dark regions are basaltic
The radius of Mars is roughly half that of Earth while its gravity is 3.7m/s2. The atmospheric
pressure is roughly 0.6% of the Earth's
General Characteristics of Mars
Gravity
What controls the thickness of the atmospheres on Mars and Earth?
Atmospheric opacity increases substantially from the mean during global dust storms. Dust in the
atmosphere causes significant heating
Atmospheric Characteristics
Surface temperatures vary with time of day, season, albedo, thermal inertia, slope, and latitude
Thermal inertia is the ability of a material to retain heat
Rocky materials have higher TI than sandy or dusty material
k = thermal conductivity
ρ = density
c = heat capacity
Thermal Inertia I = (kρc)1/2
Since diurnal curves vary with TI, if you can measure the surface temperature at several times per
day, you can model the diurnal temperature curve, estimate the TI, and hence, the physical nature
of the surface!
The Martian atmosphere has a low heat capacity Cp, so it does not absorb much solar radiation
Albedo (A) = Ireflection/I0
Surface temperatures have a wide range depending on time of day, season, albedo, thermal
inertia, slope, and latitude
Surface temperatures move toward a mean with depth
A key concept is thermal skin depth, which is the depth at which the variation between the
temperature at a given depth and the mean temperature drops by a factor of 1/e
Liquid water can only exist at pressures above 6.1mbar and 273K
The triple point in the H2O phase diagram occurs at a pressure and temperature that can occur at
Mars
Most of the time, pressures and temperatures on Mars require H2O to be in the solid or gas phase
Ice exposed at the surface will sublimate directly to water vapor under common Martian
conditions
The Phoenix Lander dug into the regolith near the north pole of Mars and found ice just a few
centimeters below the surface
After just a few sols (Martian days), some of the ice had sublimated
Subsurface ice is most stable at high latitudes on Mars
Surface/Subsurface Temperatures and Water Stability
Instead of months, time of year is measured in areocentric longitude, or LS
LSis the sun-centered angle between the position of Mars in its orbit and the position of Mars
during its northern spring equinox (LS= 0)
Orbital Characteristics
Obliquity variations can cause large changes in the Martian climate and landscape
Obliquity Variations
General Characteristics and History of Mars Exploration
Monday, January 29, 2018
1:45 PM
GEO 330 Page 1
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