Thermal models for Mars

Thermal evolutionary models of the martian interior are obtained by combining information from isotopic analysis, geologic history, and geophysical modeling. Often the initial data appear contradictory, such as the result from isotopic analysis suggesting little mantle convection over martian history versus the geologic data suggesting long-lived volcanic activity on the planet. The thermal models must be able to explain such contradictions and often evolve over time as new data are acquired...

Mars

Surface and Atmosphere MARS AN INTRODUCTION TO ITS INTERIOR, SURFACE AND ATMOSPHERE Our knowledge of Mars has changed dramatically in the past 40 years due to the wealth of information provided by Earth-based and orbiting telescopes, and spacecraft investigations. Recent observations suggest that water has played a major role in the climatic and geologic history of the planet. This textbook covers our current understanding of the planet's formation, geology,...

Historical observations

Mars has been the focus of intense scientific interest and study throughout recorded history. Even before the advent of the telescope in 1609, astronomers carefully charted the motion of Mars across the sky. The planet's obviously reddish-orange color led many ancient civilizations to name the planet after war or warrior gods. Our current use of the name Mars comes from the Roman God of War. Large martian sinuous valleys (vallis) are named after the term for Mars in different languages hence...

Eolian features

Planets with atmospheres show the effects of eolian or wind processes. Wind transports material from one location to another and causes both deposition and erosion. The physics of fluid dynamics is applied to material being transported by the wind (Greeley and Iverson, 1985). Larger material is transported by traction, the rolling of material along the surface. Slightly smaller material can bounce along the surface, a process called saltation. Pebbles are sometimes moved by impact creep, where...

US missions to Mars

The United States began its spacecraft exploration of Mars in 1964 when it launched the Mariner 3 and 4 spacecraft. Although both missions launched successfully, the solar panels powering Mariner 3 did not deploy and that mission ended up in solar orbit. Mariner 4 became the first successful flyby mission of Mars when it passed within 9920 km of the planet's surface on 14 July 1965. It returned 22 close-up photos, revealing a heavily cratered surface (Figure 1.2). Spacecraft instruments...

Winds

Pressure Thermal Tides Mars Pathfinder

Gradients in pressure and temperature resulting from solar heating produce winds in an attempt to reduce these gradients. Atmospheric pressure and temperature gradients result from three major factors seasonal changes, dust storms, and diurnal variations. The seasonal changes result from condensation and sublimation of CO2 and H2O from the polar caps. As noted above, dust storms can enhance the temperature gradient leading to stronger winds. The diurnal variations result from the temperature...

Characteristics of the present martian atmosphere

Eighteenth-century astronomers observed clouds on Mars, revealing the presence of the planet's atmosphere. Ground-based reflectance spectroscopy suggested that CO2 was a major component of the martian atmosphere based on the large number of absorption lines in the 2-4- m region. Mariners 4, 6, and 7 confirmed that CO2 was the dominant component of the martian atmosphere Table 6.1 but found that the current atmosphere is very thin, exerting an average pressure of only 700 Pa 7 mbar . The surface...

Thermal inertia and rock abundance

Viking IRTM, MGS TES, MO THEMIS, and MER Mini-TES experiments have provided insights into the variation in grain size across the martian surface through measurement of the thermophysical characteristics of the regolith. Thermal inertia of the surface materials governs the daily thermal response of the surface to solar heating. The surface temperature due to absorption of solar radiation is the equilibrium temperature Teq and can be calculated by balancing the incoming Fin and outgoing Fout...

Obliquity cycles and climate change

Long-term climate change likely results from perturbations induced by the planets and the Sun's non-spherical shape. These perturbations result in variations in Mars' orbital parameters including eccentricity, inclination, and time of perihelion and obliquity Ward, 1992 and are analogous to the Milankovitch cycles which contribute to ice ages on Earth. Although the obliquity and orbital motion are strongly chaotic and numerical solutions are only accurate for the past 60 Ma, numerical solutions...

Bulk composition of Mars

The bulk composition of Mars can be estimated from its density 3933kg m-3 and surface composition. More detailed determination of the bulk composition requires analysis of martian rocks. Although analysis of crustal materials by surface missions Viking, Mars Pathfinder, and MER and orbital spacecraft MGS TES, Odyssey THEMIS and GRS, and Mars Express OMEGA provides some information, most of our current understanding of the bulk composition of Mars comes from the martian meteorites. Analysis of...

Viking biology experiments

The Mariners 4, 6, and 7 missions had led scientists to conclude that Mars was a dry, dead world where life would never have had an opportunity to arise. The Mariner 9 discovery of channels formed by flowing water changed this perception - if water had flowed on Mars in the past, life may have arisen. The 1976 Viking missions therefore included landers with experiments to determine if the martian surface might contain life. The landers used their robotic arms to scoop up soil samples which were...

Heavy bombardment

Not all of the material present in the solar nebula was immediately accreted into the planets. A significant amount of material still remained after the planets had formed. This material underwent gravitational and collisional perturbations which caused it to cross the orbital paths of the newly formed planets. Occasionally this debris from planetary formation collided with the newly formed planet, creating impact craters on bodies with solid surfaces. The impact rates during this time are...

Remnant magnetization

Rocks containing magnetic minerals can retain a remnant magnetization indicative of the strength and polarity of the magnetic field that was present when the rock solidified. Like a compass needle, magnetic minerals align with the direction of the magnetic field lines. As long as the material remains molten, the minerals are free to realign with any changes in the magnetic field direction. The motion of the magnetic minerals is reduced as the temperature drops and the magma begins to solidify....

Shape and geodetic data

The shape of Mars is derived from detailed MOLA topography combined with gravity measurements from MGS Doppler tracking data Lemoine et al., 2001 Smith et al., 2001a . The shape is defined relative to the planet's center of mass COM . Mars' equatorial radius is 3396.200km as measured from the COM. COM is offset slightly to the north primarily because of the Tharsis Bulge , resulting in a north polar radius of 3376.189km, compared to the south polar radius of 3382.580km. Because of its rotation,...

Coordinate systems

Locating a feature on the surface requires defining a coordinate or geodetic grid. Latitude is measured in two ways because of Mars' oblate shape aerographic latitude 0 and aerocentric latitude 0' . To obtain 0, one draws a best-fit reference sphere centered on the planet's COM Figure 3.2 . A horizontal line tangent to the Figure 3.2 Martian coordinate systems are based on both aerographic and acrocentric systems. The reference sphere is the best-fit sphere centered at the planet's center of...

Regolith

The uppermost layer of the surface, composed of the fragments produced by weathering processes, is called the regolith. The terms regolith and soil are often used interchangeably in planetary applications, although terrestrial geologists argue that biologic activity is an important component of the composition and mixing processes of soil. Fragment clast size is expected to generally increase with depth. The martian regolith likely contains mixtures of soil and ice, particularly at the higher...

Clouds and dust storms

Image Fog Nasa

Ground-based observers noted that albedo markings on Mars are often obscured and correctly attributed these changes to clouds within the martian atmosphere. Martian clouds are divided into yellow clouds, white clouds, and polar hoods discussed in Section 5.3.7 . Hazes, which are optically thin while clouds are optically thick, are often seen along the terminator, particularly along the sunrise limb, and have been observed from the surface landers Figure 6.3 . These result from vapor...

Interior structure of Mars

Mars Interior

The mean density of Mars combined with geochemical mainly martian meteorite analysis and geophysical particularly from gravity, topography, and magnetic data analysis have provided new constraints on the interior structure of Mars. Mars is differentiated into a crust, mantle, and core Figure 3.9 . Gravity and topography Figure 3.9 Mars' interior structure is inferred from geophysical measurements. The crust varies in thickness between 38 and 62km. The mantle is 1700-2100km thick and the core...

Geochronology

Many elements have isotopes that are unstable, decaying to a stable isotope in a well-defined period of time. The radioactive element is called the parent element while the stable decay product is called the daughter element. The amount of daughter element at any point in time depends on the original amount of the daughter element, the original amount of the parent element, the rate at which the parent decays into the daughter element given by the decay constant, k , and the amount of time that...

Gravity analysis

The gravitational acceleration g experienced by a spacecraft orbiting a planet of mass M at a distance of r from the planet's center is where G is the universal gravitational constant. The gravitational acceleration is the integral of the gravitational potential U , therefore Since all of the planet's mass lies inside the surface, the gravitational potential exterior to the planet satisfies Laplace' s equation The general solution to Laplace's equation in spherical coordinates is Hubbard, 1984...

Volcanism

Ascraeus Mons Jpl Viking

Volcanism can produce flat lava plains or a wide variety of topographic features called volcanoes. The type of volcanic feature produced during a volcanic eruption depends on the viscosity of the magma lava involved. Viscosity depends on temperature, composition, presence absence of solid material in the melt, and amount of gas dissolved in the magma. The most important factor influencing viscosity is the amount of silicate SiO2 in the magma - higher SiO2 concentrations result in stickier...