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45 Cards in this Set

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Orbit semi major axis

1.52366 AU

(142 million miles)

AU = Astronomical Unit, the average distance from Earth to the Sun, (about 150 million km, or 93 million miles)




The amount an orbit deviates from a perfect circle. Circular is 0, between 0 and 1 are elliptical, 1 is parabolic escape orbit, and greater than 1 is hyperbolic.




Also known as Axial Tilt, it is the angle between an object's rotational axis and its orbital axis. Obliquity of Earth is ~ 23.3

Mean orbital period

686.98 Earth days = 669.6 Mars days (Sols)

686.98 Earth days = 669.6 Mars days (Sols)

Mean solar day

24h 39.6m


6.4185*10^23 kg = 0.107 Earth masses

~ 10% the mass of the Earth

Mean radius

3389.92 km

~ half the radius of the Earth

~ half the radius of the Earth

Mean escape velocity

5.027 km/sec

~ 45% of Earth mean escape velocity

Surface gravity at equator

3.711 m/sec^2

~ 38% of Earth gravity

Mean atmospheric pressure

6 mbar (< 1% of Earth's),

varies strongly with altitude, uncertainties affect entry trajectories

Mean atm pressure at sea level on Earth is ~ 1000 millibars. At 10 km elevation (height of Mt. Everest) pressure is ~ 265 millibars.

Solar constant at mean distance from Sun

588.98 watts/m^2

Power per unit area received at the average Earth-solar distance
of one “Astronomical Unit” or AU is 1366.1 watts/square meter.

Number & names of moons

2, Phobos & Deimos

Length of Northern Spring


199 days

Solar longitude (Ls) is 0° at vernal equinox (start of northern spring), 90° at summer solstice, 180° at autumnal equinox, and 270° at winter solstice.

Length of Northern Summer


183 days

Solar longitude (Ls) is 0° at vernal equinox (start of northern spring), 90° at summer solstice, 180° at autumnal equinox, and 270° at winter solstice.

Length of Northern Fall


147 days

Solar longitude (Ls) is 0° at vernal equinox (start of northern spring), 90° at summer solstice, 180° at autumnal equinox, and 270° at winter solstice.

Length of Northern Winter


158 days

Solar longitude (Ls) is 0° at vernal equinox (start of northern spring), 90° at summer solstice, 180° at autumnal equinox, and 270° at winter solstice.

Atmosphere composition

Carbon dioxide plus nitrogen, argon and traces of oxygen and water

Atmospheric variations can have a great impact on a
spacecraft that enters the atmosphere, because atmospheric uncertainties are a major contribution to
variations in entry trajectory.

Surface winds on Mars are also highly variable. During some parts of the year, the direction of the wind may be estimated from wind streaks and other surface features, but there is always the question of whether the feature is recent or was formed during a previous climatic regime (and, even if recent, under what season or condition is the inferred direction relevant).

The wind is partly influenced by the general atmospheric circulation (and thus can vary with season and local weather). The regional and possibly local settings also significantly control the wind, which includes the effects of topography, albedo, and thermal inertia.

Local dust storms

Major axis <= 2000 km, surface area < 106 km². Produces local effects on dust opacity and temperature.

Regional dust storms

At least one dimension > 2000 km but does not encircle the planet. Surface area > 106 km². Produces local and long distance effects on dust opacites and temperatures. Can last for 60 sols.

Top: Mars


Bottom: Earth

Top: Mars

Bottom: Earth

Global dust storms

Planet encircling event likely to occur in Ls range from 200º to 310º and can last for many sols. Produces strong global effects on dust opacities, temperatures and circulation (equatorial winds). Therefore dust storms have a large influence on atmospheric profiles during entry.

Hubble photos: June 26 (left) and Sept 4, 2001 (right)

Hubble photos: June 26 (left) and Sept 4, 2001 (right)

Atmospheric opacity

Outside global dust storm seasons, the optical depth typically varies from 0.1 to 2 (unitless). During storms optical depths can vary from 1 to >5. During storms, there is a hotter and therefore more expanded atmosphere. The dust particle mean radius in absence of dust devils varies from 25 nm to 30 μm.

Composition of surface rocks

Minerals containing mainly silicon, oxygen, metals. Primarily composed of the volcanic rock basalt, some parts more silica-rich than typical basalt. Localized concentrations of hematite (water bearing mineral) and olivine. Much of the surface is deeply covered by finely grained iron oxide dust.

Late Heavy Bombardment

Period just after the formation of the Solar System, with high rate of impacts on all planets of rocks and asteroids. About 60% of the surface of Mars shows a record of such impacts.

There is evidence of an enormous impact basin in the northern hemisphere (10,600 by 8,500 km) which suggests that a Pluto-sized body struck Mars about four billion years ago. The event, thought to be the cause of the Martian hemispheric dichotomy, created the smooth Borealis basin that covers 40% of the planet.

Noachian period

4.5 to 3.5 billion years ago (named after Noachis Terra). Formation of the oldest surfaces and can be identified by many large impact craters. The Tharsis bulge, created by volcanic activity, is thought to have been formed during this period followed by extensive flooding by liquid water later in the same period

HiRISE photo: Dunes in the Noachis Terra region of Mars

HiRISE photo: Dunes in the Noachis Terra region of Mars

Hesperian period

3.5 to 2.9–3.3 billion years ago (named after Hesperia Planum). Marked by the formation of extensive lava plains.

HiRISE photo: Hesperia Planum

HiRISE photo: Hesperia Planum

Amazonian period

2.9–3.3 billion years ago to present (named after Amazonis Planitia). Characterized by having few impact craters and vary a lot in terms of different rock composition. The largest volcano in our Solar System Olympus Mons formed during this period, along with lava flows elsewhere on Mars.

HiRISE photo: Serpentine dust devil in Amazonis Planiitia region of Northern Mars

HiRISE photo: Serpentine dust devil in Amazonis Planiitia region of Northern Mars

Geologic activity

Some geological activity still takes place. On February 19, 2008, images from the Mars Reconnaissance Orbiter showed evidence of an avalanche coming down from a 700 m high cliff.

There are even scientists who claim that Mars could still host volcanic activity in the form of
hydrothermic spots, similar to those found in the deep sea and, for example, Iceland (Geysirs).


Martian surface in the general sense, consisting of regolith and bedrock, with associated relief


The part of the surface material (i.e. upper regolith) that consists of unconsolidated or poorly consolidated material; i.e. any loose materials that can be distinguished from float rocks, bedrock, or strongly cohesive sediments.


A naturally occurring solid, formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. Minerals range in composition from pure elements and simple salts to very complex silicates with thousands of known forms.


Solid aggregate of minerals. Rocks are usually classified by mineral and chemical composition, by the texture of the constituent particles, by the processes that formed them, and according to particle size. Referring to the formation processes, one distinguishes igneous, sedimentary and metamorphic rock.

Igneous rock

Igneous rock

Formed through the cooling of magma. It may form with or without crystallization, either below the surface as intrusive (plutonic) rocks (e.g. granite) or on the surface as extrusive (volcanic) rocks (e.g. basalt).

Photo: Martian rock "Harrison"

Sedimentary rock

Sedimentary rock

Made up of particles and fragments derived from disintegrated rocks that are subjected to pressure and cementation.

Photo: Target rock "Ithaca", Gale Crater

Metamorphic rock

The product of existing rock subjected to changes in pressure and temperature, causing changes in mineral composition of the original rocks.

Mafic rock

Rich in magnesium and iron (the term is a contraction of “magnesium” and “ferric”).

Sulfate rock

Rich in sulfate minerals. Sulfates all contain the sulfate anion.


The native consolidated rock underlying the surface.


Continuous expanses of bedrock or surficial deposits exposed at the surface.


Unconsolidated surface material, i.e. a layer of loose, heterogeneous material which usually covers the bedrock. It includes dust, soil, broken rock and other related materials.


Very fine particles, i.e. solid particles small enough to be suspended in the atmosphere.


Pertaining to wind on Mars

Aeolian bedforms

Regularly repeated patterns of accumulations of windblown particles. Ripples, granule ripples and dunes can be distinguished, depending on their sizes and constituents.

Surface equatorial temperatures

Day: 215-293 K (-73 to 68 F, -58 to 20 C)

Night: 160-180 K (-172 to -136 F, -113 to -93C)

On Earth, the atmosphere is very important in insuring temperate temperatures.

As the atmosphere is dry, relatively thin, and composed largely of CO2, the heat capacity of the atmosphere is low and therefore absorbs little of the Sun’s incoming radiation.

This means that the
atmosphere almost doesn’t influence the daytime surface temperatures. The temperature is the result of the balance between the solar radiation absorbed at the surface and its emitted infrared radiation.

Solar wind
At Mars at the average distance from the Sun the average density of the Solar wind is 3.8 cm^3 and the average speed of the solar wind is 468 km/sec.
Originates from the Corona, the Sun’s outer atmosphere. The high temperature of the plasma near the Sun causes it to expand outwards against gravity, carrying the solar magnetic field lines along with it. The solar wind starts at the Sun as a hot dense, slowly moving plasma but accelerates outwards to become cool, much less dense at the Earth and beyond.

Most of the solar wind’s acceleration takes place near the Sun. The solar wind velocity typically lies in the range 300-1200km/s. It is most commonly around 400km/s but there are frequent high-speed streams with velocities around 700km/s.

The strong variability of the solar wind is the driving force, putting energy into the magnetosphere and ultimately causing surface charging and radiation effects. More severe but less frequent disturbances in the solar wind can be caused by coronal mass ejections.

Magnetic field

Mars shows no evidence of a current global magnetic field.

In orbit, observations have shown that part of the planet's crust has been magnetized, and that polarity reversals of its dipole fields have occurred in the past, just like on Earth.

This remnant magnetism, which is also sometimes called paleo-magnetism, composed of magnetically susceptible minerals has similar properties to that of the alternating bands found on the ocean floors of Earth.

A potential explanation is that these bands demonstrate plate tectonics on Mars four billion years ago, before the planetary dynamo ceased to function and the planet's magnetic field faded away.