Facts About Mars

Front 1

Orbit semi major axis

Back 1

1.52366 AU

(142 million miles)

Hint 1

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

Front 2

Eccentricity

Back 2

0.0934

Hint 2

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.

Front 3

Obliquity

Back 3

25.1

Hint 3

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

Front 4

Mean orbital period

Back 4

686.98 Earth days = 669.6 Mars days (Sols)

Front 5

Mean solar day

Back 5

24h 39.6m

Front 6

Mass

Back 6

6.4185*10^23 kg = 0.107 Earth masses

Hint 6

~ 10% the mass of the Earth

Front 7

Mean radius

Back 7

3389.92 km

Hint 7

~ half the radius of the Earth

Front 8

Mean escape velocity

Back 8

5.027 km/sec

Hint 8

~ 45% of Earth mean escape velocity

Front 9

Surface gravity at equator

Back 9

3.711 m/sec^2

Hint 9

~ 38% of Earth gravity

Front 10

Mean atmospheric pressure

Back 10

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

varies strongly with altitude, uncertainties affect entry trajectories

Hint 10

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

Front 11

Solar constant at mean distance from Sun

Back 11

588.98 watts/m^2

Hint 11

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

Front 12

Number & names of moons

Back 12

2, Phobos & Deimos

Hint 12

Front 13

Length of Northern Spring

(Ls=0-90)

Back 13

199 days

Hint 13

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.

Front 14

Length of Northern Summer

(Ls=90-180)

Back 14

183 days

Hint 14

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.

Front 15

Length of Northern Fall

(Ls=180-270)

Back 15

147 days

Hint 15

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.

Front 16

Length of Northern Winter

(Ls=270-360)

Back 16

158 days

Hint 16

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.

Front 17

Atmosphere composition

Back 17

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

Hint 17

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.

Front 18

Local dust storms

Back 18

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

Front 19

Regional dust storms

Back 19

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.

Hint 19

Top: Mars

Bottom: Earth

Front 20

Global dust storms

Back 20

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.

Hint 20

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

Front 21

Atmospheric opacity

Back 21

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.

Front 22

Composition of surface rocks

Back 22

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.

Front 23

Late Heavy Bombardment

Back 23

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.

Hint 23

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.

Front 24

Noachian period

Back 24

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

Hint 24

HiRISE photo: Dunes in the Noachis Terra region of Mars

Front 25

Hesperian period

Back 25

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

Hint 25

HiRISE photo: Hesperia Planum

Front 26

Amazonian period

Back 26

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.

Hint 26

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

Front 27

Geologic activity

Back 27

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.

Hint 27

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).

Front 28

Terrain

Back 28

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

Front 29

Soil

Back 29

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.

Front 30

Mineral

Back 30

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.

Front 31

Rock

Back 31

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.

Front 32

Igneous rock

Back 32

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).

Hint 32

Photo: Martian rock "Harrison"

Front 33

Sedimentary rock

Back 33

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

Hint 33

Photo: Target rock "Ithaca", Gale Crater

Front 34

Metamorphic rock

Back 34

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

Front 35

Mafic rock

Back 35

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

Front 36

Sulfate rock

Back 36

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

Front 37

Bedrock

Back 37

The native consolidated rock underlying the surface.

Front 38

Outcrop

Back 38

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

Front 39

Regolith

Back 39

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.

Front 40

Dust

Back 40

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

Front 41

Aeolian

Back 41

Pertaining to wind on Mars

Front 42

Aeolian bedforms

Back 42

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

Front 43

Surface equatorial temperatures

Back 43

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.

Hint 43

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.

Front 44

Solar wind

Back 44

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.

Hint 44

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.

Front 45

Magnetic field

Back 45

Mars shows no evidence of a current global magnetic field.

Hint 45

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.