mission to mars: project based learning benchmark...

Mission to Mars: Project Based Learning Benchmark Lessons

Dr. Anthony Petrosino, Department of Curriculum and Instruction, College of Education, University of Texas at Austin

Benchmarks content author: Elisabeth Ambrose, Department of Astronomy, University of Texas at Austin

Project funded by the Center for Instructional Technologies, University of Texas at Austin

http://www.edb.utexas.edu/missiontomars/bench/bench.html

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Table of Contents

Mars as a Solar System Body 4

Place in the Solar System 4

Physical Properties and Composition 5

The Moons of Mars 7

Mars geography 8

Mountains 10

Volcanoes 10

Valleys 11

Craters 12

Surface Rocks 14

Crust Composition 16

Atmosphere composition 17

Ice caps 17

Conditions on Mars 18

Gravity 18

Atmosphere 18

Weather, winds, storms 19

Temperatures, seasons, climate 20

Length of year 22

Length of day 22

Water on Mars 22

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Polar Ice Caps 22

Water channels 23

Surface Water 25

Previous, Current, and Future Missions to Mars 25

Mariner 4 25

Mariner 6-7 26

Mariner 9 26

Viking 1-2 27

Mars Pathfinder/Sojurner Rover 27

Mars Global Surveyor 28

2001 Mars Odyssey 29

2003 Mars Exploration Rovers 29

2005 Mars Reconnaissance Orbiter 30

Smart Lander and Long-Range Rover 30

Scout Missions 31

Sample Return and Other Missions 31

Getting to Mars 31

Escape velocity 31

Routes and travel time 33

Supplies: food, water, oxygen 35

Psychological needs/concerns 35

References 40

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Mars as a Solar System Body Place in the Solar System

The Solar System. NASA/JPL.

This picture depicts the correct

relative sizes of the 9 planets of the Solar

System in the correct order. The planets

are Mercury, Venus, Earth, Mars, Jupiter,

Saturn, Uranus, Neptune, and Pluto.

Mars is the fourth planet from the Sun. It

is one of the four inner planets. Mars

orbits at a distance of 1.52 Astronomical

Units (227,940,000 km) from the Sun.

One Astronomical Unit is equal to 1.496

x 108 km, the average distance from the

Earth to the Sun. Astronomical Units are

abbreviated A.U. Its orbit is situated

between those of Earth and the Asteroid

Belt.

Sun and planets. NASA/JPL.

This picture depicts the four gas

giant planets (Jupiter, Saturn, Uranus,

and Neptune), Earth, and the Sun. Earth

is the tiny dot between Jupiter and the

Sun. The relative sizes of the objects

are to scale, with 3200 km corresponding

to one pixel of the image.

If the relative sizes of the planets

were shrunk to be one billionth of its

actual size, the Earth would be the size

of a large marble (2 cm diameter), Mars

would be the size of a pea (1 cm

diameter), Jupiter would be the size of a

grapefruit, Saturn would be the size of an

orange, Uranus and Neptune would each

be the size of lemons, and the Sun would

be the size of a tall man.

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The relative sizes of the Mercury, Venus, Earth, and Mars. NASA/JPL.

While it is easy to compare the

relative sizes of the planets in an image,

it is more difficult to compare their

relative distances from the Sun. If the

Solar System was shrunk to one billionth

of its actual size, the Moon would be

about 30 centimeters away from the

Earth. The Sun would be 150 meters

(one and a half football fields) away from

the Earth. Mars would be 325 meters

away (three football fields), Jupiter would

be 750 meters away (5 city blocks),

Saturn would be 1500 meters away (10

city blocks), and the nearest star would

be more than 40,000 km away (twice the

circumference of the Earth!)

From the Earth, Mars looks like a

big, reddish star. A somewhat closer

view as in this image taken as the Mars

Climate Orbiter was approaching the

planet, shows the brightly lit side of Mars

that is facing the Sun.

Physical Properties and Composition

Mars has a mass of 6.4x1023 kg,

or about 100 times less than the mass of

Earth. It has a diameter of 6,000 km, or

about half that of Earth. The surface

area of Mars is about the same as the

land area of Earth. There is no evidence

of current plate tectonic activity or active

volcanism on Mars, although there is

evidence to suggest that such

phenomena have been present in the

past. Mars is made of an inner core with

a 1700 km radius, a molten mantle, and

a very thin crust that ranges from 80 km

to 30 km thick in places. The planet is

made mostly of iron. In fact, iron oxide

(rust) on the surface of Mars is what

makes the so-called “Red Planet” appear

red.

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The interior of Mars. NASA/JPL.

The surface of Mars. NASA/JPL.

Because Mars is not very

massive, it can retain only a thin

atmosphere of mostly carbon dioxide.

Carbon dioxide makes up 95.3 percent of

the atmosphere, while nitrogen at 2.7

percent, argon at 1.6 percent, oxygen at

0.15 percent, and water at 0.03 percent

make up the remainder. The carbon

dioxide on Mars does produce a small

greenhouse effect that raises the

temperature on the planet about five

degrees. The atmosphere is thick

enough to produce very large dust

storms that can be seen from Earth.

A dust devil on Mars, taken by the Mars Global Surveyor. NASA/JPL.

A Martian sunset, taken by the Imager for Mars Pathfinder. NASA/JPL.

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The red and blue colors in this

Martian sunset are caused by absorption

and scattering of light by dust in the

atmosphere.

Mars also has ice caps on both its

north and south poles. The ice caps

grow and shrink with the seasons, and

they are made of both carbon dioxide ice

(“dry ice”) and water ice. The ice caps

can be seen from Earth.

Martian North Polar Cap. NASA/JPL. The Moons of Mars

Mars has two moons named

Phobos and Deimos, Greek for fear and

panic. Phobos is the closer of the two,

orbiting Mars 9378 km above the planet’s

center. It is very small – the diameter of

the moon is only 22 km. It is very odd-

shaped, and has a mass of just 1.1x1016

kg. It is composed mostly of carbon-rich

rock and is heavily cratered. Most

astronomers think that Phobos is a

captured asteroid.

Phobos orbits Mars very quickly.

It usually rises, transverses the Martian

sky, and sets twice every Martian day.

The moon is also very close to Mars’

surface. Just as an airplane flying over

the Earth’s equator cannot be seen

above the horizon for an observer in the

United States, Phobos is so close to

Mars’ surface that it cannot be seen

above the horizon from all points on

Mars. As it orbits, it slowly spirals in

towards the Martian surface. Phobos

looses 1.8 meters of altitude per century,

and in 50 million years it will either crash

into the surface or be destroyed in the

atmosphere.

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Phobos taken from the Viking 1 Orbiter. NASA/JPL.

Deimos orbits farther out than

Phobos, and it is even smaller, with a

diameter of only 12.6 km and a mass of

1.8E15 kg. In fact, Deimos is the

smallest known moon in the Solar

System. Like Phobos, Deimos is made

of mostly cratered carbon-rich rock, is

very amorphous, and is thought to be a

captured asteroid. Like our own Moon,

Deimos orbits far enough away from

Mars that it is being slowly pushed

farther and farther away from the planet.

Deimos, taken from the Viking 2 Orbiter. NASA/JPL. Mars Geography

Like Earth, the surface of Mars

has many kinds of landforms. Some of

Mars’ spectacular features include

Olympus Mons, the largest mountain in

the Solar System. The Tharsis Bulge is

a huge bulge on the Martian surface that

is about 4000 km across and 10 km high.

The Hellas Planitia is an impact crater in

the southern hemisphere over 6 km deep

and 2000 km in diameter. And the Valles

Marineris, the dark gash in Mars’ surface

shown in the picture below, is a system

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of canyons 4000 km long and from 2 to 7

km deep.

Mars, taken by the Hubble Space Telescope. NASA/JPL.

The white patches in the map of

the Martian surface shown below are

clouds and storms in Mars’ atmosphere.

Mars with clouds and storms, taken by the Hubble Space Telescope. NASA/JPL.

Martian Topography. NASA/JPL.

This is a map of Martian

topography. In the left image, the

Tharsis Bulge can be seen in red and

white. The Valles Marineris is the long

blue gash through the middle. In the

right image, the blue spot is the Hellas

impact basin. Craters can also be seen

in the right image.

Mars Topography. NASA/JPL.

This image is a flat map of Mars,

made from data from an instrument

aboard the Mars Global Surveyor. There

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are striking differences between the

northern and southern hemispheres.

The northern hemisphere (top) is

relatively young lowlands. It is about 2

billion years old. The southern

hemisphere (bottom) consists of ancient

and heavily cratered highlands, much

like the surface of the Moon. It is about 4

billion years old. There is a very clean

boundary between the two regions,

although the reason for this sharp break

is unknown. It might be due to a very

large impact that occurred just after the

planet’s formation. The Hellas impact

basin is visible as the bright blue region

on the left side of the image. The

Tharsis Bulge is the bright red region on

the right side. It is interesting to note that

these two features are located on exact

opposite sides of the planet from each

other. Olympus Mons is the white spot

to the left of the Tharsis Bulge.

Mountains

The picture below shows the

Libya Montes, examples of mountains on

Mars. The Libya Montes were formed by

a giant impact. The mountains and

valleys were subsequently modified and

eroded by other processes, including

wind, impact cratering, and flow of liquid

water to make the many small valleys

that can be seen running northward in

the scene. This picture covers nearly

122,000 square kilometers (47,000

square miles).

Mountains on Mars. NASA/JPL. Volcanoes

There is no known current active

volcanism on Mars. All of the volcanoes

on Mars appear to be extinct. Mars also

lacks plate tectonics. Both volcanic and

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plate tectonic activity are caused by heat

flowing from the interior of a planet

toward the surface. Because Mars is

much smaller than the Earth (about half

its diameter), and is much less massive

(about 1/10 the mass of Earth), the

planet cooled off very quickly. There is

no more heat to escape from the interior

of the planet, and therefore all plate

tectonic and volcanic activity has

stopped.

The best known volcano on Mars

is Olympus Mons, which is the largest

volcano in the Solar System. It is a

shield volcano, meaning that it has

broad, gentle slopes that were formed

from the eruption of lava. It rises 24 km

(78,000 ft.) above the surrounding plains

– much higher than Mt. Everest here on

Earth. Its base is more than 700 km in

diameter, which is bigger than the state

of Missouri. It is rimmed by a cliff 6 km

(20,000 ft) high. The last time Olympus

Mons erupted was about one billion

years ago.

Olympus Mons. NASA/JPL.

Oblique view of Olympus Mons. NASA/JPL.

Elevation of Olympus Mons. Valleys

The following picture is an image

of the Valles Marineris, the great canyon

of Mars. It is like a giant version of the

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Grand Canyon. The image shows the

entire canyon system, which is over

3,000 km long, stretching over about

one-third of the planet. The canyon

averages 8 km deep and might have

formed from a combination of plate

tectonics and erosion. Several craters

are also visible around the canyon.

Valles Marineris. NASA/JPL.

Oblique view of the Valles Marineris. NASA/JPL. Craters

Like the Earth and the Moon,

Mars also has impact craters. All three

bodies have experienced approximately

the same rate of cratering, but because

of erosion, the craters have different

appearances on each surface. Because

the Moon has little to no atmosphere,

most craters there look as fresh as the

day they were made. Mars does support

a thin atmosphere, so some erosion of

craters there does take place. However,

the extent of this erosion is very small

compared to the erosion of craters that

happens on Earth.

Craters on Mars. NASA/JPL. Earth: This crater was created by a

comet or asteroid that hit the Earth

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several hundred million years ago. It is

located in the Sahara Desert in Chad,

and it is about 17 km wide. Erosion of

the crater is clearly visible.

Crater on Earth. NASA/JPL. Mars: This crater is located on the

surface of Mars. While not as eroded as

the craters on Earth, the rim of the crater

has been sculpted by ice that forms on

the ground.

Crater on Mars. NASA/JPL. Moon: These craters on the Moon are

located near the Sea of Tranquility.

Craters on the Moon show very little

erosion because the Moon has very little

atmosphere.

Craters on the Moon. NASA/JPL.

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Surface rocks

In this image of the Martian

surface taken by the Imager for Mars

Pathfinder, the colors have been

exaggerated to help show differences

among the rocks and soils. It is clear

from the image that there are three

different types of rocks. The white

arrows point to flat white rocks of

unknown age. The red arrows point to

large rounded rocks that show

weathering on their surfaces, and so

have probably been at the site for some

time. The blue arrows point to smaller,

angular rocks. These rocks have not

been weathered, and so are thought to

have been deposited or placed at this

site recently, possibly by an asteroid

impact.

Rocks on the surface of Mars. NASA/JPL. The following images of rocks on the

surface of Mars were taken by the

cameras aboard the Mars Pathfinder.

Rocks on the surface of Mars. NASA/JPL.


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Rocks on the surface of Mars. NASA/JPL. Crust composition

Mars' crust varies in thickness

across the planet. In the northern

hemisphere, the crust is only about 35

km thick, while in the southern

hemisphere, it is about 80 km thick. This

is probably caused by a period of uneven

cooling that the planet experienced. For

unknown reasons, Mars’ Northern

Hemisphere cooled more slowly than the

Southern Hemisphere, causing it to form

a smoother, thinner crust in that area.

This image shows a possible

configuration of soil and ice in the first

three feet of the surface of Mars.

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Soil composition on Mars. NASA/JPL. Atmosphere composition

Mars’ atmosphere is composed

mostly of carbon dioxide, which accounts

for 96% of the total. The rest of the

atmosphere is nitrogen, and argon, with

very small amounts of oxygen. Mars has

a very thin atmosphere; it is 200 times

less massive than the atmosphere on

Earth. It would not be possible for

people to breathe on Mars – not only is

the atmosphere very, very thin, there is

not enough oxygen. However, it is thick

enough to allow a parachute to slow an

incoming spacecraft. Mars also has

clouds and dust storms, as visible in the

pictures below.

Clouds in the Martian atmosphere. NASA/JPL.

Clouds and Storms on Mars. NASA/JPL. Ice caps

See also the benchmark lesson on Water

on Mars.

Mars has ice caps at both its

northern and southern poles. The ice is

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water ice and carbon dioxide ice (dry

ice). In ideal observing conditions, it is

possible to see the Martian ice caps from

a backyard telescope on Earth.

Mars with ice caps. NASA/JPL.

In the summer, the ice caps shrink as the

water ice evaporates, leaving behind the

carbon dioxide ice.

Martian North Polar Ice Cap. NASA/JPL.

Conditions on Mars Gravity, etc.

The acceleration due to gravity on

the surface of Mars is 3.72 m/s^2, or

about 0.38 times of Earth. The surface

magnetic field is about 800 times smaller

than that of Earth.

Atmosphere (content, density, sky

appearance)

Mars has a very thin atmosphere.

With a mass of only about 2.4E19 grams,

it is about 200 times less massive than

the atmosphere of the Earth. Of the

entire planet, only about 4 parts out of

100 million are in the atmosphere. The

surface pressure on Mars due to the

atmosphere is only 7 millibars, or about

0.007 times the pressure of one

atmosphere on Earth. Mars’ atmosphere

is made up of 95.3% carbon dioxide,

2.7% nitrogen, 1.6% argon, 0.13%

oxygen, 0.07% carbon monoxide, and

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about 0.03% water vapor. Mars has 70

times more carbon dioxide than the

Earth.

It would not be possible for a

person to survive by breathing the

Martian atmosphere. The atmosphere is

too thin and does not contain enough

oxygen to sustain human life. Any

astronauts present on the surface would

need life support equipment such as

space suits to survive. Space suits

would also protect the astronauts from

harmful radiation that can reach the

surface through the thin atmosphere, and

from the extremely cold temperatures.

Sunset on Mars. NASA, JPL.

Weather, winds, storms

Storms and carbon dioxide clouds

do form on Mars. Evidence of winds on

Mars can be seen in this image of dunes

formed on the Martian surface. The wind

that formed these dunes was blowing

from the bottom left to the top right of the

image. The image was taken by a

camera on the Mars Global Surveyor,

and is about 3 km wide.

Unlike Earth, it does not rain on

Mars. It is possible for clouds to form in

the thin atmosphere, but temperatures

are too low to allow liquid water to form.

However, water ice fog is often created

in the bottoms of Martian canyons in

early morning, and frost can form in

many places on the surface.

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Martian sand dunes. NASA/JPL.

Temperatures, seasons, climate

The average surface temperature

on Mars ranges from 180 to 270 K, or –

93 degrees C to –3 degrees C (-135

degrees F to 26 degrees F). Daytime

temperatures range from 216-226 K (-57

to -47 degrees C, or –71 to –53 degrees

F), and nighttime temperatures range

from 153-208 K (-120 to –65 degrees C,

or –184 to –85 degrees F).

Like Earth, Mars experiences

changes of seasons. On any planet,

changes of season are caused by the tilt

of the planet’s axis. As a result of a

planet’s axial tilt, the north pole of a

planet’s axis points toward the Sun at

times in its orbit around the Sun, and at

other times, it points away from the Sun.

As an example, when the north

pole of Earth’s axis is pointing toward the

Sun, the northern hemisphere receives

the most direct rays of sunlight. The Sun

travels very high in the sky during this

time, and the number of daylight hours

per day is increased. With longer days

and more direct sunlight, the northern

hemisphere is heated, causing summer.

At the same time, the opposite is true for

the southern hemisphere. That part of

the Earth receives the least amount of

direct rays of sunlight, the sun is very low

in the sky, and the days are very short.

This causes the southern hemisphere to

experience winter.

Conversely, when the north pole

of the Earth’s axis is pointing away from

the Sun, the northern hemisphere

receives the least direct rays of sunlight.

The Sun travels is very low in the sky

during this time, and the number of

daylight hours per day is decreased.

With shorter days and less direct

sunlight, the northern hemisphere is

cooled, causing winter. At the same

time, the opposite is true for the southern

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hemisphere. That part of the Earth

receives the most amounts of direct rays

of sunlight, the sun is very high in the

sky, and the days are very long. This

causes the southern hemisphere to

experience summer.

The axial tilt of a planet causes seasons.

The length and severity of

seasons on a planet are determined by

the amount of the planet’s axial tilt. A

planet with no axial tilt would have no

seasons, while one with a 90 degree

axial tilt (such as Uranus!) would have

very extreme seasons. Seasons on

Earth are moderate because Earth’s axis

is tilted by 23.45 degrees. Mars has

seasons that are very similar to Earth’s

because Mars’ axis is tilted by 23.98

degrees.

On Earth, the axial tilt is the only

reason we have seasons. The Earth’s

orbit is very nearly circular, so the

seasons are not influenced by the small

amount that the Earth is closer to or

farther from the Sun over the course of a

year. (If Earth’s distance from the Sun

was what caused the seasons, the entire

Earth would experience the same

season at the same time, which, of

course, isn’t true!)

Seasons on Mars are a little more

complicated. Mars has a more elliptical

orbit than Earth, so the small amount that

the planet is closer to or farther from the

Sun over the course of a year do make a

difference in the amount of sunlight that

reaches Mars. However, for the most

part, the seasons are caused by the tilt of

Mars’ axis.

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In terms of Mars’ climate history,

Mars is much colder now than it was in

its early days. More than 2 billion years

ago, Mars was much warmer, and

consequently, wetter.

Length of year

It takes Mars 1.88 Earth tropical

years to orbit the Sun once. This means

that one year on Mars is about 687 Earth

solar days long.

Length of day

It takes Mars 1.026 Earth solar

days to rotate once on its axis. This

means that one day on Mars is about 24

hours and 37 minutes long.

Water on Mars

Polar Ice Caps

Mars has ice caps on both its

north and south poles. The ice caps are

made of water ice and carbon dioxide ice

(dry ice). There are two kinds of ice caps

on Mars: seasonal ice caps and residual

ice caps. Seasonal ice caps accumulate

during the winter season, and evaporate

during the summer. The residual caps

remain during the entire year.

Martian North Polar Cap. NASA/JPL.

Mars’ seasonal ice caps are

entirely dry ice that is about 1 meter

thick. The southern seasonal cap

measures about 4000 km across when

its largest during southern winter, and

the northern cap measures about 3000

km across at its largest, during northern

winter. When summer temperatures rise

above 150K (-120 C), the ice sublimes

(passes directly from the solid state into

the gaseous state, bypassing the liquid

state) into the atmosphere. Large

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seasonal changes in the amount of

carbon dioxide in the atmosphere cause

large seasonal changes, up to 30%

different, in the atmospheric pressure on

Mars.

Mars’ residual caps vary by

hemisphere. The northern cap is about

1000 km across and is made of mostly

water ice. In fact, it is the main

repository of water on Mars. The

southern cap is much smaller, only about

350 km across. It is made of carbon

dioxide ice.

Martian North Polar Cap. NASA/JPL.

Water channels

While there is no running water on

Mars today, there is plenty of evidence

that it once existed on the surface. Most

of this evidence is in the form of dry

channels in the ground that were formed

by running water. Water existed on the

surface of Mars several billion years ago,

when the atmosphere of the planet was

thicker and the temperature was warmer.

Water channels on Mars. NASA/JPL.

There are two kinds of channels

on Mars that have been left by water

flows: runoff channels and outflow

channels. Runoff channels are the

equivalent of dry river beds on Mars.

They are a series of meandering,

connecting pathways that are found only

in the southern highlands. They, like the

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southern highlands, are thought to be

about 4 billion years old.

Outflow channels are channels

that were created during enormous flash

floods on Mars. After the time of free

flowing water, when the runoff channels

were formed, the climate on Mars

became very cold and much of the water

froze into ice caps or permafrost just

below the surface. About one billion

years later, volcanoes became active on

the planet and melted much of the water.

The melting water cascaded to lower

elevations in huge flash floods, carving

outflow channels as it went. Many

teardrop shaped “islands” were also

formed in the outflow channels. When

the volcanism ended, the water refroze

into the conditions that exist today.


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Surface Water

The sizes of the outflow channels

indicate that there was once a great deal

of water present on the surface of Mars.

While some of it has frozen out into the

northern residual ice cap, the majority of

the water is trapped just below the

surface in permafrost.

Soil composition on Mars. NASA/JPL. Previous, Current, and Future Missions to Mars Mariner 4

Mariner 4 was a small robotic

spacecraft that was sent to Mars on

November 28, 1964 to complete one

flyby. It flew over Mars in July, 1965 and

took pictures of the surface with its digital

tape recorder. The images showed

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lunar-type impact craters. After its flyby,

it continued in orbit around the Sun for

three years.

Mariner 6-7

Mariner 6 and Mariner 7 were

identical small robotic spacecraft that

were launched on July 31, 1969 and

August 5, 1969, respectively. They

arrived at Mars at about the same time

and completed one flyby. Mariner 6 flew

over the Martian equator, and Mariner 7

flew over the southern polar region. Both

had imaging equipment, and they sent

back hundreds of pictures. They also

analyzed the Martian atmosphere with

remote sensing equipment. The data

that Mariner 6 and Mariner 7 collected

confirmed that the dark lanes seen on

Mars from Earth were not canals, as was

previously thought.

Mariner 9

Mariner 9 was also a small robotic

spacecraft, and it was launched on May

30, 1971. Unlike Mariner 4, 6, and 7,

which simply flew by Mars, Mariner 9

was designed to establish an orbit

around the planet. It did so successfully,

and continued to orbit for almost a year.

Mariner 9 used its imaging instruments to

make a map of the entire surface of

Mars. As a result, many previously

unknown features of Mars were

discovered, including Olympus Mons and

Valles Marineris, and dry river beds.

Close up images were also taken of the

two Martian moons, Phobos and Deimos.

Mariner 9. NASA/JPL.

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Viking 1-2

Viking 1 and 2 were identical

robotic spacecraft launched on August

20, 1975 and September 9, 1975

respectively. They were the first man-

made spacecraft to land on another

planet. Each Viking spacecraft consisted

of an orbiter and a lander. Each orbiter

and lander flew to Mars together, and

then decoupled in the Martian

atmosphere. The lander descended to

the ground and the orbiter continued to

orbit the planet. The entire mission was

designed to continue for 6 weeks after

landing, but all 4 components continued

to be active long after this deadline had

passed. The Viking 1 orbiter continued

to fly over the Martian surface for a full

three years, and the lander lasted 7

years on the surface of Mars. The Viking

2 orbiter and lander both lasted for four

years.

The Viking 1 and 2 landers

descended to two different parts of Mars,

but they carried out the same types of

experiments. While on the ground, they

performed tests of the Martian soil to

look for signs of life. However, no such

signs were detected. Both the landers

and the orbiters sent many hundreds of

images of the surface of Mars back to

Earth.

Viking Lander. NASA/JPL. Mars Pathfinder/Sojurner Rover

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Mars Pathfinder was a robotic

spacecraft that was launched on

December 4, 1996. It landed on Mars on

July 4, 1997, using a parachute and

airbags to cushion the fall. Upon

landing, Pathfinder unfolded its

instruments and deployed a small mobile

robot called Sojurner Rover. The lander

was renamed the Carl Sagan Memorial

Station after successful setup on the

Martian surface.

Mars Pathfinder landed in an

outflow channel littered with many

different kinds of rocks. Cameras on the

lander sent back over 16,500 images of

the Martian surface, and cameras on the

Sojurner Rover sent back another 500

more. In addition, Pathfinder completed

more than 15 chemical analyses of the

rocks and soil, and it studied the wind

and weather of the planet.

Mars Pathfinder. NASA/JPL.

Airbags landing system for Mars Pathfinder. NASA/JPL. Mars Global Surveyor

Mars Global Surveyor is a robotic

spacecraft designed to study Mars while

in a polar orbit around the planet. It was

launched from Earth on November 7,

1996. Mars global Surveyor completed

its mission in January 2001, and as it is

still orbiting Mars today, it is currently in

an extended mission phase. The

satellite has returned more data about

Mars than all of the previous missions to

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Mars combined. It has sent back

thousands of images including 3-D

images of the northern polar ice cap,

studied the magnetic field of Mars, found

possible locations for water, and studied

the Martian moons.

Mars Global Surveyor. NASA/JPL. 2001 Mars Odyssey

2001 Mars Odyssey is a robotic

spacecraft that was launched on April 7,

2001. It is currently in orbit around Mars,

collecting images and data to help

scientists determine the soil and rock

composition, the amount of water on

Mars, the history of the climate of Mars,

and the extent of radiation on the planet.

Mars Odyssey. NASA/JPL. 2003 Mars Exploration Rovers

Two identical rovers will be

launched between May and July 2003,

bound for Mars. The rovers will be much

like the Sojurner Rover, but they will be

much more powerful. Like Mars

Pathfinder, the Rovers will enter the

Martian atmosphere directly, slowed by

parachutes. Then airbags will shelter the

robots as they bounce approximately 12

times and roll to a stop. Upon landing,

30

the spacecraft will unfold and the Rover

will deploy. Unlike Pathfinder, the

Rovers will have all the scientific

instruments on board, and they will be

able to travel up to 100 yards each

Martian day. With no need to return to

the landing site, the Rovers will be able

to explore a comparatively large area of

the Martian surface. The Rovers, which

will land in different areas on Mars, will

send back images from their cameras

and data about the Martian soils, which

they will be able to analyze at very small

scales.

Mars Exploration Rover. NASA/JPL. 2005 Mars Reconnaissance Orbiter

This robotic spacecraft, planned for

launch in 2005, will be designed to

image the surface of Mars to even

smaller scales. It will map the

surface of the planet with sufficient

resolution to be able to see rocks the

size of beach balls. Hopefully the

data it collects will allow scientists to

understand better the location and

amount of water on Mars.

Mars Reconnaissance Orbiter. NASA/JPL.

Smart Lander and Long-Range Rover

31

The Smart Lander and Long-

Range Rover are planned for launch by

2007. They will be designed to use a

new precise landing method that should

allow landings in otherwise inaccessible

areas. The spacecraft will also be a

laboratory for even better surface

measurements.

Scout Missions

Scout Missions, which could be

small airborne craft or small landers, are

also planned for 2007 launch. They

would help increase the scale of airborne

observations or increase the number of

sites on Mars that have been visited by

human spacecraft.

Sample Return and Other Missions

NASA plans many other missions

to Mars after 2010. One type of mission

includes a spacecraft that would land on

Mars, collect samples of Martian soil,

and return those samples to Earth. This

type of mission might be underway as

soon as 2011, but for now the first

Sample Return mission is slated for

2014, and the second for 2016.

Getting to Mars Escape velocity

Launch of the Mars Pathfinder Mission.

NASA/JPL.

The first problem facing a

potential trip to Mars is leaving Earth.

Specifically, this problems deals with the

enormous amount of energy necessary

to break free from the Earth’s

gravitational field and start traveling

towards Mars, or anywhere else in the

Solar System. To find out what energy,

and therefore speed, is necessary to

32

escape Earth’s gravity, let us consider

the energy of a rocket at Earth’s surface:

E = ½ mrocket vinitial

2 – GMearthmrocket/Rearth Energy is the sum of kinetic and potential

energies. Here, vinitial is the initial

velocity, mrocket is the mass of the rocket,

and Mearth and Rearth are the mass of the

Earth and the radius of the Earth. Now,

because the energy of the rocket is

constant as it travels upward, we can

equate the energy of the rocket at the

surface to the energy of the rocket at its

maximum altitude:

½ mrocket vinitial

2 – GMearth mrocket /Rearth = ½ mvfinal

2 – GMearth mrocket /rmaximum. Here, vfinal is the final velocity and rmaximum

is the maximum height. However, at its

maximum height, vfinal = 0, so the

equation becomes

½ mrocket vinitial

2 – GMearth mrocket /Rearth = – GMearth mrocket /rmaximum. Solving for vi, we have vinitial

2 = 2GMearth(1/Rearth – 1/ rmaximum).

Setting rmaximum = 8, which is the

condition for gravitational escape, vinitial

becomes vescape and we have

vescape = sqrt(2GMearth/Rearth). The same logic can be applied to any

planet, so the equation for escape

velocity can be generalized to

vescape = sqrt(2GM/R). Thus, the escape velocity from any

planet depends on the mass of the

planet and the radius of the planet. For

example, let us assume that we have a

spacecraft on Earth that we are trying to

send into space. Mearth = 5.98x1024 kg,

and Rearth = 6.37x106 m, so we get:

vescape = sqrt (2GM/R)

vescape = sqrt (2(6.67x10-11 Nm2/kg2)(5.98x1024 kg)/(6.37x106 m)) vescape = 1.12 x104 m/s, or about 11 km/s. Now, let us assume astronauts have

successfully completed their mission on

33

Mars and need to calculate the escape

velocity on Mars so they can travel back

to Earth. Mmars = 6.42x1023 kg, and Rmars

= 3.397x106 m, so we get:

vescape = sqrt (2GM/R) vescape = sqrt (2(6.67x10-11 Nm2/kg2)(6.42x1023 kg)/(3.397x106 m)) vescape = 5.0 x103 m/s, or about 5 km/s. Routes and travel time

There are many different possible

routes to take when sending a spacecraft

to Mars. As each trip covers a different

distance, each takes different amounts of

time and fuel.

Perhaps the most familiar type of

route involves sending the spacecraft out

when Mars is about 45 degrees ahead of

Earth in its orbit. This happens once

every 26 months. The spacecraft

powers outward and catches up with

Mars in about 260 days. For the return

trip, which also takes 260 days, the

spacecraft simply leaves Mars when

Earth is slightly ahead in its orbit, and

spirals into Earth’s orbit, catching up with

the planet. In this scenario, a team

arriving on Mars would be able to spend

460 days there. The entire trip would

take about two and a half years. This

type of route is known as a conjunction

class route because the spacecraft

arrives on Mars or Earth when that

planet is in conjunction with where the

other planet was when the spacecraft

left.

The Sun, Earth, Mars configuration upon launch from Earth.

34

The Sun, Earth, Mars configuration upon arrival at Mars.

A different type of route is known

as an opposition class route, which is

similar in style to conjunction class

routes. It is called opposition class

because Earth and Mars make their

closest approach sometime during the

trip. A spacecraft would have to leave

Earth when Mars was significantly ahead

in its orbit, and the trip would take 220

days. During the return trip, the

spacecraft would spiral inside Earth’s

orbit and catch up to the planet from the

back. The return trip would take 290

days. To time the orbits correctly, there

would only be 30 days available to stay

on the surface of Mars.

Lower thrust rockets can also

travel to Mars using less direct means.

These types of spacecraft spiral out of

Earth’s gravitational field, and arrive at

Mars in 85 days. Part of the ship

detaches to drop off the astronauts and

their gear, and the return module

continues to fly by the planet. The return

module will rendezvous with Mars again

in 131 days, allowing the astronauts to

catch their ride home.

There are many other proposed

ways to get astronauts to and from the

red planet. For example, one scenario

envisions astronauts launching from

Earth and landing on one of Mars’

moons. The astronauts could then set

up a base of operation from which they

could make many trips to the surface of

the planet. In another proposal, a space

station that acts as a permanent ferry

35

could be put in orbit between the two

planets. Smaller spacecraft could then

taxi astronauts between Earth and the

space station and between the space

station and Mars. This situation would

allow many more frequent trips for many

more travelers back and forth between

the planets.

Supplies: food, water, oxygen.

Freeze dried ice cream.

Every person on board a

spacecraft bound for any Solar System

body needs to have access to a

minimum amount of food, water, and

other supplies. Some of these items,

such as air and water, can be filtered and

recycled, while others, such as food,

cannot. For one day on the spacecraft,

one person typically needs 1 kg of

oxygen, 0.5 kg of dry food and 1 kg of

whole food, 4 kg of drinking water, and

26 kg of wash water. Of these staples,

80% of the oxygen, 80% of the drinking

water, and 90% of the wash water can

be recycled. None of the food can be

recycled. For a one way flight lasting

200 days, this translates to 3,440 kg of

supplies needed. Once on the surface of

Mars, oxygen and water can be

manufactured by the astronauts. Food is

therefore the only supply to bring to the

surface, and for a 600 day stay for four

people, 1,200 kg of dry food and 2,400

kg of whole food will be needed.

Psychological needs/concerns

Taking a trip to Mars would be

unlike anything ever experienced by

humans before. As they travel away at

thousands of kilometers per hour in a tiny

capsule, the Earth would get smaller and

36

smaller until it was just a tiny dot. The

feeling of empty space all around would

be almost crushing, leaving no doubt of

the tiny insignificance of the speck of a

spacecraft. And how would people

handle living together, cramped in a tiny

space with no escape for three years?

Communication with Earth would take

longer and longer, eventually causing

there to be 20 minute delays between

messages. If problems aboard the

spacecraft emerged, there would be little

or no help available from Earth. The

threat of death would be woven into

everything the astronauts did. A tiny hull

breach by a small meteorite or a flare

from the Sun would pose fatal hazards

that the crew could not prepare for or fix.

What would be the psychological effects

of such a journey?

It is possible to get a glimpse of

what life might be like on such a journey

by looking at similar environments here

on Earth. Environments such as that on

board a submarine, the International

Space Station, or a remote scientific

camp in Antarctica mimic the

psychological problems that might be

present during a trip to Mars. Examples

of these psychological problems could

include concerns about a limited amount

of resources, the unchanging social

group, social isolation, limited

communication with the outside world, a

self-contained ecosystem, the constant

sense of danger, physical confinement,

lack of privacy, lack of separation

between work and non-work, limited

opportunity for variety and change,

limited sensory deprivation, and

dependence on machine-dominated

environment.

As a specific example, travelers to

Antarctica are very cut off from the

outside world, just as astronauts bound

for Mars would be. Neither would be

37

able to contact their loved ones

whenever they wished, and both would

be so far removed from the recognizable

world that no trace of it would remain.

Also, people in Antarctica must be very

careful with their equipment, food, and

supplies in order to stay alive in the

bitterly cold, harsh conditions.

Astronauts bound for Mars would share

these types of concerns. However,

people living in Antarctica would have

plenty of air to breathe and plenty of

water to drink. They would not have to

bring these supplies with them or be

concerned that they might run out. They

would also have plenty of space – if one

member of an Antarctica team got

annoyed with another, he or she would

have the whole continent to walk away

and be separate for a while. Astronauts,

however, would be very confined with no

escape from each other, and they would

be very worried about the supply of air

and water.

On the International Space

Station, astronauts deal with limited

supplies of air, water, and food every

day. They also live in very small

quarters and must be able to cooperate

in order to survive. These conditions

would be very similar to those

experienced by astronauts bound for

Mars. However, if astronauts aboard the

ISS ever got homesick or frightened,

they merely have radio down to Earth to

speak with their families or friends, or to

look out the window to see that Earth is

just a short flight away. In the event of a

major disaster that threatened the lives

of those aboard, emergency escape

vehicles are available to shuttle the men

and women back to their home planets.

However, aboard spacecraft bound for

Mars, no such quick communication or

emergency ride home would exist. As

38

the ship got farther and farther away

from the Earth, radio messages would

take longer and longer to reach them.

Also, the Earth itself would shrink to the

size of a tiny dot, similar to the other

stars. No one in human history has ever

been so far from our home planet, and

the psychological effects of seeing Earth

nearly disappear into the darkness of

space are much unknown.

Perhaps the best analogue

relating to travel to Mars would be that of

a person in a submarine. Living on a

submarine for an extended period of time

would certainly be similar to living in a

spaceship going to Mars. In both

situations, the people on board would be

living in very cramped, tight quarters, and

they would be forced to get along to

survive. They would be breathing filtered

air and drinking filtered water. All

necessary food and personal supplies

would have to be brought on board the

ship before it departed. In addition,

communication with the outside world

would be limited and delayed, resulting in

only sporadic contact with the crew’s

loved ones and friends at home.

Perhaps most similar would be the

dependence on machines for life and

safety and the imminent threat of death if

those machines fail. Just as all aboard

the submarine would be killed in the

event of a hull breach, or a fire, so would

all be killed in a spaceship bound for

Mars. However, it is important to note

that if a crew member became very ill or

if an emergency happened that was not

immediate, the submarine (unlike the

spacecraft) could always return to the

surface in a relatively short time to

secure help.

In order to alleviate some of these

potential problems that might arise

during a mission to Mars, studies are

being done to determine the types and

39

numbers of people that would best

handle the enormous stress and that

best get along in these types of

environments. Technology is also being

developed to help determine when an

astronaut is in psychological distress,

and to develop strategies for dealing with

the distress that do not involve returning

to the Earth. For example, computers

can now discern the emotional inflection

in a person’s voice to look for signs of

emotional trouble. If the computer does

find that someone is in need of help, it is

programmed to suggest ways to alleviate

the problem, such as recommending

extra rest, extra food, or possibly

medications.

40

The Benchmark Lessons were developed with the help of the following sources: Alpert, Mark. “How To Go To Mars.” Scientific American, March 2000, pp. 44-51. Bill Arnet’s “The Nine Planets” website, http://nineplanets.org Begley, Sharon. “The Search for Life.” Newsweek, December 6, 1999, pp. 54-61. Chaisson, Eric, and McMillan, Steve. Astronomy Today. Prentice Hall, Upper Saddle

River, New Jersey, 1999. “Cognitave States.” Discover, May 2001, pp. 35. Hayden, Thomas. “A Message, But Still No Answers.” Newsweek, December 6, 1999, pp. 60. JPL’s Mars for Teachers site, http://mars.jpl.nasa.gov/classroom/teachers.html JPL’s Mars Missions website, http://mars.jpl.nasa.gov/missions/ JPL’s Planetary Photojournal, http://photojournal.jpl.nasa.gov/ Mars Pathfinder Science Results Directory,

http://mars.jpl.nasa.gov/MPF/science/science-index.html Murr, Andrew and Giles, Jeff. “The Red Planet Takes a Bow.” Newsweek, December

6, 1999, pp. 61. The NASA Image Exchange, http://nix.nasa.gov/ NASA Goddard Space Flight Center

http://svs.gsfc.nasa.gov/stories/MOLA/index.html NASA Goddard Space Flight Center, Earth Science Gallery

http://www.gsfc.nasa.gov/gsfc/newsroom/tv%20page/g00-016_earth.html Oberg, James, and Aldrin, Buzz. “A Bus Between the Planets.” Scientific American, March 2000, pp. 58-60. Robinson, Kim Stanley. “Why We Should Go to Mars.” Newsweek, December 6, 1999, pp. 62. Serway, Raymond A. Principles of Physics. Saunders College Publishing, Harcourt Brace College Publishers, Austin, 1994.

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Simpson, Sarah. “Staying Sane in Space.” Scientific American, March 2000, pp. 61-62. Singer, Fred S. “To Mars By Way of Its Moons.” Scientific American, March 2000, pp. 56-57. Weed, William Speed. “Can We Go To Mars Without Going Crazy.” Discover, May

2001, pp. 36. Wilford, John Noble. “Photos Bolster Idea of Water, and Possibly Life, on Mars.” New

York Times, 2/20/03 Yam, Philip. “Invaders from Hollywood.” Scientific American, March 2000, pp. 62-63. Zeilik, Michael, Gregory, Stephen A., and Smith, Elske v. P. Introductory Astronomy

and Astrophysics. Saunders College Publishing, Harcourt Brace Jovanovich College Publishers, Austin, 1992.

Zorpette, Glenn. “Why Go To Mars?” Scientific American, March 2000, pp. 40-43. Zurbin, Robert. “The Mars Direct Plan.” Scientific American, March 2000, pp. 52-55.

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