This material was developed for the Live From Mars project
by Passport to Knowledge. Live
From Mars was a precursor to Mars Team Online.
Activity 5.1: Today's Weather on Mars
Teacher Background: Seasons, weather and climate on Earth and Mars
| The primary influence on Earth's seasonal temperature
changes arises from the fact that its axis of rotation (its daily
spin on an imaginary North Pole/South Pole line) is tilted relative
to the plane of its orbit (its yearly path around the Sun). This tilt
amounts to about 23 and a half degrees.
Mars' axis of rotation is also tilted to the plane of its orbit:
about 25 degrees (almost the same as Earth). Thus, Mars also has
seasons. As on Earth, scientists call these seasons summer, fall,
winter and spring with opposite seasons occurring simultaneously
in the northern and southern hemispheres. However, since Mars takes
almost twice as long to go around the sun as does Earth, its seasons
are almost twice as long as ours.
The Earth is actually closest to the Sun in early January and
farthest from the Sun in early July. However, Earth's orbit is so
close to circular that the tilt of our planet's axis has far more
to do with temperature differences from summer to winter than our
planet's distance from the Sun. Mars' orbit is considerably more
elliptical than Earth's. Mars' distance from the Sun varies from
as little as approximately 128 million miles (207 million kilometers)
to as much as about 154 million miles (249 million kilometers).
Thus, at times, Mars is about 20% closer to the Sun than at other
times and this changing distance from the Sun also significantly
influences its seasons.
Because a planet travels fastest around the Sun when it is closest
to it and slowest when it is farthest away, this also has an effect
on the length of the seasons in the different hemispheres. During
the current epoch, Mars is closest to the Sun when it's summer in
the southern hemisphere. Thus, southern hemisphere summers on Mars
are currently shorter but warmer than those in the northern hemisphere,
while northern hemisphere winters are shorter but colder than those
in the southern hemisphere. Southern hemisphere summer temperatures
can be as much as 60°F degrees (33°C) warmer than those
in the northern hemisphere.
Because Mars is farther from the Sun than Earth, its average seasonal
temperatures are, as you would imagine, colder than on earth. Mars
has an atmosphere that's mostly carbon dioxide. This creates a greenhouse
effect, but because the atmosphere is so thin, the resulting increase
in global temperature is only about 5 to 10 degrees. Overall, Mars
is much colder than Earth.
On a warm summer afternoon, near the Martian equator, the surface
temperature can occasionally climb to 65° F (18°C). Even
a few centimeters above the surface, however, temperatures are lower.
And at this same spot, the temperature at sunset will have dropped
to below freezing and during the night the thermometer will plunge
to more than 100 degrees below zero F. Around Mars' Northern polar
cap, during the long winter nights, temperatures can fall to as
much as 200 degrees below zero F!
Normally, the thin Martian atmosphere is clear and the planet's
surface can be easily seen. Occasionally, there are clouds. The
white or blue-white clouds are composed of H2O ice crystals
or, more commonly, carbon dioxide ice crystals. These can be seen
around the summits of Mars' huge, extinct volcanoes, along the sunrise
limb of the planet or in the canyons. Yellowish clouds are the result
of fine grains of Martian desert dust being blown into the air.
Occasionally, especially when warm summers come to the Southern
hemisphere, giant dust storms spread to cover most of the planet
for weeks in billowing clouds that are several miles high.
Martian surface winds are normally quite light (between about
4 and 15 miles per hour [6.5Ð24 km/hour]). On occasion, however,
surface winds gust to about 50 miles (80 km) per hour and, during
dust storms can blow at over 300 miles (480 km) per hour. Because
the Martian atmosphere is so thin, however, you would feel much
less pressure from the wind than if you stood in a similar speed
wind on earth.
Light frosts do occur on Mars and light snows may occasionally
fall, but most of the build up in the Martian polar caps during
the winter months is due to direct condensation of H2O and carbon
dioxide out of the atmosphere.
| The Martian Sun Times
An interesting multidisci-
plinary extension using
Viking data invites stu-
dents to become weather
reporters for The Martian
Sun-Times can be found
online. For the full activity,
Skills involved include
Data, Identifying Variables,
Activity I: Seasons on
Mars and Earth: Endless
Activity II: Today on Mars
and Earth: Hot is a
Activity III: Atmospheric
Conditions on Mars and
Earth: Is It All Sun All the
Activity IV: Probing Earth:
What Should We Pack?
The project, developed at
the University of
Chicago, also suggests the
teacher may want to
have encyclopedia and
other book resources
available for students to
read about the Dust
Bowl which took place in
the Great Plains region of
the United States in the
1930s. Students will find
interesting the songs
written by Woody
Guthrie about the effects
of the Dust Bowl...
Students will research temperature and wind data locally, nationally
and internationally and compare these to conditions on Mars, and draw
conclusions about differences and causes.
map of the world
map of Mars
weather data maps of Mars (con-
tained in the Teacher Materials)
newspaper (showing weather
Engage Ask students about temperature and wind. What
is the hottest they can ever remember it being in their town? The coldest?
What's the average wind speed? How high are wind speeds in a hurricane?
Explore/Explain Explain to the students that they will
research temperature and wind conditions on Earth and then compare these
to our neighbor world, Mars.
If your school has a weather station, ask students to make daily
records of maximum and minimum temperatures and the relative humidity
over the course of a couple of weeks. If your school has the necessary
equipment, have students record the average and peak wind speeds
as well. If your school (or another school in your area) has kept
such records over the past year, have students access these records
and examine them. From this data or other sources such as the
weather office at a local TV or radio station, The Weather Channel,
the National Weather Service or the World Almanac, ask them to
research the average daytime high and nightime low temperature
records in their area for each month of the year, as well as the
all-time high and low temperature records for their state, the
country and the world.
Ask students to examine the average high and low temperatures
in their area at different times of the year (especially summer
and winter). Ask them to consider the length of day and night
and the height of the sun in the sky, but also such factors as
relative humidity, elevation, wind direction, ocean influences,
etc. Tell students to research the average high and low temperatures
in January and July in San Francisco, Miami, Rio de Janeiro, Quito,
Riyadh, Jakarta and Sydney. Have them post these temperatures
on their world map. How do these temperatures and day-night temperature
differences vary with latitude? Consider other factors such as
distance from equator, elevation, tropical or desert environment,
or ocean influences.
Next turn students' attention to Mars. Have students access
Viking-based Mars temperature data from the Web, or give teams
copies of the temperature data sheets in your Teacher Materials.
After helping students become familiar with these temperature
maps, have them compare these maps to the surface features of
Mars. Ask them to make tables (on paper, or as computer spreadsheets)
of the average daytime high and nightime low temperatures during
summer and winter on Mars, for latitudes at 45 and 80 degrees
north and south latitude by averaging temperatures at longitudes
of 0, 90, 180 and 270 degrees. Next, have students compute the
difference between daytime highs and nightime lows for each of
these locations. Challenge them to explain the temperatures and
day-night temperature differences that they observe. Have them
compare the maximum and minimum temperatures they observe on Mars
with the temperature records for their city, state, country and
Earth as a whole.
Give students information about the average and peak winds on
Mars and have them compare these to average winds in their area.
Compare the wind speeds in Martian dust storms with the winds
in such terrestrial storms as hurricanes and tornadoes.
| Note: The primary landing site on Mars for the Pathfinder
spacecraft is in the area of Ares Vallis, somewhere around latitude
20 degrees north and longitude 31 degrees at a time that will be
late summer in Mars' northern hemisphere. Challenge your students
to come up with a weather forecast for the date of the landing (July
4, 1997) for this landing site and a general temperature forecast
for the next six months on Mars (that is, through December 1997)
for this location.
| Expand/Adapt/ Connect Teachers
can introduce the formulas for converting Celsius to Fahrenheit
and vice versa, as well as kilometers per hour to miles per hour,
and give their students practice manipulating the algebraic equations.
Teachers of students in higher grades can use this Activity
to give students experience in graphing such variables as maximum
temperature, minimum temperature and temperature difference against
time or longitude, and superimposing graphs of Earth data with
corresponding graphs from Mars.
Have teams of students research and prepare weather reports for
different locations on Mars. Then with appropriate graphics and
maps which they prepare themselves, have them deliver 3 to 5 minute"Team
Coverage" weather reports from around the Red Planet for the latest
edition of the"Interplanetary News Network" (which premiered with
weathercasts for Pluto and Neptune during our previous Live from
the Hubble Space Telescope Module). Suggest that a student report
from both the North and South polar caps. Others can be stationed
on top of Olympus Mons, and on the equatorial plains near Valles
Marineris and in front of a monstrous dust storm heading their
way. Videotape the broadcasts, and send us copies at PTK.
Tell students that they are meteorologists on board the first
human mission to Mars and ask them to write excerpts from their
Weather Log compiled over a year's stay on the surface of the
Red Planet. Students could either stay where they landed, or ask
them to imagine that their team has been equipped with a special
roving vehicle that will allow them to travel to the exotic locations
to be found all over Mars.
Real Science, Real
Scientists ...Real Time
Tracking Martian Weather with actual
Some of the most revolutionary aspects of contemporary science
and science education arise from the new tools used to collect
and share data, and new approaches to involving secondary school
students directly in the analysis of raw data.
Martian weather data will return to Earth at the speed of light,
be shared in near real time with the Principal Investigators (P.I.'s)
for each of the science instruments, and then--again in near real
time--be made available to other researchers and the general public
over the Internet. This special Expand section is intended to
give the reader of the Print Guide sufficient information and
motivation to go on-line, where you will find full details about
how to access and use the incoming stream of new Martian data
Both MPF and MGS have instruments recording weather information:
here are excerpts from NASA briefings:
"...The Imager for Mars Pathfinder is a stereo imaging system
with color capability provided by a set of selectable filters
for each of the two camera channels... A number of atmospheric
investigations are carried out using IMP images. Dust particles
in the atmosphere are characterized by observing Phobos at night.
Water vapor abundance is measured by imaging the Sun through filters
in the water vapor absorption band ...Images of wind socks located
at several heights above the surrounding terrain are used to assess
wind speed and direction ...The IMP investigation also includes
the observation of wind direction using a small wind sock mounted
above a reference grid, and a calibration and reference target
mounted to the lander.
Atmospheric Structure Instrument/Meteorology
The ASI/MET is an engineering subsystem which acquires atmospheric
information during the descent of the lander through the atmosphere
and during the entire landed mission... Data acquired during the
entry and descent of the lander permits the reconstruction of
profiles of atmospheric density, temperature and pressure from
altitudes in excess of 100 km to the surface.
...The ASI/MET instrument hardware consists of a set of temperature,
pressure and wind sensors... Temperature is measured by thin wire
thermocouples mounted on a meteorological mast that is deployed
after landing. The location of one thermocouple is chosen to measure
atmospheric temperature during descent, and three more monitor
atmospheric temperatures 25, 50, and 100 cm above the surface
during the landed mission. Pressure is measured by a Tavis magnetic
reluctance diaphragm sensor similar to that used by Viking, both
during descent and after landing. The wind sensor employs six
hot wire elements distributed uniformly around the top of the
mast. Wind speed and direction 100 cm above the surface are derived
from the temperatures of these elements.
Mars Global Surveyor
| In late 1997 and more especially on through 1998,
Mars Global Observer will also provide weather information, along
with global imagery, topographic mapping and soil and rock profiles.
Here's what the MGS Radio Science team at Stanford University intend:
The MGS Radio Science Team will employ a technique called radio
occultation to probe the Martian atmosphere. Twice per orbit,
MGS will be occulted by Mars and an ultrastable radio transmission
from the spacecraft to Earth will pass through and be perturbed
by the thin atmosphere of Mars. (ed. As the spacecraft goes behind
Mars and then emerges from behind the planet--"occultation"--
the radio signal returning to Earth will be affected by the varying
amount and character of the Martian atmosphere through which it's
being transmitted.) ...Analysis of the perturbations ...will yield
profiles of the temperature and pressure of that atmosphere as
a function of height above the planet's surface. Team members
are hopeful that sophisticated inversion techniques which they
are developing will permit the derivation of temperature and pressure
profiles with a resolution of 10 meters!
The atmospheric profiles will provide the basis for the Daily
Martian Weather Report which will be posted to this page (ed.
note: see URL listing below) as raw data is collected and analyzed.
Please come back and find out about the Martian climate, the atmospheric
temperatures and pressures, the effects of Martian dust storms
(massive temperature inversions), and the very interesting seasonal
variations which occur as polar ice caps form and thaw.
to access Real Science, Real Time
The Live From Mars Web site will provide updated links to all
the weather data and imagery returning from both missions. It
will also point to curriculum materials developed by the research
teams who built and use the various instruments. Encouraging P.I.'s
and their co-workers to engage directly in Education and Outreach
is another innovative aspect of these missions. Just as with the
Live From Mars project, it's a chance for your students to engage
in Real Science, with Real Scientists.
| MGS Radio
To fully appreciate the significance of the MGS radio occultation
measurements, think about this. If you were to launch a weather
balloon from the surface of Mars, you would be able to measure
the temperature and pressure at many heights as the balloon rose
through the Martian atmosphere. You would essentially be able
to collect one profile each of atmospheric temperature and pressure.
Using the radio occultation technique, the MGS scientists have
the potential to collect two of these sets of profiles for each
orbit of the MGS spacecraft. With 12 orbits per day and 687 days
in a Martian year, the Radio Science Team members may gather as
much data on the Martian atmosphere as if they were able to release
many thousands of weather balloons at various locations on the
red planet and measure the temperature and pressure at 10 meter
intervals above the Martian surface!