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THEMIS Views Mars in a New Light

These images were recorded by THEMIS on 19 February 2002.

Here are two images of the same area of Mars.  It shows an area approximately 300 kilometers (186 miles) wide.  The top image was taken by Viking in 1976.  The lower image is a daytime infrared image from THEMIS.  You can spot many of the same surface features in both pictures.  The difference between the two is what you might see if you put on night vision goggles.  In the THEMIS image, the bright areas are warm and the dark areas are cold.


At Mars, it is now the end of the summer in the southern hemisphere.  In the north, winter is ending.  The coldest regions have a temperature of -100 degrees Celsius (-150 degrees Fahrenheit).  The THEMIS infrared camera can take the same kind of picture during the day or night.  The night pictures allow the scientist to see things they can not see during the day.  The temperature on Mars plunges when the sun goes down.  The dusty sandy areas lose warmth very quickly but rocks will stay warm.  When the sun rises, the rocks will stay cooler while the sandy areas will warm quickly.

The following images are about 32 kilometers (20 miles) wide.  Features as small as 150 meters (500 feet can) be seen.

In this first picture, you can see the effect of sun on steep slopes and the dark walls are in shadow.  You are seeing the heat of the sun, not its light.  The circular features are impact craters.

Thermal image of Terra Sirenum

THEMIS has ten filters to create a color image of the data.  This is the first color infrared image of the surface of Mars.  Color infrared images show different rocks and minerals present on the surface of Mars.  A major objective of the THEMIS investigation is to map the entire surface of Mars looking for the most interesting and exciting minerals.  Some of these may have been formed in water and these areas are the beacons for places you want to send future rovers, landers and sample return missions.

Terra Sirenum in infrared

The scientists had no idea what to expect when they first got to see Mars at night.  What you see here are temperature variations during the night.  During the day, the rocks are colder than the sandy areas, but at night they hold onto the warmth from the daytime sun.  The bright area you see around the rim of the crater is rocks that remain millions of years after that crater was formed.  The channel you see there is about a half a mile across and is full of cold dust.  The scientists do not know why this channel is full of cold dust, but it will be extremely interesting to try to find out!

Ancient channels

Phil Christensen describes this as a picture of "a disruptive terrain produced by the rapid removal of underground water."  The cold dark squares you see are mesas standing thousands of feet above the canyon floors beneath them.  They are about 8 kilometers (5 miles) across and are covered in dust.  The cliffs and steep slopes of these canyons are covered by rocks.  It will be very interesting to determine how these rocks accumulated and why they remain millions of years after these mesas were formed.

Hydaspis Chaos

When the scientists can see the presence of rocks, it raises many questions.  What kind of rocks are they?  Why are they there?  How did they get there?  At night, the camera can also see other "hot spots".  It will take time to find out if something is an outcropping of rocks, an underground hot spring or perhaps an active volcano.  Scientists are very excited, this is only the beginning of a mission which will last many years.  For each new thing they spot, they will form a hypothesis and then test that hypothesis.  As you know from your school science projects, it takes a long time to process all your data and prove your theory.  What you end up proving may not be what you thought in the beginning.  This is what the Mars scientists are doing now.

For more information about THEMIS, go to:

- 1 March 2002


Last Updated:
8 January 2015

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