MARS ODYSSEYOctober 24, 2001

Thermal Emission Imaging System (THEMIS)

• Visible Imaging System

– Visible-light images with 18 meters per pixel resolution

• Infrared Imaging System

– Infrared data set with 100 meters per pixel resolution

Reviewing features on Mars as seen in THEMIS visible images

and MOLA shaded relief context images

THEMIS Visible Image

Context Image:

MOLA Shaded Relief

-19N, 173E

THEMIS THEMIS visible imagesvisible images are taken during are taken during the afternoon the afternoon and the sun is and the sun is shining from the shining from the leftleft

Most THEMIS visible imagesMost THEMIS visible imagesare ~18 km acrossare ~18 km across

CONTEXT CONTEXT imagesimages appear to appear to have the sun have the sun shining from shining from the rightthe right

2N, 237E2N, 237E

THEMIS Visible Image

Context Image

2N, 237E2N, 237E

THEMIS Visible Image: Caldera

Context Image

THEMIS Visible Image

Context Image

-20N, 240E

THEMIS Visible Image: Lava Flow

Context Image

-20N, 240E

THEMIS Visible Image

Context Image

-14N, 307ECoprates Chasma

THEMIS Visible Image: Canyon plateau,

landslides and floor

Context Image

-14N, 307ECoprates Chasma

Landslide closeups

THEMIS visible images

Melas Melas ChasmaChasma-9N, 282E-9N, 282E

Ius Chasma-7N, 275E

Candor Chasma -7N, 290E Candor Chasma -7N, 290E

Candor Chasma -7N, 290E Candor Chasma -7N, 290E

Layers within Valles Marineris

THEMIS Visible Image

Context Image

-47N, 19E

THEMIS Visible Image: Sand Dunes

Context Image

-47N, 19E

THEMIS Visible Image

Context Image

55N, 190E

THEMIS Visible Image: Splosh

Crater with central peak and slumps

Context Image

55N, 190E

Central Peak

Slumps

Hale Crater -35N, 324E Hale Crater -35N, 324E

Gullies found in crater walls

Hale Crater -35N, 324E Hale Crater -35N, 324E

22N, 126E22N, 126E

THEMIS Visible Image

Context Image

22N, 126E22N, 126E

THEMIS Visible Image: Channel

Context Image

THEMIS Visible Image

Context Image

18N, 329E

THEMIS Visible Image: Streamlined

Islands

Context Image

18N, 329E

-3N, 331E-3N, 331E

THEMIS Visible Image

Context Image

-3N, 331E-3N, 331E

THEMIS Visible Image: Chaos

Terrain

Context Image

THEMIS Visible Image

Context Image

25N, 255E25N, 255E

THEMIS Visible Image:

Graben/Fractures

Context Image

25N, 255E25N, 255E

THEMIS Visible Image

Context Image

-15N, 175E

THEMIS Visible Image: Dust Devil

Tracks

Context Image

-15N, 175E

-5N, 200E-5N, 200E

THEMIS Visible Image

Context Image

-5N, 200E-5N, 200E

THEMIS Visible Image: Yardangs

Context Image

Introduction to Infrared Light

and Imaging

Behavior of Light– Reflect– Transmit– Absorb– Emit

• In the visible, we are seeing reflected light

• In the infrared, we are detecting emitted energy

Infrared Energy/Light

• Primarily thought of as heat (thermal radiation) • Is part of the EM spectrum• Infrared energy is just beyond the red portion of

the visible light spectrum – we can not see infrared energy with our eyes

• Any object that has a temperature above absolute zero (~-273C or ~-460F) radiates in the infrared

• Just about everything emits energy in the infrared – Everything glows!

Video – Seeing in the Infrared

ASU’s IR Camera

• Gray-scale not color

• Everything is relative!– Hot = Bright– Cold = Dark

Introduction to Heating Effects

Heating Effects

• Sunlight versus shadow• Black versus white (Albedo)

– What would you rather stand on:• Black asphalt parking lot• White concrete sidewalk

– Albedo: A measure of how much light is being reflected

• Dark colored material: reflects little light, absorbs a lot of light = low albedo

• Light colored material: reflects a lot of light, absorbs little light = high albedo

Heating Effects

Heating Effect Visible Day IR Night IRSunlight High

Low

Albedo High

Low

TI High

Low

Shadow Mapping Activity: Shadow and Sun Effects

Materials Needed:

-Notebook

-IR Thermometers

-Pencil

-Colored pencils

Shadow Mapping Activity: Shadow and Sun Effects

1. Find an object which is casting a large shadow and will be in the sunlight for most of the day.

2. Record the current time, and sketch (as seen from above) the shadow cast by the object. Be sure to indicate which way is north on sketch.

3. Using the IR thermometer, measure the temperature of the object and the surrounding ground at the points indicated in the sample drawing.

4. Create a temperature scale and color your temperature map.

Temperature in Black and White Activity: Albedo Effects

Materials Needed:

-Notebook

-IR Thermometers

-Black and white albedo samples

-Stopwatch

-Colored pencils

Heating Effects

Heating Effect Visible Day IR Night IRSunlight High

Low

Albedo High

Low

TI High

Low

Heating Effects

Heating Effect Visible Day IR Night IRSunlight High Bright Hot N/E

Low Dark Cold N/E

Albedo High Bright Cold N/E

Low Dark Hot N/E

TI High

Low

Thermal Inertia

• Thermal Inertia (TI) = measures the amount of energy it takes to heat up a materials and how long it takes that material to cool down after the energy source is removed

• High TI = requires more energy to heat up and cool down

• Low TI = requires less energy to heat up and cool down

Thermal Inertia

• Think of a sandy beach during the day:

As you walk around, what is really hot?

• Think of that same sandy beach at night:

What is the temperature like of the sand? How about the rocks?

What takes more energy to be heated up and cool down (loose it’s heat)? = High TI

What takes less energy to heat up and cool down (heats up and cools down more quickly)? = Low TI

Thermal Inertia

• TI is related to grain size– Rocks– Sand– “Dust”/finer grained materials

Heating Effects

Heating Effect Visible Day IR Night IRSunlight High Bright Hot N/E

Low Dark Cold N/E

Albedo High Bright Cold N/E

Low Dark Hot N/E

TI High

Low

Heating Effects

Heating Effect Visible Day IR Night IRSunlight High Bright Hot N/A

Low Dark Cold N/A

Albedo High Bright Cold N/A

Low Dark Hot N/A

TI High N/A N/A Hot

Low N/A N/A Cold