# Presentation: 529366

## Determining surface characteristics at candidate MSL landing sites using THEMIS high-resolution orbital thermal inertia data

- Robin Fergason
- Philip Christensen
- MSL Landing Site Selection Workshop
- May 31, 2006

## Thermal Inertia Background

- Used to infer a particle size of the surface layer
- Helps to identify features, their location and extent on the surface, and their particle size
- Detect exposed bedrock and dust

## Exposed Bedrock

- 800

- 260

- 67.6 E

- Nili Patera

- 66.9 E

- 8.7 N

- 9.5 N

- Ares Valles

*Rogers et al., 2005*

*Christensen et al., 2003a; 2005*

- 950

- 190

- 341.6 E

- 341.3 E

- 5.9 N

- 6.4 N

**3.4 km**

**3.5 km**

- THEMIS-derived thermal inertia overlain onto THEMIS visible

## Hebes Chasma Interior Layered Deposits

- V10052001

- 800 m

- TI: 190-245

- TI: 275-360

- TI: 290-420

- TI: 125-145

- 125

- 615

*Fergason et al.,* submitted

## Thermal Inertia Background

- I = (ρkc)1/2
-     ρ – bulk density
-     k – conductivity
-     c – specific heat

- Thermal inertia measures a material’s resistance to change in temperature

## THEMIS-derived thermal inertia

- Use thermal model developed by H. H. Kieffer
- Ls, latitude, local time from spacecraft ephemeris
- TES-derived albedo (8ppd)
- MOLA-derived elevations (128 epd)
- TES-derived dust opacity (2 ppd) every 30° Ls
- Radiance at 12.57 μm (Band 9) is converted to brightness temperature, correcting for drift and wobble of the spacecraft
- Interpolate upon a 7-D look-up table

## THEMIS-derived Thermal Inertia Uncertainties

- Uncertainties are primarily due to:
-        (1) instrument calibration
-        (2) uncertainties in model input parameters
-        (3) thermal model uncertainties
- Variations in thermal inertia within a single image are accurate and represent differences in the physical properties of the surface

## Comparison with TES

- 25

- 600

- 180 E

- 40 S

- 40 N

- 180 E

- 180 E

- 40 S

- 40 N

- 180 E

- THEMIS

- TES

*Fergason et al.,* submitted

## Comparison of Mini-TES and THEMISThermal Inertia

- Comparison of Mini-TES and THEMISThermal Inertia

*Fergason et al.*, 2006

- 250

- 430

## Landing Site Characterization

- Identify regions of very high or very low thermal inertia
- TI > 400 likely has rocky surface [*Nowicki*, 2006]
- TI < 100 is likely dusty and not drivable
- Evaluate surface properties of the candidate landing sites
- Predicted surface temperature for the primary mission
- Rover design temperature limits: 145 - 310 K
- Maximum diurnal temperature range: 145 K

## Opportunity THEMIS Temperature Mosaic - 2003

## Opportunity THEMIS Temperature Mosaic - 2006

## 63.2 E

- 570

- 175

- 26.8 N

- 26.3 N

- 62.6 E

*Fergason et al.,* submitted

## THEMIS Day and Night IR

## Slide 15

## Predicting Surface Temperature

- Thermal inertia is derived from THEMIS image
- The derived thermal inertia value is then used to calculate the surface temperature for a given local time and season

-    Can predict the minimum surface kinetic  temperature during the primary mission

## ASU Will Provide

- Interpretations of THEMIS and TES thermal inertia data for all candidate landing sites
- Thermal inertia mosaics of candidate landing site regions (100 m)
- Relative thermal inertia values

## ASU Will Provide

- Individual thermal inertia images of specific areas of interest (100 m)
- Thermal inertia values of specific morphologies
- Predicted temperature maps of candidate landing site regions (100 m)
- Predict range of temperatures
- Derive maximum diurnal temperature range