# Presentation: 831637

## Compositional Mapping of Saturn's Satellites with Cassini VIMS

**Compositional Mapping of Saturn's Satellites with Cassini VIMS**

**Dr. Roger N. Clark**
**Cassini Visual and Infrared**
**Mapping Spectrometer**
**(VIMS)**

**U. S. Geological Survey**
**Denver, Colorado**

## Compositional Mapping of Saturn's Satellite Dione with Cassini VIMS and Implications for Dark Material in the Saturn System

- This Charm talk is based on a paper of the same title
- being submitted to the Icy Satellites Cassini *Icarus* special issue
- Authors:
- R. N. Clark (USGS),  R. H. Brown (U. Ariz.),  R. Jaumann (DLR),  D. P. Cruikshank (NASA Ames),  B. Buratti (JPL),  K. H. Baines (JPL),  R. M. Nelson (JPL),  P. D. Nicholson (Cornell U),  J. M. Moore (NASA Ames).   J. Curchin (USGS),  T. Hoefen (USGS), and  K. Stephan  (DLR)

## Saturn

- Mimas

- B Ring Shadow

- A Ring

- Light passing through Cassini division

- F Ring

- C Ring Shadows

## Cassini ISS:

- Imaging Science Subsystem

## Cassini VIMSVisual and Infrared Mapping Spectrometer

**Cassini ****VIMS****Visual**** ****and**** ****Infrared**** ****Mapping**** ****Spectrometer**

**Red = 5.02 microns**
**Green = 2.71 microns**
**Blue    = 1.06 microns**

## VIMSVisual and Infrared Mapping Spectrometer

**VIMS****Visual**** ****and**** ****Infrared**** ****Mapping**** ****Spectrometer**
**0.35 to 5.2 microns in 352 wavelengths**
**IFOV: 0.5 x 0.5 mrad (standard)**
**(0.5 mrad = 1.7 arc-minutes)**
**High resolution IR: 0.5 x 0.25 mrad**
**High resolution VIS: 0.17 x 0.17 mrad**
**Images up to 64 x 64 pixels square.**** **

## Slide 7

## Phoebe

- ISS Images 11 June 2004

**Clark et al.,**, Compositional maps of
- Saturn's moon Phoebe from imaging
- spectroscopy,   *Nature*,
- doi:10.1038/nature03558 May, 2005.

## Clark et al.,, Compositional maps of 

**Clark et al.,**, Compositional maps of
- Saturn's moon Phoebe from imaging
- spectroscopy,   *Nature*,
- doi:10.1038/nature03558 May, 2005.

## Clark et al.,, Compositional maps of 

**Clark et al.,**, Compositional maps of
- Saturn's moon Phoebe from imaging
- spectroscopy,   *Nature*,
- doi:10.1038/nature03558 May, 2005.

## Detection of Multiple Componentson Phoebe with VIMS

**Detection of ****Multiple Components****on Phoebe with VIMS**

**Water Ice**
**Bound Water**
**Trapped CO****2**
**Broad 1-micron feature (Fe****2+****)**
**2.2-micron feature (probable Al-OH, phyllosilicates)**
**2.42-micron feature (cyanide compounds?)**
**3.3-micron features (probable organics)**
**3.6 micron feature (origin ?)**
**Broad 3.8-micron feature (origin ?)**
**Broad 4.5-micron feature (origin ?)**
**4.51-micron feature (probable Nitrile, a CN compound)**

## Iapetus

- 31 December 2004

- ISS_00CIA_GLOBCOLA001 (1030 m/pxl)

- 730 km in radius
- inclined orbit (15°)
- 59 RS orbit
-  extremely dark leading
-        hemisphere

## What is the source of Iapetus’ striking albedo dichotomy?

**What is the source of Iapetus’ striking albedo dichotomy?**
**Iapetus’ leading hemisphere is dark (~4%) and reddish**
**Iapetus’ trailing hemisphere is bright (~60%) and contains water ice**
**Endogenic source? **
**Exogenic source? **
**            ****Phoebe?    Hyperion?    Titan (tholins)?**
**Why is Iapetus’ orbit inclined?**
**What is the source of the equatorial “belt”?**
**~2000 km long chain of mountains, 20 km high (65,000 feet)**
**Aligned along the equator**

## Iapetus

- Dark material streaksin transition zone

**CO****2**

*xCN?*

**H****2****O**
**or**
**NH**

*CN?, 2.42-micron*

**H****2****O**
**or**
**NH**

## VIMS IapetusConclusions

**VIMS Iapetus****Conclusions**

**Several compounds are common on both Phoebe and Iapetus:**
**Cyanide(?) Compounds (2.42 and 4.7-4.8 micron features)**
**Trapped CO****2**** (4.26 microns)**
**Bound Water as well as H****2****O, trace organics.**
**But Phoebe has more diversity in compounds *****(detected so far)***** including Fe****2+****, probable nitriles.**
**Iapetus has CO****2**** frost but Phoebe does not.**

- Hyperion ISS

## Hyperion ISS

*2.42-micron*

*CO**2*

## Rhea

**Targeted flyby on Rev 18 (ORS+RSS+RADAR); **
**Quasi-targeted flyby on Rev 49 (ORS+RADAR)**

- 765 km in radius
- 8.74 RS orbit		light wispy streaks on anti-Saturn hemisphere

## Rhea: all Ice

## Dione:

**Dione:**
**Targeted flyby on Rev 16**
**(ORS, RSS, RADAR)**
**Close flyby on Rev 50**

- 	**560 km in radius****	****	****light wispy streaks on**
**	****6.26 R****S**** orbit****	****	****	****	**** trailing hemisphere.**

- 14 December 2004

## Dione: VIMS 2.4-m reflectance

- Dione: VIMS 2.4-m reflectance

## Dione: VIMS 2.4-m reflectance

- Dione: VIMS 2.4-m reflectance

**Direction of**
**incident sunlight**

**A**

**B**

**A**

**D**

**C**

**Terminator**

## Dione: VIMS 2.0-m ice band strength

- Dione: VIMS 2.0-m ice band strength

## Dione: VIMS 2.0-m ice band strength

- Dione: VIMS 2.0-m ice band strength

**Direction of**
**incident sunlight**

**A**

**C**

**A**

**B**

**D**

## Dion

## Enceladus

- 15 February 2005

- 260 km in radius
- 3.95 RS orbit
- Possible source of E-ring
-  Very bright surface.
- Enceladus:Dione in 1:2 resonance

**Is Enceladus currently**
**       ****geologically active? ****YES!**
**Is Enceladus a source**
**       ****of the E-ring? ****YES!**
**Composition?**
**What is the source of **
**            ****grooved terrain?**
**Tectonism?**
**Cryovolcanism? **
**Expansion/contraction?**

## Enceladus

- 15 February 2005

## Enceladus

- 30 m/pixel

**Notice “soft” craters**

**Enceladus**

## Enceladus: nothing but Ice.......?

## But Wait!

## Slide 36

## Slide 38

## Saturn as seen with Cassini VIMS

**Saturn as seen with Cassini VIMS**

**A**

**B: red = methane band strength**

- shadow

## VIMS spectra of Saturn’s rings showclassic Ice signatures.

**VIMS spectra of Saturn’s rings show****classic Ice signatures.**

## 2.42-micron

*2.42-micron*

## H2O

**H****2****O**
**CO****2**
**CN****(?)**

**H****2****O**
**CO****2**
**CN****(?)**

**H****2****O**
**CO****2**** (trace)**
**CN****(?)**

**CH,**
**CN**

**H****2****O**
**(CO****2****)**

**H****2****O**
**CO****2**

**H****2****O**

**H****2****O**
**(CO****2****)**

**H****2****O**
**CN****(?)**

**Compositions from VIMS**

- HCN clouds

**H****2****O**
**CO****2**
**CN****(?)**

## Conclusions

**Conclusions**

**Saturn’s satellites are dominated by icy surfaces with trace materials:**
**Compounds with 2.42-micron feature (cyanide compounds? Or ???)**
**Seen on Phoebe, Iapetus, Hyperion, Dione and the F-ring**
**Trapped CO****2**** (4.26 microns)**
**All objects where we have adequate signal-to-noise ratios, but generally stronger further from Saturn.  ****(SO FAR: NOT IN THE RINGS)**
**The presence of the 2.42-micron feature throughout the Saturn system implies:.**
**The dark material is compositionally similar throughout the system.**
**Common origin?**
**The pattern of dark material on Dione implies an external origin.**

## Questions?

**Phoebe**

**Iapetus**

**Dione**

**Mimas**

**Titan**

**Tethys**

**Rhea**

**Enceladus**