1. Evidence Supporting An Ignimbrite Origin For The Medusae Fossae
Formation, Mars
James R. Zimbelman
Center for Earth and Planetary Studies
National Air and Space Museum
Smithsonian Institution
Washington, D.C

2. Enigmatic deposits along the highland-lowland boundary
Medusae Fossae Formation (MFF)
Enigmatic deposits along the highland-lowland boundary
(15°S to 15°N latitude, 135° to 235°E longitude)
A variety of hypotheses of origin have been proposed:
Welded/nonwelded ignimbrites
(Malin, 1979; Scott and Tanaka, 1982, 1986)
Aeolian deposits
(Ward, 1979; Carr, 1981; Scott and Tanaka, 1986)
Polar layered materials
(Schultz and Lutz, 1988)
Chemically altered basement
(Forsythe and Zimbelman, 1988)
Carbonate platform
(Parker, 1991)
Rafted pumice (northern ocean)
(Mouginis-Mark, 1993)
(from Scott and Tanaka, 1986)
Eastern portion of MFF units

3. portions of Mars Charts MC8SE and MC16NE
Regional mapping of
portions of Mars Charts
MC8SE and MC16NE
Global MFF units have
been subdivided into
three sub-units
(numbered 1 to 3,
bottom to top)

4. (from Kelly Bender and Jayme Harris, ASU)
THEMIS (as of 5/03)
(from Kelly Bender and Jayme Harris, ASU)
MOLA shaded relief

5. THEMIS daytime IR image I01665006 (taken 4/30/02) Center lat.: 5.56°N
Center long.: 218.2°E
100 m/pixel
15.43 H local time
< context image:
NASA/MOLA
< Band 9
(northern
portion of
image was
blank)
Width: 32 km

6. 5 km Competent layer exposed within Amm scarp
Erosion to level of
cool, competent layer
Brightness temperatures (15.43 H local time) K K
Competent layer exposed within Amm scarp 3

7. Multiple dark bands within MFF materials (at MOC resolution)
~200 km from the
THEMIS scarp area
~Parallel layers
Tens of meters
thick
Possible additional
layers not well
exposed