surface magnetization of terra meridiani , mars
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Surface Magnetization of Terra Meridiani , Mars. Renee French Earth 438 Winter 2014. Opportunity looking out on Santa Maria Crater, sol 2466 (~7 years). Motivation. - PowerPoint PPT PresentationTRANSCRIPT
Surface Magnetization of Terra Meridiani, Mars
Renee French
Earth 438
Winter 2014
Opportunity looking out on Santa Maria Crater, sol 2466 (~7 years)
Motivation• Terra Meridiani has been proposed as a site of past seafloor
spreading due to magnetic offsets in the MGS Magnetometer data at 400 km altitude (Connerney et al., 2005)– If this data is continued to the surface, are the magnetic offsets still
observed?
– Can magnetic offsets, and thus transform faults, be tied to other geologic features (i.e., offset craters, regional differences in geology)?
– What other mechanisms can produce the observed magnetization?
– Any other data to suggest that Terra Meridiani was once an active plate boundary?
– Can data from MER Opportunity provide any ground truth for this hypothesis?
Location
Image credit: NASA
Geologic Investigation
Image Credit: NASA/JPL/ASU
Squyres and Knoll (2005)
Trough x-stratImage 3cm wide
Hematite spherules
Squyres et al. (2006)
Squyres et al. (2006)
Burns Formation Facies
McLennan et al. (2005)
• Data best supports eolian environment with a fluctuating groundwater table
From Acuña et al. (1999): Measured vertical component of the magnetic field (no altitude correction). Includes aerobraking data. Solid line is the boundary between the northern lowlands and southern highlands.
Martian Magnetization
Martian Magnetization
From Connerney et al. (2005): Measured radial (vertical) component of the magnetic field at 400km altitude
Past Seafloor Spreading?
Map of the magnetic field at 400 km altitude (Connerney et al., 2005). Dashed lines represent transform faults, letters refer to impact basin names.
Map of the magnetic field as a function of latitude (Connerney et al., 2005). Green and orange represent profiles taken to the west and east of the central meridian, respectively.
Methods• 2D Fourier Transform
• Downward continuation; k>25 filtered out
• Inverse Fourier Transform
• Geologic units from Scott and Tanaka (1986), Greeley and Guest (1987).
Results: Raw Data
Accuracy Test
Aerobraking:Max: 278Min: -268
DC’ed:Max: 437Min: -247
Surface Magnetization
Impact influence?
Basins are from Schultz et al. (1982) and Schultz and Frey (1990)
Basins:1-Chryse2- Ladon3- Aram Chaos4- overlapped by Newcomb5- overlapped by Schiaparelli6- Cassini
Tectonic influence?
“Great faults” from Connerney et al. (2005)
Topography
20N, 20E20N, 20E
20S, 340E 20S, 340E
Geology
Subdued crater unit
Etched unitCratered unit
Dissected unit
Ridged Plains material
Chaotic material
Older Channel material
Hilly unit
Mottled Smooth Plains unit
Ridged unit
Crater materials
Smooth unit
Undivided materialCratered unit
Hilly unit
Crater materials
Ridged Plains material
Smooth unit
Scott and Tanaka (1986), Greeley and Guest (1987)
All units are interpreted as some type of igneous rock
20S, 340E
20N, 20E
Discussion• Downward continued field agrees well with low altitude data.
• Offsets observed by Connerney et al. (2005) at altitude are also observed at the surface– No other geophysical signature of faults
• Possible influence from multi-ring basins– May not be a source of magnetization, but rather weaken the intensity
• Magnetic mineralogy constrained by Opportunity– Will use when considering source models
• Geologic history from Burns formation does not match a seafloor spreading environment– However, this outcrop is only 7 m thick
Image Credit: Voyage to the Planets, BBC